How is the impedance of speaker systems measured? Test of bookshelf Hi-Fi acoustics in the mid-price category. Special shape of dust caps on speakers - necessity or decoration

Even during periods of economic crisis, the flow of true music connoisseurs does not dry out, for whom it is important not just to listen, but also to hear their favorite compositions as they sounded “live”, from the stage. Of course, it is not difficult to satisfy such a need today - if only there was money! Well, if finances are tight, but you still want to listen to Hi-Fi music, what should you do? For this purpose, we decided to test such shelf units. speaker systems, which successfully combine Hi-Fi sound quality and an affordable price corresponding to the average price category. Of course, these are not “sophisticated” acoustics, but if we compare floor-standing acoustics with bookshelf speakers according to the “price/quality” criterion, then the latter even come out on top. The only thing I want to warn you about in advance. Bookshelf monitors do not always have ideal bass depth, but this deficiency is more than compensated by the excellent sound of the speakers at low volumes. But in the end, who do we listen to music for - for our neighbors or for ourselves? Well, choosing a suitable speaker from the twelve tested models will be easier. So think, compare, enjoy!

Criteria for evaluation

Since we are talking about an established category of classic monitors, testing will be standard. The amplitude-frequency response and nonlinear distortion coefficient will objectively show to what extent the monitor design corresponds to the acoustic parameters. At the same time will be studied design features each model, and a total design assessment will be obtained as a whole. During testing, the sound character of each speaker system will be examined simultaneously. As a rule, bookshelf formats rarely combine good bass depth and high playback quality, so this indicator will be mentioned in testing, but only as a reference. But as for the characteristics of the reproduction of the upper register, which is extremely important for the presentation of musical material, here the testing will be quite thorough. The nature of the sound at low volumes will also be indicated separately, which indicates the smooth (almost linear) dynamics of the speaker systems. The timbral authenticity of the music scene will not be left without attention. Taken together, all this will make up the sound rating.

Acoustic Energy 301

• Sound: 4
• Construction: 4
• Cost: 4

Advantages:

• great detail
• timbre accuracy

Flaws:

• there is a lack of air

When developing the 300 series, British designers managed to embody exquisite laconicism. Covered with white or black varnish, the speakers look neutral and strict. The joints of the panels, like the rest of the body elements, are made delicately, without any frills such as fasteners or protruding screws - in all respects, this bookshelf model is made in the classic style of “professional” Hi-Fi acoustics. The front panel of the Acoustic Energy 301, which is finished with a black rubber-like coating, houses a proprietary 28mm fabric dome tweeter and a proprietary 110mm woofer made of bent anodized aluminum. By the way, the legendary AE1 monitors, recognized by experts as a standard, once had exactly this type of head.

The output hole of the slotted bass reflex is also located at the bottom of the front panel. This original engineering solution has several advantages. Firstly, these speakers can be placed almost anywhere, even almost moved to the wall without fear of distorting the sound - thereby simplifying the installation of the speakers. Secondly, the bass reflex on the front panel does not distort the frequency response in the mid-bass region, and at the same time allows for better matching of the lowest frequencies with the room parameters. And this detail: the solid internal volume of the speaker (with a height of 300 mm and a width of 185 mm, the depth of the speaker is 250 mm) made of massive MDF sheets also ensures excellent bass sound. With such capabilities, this shelf model of the monitor is practically not inferior to its more expensive floor-standing “brothers,” especially when working in small rooms.

Sound

And if we are talking about sound quality, it should be noted that there is no even subtle coloration in almost the entire range. Despite the fact that even the smallest nuances of music can be clearly heard on the Acoustic Energy 301 speakers, the timbres are almost natural. This indicates that the monitor's frequency scale is balanced in both level and dynamics, and these speakers produce consistent sound. Despite the fact that the bass register is very clearly distinguishable and the middle range is perfectly audible, at the highest frequencies there is no, no, and the slightest rise slips in, which is especially noticeable on complex musical material, when its perception is somewhat reduced. This picture is typical for both high and low volumes.

Measurements

With equal amplitude frequency response at the highest frequencies it starts to go up a little. The decline in the low-frequency region is uniform. The bass is of high quality, of medium depth. The THD is quite low and is virtually independent of the volume level. Impedance is unstable.

Bowers & Wilkins 685

• Sound: 3
• Construction: 3
• Cost: 5

Advantages:

• good sound
• design

Flaws:

• slight change in timbres
• slight distortion
• presence of noise

This bookshelf model of the speaker system is a bright representative of the junior line of the British company Bowers & Wilkins. The old design of the speakers incorporates the technologies of the flagships of this manufacturer. Of course, we are talking only about inexpensive ones, but at the same time optimal solutions. First of all, these are Nautilus conical tubes for the tweeter, Kevlar diffusers, as well as a proprietary bass reflex port with the original golf ball surface. The two-layer aluminum tweeter dome is insulated with a special material, with the help of which it was possible to obtain surround sound. In the dynamics of mid and low frequencies, the recoil at the upper limit is smoothed out by a static bullet. The crossover responsible for sound purity is extremely simple. The body of the speakers is covered with film, but the front panel pleases with a velvety material that is pleasant to the touch.

Sound

This model is characterized by an open and bright sound with a good level of detail. The bass is accurate and fast, but could be more concentrated, but the noise makes itself felt. However, sound localization is very clear. The audiophile will not be pleased with the low dynamic range. In the mid-frequency range, the timbres of instruments are greatly simplified, and the high-frequency region is not heard as well as we would like and does not give the impression of airiness and spaciousness.

Measurements

In the ranges of 2.5 kHz and 6-7 kHz, irregularities appear, which can be eliminated by turning the speaker 30°. At the same time, the frequency balance goes somewhat into the low-frequency range. Characterized by extremely low SOI. The impedance is very unstable.

Canton Chrono 503.2

• Sound: 4
• Construction: 5
• Cost: 5

Advantages:

• clean high frequencies
• meticulous transmission of timbres

Flaws:

• Low frequency range is weak at low volumes

The German model Chrono 503.2 is characterized by excellent sound reproduction and traditionally high quality control. Although the manufacturer stated a glossy finish, the speaker body is covered with film, and only the front panel is glossy. On relatively compact speaker An impressive speaker (diameter 180 mm) with a traditional aluminum diffuser for this company is installed. To ensure the maximum possible linear and long piston stroke of the diffuser, the suspension is made in the shape of a wave. The tweeter is equipped with a lightweight 25 mm dome made of a durable alloy of aluminum and magnesium, which is also covered with a metal grill for reliability. The mobility of the speakers has also been thought out: so that they can be mounted on a stand or bracket, there are two threaded holes in the bottom of the speaker.

Sound

The speakers reproduce almost all musical genres quite clearly, with almost perfect frequency balance. Therefore, it is not surprising that the timbres of instruments sound practically without distortion, even subtle nuances. Although there is no increased emotionality expected with such parameters, the wide and smooth dynamic range of the speakers very reliably conveys the musical idea of ​​any genre - in this the speakers can be considered universal. The lower frequencies are collected and clearly distinguishable, but the bass is still not deep enough, and when the volume is lowered, it begins to “go away” barely noticeably. When you get acquainted with the speakers, you get the impression that the range of the upper register is too large, but after listening, you understand that high frequencies appear at those moments when it is necessary, and in sufficient quantities, without excesses. It is worth noting that uppercase The speakers are crystal clear, which music fans will appreciate.

Measurements

Speaking of good dynamic qualities this model, it should be noted that the ideal sound largely depends on the angle at which you listen: the monitor’s directivity is quite narrow. The nonlinear distortion coefficient is small, and a good margin is noticeable at low frequencies. Impedance is unstable.

Chario Syntar 516

• Sound: 3
• Construction: 4
• Cost: 4

Advantages:

• emotional and bright presentation
• precise localization

Flaws:

• simplification of timbres

The classic style of the Italian monitor is primarily distinguished by its natural wood veneer finish - both inside and outside, which significantly increases the durability of the speaker. The entire process of processing the body parts and their further assembly is carried out manually, which again increases the impeccable quality. Then the finished products are necessarily tested - without this, the speakers do not go on sale. The tweeter membrane (Silversoft Neodium model) is coated with silver aluminum powder - the same technology is used in monitors of the leading brand line. It is worth noting that the tweeter also reproduces a significant part of the mid-frequency range (from approximately 1 kHz). The double-curved shape of the mid/bass speaker diffuser was specially selected taking into account the recommendations of psychoacoustics. The asymmetrical hole in the bottom of the speakers is the bass reflex port. In order for it to work correctly, high rubber feet are attached to the bottom of the speaker.

Sound

This speaker system is characterized by both slowness and softness, complemented by an active and clear upper register. At the same time, the timbre picture is somewhat blurred, which is why sound nuances are veiled. Despite this, the speakers still reproduce musical compositions of different genres quite accurately and emotionally. The bass is so deep that it even stands out in the overall sound picture. Soundstage localization is good, but lacks transparency, which is especially noticeable when listening to complex compositions. As the volume is lowered, the bass begins to weaken, but the sound remains emotional and dynamic.

Measurements

The optimal amplitude-frequency response was recorded when the speaker was rotated by 30°. The model is characterized by relatively good unevenness with an even and smooth roll-off to low frequencies. The coefficient of nonlinear distortion is quite even - from the highest to the lowest frequencies. The impedance is quite stable.

Dynaudio DM 2/7

• Sound: 5
• Construction: 5
• Cost: 5

Advantages:

• authenticity of timbres
• clean highs

Flaws:

• excessive severity in sound delivery

In the group of bookshelf monitors, the Danish company Dynaudio is represented by the DM line. As you would expect, the company has designed the speakers in its signature style: a massive front gray panel is slightly thicker than the side walls to more effectively dampen unwanted resonances. The same applies to the body as a whole: it is delicately muffled and immaculately finished with classic veneer. The 28mm silk dome of the branded tweeter is treated with a special impregnation, but the midrange/bass driver cone is made of magnesium silicate polymer, which has proven itself well in the world of acoustics. The voice coils are wound on a Kapton frame with lightweight aluminum wire, and when paired with a powerful magnetic system, they produce excellent dynamics and sensitivity. The designers of these speakers paid great attention to maximizing impedance equalization to minimize speaker dependence on the amplifier.

Sound

The speakers reproduce music freely and naturally, and the beautiful sound of the tones transforms the sound stage into a natural one, producing an expressive and balanced sound. Indeed, you get the impression that you are at a “live” concert and can clearly hear where which instrument is located. Low frequencies are tight, energetic and distinct. The upper register is refined, clean and expressive. All the details are well worked out in the sound and there is no coloration. It is also worth noting that the speakers play equally confidently at both low and high volumes.

Measurements

The amplitude-frequency response is a flat line with a slightly noticeable shift into the HF range. The model is characterized by a broad focus. The nonlinear distortion coefficient is stable and low, as is the impedance. In total - excellent results.

Magnat Quantum 753

• Sound: 5
• Construction: 4
• Cost: 4

Advantages:

• precise tones
• clear sound stage

Flaws:

This bookshelf monitor from the German company Magnat Audio-Produkte from the Quantum 750 line is perhaps one of the most impressive of the speakers under review. To minimize cabinet resonance, the front panel of the speaker is made of a double-layer 40 mm plate, the thickness of the podium is 30 mm. The legendary German solidity is emphasized by the muted, austere matte surface of the case, and only the podium with the front panel playfully sparkle with careful polishing. The Fmax tweeter (by the way, a proprietary development of Magnat) has a dome made of a double fabric compound, which provides an extended working band. As for the midrange/woofer cone, it is made of aluminum coated with ceramic particles. This model also features a well-ventilated voice coil. The shape of the aluminum speaker basket was also thought out so that the air flow passes freely and reduces potential resonances. The large bass reflex output is located on the rear wall of the monitor. Assembled from high-quality elements, the crossover is almost perfectly tuned to the phase and amplitude of the signal, thanks to which the resolution of this model is much higher than average.

Sound

The sound of the monitor is characterized by emotional and dynamic playing with excellent transmission of the entire spectrum of instrumental timbres - the localization of sound sources is simply excellent. The sound stage is clean, large-scale and deep, details are worked out to the maximum and do not intertwine, there are practically no extraneous sounds. The high frequencies are characterized by an open sound with a feeling of airiness and, nevertheless, the upper range is very correct and unobtrusive. The bass is clear and fast, with medium depth. In this range there is enough naturalness due to the fact that the feed density “falls” a little. As the volume decreases, the emotionality of the speakers decreases somewhat.

Measurements

With minimal unevenness in the frequency response, a slight frequency imbalance towards high frequencies is noticeable, which, however, is unlikely to affect the tonal balance - we can say that this is not bad at all for budget monitors. Although the total harmonic distortion varies within 1% depending on the volume, there is no noticeable resonance. It should be noted that the SOI margin is good at low frequencies. Impedance is stable.

Martin Logan Motion 15

• Sound: 4
• Construction: 4
• Cost: 3

Advantages:

• the presentation of the material is lively and energetic
• tight and fast bass

Flaws:

• works a little at low volume

The design of this monitor is pleasing to the eye with a filigree finish on the case and a beautiful protective steel grille on the front panel. And underneath it is the highlight - an expensive ultra-high-resolution ribbon tweeter that allows you to produce clear, accurate and dynamic sound. The speaker body is assembled from 19 mm MDF boards, and only the aluminum front panel of the monitor is anodized black, which gives it solemnity and severity. In the same color scheme The diffuser of the mid/bass emitter with a long stroke is also made - appearance columns are laconic and strict. As for the speakers, their work is coordinated by a crossover with improved characteristics - the manufacturer achieved this effect through the use of polypropylene capacitors and electrolytes with a low loss coefficient. On back panel The speakers have a bass reflex port.

The manufacturer has provided thermal and current protection for the monitor.

Sound

These speakers have one peculiarity: they do not like to work at medium and low volumes - in such cases, only mid frequencies remain in the range, and the dynamics become boring and sluggish. But as the volume increases, the elastic and fast bass “cuts through” more and more clearly, and the upper range becomes clearer. And although the lower middle continues to dominate and does not give way, the music is presented more and more energetically and more sharply. It must be admitted that when the speakers are operating in any volume mode, no extraneous sounds are heard. Moreover, after-sounds sometimes disappear even where they could be. It is worth noting that although this model of “shelf speakers” simplifies the timbres of instruments, a ribbon tweeter with increased sound output helps the situation and gives the mid-upper range a particularly delicate portrayal. Therefore, despite the minor listed errors of the monitor, music lovers appreciate the performance of this speaker.

Measurements

In the high-frequency region, unevenness in the amplitude-frequency response is clearly visible, and the sensitivity towards low frequencies drops quite sharply. The speakers are characterized by a wide directivity. Although the coefficient of nonlinear distortion in the midrange region has slight increases, it still remains below 1%. The impedance is relatively stable.

MK Sound LCR 750

• Sound: 5
• Construction: 5
• Cost: 4

Advantages:

• sound is focused, clear
• good transmission of timbres

Flaws:

• truthfully reflect the shortcomings of studio recording

The laconic design of the speakers from M&K Sound is easily recognizable: strict black color and the absence of even a hint of the slightest decoration. The manufacturer believes that it is much more important to focus on quality, in which the Americans have achieved excellent results - today, among professionals, these acoustic systems have rightfully gained a reputation as the standard of control acoustics. The 750 series, designed for home cinemas, also corresponds to this flattering characteristic, in which the 750 LCR bookshelf monitor stands out with its solid dimensions. The speaker is quite original and stands out even among the models we are considering. Among its main features are the closed housing, due to which bass output is minimized, as well as the installation of two drivers at once - mid- and low-frequency, which significantly increases the dynamic range of the monitor. Another know-how of the manufacturer - a 25 mm silk tweeter installed at an angle of 4.7° to the front plane optimizes the dispersion of various frequencies.

Polypropylene diffusers with mineral filler in combination with the installed phase-focused crossover significantly improved the acoustic parameters of the monitor. For ease of use, the rear panel of the speaker has threaded holes for one or another monitor mounting option.

Sound

With smooth sound, the speakers perfectly control almost any musical material. Almost all instruments are clearly audible on the sound stage, both in timbre and in space. There is nothing superfluous in the overall musical picture, and all dynamic shades are heard clearly. And since the 750 LCR model does not add the slightest emotional coloring, to an unprepared listener this sound may even seem somewhat dry. However, this is how it should be.

Measurements

Deviations in the frequency response of the monitor are so small that there can be no talk of any distortion of the tonal balance. In this case, optimal results were obtained when the column was rotated by 30°. The vanishingly small SOI increases very smoothly towards low frequencies, and only at low volumes reaches 5%. Impedance is stable. In general, we can state a quite good result.

PSB Imagine B

• Sound: 5
• Construction: 5
• Cost: 3

Advantages:

• true transmission of timbres
• smooth dynamics

Flaws:

• limited high frequency range

The basis for why the Canadian company PSB has been successfully selling the Imagine line for several years now was the original design development of the monitors, which made it possible to achieve the extraordinary acoustic parameters of these speakers. And although the originality and elegance of the speakers were duly noted by the prestigious RedDot design award, it was the magnificent specifications. Judge for yourself. In the speaker housing, finished with natural veneer, you will not find right angles - the curved walls of the line’s monitors resemble the bizarre intersection of several cylinders at once, which gives the impression of being “cosmic”. However, at the same time, the design looks strong and solid, and all the bends “work” exclusively to achieve ideal sound, eliminating the appearance of standing waves and the birth of internal resonances. However, the latest technical developments embodied in PSB speakers also contribute to achieving this goal. Let's take a 25mm tweeter for example. Its titanium dome is equipped with an acoustic lens and is cooled by magnetic fluid; the column uses a powerful neodymium magnet. Another effective one engineering solution: the polypropylene cone of the midrange/bass speaker is supplemented with a clay-ceramic filler, which again improves the sound quality. The bass reflex output is located on the rear wall.

Sound

Thanks to such design solutions, the speakers produce a collected and perfectly balanced sound. Monitors are characterized by excellent localization and natural timbres, so the sound stage is perceived almost as if it were alive. Note that even at low volumes the monitors play freely and naturally. True, the high-frequency range is a little limited, which is why the airiness suffers a little. Speaking of detail, it should be noted that sometimes monitors lose the smallest nuances, but even in such cases they delight with the expressiveness and richness of the music. The bass is not very deep, but quite bright. The mid-range is also good - the sound is correct and accurate.

Measurements

Although the frequency response of the monitor runs very smoothly along the acoustic axis, the listener still should not turn the speakers to the side, otherwise the high frequencies will begin to fade. The coefficient of nonlinear distortion throughout the entire range is low and shows stability - right down to the lower frequency limit. Impedance is stable.

Rega RS1

• Sound: 5
• Construction: 4
• Cost: 4

Advantages:

• the upper register is transparent, sounds clean and easy
• wide dynamic range

Flaws:

• the sound is a little colored

The only series of bookshelf monitors RS was developed by the British company Rega specifically to complement other Hi-Fi audio equipment produced by the same manufacturer. Therefore, it is not surprising that the RS1 model we tested incorporated the most interesting solutions premium class, while remaining quite affordable in terms of price. Despite the compactness and small thickness of the panels, the speakers look elegant and rich - primarily thanks to the careful veneer finishing and strict classic design. The drivers, designed and assembled within the company itself, are assembled by hand, and here we can talk about the highest quality of the speakers. Behind the 19mm tweeter is a chamber whose original shape contributes to optimal damping of acoustic waves. The midbass diffuser is made of paper.

Thanks to the smooth frequency operation of the speaker, it can be integrated with a tweeter. To do this, you need a crossover that has good phase synchrony. There is a bass reflex port on the rear panel.

Sound

Although the Rega RS1 speaker conveys tonal nuances quite accurately, due to the barely noticeable coloring, the sound stage loses a little transparency. Again, the upper register is a little missing, although it is completely clean. All the details are heard, but they are also hidden a little. In general, the reproduced material is presented clearly and expansively. Although the bass is reproduced accurately, it does not always have enough weight. In addition, sound localization in the RS1 speakers is a little blurry. But as for complex symphonic music, the monitor does not cope so well, and the sound material becomes more difficult to understand. However, if you listen to music at low volume, the speaker reproduces almost perfectly.

Measurements

In the range of the upper mids and high frequencies, due to the unevenness of the frequency response, the speakers sound slightly different. This can be corrected if the speaker is rotated 30°. Although the coefficient of nonlinear distortion is unstable, this indicator has practically no effect on the sound quality - it is less than one percent. Impedance is unstable.

Triangle Color Bookshelf

• Sound: 5
• Construction: 4
• Cost: 5

Advantages:

• live open sound
• clear transmission of timbres

Flaws:

• some excess bass

As is typical for the French, Triangle has combined the highest quality with grace and elegance in the production of speaker systems. This is most clearly confirmed by the stylish Color line, the speakers of which delight music lovers with an impeccable lacquered finish. The buyer can choose from monitors in colors of red, black and white. Speaking about the Bookshelf bookshelf, first of all we should note its tweeter with a titanium membrane and coated special composition paper diffuser for mid/bass speakers. The originality of the speaker is complemented by a fabric and wide corrugated suspension, as well as a dust cap made in the shape of a bullet. The crossover uses effective technologies that once pleased Magellan's top line - now the bookshelf also has this know-how. Let us add that the bass reflex output is located on the rear panel of the speaker.

Sound

The monitor produces very lively and natural sound with very high timbre accuracy. The reproduction of sound material is relaxed and natural.

The power of musical sound recreates a live performance remarkably accurately. The bass is well-formed and pleasantly deep. Sometimes it seems that there is even too much of it. The sound is very clear and detailed – the slightest nuances do not escape the listener. The speakers of this model perfectly reproduce compositions of any complexity, and even at low volumes the sound quality does not deteriorate.

Measurements

The imbalance in the frequency response detected in the high-frequency range is eliminated traditionally - it is enough to turn the column by 30°. The nonlinear distortion factor is quite low, but at mid frequencies it becomes higher, although it does not exceed 1%. At high volumes, distortion in the upper bass is noticeable. Impedance is unstable.

Wharfedale Jade 3

• Sound: 3
• Construction: 3
• Cost: 4

Advantages:

• good attention to detail

Flaws:

• the dynamics are a little weakened
• inaccurate localization

What sets the British company Wharfedale apart is its meticulous approach to the production of budget lines. For example, to the Jade 3 model, the only three-way monitor in our test. But if other manufacturers classify large and heavy monitors with curved panels as top brands, the British chose this form for the bookshelf solely for pragmatic reasons - auxiliary bulkheads dampen unwanted resonance inside the sealed case and minimize harmful sound coloration. At the border of 3 kHz, the tweeter with an aluminum dome neatly gives way to the midrange driver, whose diffuser is made of an aluminum-cellulose composite. And already in the range of 350 Hz, the main dynamic load passes to the low-frequency speaker, which is equipped with a woven diffuser made of reinforced fabric consisting of carbon and fiberglass threads. It is pertinent to note here that this combination of materials turns the diffuser into a flawless piston, which eliminates the unwanted resonance phenomena characteristic of metal diffusers. Let us add that the speaker speakers operate in a sealed volume, and the ideal linearity of the crossover phase signal is the result of computer optimization.

Sound

According to the established corporate tradition, all Wharfedale monitors sound equally beautiful. In the acoustic space, all musical instruments are clearly placed in their places, and the sound stage is clean and spacious. The speakers produce bass, as well as the upper register, carefully, non-aggressively, as if afraid to upset the balance of the reproduced sound picture. This model is characterized by a combination of soft presentation of sound images with optimal sound detail. It is worth noting that the monitor behaves very well even at low volumes.

Measurements

The amplitude-frequency response of the speaker is almost perfectly flat, but in the upper range it behaves unusually: after an unexpected decline, a sharp rise is immediately recorded. The bass range is quite deep. The nonlinear distortion coefficient is pleasing: at all ranges it is almost exclusively smooth and as low as possible. The low frequency range shows a solid margin. The impedance is quite stable.

conclusions

Comparing the results of speaker measurements in our test laboratory, we came to the conclusion that comparing bookshelf speakers is not as interesting as in the past. All tested monitors showed almost similar, even amplitude-frequency characteristics with minor deviations that did not affect perception, as well as a very low coefficient of nonlinear distortion, which again did not go into the critical zone even in the bass region. It’s not surprising, because there are practically no speaker manufacturers left who do not use computer modeling tools in their work, and this is a guarantee of high quality! Again, no matter what the body shape of the speakers we tested, we did not notice any serious distortions, because every manufacturer now has the ability to correctly calculate damping elements. As a result, the design of all tested speakers was rated quite highly.

True, two models still need to be noted - MK Sound LCR 750 and Dynaudio DM 2/7. Initially, manufacturers aimed these developments, like their previous lines, at the professional acoustics market, focusing on maximum accuracy in transmitting musical material. They achieved their goal: the named models are bookshelf acoustics, designed at a professional level. This means that these speakers sound neutral and even seem “dry”, but this is precisely one of the most important requirements from professionals - not the slightest “embellishment”!

And if we are talking about beautiful and comfortable sound, we note that most of the tested monitors meet these criteria perfectly. Most of the speakers tested have such features as accurate sound localization, accuracy in the transmission of timbres, well-defined bass - everything that is so valued by true music lovers. Based on the test results, it is worth noting the main advantages of bookshelf speakers: dense, rich sound from PSB Imagine B, accurate presentation of material from Canton Chrono 503.2, open airy image from Rega RS1, defiantly aggressive pressure from MartinLogan Motion 15. However, there are no winners. Therefore, we give the palm of our test to

I myself came across this topic a long time ago, but I decided to figure it out when I began to seriously study acoustic measurements. I did a little digging on the Internet, talked a little with friends, and in the end I came up with this article, which I hope will help in our difficult task.

Impedance – this is the complex (impedance) resistance of a two-terminal network for a harmonic signal, which has active and reactive components. Typically the impedance of speaker systems is 4, 6 or 8 ohms. Impedance is also the ratio of the complex amplitude of the voltage of a harmonic signal applied to a two-terminal network to the complex amplitude of the current flowing through a two-terminal network.

Example of speaker impedance:

Unlike a resistor, the electrical resistance of which characterizes the ratio of voltage to current across it, an attempt to apply the term electrical resistance to reactive elements (inductor and capacitor) leads to the fact that the resistance of an ideal inductor tends to zero, and the resistance of an ideal capacitor tends to infinity .

Resistance correctly describes the properties of the coil and capacitor only at direct current. In the case of alternating current, the properties of the reactive elements are significantly different: the voltage across the inductor and the current through the capacitor are not zero. This behavior is no longer described by resistance, since resistance assumes a constant, time-independent ratio of current and voltage, that is, the absence of phase shifts of current and voltage.

It would be convenient to have some characteristic for reactive elements, which would, under any conditions, relate the current and voltage across them like resistance. Such a characteristic can be introduced if we consider the properties of reactive elements under harmonic influences on them. In this case, the current and voltage are related by some stable constant (similar in a sense to resistance), which is called electrical impedance (or simply impedance). When considering impedance, a complex representation of harmonic signals is used, since it is this that allows one to simultaneously take into account both the amplitude and phase characteristics of signals and systems.

In general, the value of the total electrical resistance (impedance) of an acoustic system will not tell the buyer anything related to the sound quality of a particular product. The manufacturer indicates this parameter only so that the resistance is taken into account when connecting the speaker system to the amplifier. If the speaker impedance value is lower than the recommended amplifier load value, the sound may be distorted or short-circuit protection will operate; if higher, the sound will be much quieter than with the recommended resistance.

If you imagine an acoustic system as a four-terminal network to the input terminals of which a signal generator is connected, then depending on the frequency of the supplied signal and the composition of your filter + emitter, the impedance will change. The change is nonlinear and can be capacitive in one frequency range and inductive in another. The more complex the filter in your speaker system, the more changes in impedance.

The impedance of a speaker system depends on frequency. But when using an amplifier with feedback in terms of current - ITUN (voltage controlled current source) or semi-ITUN (an amplifier such as, for example, is widely known among the people M.F. 1), such an indicator as dependence on frequency, of course disappears. Because there is no longer dependence on resistance different frequencies, which means that the current passing through the coil no longer changes as much. It only works because the current does not exceed certain values. But I will add that ITUN and MF1 (semi-ITUN) are not the same thing, since ITUN has only current feedback, and MF1 has a combined current and voltage feedback. Therefore, MF1 can be called "semi-ITUN" since it combines combined feedback.

I would like to draw your attention to the fact that ITUN has slight climb high frequencies , and this is due precisely to the fact that the current that passes through the HF speaker coil no longer “fails” and the speaker plays more smoothly. Exactly the same effect (raising high frequencies) is present in MF1 for the same reason, but the effect on low frequencies is less, thus, M.F. 1 is more universal in terms of AC and complex load, relative to pure ITUN.

And in the case of a VUN (voltage controlled voltage source), which are the vast majority of amplifiers, it can, at a moment of low resistance, create such a current that will damage the output stage due to overcurrent. In another case, if the resistance is too high, then there will be a dip in this part of the frequency response, which, together with the peak (which arises from low resistance), will give large distortions, and several times.

Once again, a reminder for those who want to create homemade speakers or modify something. At a minimum, to obtain a satisfactory result, you need to have on hand complex for these measurements and at least some knowledge in electrical engineering.

Conclusion. When creating, modifying or altering speaker systems, special attention should be paid to impedance. It can be measured using a computer, a simple attachment box and a program such as L spL ab, or as when measuring vehicle parameters, but in this case you need to have a calibrated (20 - 20,000 Hz) millivoltmeter. And also, for confidence, use an amplifier with current feedback - ITUN or semi-ITUN, which is the beloved and well-known MF1 from Linkor.

I would like to make a special thank you DTS y, for assistance in writing an article and solving some of the nuances. Well, as usual, I prepared an article LDS , which was specially written for the site website.

Comparative testing of Edifier and Microlab stereo speakers (April 2014)

Power

By the word power in colloquial speech, many mean “power”, “strength”. Therefore, it is quite natural that buyers associate power with volume: “The more power, the better and louder the speakers will sound.” However, this popular belief is completely wrong! It is not always the case that a speaker with a power of 100 W will play louder or better than one that has a power rating of “only” 50 W. The power value rather speaks not about volume, but about the mechanical reliability of the acoustics. The same 50 or 100 W is not a sound volume at all, published by the column. Dynamic heads themselves have low efficiency and convert only 2-3% of the power of the electrical signal supplied to them into sound vibrations (fortunately, the volume of the sound produced is quite enough to create sound). The value indicated by the manufacturer in the passport of the speaker or the system as a whole only indicates that when a signal of the specified power is supplied, the dynamic head or speaker system will not fail (due to critical heating and interturn short circuit of the wire, “biting” of the coil frame, rupture of the diffuser , damage to flexible suspensions of the system, etc.).

Thus, the power of an acoustic system is a technical parameter, the value of which is not directly related to the loudness of the acoustics, although it is somewhat related to it. The rated power values ​​of the dynamic heads, amplifier path, and speaker system may be different. They are indicated, rather, for orientation and optimal pairing between the components. For example, an amplifier of significantly lower or significantly higher power can damage the speaker in the maximum positions of the volume control on both amplifiers: on the first - due to the high level of distortion, on the second - due to the abnormal operation of the speaker.

Power can be measured different ways and under various test conditions. There are generally accepted standards for these measurements. Let's take a closer look at some of them, most often used in the characteristics of products from Western companies:

RMS (Rated Maximum Sinusoidal power— set maximum sinusoidal power). Power is measured by applying a 1000 Hz sine wave until a certain level of harmonic distortion is reached. Usually in the product passport it is written like this: 15 W (RMS). This value indicates that the speaker system, when supplied with a 15 W signal, can operate for a long time without mechanical damage to the dynamic heads. For multimedia acoustics, higher power values ​​in W (RMS) compared to Hi-Fi speakers are obtained due to measurements at very high harmonic distortion, often up to 10%. With such distortion, it is almost impossible to listen to the sound due to strong wheezing and overtones in the dynamic head and speaker body.

PMPO(Peak Music Power Output peak music power). In this case, power is measured by applying a short-term sine wave of less than 1 second duration and a frequency below 250 Hz (usually 100 Hz). In this case, the level of nonlinear distortions is not taken into account. For example, the speaker power is 500 W (PMPO). This fact suggests that the speaker system, after playing a short-term low-frequency signal, did not have any mechanical damage to the dynamic heads. Watt power units (PMPO) are popularly called “Chinese watts” due to the fact that power values ​​using this measurement technique reach thousands of watts! Imagine - active speakers for a computer, they consume 10 V*A electrical power from the AC mains and develop a peak musical power of 1500 W (PMPO).

Along with Western ones, there are also Soviet standards for different kinds power. They are regulated by GOST 16122-87 and GOST 23262-88, which are still in force today. These standards define concepts such as rated, maximum noise, maximum sinusoidal, maximum long-term, maximum short-term power. Some of them are indicated in the passport for Soviet (and post-Soviet) equipment. Naturally, these standards are not used in world practice, so we will not dwell on them.

We draw conclusions: the most important in practice is the value of power indicated in W (RMS) at harmonic distortion (THD) values ​​of 1% or less. However, comparison of products even by this indicator is very approximate and may have nothing to do with reality, because sound volume is characterized by sound pressure level. That's why information content of the indicator “speaker system power” zero.

Sensitivity

Sensitivity is one of the parameters indicated by the manufacturer in the characteristics of speaker systems. The value characterizes the intensity of the sound pressure developed by the speaker at a distance of 1 meter when a signal is supplied with a frequency of 1000 Hz and a power of 1 W. Sensitivity is measured in decibels (dB) relative to the hearing threshold (zero sound pressure level is 2*10^-5 Pa). Sometimes the designation used is the characteristic sensitivity level (SPL, Sound Pressure Level). In this case, for brevity, in the column with units of measurement, dB/W*m or dB/W^1/2*m is indicated. It is important to understand that sensitivity is not a linear proportionality coefficient between sound pressure level, signal power and distance to the source. Many companies indicate the sensitivity characteristics of dynamic drivers measured under non-standard conditions.

Sensitivity is a characteristic that is more important when designing your own speaker systems. If you do not fully understand what this parameter means, then when choosing multimedia acoustics for a PC, you can not pay special attention to the sensitivity (fortunately, it is not often indicated).

frequency response

Amplitude-frequency response (frequency response) in the general case is a graph showing the difference in the amplitudes of the output and input signals over the entire range of reproduced frequencies. The frequency response is measured by applying a sinusoidal signal of constant amplitude when its frequency changes. At the point on the graph where the frequency is 1000 Hz, it is customary to plot the 0 dB level on the vertical axis. The ideal option is in which the frequency response is represented by a straight line, but in reality such characteristics do not exist in acoustic systems. When considering the graph, you need to pay special attention to the amount of unevenness. The greater the unevenness value, the greater the frequency distortion of the timbre in the sound.

Western manufacturers prefer to indicate the range of reproduced frequencies, which is a “squeeze” of information from the frequency response: only the limiting frequencies and unevenness are indicated. Let's say it says: 50 Hz - 16 kHz (±3 dB). This means that this acoustic system has reliable sound in the range of 50 Hz - 16 kHz, but below 50 Hz and above 15 kHz the unevenness increases sharply, the frequency response has a so-called “blockage” (a sharp decline in the characteristics).

What does this mean? A decrease in the level of low frequencies implies a loss of richness and richness of the bass sound. The rise in the low-frequency region causes a sensation of booming and humming of the speaker. In the blockages of high frequencies, the sound will be dull and unclear. High frequencies indicate the presence of irritating, unpleasant hissing and whistling sounds. In multimedia speakers, the magnitude of the frequency response unevenness is usually higher than that of the so-called Hi-Fi acoustics. All advertising statements by manufacturers about the frequency response of speakers of the type 20 - 20,000 Hz (theoretical limit of possibility) should be treated with a fair amount of skepticism. At the same time, the unevenness of the frequency response is often not indicated, which can amount to unimaginable values.

Since manufacturers of multimedia acoustics often “forget” to indicate the unevenness of the frequency response of the speaker system, when encountering a speaker characteristic of 20 Hz - 20,000 Hz, you need to keep your eyes open. There is a high probability of buying a thing that does not even provide a more or less uniform response in the frequency band 100 Hz - 10,000 Hz. It is impossible to compare the range of reproduced frequencies with different irregularities.

Nonlinear distortion, harmonic distortion

Kg harmonic distortion factor. An acoustic system is a complex electroacoustic device that has a nonlinear gain characteristic. Therefore, the signal will necessarily have nonlinear distortion at the output after passing through the entire audio path. One of the most obvious and easiest to measure is harmonic distortion.

The coefficient is a dimensionless quantity. It is indicated either as a percentage or in decibels. Conversion formula: [dB] = 20 log ([%]/100). The higher the harmonic distortion value, the worse the sound usually is.

The kg of speakers largely depends on the power of the signal supplied to them. Therefore, it is stupid to make absentee conclusions or compare speakers only by harmonic distortion coefficient, without resorting to listening to the equipment. In addition, for the working positions of the volume control (usually 30..50%), the value is not indicated by the manufacturers.

Total electrical resistance, impedance

The electrodynamic head has a certain resistance DC, depending on the thickness, length and material of the wire in the coil (this resistance is also called resistive or reactive). When a music signal, which is alternating current, is applied, the resistance of the head will change depending on the frequency of the signal.

Impedance(impedans) is the total electrical resistance to alternating current measured at a frequency of 1000 Hz. Typically the impedance of speaker systems is 4, 6 or 8 ohms.

In general, the value of the total electrical resistance (impedance) of an acoustic system will not tell the buyer anything related to the sound quality of a particular product. The manufacturer indicates this parameter only so that the resistance is taken into account when connecting the speaker system to the amplifier. If the speaker impedance value is lower than the recommended amplifier load value, the sound may be distorted or short-circuit protection will operate; if higher, the sound will be much quieter than with the recommended resistance.

Speaker housing, acoustic design

One of the important factors influencing the sound of an acoustic system is the acoustic design of the radiating dynamic head (speaker). When designing acoustic systems, the manufacturer usually faces the problem of choosing an acoustic design. There are more than a dozen species.

Acoustic design is divided into acoustically unloaded and acoustically loaded. The first implies a design in which the vibration of the diffuser is limited only by the rigidity of the suspension. In the second case, the oscillation of the diffuser is limited, in addition to the rigidity of the suspension, by the elasticity of the air and the acoustic resistance to radiation. Acoustic design is also divided into single and double acting systems. A single-action system is characterized by the excitation of sound traveling to the listener through only one side of the diffuser (the radiation from the other side is neutralized by the acoustic design). The double-acting system involves using both surfaces of the diffuser to produce sound.

Since the acoustic design of the speaker has virtually no effect on high-frequency and mid-frequency dynamic drivers, we will talk about the most common options for low-frequency acoustic design of the cabinet.

An acoustic scheme called a “closed box” is very widely applicable. Refers to a loaded acoustic design. It is a closed case with a speaker diffuser displayed on the front panel. Advantages: good frequency response and impulse response. Disadvantages: low efficiency, need for powerful amplifier, high level harmonic distortion.

But instead of having to deal with the sound waves caused by vibrations on the back of the diffuser, they can be used. The most common option among double-action systems is the bass reflex. It is a pipe of a certain length and cross-section mounted in a housing. The length and cross-section of the bass reflex are calculated in such a way that at a certain frequency, oscillations of sound waves are created in it, in-phase with the oscillations caused by the front side of the diffuser.

For subwoofers, an acoustic circuit commonly called a “resonator box” is widely used. Unlike the previous example, the speaker diffuser is not located on the housing panel, but is located inside, on the partition. The speaker itself does not directly participate in the formation of the low frequency spectrum. Instead, the diffuser only excites low-frequency sound vibrations, which then increase many times in volume in the bass reflex pipe, which acts as a resonant chamber. The advantage of these design solutions is high efficiency with small dimensions of the subwoofer. Disadvantages manifest themselves in deterioration of phase and impulse characteristics, the sound becomes tiring.

The optimal choice would be medium-sized speakers with a wooden body, made in a closed circuit or with a bass reflex. When choosing a subwoofer, you should pay attention not to its volume (even inexpensive models usually have sufficient reserve for this parameter), but to reliable reproduction of the entire low frequency range. In terms of sound quality, speakers with thin bodies or very small sizes are the most undesirable.

Speaker system (General concepts and frequently asked questions)

1. What is an acoustic system (AS)?

This is a device for effective radiation of sound into the surrounding space in the air, containing one or more loudspeaker heads (SG), the necessary acoustic design (AO) and electrical devices, such as transition filters (PF), regulators, phase shifters, etc. See also: on our website.

2. What is a loudspeaker head (HL)?

This is a passive electro-acoustic transducer designed to convert signals audio frequency from electric to acoustic form.

3. What is a passive converter?

This is a converter that does NOT increase the energy of the electrical signal entering its input.

4. What is acoustic design (AO)?

This is a structural element that ensures effective radiation of GG sound. In other words, in most cases, the AO is the speaker body, which can take the form of an acoustic screen, box, horn, etc.

5. What is a single-way speaker?

Essentially the same as broadband. This is a speaker system, all of whose main generators (usually one) operate in the same frequency range (i.e., filtering of the input voltage using a filter, as well as no filters themselves).

6. What is a multi-way speaker?

These are speakers whose main generators (depending on their number) operate in two or more different frequency ranges. However, directly counting the number of GGs in the speakers (especially those released in previous years) may not say anything about the real number of bands, since several GGs can be allocated to the same band.

7. What are open speakers?

This is an AS in which the influence of air elasticity in the volume of the AO is negligible, and the radiation from the front and rear sides of the moving GG system is not isolated from each other in the LF region. It is a flat screen or box, the back wall of which is either completely absent or has a number of through holes. The greatest influence on the frequency response of speakers with AO open type are influenced by the front wall (in which the GGs are mounted) and its dimensions. Contrary to popular belief, the side walls of an open-type AO have very little effect on the characteristics of the speaker. Thus, it is not the internal volume that is important, but the area of ​​the front wall. Even with its relatively small size, bass reproduction is significantly improved. At the same time, in the midrange and, especially, high-frequency regions, the screen no longer has a significant effect. A significant disadvantage of such systems is their susceptibility to acoustic “short circuit”, which leads to a sharp deterioration in low frequency reproduction.

8. What are closed-type speakers?

This is an AS in which the elasticity of the air in the volume of the AO is commensurate with the elasticity of the moving GG system, and the radiation from the front and rear sides of the movable GG system is isolated from each other over the entire frequency range. In other words, this is a speaker whose housing is hermetically sealed. The advantage of such speakers is that the rear surface of the diffuser does not radiate and, thus, there is no acoustic “short circuit” at all. But closed systems have another drawback - when the diffuser oscillates, it must overcome the additional elasticity of the air in the AO. The presence of this additional elasticity leads to an increase in the resonant frequency of the moving system of the GG, as a result of which the reproduction of frequencies below this frequency deteriorates.

9. What is a speaker with a bass reflex (FI)?

Striving to get enough good reproduction LF with a moderate volume of AO is achieved quite well in so-called phase-inverted systems. In the AO of such systems a slot or hole is made into which a tube can be inserted. The elasticity of the volume of air in the joint resonates at some frequency with the mass of air in the hole or tube. This frequency is called the PI resonant frequency. Thus, the AS as a whole becomes consisting of two resonant systems - the moving system of the GG and the AO with a hole. With the correctly selected ratio of the resonant frequencies of these systems, the reproduction of low frequencies is significantly improved compared to a closed-type AO with the same volume of AO. Despite the obvious advantages of speakers with FI, very often such systems, made even by experienced people, do not give the results expected from them. The reason for this is that in order to obtain the desired effect, FI must be correctly calculated and configured.

10. What is bass-reflex?

Same as FI.

11. What is a crossover?

Same as a transition or crossover filter.

12. What is a transition filter?

This is passive electrical diagram(usually consisting of inductors and capacitors), which is turned on before the input signal and ensures that each GG in the speaker is supplied with voltage only at the frequencies that they must reproduce.

13. What are the “orders” of transition filters?

Since no filter can provide absolute voltage cutoff at a given frequency, the PF is designed at a specific crossover frequency, beyond which the filter provides a selected amount of attenuation, expressed in decibels per octave. The amount of attenuation is called slope and depends on the design of the PF. Without going into too much detail, we can say that the simplest filter - the so-called first-order PF - consists of just one reactive element - capacitance (cut off the low frequencies if necessary) or inductance (cut off the high frequencies if necessary) and provides a slope of 6 dB/oct. Twice the steepness - 12dB/oct. - provides a second-order PF containing two reactive elements in the circuit. Attenuation 18dB/oct. provides a third-order PF containing three reactive elements, etc.

14. What is an octave?

In general, this is doubling or halving the frequency.

15. What is the AC working plane?

This is the plane in which the emitting holes of the GG AS are located. If the GG of a multi-band speaker are located in different planes, then the one in which the emitting holes of the HF GG are located is taken as the working one.

16. What is an AC work center?

This is a point lying on the working plane from which the distance to the speaker is measured. In the case of single-way speakers, the geometric center of symmetry of the radiating hole is taken as it. In the case of multi-band speakers, it is taken to be the geometric center of symmetry of the emitting holes of the HF main generator or the projections of these holes onto the working plane.

17. What is the AC working axis?

This is a straight line passing through the working center AC and perpendicular to the working plane.

18. What is the nominal impedance of the speakers?

This is specified in technical documentation active resistance, which replaces the impedance module of the speaker when determining the electrical power supplied to it. According to the DIN standard, the minimum value of the speaker impedance module in a given frequency range should not be less than 80% of the nominal.

19. What is the impedance of speaker systems (AS)?

Without delving into the basics of electrical engineering, we can say that impedance is the TOTAL electrical resistance of the speaker (including crossovers and main generators), which, in the form of a rather complex dependence, includes not only the familiar active resistance R (which can be measured with a regular ohmmeter), but also and reactive components represented by capacitance C (capacitance, depending on frequency) and inductance L (inductive reactance, also dependent on frequency). It is known that impedance is a complex quantity (in the sense of complex numbers) and, generally speaking, is a three-dimensional graph (in the case of speakers it often looks like a “pig tail”) in amplitude-phase-frequency coordinates. It is precisely because of its complexity that when they talk about impedance as a numerical value, they talk about its MODULE. Of greatest interest from the point of view of research are the projections of the “pig’s tail” onto two planes: “amplitude-from-frequency” and “phase-from-frequency”. Both of these projections, presented on the same graph, are called “Bode plots”. The third amplitude-versus-phase projection is called the Nyquist plot. With the advent and proliferation of semiconductors, audio amplifiers began to behave more or less like sources of “constant” voltage, i.e. they, ideally, should maintain the same voltage at the output, regardless of what load is placed on it and what the current demand is. Therefore, if we assume that the amplifier driving the GG speaker is a voltage source, then the impedance of the speaker will clearly indicate what the current consumption will be. As already mentioned, impedance is not only reactive (that is, characterized by a non-zero phase angle), but also changes with frequency. Negative phase angle, i.e. when the current leads the voltage, due to the capacitive properties of the load. A positive phase angle, i.e. when the current lags behind the voltage, is due to the inductive properties of the load.
What is the impedance of typical speakers? The DIN standard requires that the impedance of the speaker does not deviate from the specified rating by more than 20%. However, in practice, everything is much worse - the deviation of the impedance from the rating is on average +/-43%! As long as the amplifier has a low output impedance, even such deviations will not introduce any audible effects. However, as soon as a tube amplifier with an output impedance of the order of several Ohms (!) is introduced into the game, the result can be very disastrous - coloration of the sound is inevitable.
Speaker impedance measurement is one of the most important and powerful diagnostic tools. An impedance graph can tell you a lot about what a given speaker is like without even seeing or hearing it. Having an impedance graph in front of your eyes, you can immediately tell what type of speaker the data is - closed (one hump in the bass area), bass reflex or transmission (two humps in the bass area), or some type of horn (a sequence of evenly spaced peaks). You can judge how well the bass (40-80Hz) and the lowest bass (20-40Hz) will be reproduced by certain speakers by the shape of the impedance in these areas, as well as by the quality factor of the humps. The “saddle” formed by two peaks in the low-frequency region, typical of a bass reflex design, indicates the frequency to which the bass reflex is “tuned”, which is usually the frequency at which the low-frequency response of the bass reflex drops by 6 dB, i.e. approximately 2 times. From the impedance graph you can also understand whether there are resonances in the system and what their nature is. For example, if you carry out measurements with sufficient frequency resolution, then perhaps some kind of “notches” will appear on the graph, indicating the presence of resonances in the acoustic design.
Well, perhaps the most important thing that can be taken away from the impedance graph is how heavy this load will be for the amplifier. Since the AC impedance is reactive, the current will either lag behind the signal voltage or lead it by a phase angle. In the worst case, when the phase angle is 90 degrees, the amplifier is required to deliver maximum current while the signal voltage approaches zero. Therefore, knowing the “passport” 8 (or 4) Ohms as a nominal resistance does NOT give anything at all. Depending on the phase angle of the impedance, which will be different at each frequency, certain speakers may be too tough for one or another amplifier. It is also very important to note that MOST amplifiers DO NOT seem to us to be unable to handle speakers simply because at TYPICAL volume levels acceptable in TYPICAL home environments, TYPICAL SPEAKERS DO NOT require more than just a few Watts to be "powered" by a TYPICAL amplifier.

20. What is the rated power of the GG?

This is a given electrical power at which the nonlinear distortions of the GG should not exceed the required ones.

21. What is the maximum noise power of the GG?

This is the electrical power of a special noise signal in a given frequency range, which the generator can withstand for a long time without thermal and mechanical damage.

22. What is the maximum sinusoidal power of the GG?

This is the electrical power of a continuous sinusoidal signal in a given frequency range, which the GG can withstand for a long time without thermal and mechanical damage.

23. What is the maximum short-term power of the GG?

This is the electrical power of a special noise signal in a given frequency range, which the GG can withstand without irreversible mechanical damage for 1 s (tests are repeated 60 times with an interval of 1 min.)

24. What is the maximum long-term power of the GG?

This is the electrical power of a special noise signal in a given frequency range, which the GG can withstand without irreversible mechanical damage for 1 minute. (tests are repeated 10 times with an interval of 2 minutes)

25. All other things being equal, speakers with what nominal impedance is more preferable - 4, 6 or 8 Ohms?

In general, a speaker with a higher nominal impedance is preferable, since such a speaker represents a lighter load for the amplifier and, therefore, is much less critical to the choice of the latter.

26. What is the impulse response of speakers?

This is her response to the “ideal” impulse.

27. What is an “ideal” impulse?

This is an instantaneous (rise time equal to 0) increase in voltage to a certain value, “stuck” at this constant level for a short period of time (say, a fraction of a millisecond) and then an instantaneous decrease back to 0V. The width of such a pulse is inversely proportional to the signal bandwidth. If we wanted to make a pulse infinitely short, then in order to transmit its shape completely unchanged, we would need a system with an infinite bandwidth.

28. What is the transient response of speakers?

This is its response to a “step” signal. The transient response gives a visual representation of the behavior of all GG AS over time and allows one to judge the degree of coherence of the AS radiation.

29. What is a step signal?

This is when the voltage at the input to the AC instantly increases from 0V to some positive value and remains so for a long time.

30. What is coherence?

This is the coordinated occurrence of several oscillatory or wave processes in time. In relation to speakers, it means the simultaneous arrival of signals from different GGs to the listener, i.e. actually reflects the fact of preservation of the phase integrity of information.

31. What is GG polarity?

It's a certain polarity electrical voltage on the terminals of the GG, causing the movement of the movable system of the GG in a given direction. The polarity of a multiband speaker is determined by the polarity of its LF GG.

32. What is a GG connection in absolute positive polarity?

This is connecting the GG to a voltage source in such a way that when an electric voltage of positive polarity is applied to it, the coil moves forward from the magnet gap, i.e. air compression takes place.

33. What is the frequency response of AC?

This is the amplitude-frequency characteristic, i.e. dependence on the frequency of the sound pressure level developed by the speaker at a certain point in the free field, located at a certain distance from the working center (usually 1 m).

34. What is polar characteristic?

This is a graphical dependence under free field conditions of the sound pressure level (for a given frequency band and distance from the working center of the GG) on the angle between the working axis of the GG and the direction to the measurement point.

35. What conventional parts is the frequency range divided into for convenience of verbal description?

• 20-40Hz - lower bass
• 40-80Hz - bass
• 80-160Hz - upper bass
• 160-320Hz - lower midbass
• 320-640Hz - midbass
• 640-1.280Hz - upper midbass
• 1.28-2.56kHz - lower middle
• 2.56-5.12kHz - middle
• 5.12-10.24 kHz - upper mid
• 10.24-20.48 kHz - top

36. What are the names of the variable regulators that can be seen on some speakers?

Attenuators. They are sometimes called acoustic equalizers.

37. What is the purpose of attenuators?

Depending on the calibration, increase and/or decrease the voltage supplied to one or another GG, which, accordingly, leads to an increase and/or decrease in the sound pressure level in a certain frequency range. Attenuators do not make changes to the shape of the frequency response of individual generators, but they change the GENERAL appearance of the frequency response of the speakers by “raising” or “lowering” certain parts of the spectrum. In some cases, attenuators allow, to one degree or another, to “adapt” the speakers to specific listening conditions.

38. What is speaker sensitivity?

Speaker sensitivity is often and widely confused with efficiency. Efficiency is defined as the ratio of the ACOUSTIC power supplied by the speakers to the ELECTRICAL power consumed. Those. the question is formulated as follows: if I put 100 electrical watts into the speaker, how many acoustic (sound) watts will I get? And the answer to it is “a little, a little.” The efficiency of a typical moving coil generator is about 1%.
Efficiency is usually given in the form of the sound pressure level generated by the speaker at a given distance from the operating center of the speaker with an input power of 1 W, i.e. in Decibels per Watt per meter (dB/W/m). However, knowledge of this value cannot be called useful, since it is extremely difficult to determine what the input power of 1 W is for these specific speakers. Why? Because there is a dependence on both impedance and frequency. Give a speaker with an impedance of 8 Ohms at 1 kHz a signal of the same frequency and a level of 2.83 Volts, and yes, without a doubt, you will power the speaker with a power of 1 W (according to Ohm's law, “power” = “voltage squared” / “resistance” "). And here a big “BUT” comes up - not only is the speaker impedance inconsistent and depends on frequency, but at lower frequencies it can decrease dramatically. Let's say up to 2 ohms at 200 Hz. Having now powered the speakers with the same 2.83 Volts, but at a frequency of 200 Hz, we will thereby require the amplifier to give us 4(!) times more power. For the same sound pressure level, speakers at 1 kHz are four times more efficient than speakers at 200 Hz.
Why does efficiency matter at all? If half a century ago audio engineers were very concerned about the problem of power transfer (and telecommunications engineers are still interested in this today!), then with the advent of semiconductor devices, audio amplifiers began to behave more or less like “constant” voltage sources - they support the same output voltage regardless of what load is placed on it and what the current consumption is. That is why it is NOT EFFICIENCY that comes to the fore, but voltage SENSITIVITY, i.e. how loud the speaker plays at a given amplifier output voltage. Voltage sensitivity is usually defined as the sound pressure level developed by the speaker at a distance of 1 meter from the operating center of the speaker at a terminal voltage of 2.83 Volts (i.e., the voltage required to dissipate 1 Watt into an 8-ohm resistor).
The advantage of specifying sensitivity instead of efficiency is that it always remains constant regardless of speaker impedance, since the amplifier is assumed to always be able to supply enough current to maintain 2.83 volts. The closer the speaker impedance module approaches that of a pure 8-ohm resistor, the higher the degree of equivalence of these two criteria. However, in the case when the speaker impedance differs significantly from 8 Ohms, the benefit of knowing the efficiency is reduced to nothing.
The voltage sensitivity of the speakers is important, in particular, when selecting the “amplifier - speaker” pair. If you have a 20W amplifier, you better think hard about speakers with VERY high sensitivity, because otherwise you will never listen to loud music. And conversely, if you take a speaker with a sufficiently high sensitivity - say, 100 dB / 2.83V / m, then it may turn out that a 5-watt amplifier is enough for your eyes in the sense that spending $ 10,000 on an amplifier with a power of 600 Watts with such speakers would be a waste of money.
However, despite the fact that it is completely obvious to everyone that voltage sensitivity is a more than important parameter of the speaker system, many people still do not want to consider it properly. The problem is that speakers tend to have an uneven frequency response, and therefore finding the peak value among all its slabs and making statements like “Since the speaker plays the loudest at this frequency, that means this is the sensitivity!” is for the marketing departments of companies. , producing AS, THE GREAT TEMPTATION.
So what is the actual sensitivity of typical speakers? It turns out that it is about 85-88 dB/2.83V/m. The share of such speakers is about 40%. It is curious that speakers with low sensitivity (less than 80) are mainly panel speakers of all kinds, and speakers with high sensitivity (more than 95) are professional monitors. And this is not surprising. Achieving great sensitivity requires heroic engineering efforts, which, of course, ALWAYS come at a cost. And the vast majority of speaker designers are constrained by BUDGET limits, which only means that they will ALWAYS look for compromises, saving on the size of magnets, the shape of moving coils and diffusers.
It is also worth noting that the actually measured sensitivity is ALWAYS LESS than that indicated by the manufacturer in the documents. Manufacturers are always too optimistic.

39. Do I need to install speakers on spikes?

Very desirable.

40. What are the thorns for?

In order to minimize the transmission of vibration from the acoustic design of the speaker to objects in contact with it (room floors, shelves, for example). The effect of using spikes is based on a radical reduction in the area of ​​contacting surfaces, which is reduced to the area of ​​the tips of the spikes/cones. It is important to understand that installing speakers on spikes does NOT eliminate cabinet vibrations, but only reduces the efficiency of their further propagation.

41. Does the location of the spikes under the speaker matter?

The most unfavorable support for the speaker is to install it on 3 (three) metal spikes/cones, one of which is placed in the middle at the rear wall, and the other two are located at the two front corners. This arrangement of the speakers “gives free rein” to almost ALL body resonances.

42. How to minimize cabinet resonances of speakers?

The most IN THE BEST WAY To reduce the cabinet resonances of the speakers, due to how and on what they are installed, is to use a vibration-absorbing material such as dense padding polyester as a gasket.

43. In what cases is the use of bi-wiring/bi-amping justified?

Bi-wiring does NOT have any basis physical basis and, as a result, has NO audible effect, and therefore is absolutely meaningless.
Bi-amping comes in two types: false and literate. You can see what this means. Despite the existence of physical validity of the application, the effect of bi-amping is vanishingly small.

44. Does the external finish of the speakers (vinyl film, natural veneer, powder paint, etc.) affect the sound?

No, it does NOT affect the sound in any way. Only for the PRICE.

45. Does the interior finishing (foam rubber, mineral wool, padding polyester, etc.) of the speaker affect the sound?

The purpose of ANY "stuffing" of speakers with anything is the desire or need to suppress standing waves that arise inside any acoustic design, the presence of which can seriously degrade the characteristics of the speaker. Therefore, the entire “influence” of interior finishing on sound comes down to how well this finishing prevents the occurrence of standing waves. The presence of internal resonances can be assessed, for example, by the results of impedance measurements carried out with high resolution by frequency.

46. ​​Do grills, as well as other decorative frames of the front panels of speakers or individual GGs (for example, metal mesh) affect the sound?

Strictly speaking, YES, they do. And in most cases this can be seen with your own eyes during measurements. The only question is, can it still be heard? In some cases, when this influence exceeds 1dB, it is quite possible/real to hear it in the form of some “roughness” in the sound, usually in the HF region. The influence of fabric “scenery” is minimal. As the rigidity of the “scenery” increases (especially for metal products), the degree of visibility increases.

47. Are there any real benefits to speakers with rounded corners?

There are none.

48. Special shape of dust caps on speakers - necessity or decoration?

The answer can only be speculative. Nowadays, when laser vibrometry is (or CAN be used) used to monitor the "behavior" of the diaphragm surface during reciprocating movement, it may well be that the shape of the caps is NOT chosen at random and NOT for beauty, but to optimize the performance of the diaphragm in the piston mode. In addition, dust caps in some cases help level out the frequency response (usually in the 2-5 kHz region).

49. What is piston mode?

This is a mode in which the ENTIRE surface of the GG diffuser moves as one.
It is very convenient to explain this concept using the example of a broadband GG. In the low-frequency region, the rate of change in the phase of the signal in the voice coil is less than the speed of propagation of mechanical excitation in the diffuser material, and the latter behaves as a single whole, i.e. vibrates like a piston. At these frequencies, the frequency response of the GG has a smooth shape, which indicates the absence of partial excitation of individual sections of the diffuser.
Usually, GG developers strive to expand the area of ​​piston action of the diffuser towards the HF by giving a special shape to the cone generatrix. For a properly designed cellulose cone, the area of ​​piston action can be approximately defined as a sound wavelength equal to the circumference of the cone at the base of the cone. At medium frequencies, the rate of change in the phase of the signal in the voice coil exceeds the speed of propagation of mechanical excitation in the diffuser material and bending waves arise in it; the diffuser no longer vibrates as a single whole. At these frequencies, the damping rate of mechanical vibrations in the diffuser material is still not high enough and the vibrations, reaching the diffuser holder, are reflected from it and propagate through the diffuser back towards the voice coil.
As a result of the interaction of direct and reflected vibrations in the diffuser, a picture of standing waves arises, and areas with intense antiphase radiation are formed. At the same time, sharp irregularities (peaks and dips) are observed in the frequency response, the range of which can reach tens of dB in a non-optimally designed diffuser.
At HF, the attenuation rate of mechanical vibrations in the diffuser material increases and standing waves are not formed. Due to the weakening of the intensity of mechanical vibrations, high-frequency radiation occurs predominantly in the diffuser area adjacent to the voice coil. Therefore, to increase HF reproduction, horns are used, attached to a moving GG system. To reduce the unevenness of the frequency response, various damping (increasing the attenuation of mechanical vibrations) additives are added to the mass for the manufacture of GG diffusers.

50. Why do most speakers generally use several GGs (two or more)?

First of all, because high-quality sound radiation in different parts of the spectrum places too different demands on the GG, which a single GG (broadband) is not able to fully satisfy, at least purely physically (in particular, see the previous paragraph). One of the key points is a significant increase in the directivity of the radiation of any GG with increasing frequency. Ideally, the gas generators in the system should not only operate in piston mode, which, generally speaking, entails a sharp increase in the total number of gas generators in the system (and, accordingly, an increase in the number of transition filters, which automatically causes a sharp increase in the complexity and cost of the product), but also be characterized by omnidirectional radiation, which is only possible under the condition that the linear size of the GG is much LESS than the wavelength of the radiation it emits. Only in this case will the GG have good dispersion.
As long as the frequency is low enough, this condition is satisfied and the GG is omnidirectional. With increasing frequency, the radiation wavelength decreases and, sooner or later, becomes COMPARABLE to the linear dimensions of the GG (diameter). This, in turn, leads to a sharp increase in the directivity of the radiation - the GG eventually begins to emit like a spotlight, straight forward, which is completely unacceptable. Let's take, for example, a burdock bass with a diameter of 30 cm. At a frequency of 40 Hz, the wavelength of the radiation is 8.6 m, which is 28 times greater than its linear size - in this area such a woofer is omnidirectional. At a frequency of 1,000 Hz, the wavelength is already 34 cm, which is already literally COMPARABLE to the diameter. At this frequency, the dispersion of such a bass driver will be radically worse, and the radiation will be extremely directional. Traditional two-way speakers with a transition frequency in the region of 2-3 kHz - which corresponds to wavelengths of 11-17 cm - are equipped with woofers with linear dimensions of exactly the same order, which leads to a SHARP deterioration in the polar characteristics of the speakers in the specified area, shaped like a dip or gorge. The failure is due to the fact that while the LF of the GG in a given area becomes highly directional, the tweeter (usually 1.5-2 cm in diameter) in the same area is almost omnidirectional.
In particular, this is why good THREE-WAY speakers are always BETTER than good TWO-WAY speakers.

51. What is variance?

In this context, the same as "emissivity in different directions."

52. What is a radiation pattern?

Same as polar characteristic.

53. What is frequency response unevenness?

This is the difference (expressed in dB) between the maximum and minimum sound pressure levels in a given frequency range. You can often read in the literature that peaks and dips in the frequency response of already 1/8 octave are not taken into account. However, this approach is not progressive, since the presence of serious peaks and dips in the frequency response (even narrow ones) indicates poor quality of the diffuser, the presence of standing waves in it, i.e. about the shortcomings of the GG.

54. Why are the heads in speakers sometimes turned on in different polarities?

Since transition filters in ANY case change (or, as they say, rotate) the phase of the input signal - the higher the order of the filter, the greater the phase shift - then in some cases the situation develops in such a way that in the transition zone signals from different GGs “meet” in out of phase, which leads to serious distortions in the frequency response, which look like steep dips. Switching on one of the GGs in a different polarity leads to the fact that the phase is reversed by another 180 degrees, which often has a beneficial effect on equalizing the frequency response in the transition zone.

55. What is cumulative spectrum attenuation (CSF)?

This is a set of axial frequency response of the speaker, obtained with a certain time interval during the attenuation of a single pulse applied to it, and displayed on one three-dimensional graph. Since, being an electromechanical system, the speaker is an “inertial” device, the oscillatory processes continue for some time even after the termination of the pulse, gradually fading over time. Thus, the graph of the cumulative attenuation of the spectrum clearly shows which areas of the spectrum are characterized by increased post-pulse activity, i.e. allows you to identify the so-called delayed resonances of the speakers.
The “cleaner” the ECG graph of speakers looks in the region above 1 kHz, the higher the chance that such speakers will be subjectively assessed by listeners as distinguished by “great transparency,” “lack of graininess,” and “sound purity.” Conversely, speakers that are said to sound “grainy” or “harsh” are almost 100% likely to have a strong “ridged” GSV graph (although, of course, factors such as non-linear distortion and frequency imbalance can also play a role your role).

56. What are the names of the peculiar dividers of bizarre shape or geometry that are placed on top of some GGs?

Phase shifters, deflectors, acoustic lenses.

57. Why are phase shifters used?

In any case, not for beauty, but for the supposed improvement of the dispersion characteristics of the speaker.

58. Does the material from which the GG diffuser is made (silk, metal, paper, polypropylene, Kevlar, carbon, composite, etc.) have any effect on the sound?

In the sense that, depending on the material used, can the sound be “silk”, “paper”, “plastic”, “metal” and all sorts of other things, then the answer is NO, it cannot. The material of a well-designed diffuser does NOT have any effect on the sound in the DIRECT sense. So what is the point of using DIFFERENT materials when making diffusers? The point is that any competent developer strives, in fact, for only one goal: to use a material for the production of diffusers that would simultaneously satisfy the following requirements: it would be rigid, light, durable, well damped, inexpensive and, most importantly, easy replicable, especially for mass production purposes. In the context of column construction, all the materials listed above (as well as all sorts of others not included in the list) differ from each other only in the characteristics and properties just listed. And this difference, in turn, affects only and exclusively approaches to reducing the audible sound coloration that appears due to resonances arising in the diaphragms.

59. Is it true that good, “real” bass can only be obtained from speakers with large mug bass drivers, 30 centimeters in diameter?

No that's not true. The quantity and quality of bass depend very little on the size of the woofer.

60. What then is the meaning of big mug bass players?

A large woofer has a larger surface area and therefore moves a larger mass of air than a smaller woofer. Hence, sound pressure, developed by such a bass driver is also greater, which directly affects sensitivity - speakers with large bass drivers, as a rule, have very high sensitivity (usually above 93dB/W/m).

12/25/2005 Globalaudio

We continue our tradition and publish another article in the “testing methods” series. Articles such as these serve as both a general theoretical framework to help readers gain an introduction to the topic, and specific guidance for interpreting test results obtained in our laboratory. Today's article on the methodology will be somewhat unusual - we decided to devote a significant part of it to the theory of sound and acoustic systems. Why is this necessary? The fact is that sound and acoustics are practically the most complex of all the topics covered by our resource. And, perhaps, the average reader is less savvy in this area than, say, in assessing the overclocking potential of various Core 2 Duo steppings. We hope that the reference materials that formed the basis of the article, as well as a direct description of the measurement and testing methodology, will help fill some gaps in the knowledge of all lovers of good sound. So, let's start with the basic terms and concepts that any novice audiophile must know.

Basic terms and concepts

A short introduction to music

Let's start in an original way: from the beginning. From what sounds through the speakers, and about other headphones. It just so happens that the average human ear can distinguish signals in the range from 20 to 20,000 Hz (or 20 kHz). This fairly substantial range, in turn, is usually divided into 10 octaves(can be divided by any other quantity, but 10 is accepted).

In general octave is a frequency range whose boundaries are calculated by doubling or halving the frequency. The lower limit of the next octave is obtained by doubling the lower limit of the previous octave. Anyone familiar with Boolean algebra will find this series strangely familiar. Powers of two with an added zero at the end in their pure form. Actually, why do you need knowledge of octaves? It is necessary in order to stop the confusion about what should be called lower, middle or some other bass and the like. The generally accepted set of octaves clearly determines who is who to the nearest hertz.

Octave number	Lower limit, Hz	Upper limit, Hz	Name	Title 2
			Deep Bass
			Mid Bass	Subcontrol
			Upper Bass
			Lower middle
			Actually the middle
			Upper middle
			Bottom top
			Middle top
			Upper high
			Upper octave

The last line is not numbered. This is due to the fact that it is not included in the standard ten octaves. Pay attention to the column "Title 2". This contains the names of the octaves that are highlighted by musicians. These “strange” people have no concept of deep bass, but they have one octave above - from 20480 Hz. That is why there is such a discrepancy in numbering and names.

Now we can talk more specifically about the frequency range of speaker systems. We should start with some unpleasant news: there is no deep bass in multimedia acoustics. The vast majority of music lovers have simply never heard 20 Hz at a level of -3 dB. And now the news is pleasant and unexpected. There are no such frequencies in a real signal either (with some exceptions, of course). An exception is, for example, a recording from an IASCA Competition judge's disc. The song is called "The Viking". There, even 10 Hz are recorded with a decent amplitude. This track was recorded in a special room on a huge organ. The judges will decorate the system that wins over the Vikings with awards, like a Christmas tree with toys. But with a real signal everything is simpler: bass drum - from 40 Hz. Hefty Chinese drums also start from 40 Hz (among them, however, there is one megadrum. So it starts playing as early as 30 Hz). Live double bass is generally from 60 Hz. As you can see, 20 Hz is not mentioned here. Therefore, you don’t have to worry about the absence of such low components. They are not needed to listen to real music.

The figure shows a spectrogram. There are two curves on it: purple DIN and green (from old age) IEC. These curves display the spectrum distribution of the average musical signal. The IEC characteristic was used until the 60s of the 20th century. In those days, they preferred not to mock the squeaker. And after the 60s, experts noticed that listener preferences and music had changed somewhat. This is reflected in the great and mighty DIN standard. As you can see, there are much more high frequencies. But there was no increase in bass. Conclusion: no need to chase super-bass systems. Moreover, the desired 20 Hz was not put in the box there anyway.

Characteristics of acoustic systems

Now, knowing the alphabet of octaves and music, you can begin to understand the frequency response. Frequency response (amplitude-frequency response) - dependence of the oscillation amplitude at the device output on the frequency of the input harmonic signal. That is, the system is supplied with a signal at the input, the level of which is taken as 0 dB. From this signal, speakers with an amplification path do what they can. What they usually end up with is not a straight line at 0 dB, but a somewhat broken line. The most interesting thing, by the way, is that everyone (from audio enthusiasts to audio manufacturers) strives for a perfectly flat frequency response, but they are afraid to “strive.”

Actually, what is the benefit of the frequency response and why do the authors of TECHLABS constantly try to measure this curve? The fact is that it can be used to establish real frequency range boundaries, and not those whispered by the “evil marketing spirit” to the manufacturer. It is customary to indicate at what signal drop the boundary frequencies are still played. If not specified, it is assumed that the standard -3 dB was taken. This is where the catch lies. It is enough not to indicate at what drop the boundary values ​​were taken, and you can absolutely honestly indicate at least 20 Hz - 20 kHz, although, indeed, these 20 Hz are achievable at a signal level that is very different from the prescribed -3.

Also, the benefit of the frequency response is expressed in the fact that from it, although approximately, you can understand what problems the selected system will have. Moreover, the system as a whole. The frequency response suffers from all elements of the path. To understand how the system will sound according to the schedule, you need to know the elements of psychoacoustics. In short, the situation is like this: a person speaks within medium frequencies. That’s why he perceives them best. And at the corresponding octaves the graph should be the most even, since distortions in this area put a lot of pressure on the ears. The presence of tall narrow peaks is also undesirable. The general rule here is that peaks are heard better than valleys, and a sharp peak is heard better than a flat one. We will dwell on this parameter in more detail when we consider the process of measuring it.

Phase frequency response (PFC) shows the change in the phase of the harmonic signal reproduced by the speaker depending on the frequency. Can be uniquely calculated from the frequency response using the Hilbert transform. The ideal phase response, which says that the system has no phase-frequency distortions, is a straight line passing through the origin of coordinates. Acoustics with such a phase response are called phase-linear. For a long time this characteristic was not paid attention to, since there was an opinion that a person is not susceptible to phase-frequency distortions. Now they measure and indicate in the passports of expensive systems.

Cumulative Spectral Attenuation (CSF) - a set of axial frequency response (frequency response measured on the acoustic axis of the system), obtained with a certain time interval during the attenuation of a single pulse and reflected on one three-dimensional graph. Thus, from the GLC graph one can accurately say which regions of the spectrum will decay at what speed after the pulse, that is, the graph allows one to identify delayed resonances of the AS.

If the KZS has many resonances after the upper middle, then such acoustics will subjectively sound “dirty”, “with sand on the high frequencies”, etc.

AC impedance - this is the total electrical resistance of the speaker, including the resistance of the filter elements (complex value). This resistance contains not only active resistance, but also the reactance of capacitors and inductances. Since reactance depends on frequency, impedance is also entirely dependent on it.

If they talk about impedance as a numerical quantity, completely devoid of complexity, then they speak about its modulus.

The impedance plot is three-dimensional (amplitude-phase-frequency). Usually its projections on the amplitude-frequency and phase-frequency planes are considered. If you combine these two graphs, you get a Bode plot. And the amplitude-phase projection is a Nyquist plot.

Considering that impedance depends on frequency and is not constant, you can easily determine from it how difficult the acoustics are for an amplifier. Also, from the graph you can tell what kind of acoustics it is (ZYa - closed box), FI (with a bass reflex), how individual sections of the range will be reproduced.

Sensitivity - see Thiel-Small parameters.

Coherence - coordinated occurrence of several oscillatory or wave processes in time. This means that the signal from different GG acoustic systems will arrive at the listener simultaneously, that is, it indicates the safety of phase information.

Listening Room Meaning

The listening room (among audiophiles is often shortened to KdP), and its conditions are extremely important. Some put the CDP in first place in importance, and only after that - acoustics, amplifier, source. This is somewhat justified, since the room is capable of doing whatever it wants with the graphs and parameters measured by the microphone. Peaks or dips in the frequency response may appear that were not observed during measurements in a quiet room. Both the phase response (following the frequency response) and the transient characteristics will change. In order to understand where such changes come from, we need to introduce the concept of room modes.

Room mods are the beautifully named room resonances. The sound is emitted by the speaker system in all directions. Sound waves bounce off everything in the room. In general, the behavior of sound in a single listening room (CLR) is completely unpredictable. There are, of course, calculations that allow us to evaluate the influence of various modes on sound. But they exist for an empty room with an idealized finish. Therefore, it is not worth presenting them here; they have no practical value in everyday life.

However, you must know that resonances and the reasons for their appearance directly depend on the frequency of the signal. For example, low frequencies excite room modes, which are determined by the size of the CDP. Bass boominess (resonance at 35-100 Hz) is a clear representative of the appearance of resonances in response to a low-frequency signal in a standard room of 16-20 m 2. High frequencies give rise to slightly different problems: diffraction and interference of sound waves appear, which make the directivity characteristics of the speakers frequency-dependent. That is, the directionality of the speakers becomes increasingly narrow with increasing frequency. It follows from this that the listener will receive maximum comfort at the intersection of the acoustic axes of the speakers. And only him. All other points in space will receive less information or receive it distorted in one way or another.

The influence of the room on the speakers can be significantly reduced if the control panel is muffled. For this, various sound-absorbing materials are used - from thick curtains and carpets to special slabs and cunning configurations of walls and ceilings. The quieter the room, the more the speakers contribute to the sound, and not the reflections from your favorite computer desk and pot of geraniums.

Recipes for placing speakers in a room

Vandersteen recommends placing speakers along the long wall of the room at points where low-frequency modes are least likely to occur. You need to draw a plan of the room. On the plan, divide the long wall successively into three, five, seven and nine parts, draw the corresponding lines perpendicular to this wall. Do the same with the side wall. The intersection points of these lines will indicate those places where the excitation of low frequencies in the room is minimal.

Lack of bass, lack of tight and clear bass:

try moving the speakers closer to the back wall;

check whether the stands under the speakers are stable: if necessary, use spikes or conical legs;

Check how solid the wall behind the speaker is. If the wall is flimsy and makes noise, place the speaker in front of a strong (solid) wall.

The stereo image does not extend beyond the space limited by the speakers:

move the speakers closer to each other.

There is no depth of sound space. There is no clear sound image in the center between the speakers:

select the optimal height for the speakers (use stands) and your listening position.

Sharp annoying sound in the mid and high frequencies:

if the speakers are new, warm them up on a music signal for several days;

Check for strong reflections from side walls or the floor in front of the listener.

Distortions

From subjectivism we need to move on to technical concepts. It's worth starting with distortions. They are divided into two large groups: linear and nonlinear distortions. Linear distortion do not create new spectral components of the signal; they change only the amplitude and phase components. (They distort the frequency response and phase response, respectively.) Nonlinear distortion make changes to the signal spectrum. Their number in the signal is presented in the form of nonlinear distortion and intermodulation distortion coefficients.

Harmonic distortion factor (THD, THD - total harmonic distortion) is an indicator characterizing the degree to which the voltage or current shape differs from the ideal sinusoidal shape. In Russian: a sinusoid is supplied to the input. At the output, it does not resemble itself, since the path introduces changes in the form of additional harmonics. The degree of difference between the signal at the input and output is reflected by this coefficient.

Intermodulation distortion factor - this is a manifestation of amplitude nonlinearity, expressed in the form of modulation products that appear when a signal is applied, consisting of signals with frequencies f 1 And f 2(based on the recommendation of IEC 268-5, frequencies are taken for measurements f 1 and f 2, such that f 1 < f 2/8. You can take another relationship between frequencies). Intermodulation distortion is assessed quantitatively by spectral components with frequencies f 2±(n-1) f 1, where n=2,3,... At the system output, the number of extra harmonics is compared and the percentage of the spectrum they occupy is estimated. The result of the comparison is the intermodulation distortion coefficient. If measurements are carried out for several n (usually 2 and 3 are sufficient), then the final intermodulation distortion coefficient is calculated from the intermediate ones (for different n) by taking the square root of the sum of their squares.

Power

We can talk about it for a very long time, since there are many types of measured speaker powers.

A few axioms:

Volume does not depend only on power. It also depends on the sensitivity of the speaker itself. And for an acoustic system, sensitivity is determined by the sensitivity of the largest speaker, since it is the most sensitive;

the indicated maximum power does not mean that you can apply it to the system and the speakers will play perfectly. Everything is just more unpleasant. Maximum power for a long time with a high probability of damaging something in the dynamics. Manufacturer's warranty! Power should be understood as an unattainable limit. Only less. Not equal, and certainly not more;

little of! At maximum power or close to it, the system will play extremely poorly, because distortion will increase to completely indecent values.

The power of the speaker system can be electrical or acoustic. It is unrealistic to see the acoustic power on a box with acoustics. Apparently, so as not to scare off the client with a small number. The fact is that the efficiency (efficiency factor) of the GG (loudspeaker head) in a very good case reaches 1%. The usual value is up to 0.5%. Thus, the acoustic power of a system can ideally be one hundredth of its electrical potential. Everything else is dissipated in the form of heat, spent on overcoming the elastic and viscous forces of the speaker.

The main types of powers that can be seen on acoustics are: RMS, PMPO. This is electrical power.

RMS(Root Mean Squared - root mean square value) - average value of the supplied electrical power. Power measured in this way has a meaning. Measured by applying a sinusoid with a frequency of 1000 Hz, limited at the top given value THD. It is imperative to study what level of nonlinear distortion the manufacturer considered acceptable, so as not to be deceived. It may turn out that the system is stated at 20 watts per channel, but the measurements were carried out at 10% SOI. As a result, it is impossible to listen to acoustics at this power. Also, the speakers can play at RMS power for a long time.

PMPO(Peak Music Power Output - peak music output power). What is the benefit of a person knowing that his system may suffer a short, less than a second, low frequency sine wave with high power? However, manufacturers are very fond of this option. After all, on plastic speakers the size of a child’s fist there can be a proud number of 100 Watts. There were no healthy boxes of Soviet S-90s lying around! :) Oddly enough, such figures have very little relation to the real PMPO. Empirically (based on experience and observations) you can obtain approximately real watts. Let's take the Genius SPG-06 as an example (PMPO-120 Watt). It is necessary to divide PMPO into 10 (12 Watts) and 2 (number of channels). The output is 6 watts, which is similar to the real figure. Once again: this method is not scientific, but is based on the author’s observations. Usually works. In reality, this parameter is not so large, and the huge numbers are based only on the wild imagination of the marketing department.

Thiel-Small parameters

These parameters completely describe the speaker. There are parameters both constructive (area, mass of the moving system) and non-structural (which follow from the constructive ones). There are only 15 of them. In order to roughly imagine what kind of speaker is working in the column, four of them are enough.

Speaker resonant frequency Fs(Hz) - resonance frequency of a speaker operating without acoustic design. Depends on the mass of the moving system and the rigidity of the suspension. It is important to know, since below the resonant frequency the speaker practically does not sound (the sound pressure level drops strongly and sharply).

Equivalent Volume Vas(liters) - the useful volume of the housing required for the speaker to operate. Depends only on the diffuser area (Sd) and the flexibility of the suspension. It is important because, when working, the speaker relies not only on the suspension, but also on the air inside the box. If the pressure is not what is needed, then the speaker will not work perfectly.

Full quality factor Qts - the ratio of elastic and viscous forces in a moving dynamic system near the resonance frequency. The higher the quality factor, the higher the elasticity in the dynamics and the more readily it sounds at the resonant frequency. It consists of mechanical and electrical quality factors. Mechanical is the elasticity of the suspension and the corrugation of the centering washer. As usual, it is the corrugation that provides greater elasticity, and not the external suspensions. Mechanical quality factor - 10-15% of total quality factor. Everything else is the electrical quality factor formed by the magnet and the speaker coil.

DC resistance Re(Ohm). There is nothing special to explain here. Resistance of the head winding to direct current.

Mechanical quality factor Qms- the ratio of elastic and viscous forces of the speaker; elasticity is considered only for the mechanical elements of the speaker. It is made up of the elasticity of the suspension and the corrugation of the centering washer.

Electrical quality factor Qes- the ratio of elastic and viscous forces of the speaker, elastic forces arise in the electrical part of the speaker (magnet and coil).

Diffuser area Sd(m2) - measured, roughly speaking, with a ruler. It has no secret meaning.

Sensitivity SPL(dB) - sound pressure level developed by the loudspeaker. Measured at a distance of 1 meter with an input power of 1 Watt and a frequency of 1 kHz (typical). The higher the sensitivity, the louder the system plays. In a two-way or more-way system, the sensitivity is equal to the SPL of the most sensitive speaker (usually the bass mug).

Inductance Le(Henry) is the inductance of the speaker coil.

Impedance Z(Ohm) is a complex characteristic that appears not on direct current, but on alternating current. The fact is that in this case, the reactive elements suddenly begin to resist the current. Resistance depends on frequency. Thus, impedance is the ratio of the complex voltage amplitude and the complex current at a certain frequency. (Frequency dependent complex impedance, in other words).

Peak power Pe(Watt) is PMPO, which is discussed above.

Weight of the moving system mms(d) is the effective mass of the moving system, which includes the mass of the diffuser and the air oscillating with it.

Relative hardness Cms(meters/newton) - flexibility of the moving system of the loudspeaker head, displacement under the influence of mechanical load (for example, a finger that aims to poke the speaker). The higher the parameter, the softer the suspension.

Mechanical resistance Rms(kg/sec) - active mechanical resistance of the head. Everything that can provide mechanical resistance in the head is included here.

Motor power BL- the value of magnetic flux density multiplied by the length of the wire in the coil. This parameter is also called the power factor of the speaker. We can say that this is the power that will act on the diffuser from the magnet.

All of the above parameters are closely interrelated. This is pretty obvious from the definitions. Here are the main dependencies:

Fs increases with increasing rigidity of the suspension and decreases with increasing mass of the moving system;

Vas decreases with increasing suspension rigidity and increases with increasing diffuser area;

Qts increases with increasing rigidity of the suspension and mass of the moving system and decreases with increasing power B.L..

So, now you are familiar with the basic theoretical apparatus necessary to understand articles on acoustic systems. Let's move on directly to the testing methodology used by the authors of our portal.

Testing methodology

Frequency response Measurement technique and interpretation

At first this section Let's deviate a little from the main topic and explain why all this is being done. Firstly, we want to describe our own method for measuring frequency response so that the reader does not have any additional questions. Secondly, we will tell you in detail how to perceive the resulting graphs and what can be said from the given dependencies, as well as what should not be said. Let's start with the methodology.

Measurement microphone Nady CM-100

Our technique for measuring frequency response is quite traditional and differs little from the generally accepted principles of conducting detailed experiments. Actually, the complex itself consists of two parts: hardware and software. Let's start with a description of the real devices that are used in our work. As a measuring microphone, we use a high-precision condenser microphone Behringer ECM-8000 with an omnidirectional polar pattern (omnidirectional), which has quite good parameters at a relatively low price. So to speak, this is the “heart” of our system. This instrument is designed specifically for use with modern technology as part of budget measurement laboratories. We also have at our disposal a similar microphone, the Nady CM-100. The characteristics of both microphones practically repeat each other, however, we always indicate with which microphone a particular frequency response was measured. As an example, here are the stated technical characteristics of the Nady CM-100 microphone:

impedance: 600 Ohm;

sensitivity: -40 dB (0 dB = 1 V/Pa);

frequency range: 20-20000 Hz;

maximum sound pressure: 120 dB SPL;

power supply: phantom 15…48 V.

Frequency response of the measuring microphone

M-Audio AudioBuddy microphone preamplifier

We use an external compact solution, M-Audio AudioBuddy, as a microphone preamplifier. The AudioBuddy preamplifier is designed specifically for use in digital audio recording and is optimized for use with microphones that require phantom power. Plus, the user has independent outputs at his disposal: balanced or unbalanced TRS. The main parameters of the preamplifier are:

frequency range: 5-50,000 Hz;

microphone gain: 60 dB;

microphone input impedance: 1 kOhm;

instrument gain: 40 dB;

instrument input impedance: 100 kOhm;

power supply: 9 V AC, 300 mA.

Sound card ESI Juli@

For further analysis, the signal from the amplifier output is fed to the input of a computer audio interface, which uses an ESI Juli@ PCI card. This decision can safely be classified as semi-professional or even entry-level professional devices. Main parameters:

number of I/O: 4 inputs (2 analog, 2 digital), 6 outputs (2 analog, 4 digital);

ADC/DAC: 24-bit/192 kHz;

frequency range: 20 Hz - 21 kHz, +/- 0.5 dB;

dynamic range: ADC 114 dB, DAC 112 dB;

inputs: 2 analog, 2 digital (S/PDIF Coaxial);

outputs: 2 analog, 2 digital (S/PDIF Coaxial or Optical);

MIDI: 1 MIDI input and 1 MIDI output;

interface: PCI;

synchronization: MTC, S/PDIF;

Drivers: EWDM driver support for Windows 98SE/ME/2000 and XP, MAC OS 10.2 or older.

In general, the unevenness of the path of the entire system in the frequency range 20-20000 Hz lies within +/- 1...2 dB, so our measurements can be considered quite accurate. The main negative factor is that all measurements are carried out in an average living room with standard reverberation. The area of ​​the room is 34 m2, the volume is 102 m3. The use of an anechoic chamber, naturally, increases the accuracy of the result obtained, but the cost of such a chamber is at least several tens of thousands of dollars, so only large manufacturers of acoustic systems or other very wealthy organizations can afford such a “luxury”. However, there are also tangible advantages to this: for example, the frequency response in a real room will always be far from the frequency response that was obtained by the manufacturer in the test chamber. Therefore, based on our results, we can draw some conclusions about the interaction of specific acoustics with the average room. This information is also very valuable, because any system will be operated in real conditions.

Popular utility RightMark Audio Analyzer

The second important point is the software part. We have several professional software packages at our disposal, such as RightMark Audio Analyzer ver. 5.5 (RMAA), TrueRTA ver. 3.3.2, LSPCad ver. 5.25, etc. As a rule, we use the convenient RMAA utility; provided it is freely distributed and constantly updated, it is very practical and provides high accuracy of measurements. In fact, it has already become a standard among test packages throughout the RuNet.

Program TrueRTA

Measuring module JustMLS programs LSPCAD

It would seem that any measurement should be carried out according to strictly established rules, but in the field of acoustics there are too many of these rules, and they often diverge somewhat from each other. For example, the basic standards and measurement methods are given in several very significant documents at once: outdated GOSTs of the USSR (GOST 16122-87 and GOST 23262-88), IEC recommendations (publications 268-5, 581-5 and 581-7), German DIN standard 45500, as well as American AES and EIA regulations.

We make our measurements as follows. The acoustic system (AS) is installed in the center of the room at the maximum distance from walls and three-dimensional objects; a high-quality stand 1 m high is used for installation. The microphone is installed at a distance of about a meter on a straight axis. The height is chosen in such a way that the microphone “looks” at approximately the central point between the midrange and tweeter speakers. The resulting frequency response is called the characteristic taken on the direct axis, and in classical electroacoustics it is considered one of the most important parameters. It is believed that the fidelity of reproduction directly depends on the unevenness of the frequency response. However, read about this below. We also always measure the angular characteristics of the system. Ideally, it is necessary to obtain a whole set of dependencies in the vertical and horizontal planes in increments of 10...15 degrees. Then it is quite reasonable to draw conclusions about the directional pattern of the speakers and give advice on the correct placement in space. In fact, the angular frequency response is no less important than the frequency response along the straight axis, since they determine the nature of the sound reaching the listener after reflection from the walls of the room. According to some reports, the share of reflections at the listening point reaches 80% or more. We also remove all possible characteristics of the path with all available frequency adjustments, modes such as 3D, etc.

Simplified flowchart of the measurement process

You can tell a lot from these graphs...

Subjective listening

So, the frequency response graphs have been obtained. What can you say after studying them in detail? In fact, a lot can be said, but it is impossible to unambiguously evaluate the system based on these dependencies. Not only is the frequency response not a very informative characteristic, and a whole series of additional measurements are required, for example, impulse response, transient response, cumulative spectrum attenuation, etc., but even from these comprehensive dependencies it is quite difficult to give an unambiguous assessment of acoustics. Strong evidence of this can be found in the official statement of the AES (Journal of AES, 1994) that subjective assessment is simply necessary to obtain a complete picture of the acoustic system in combination with objective measurements. In other words, a person can hear a certain artifact, but it is possible to understand where it comes from only by making a series of precise measurements. Sometimes measurements help to identify an insignificant defect that can easily slip past your ears when listening, and you can “catch” it only by focusing your attention on this particular range.

First, you need to break the entire frequency range into characteristic sections so that it is clear what we are talking about. Agree, when we say “mid frequencies”, it is not clear how much it is: 300 Hz or 1 kHz? Therefore, we suggest using a convenient division of the entire sound range into 10 octaves, described in the previous section.

Finally, we move directly to the moment of subjective description of sound. There are thousands of terms for assessing what is heard. The best option is to use some kind of documented system. And there is such a system, it is offered by the most authoritative publication with a half-century history, Stereophile. Relatively recently (in the early 90s of the last century), an acoustic dictionary, Audio Glossary, edited by Gordon Holt, was published. The dictionary contains an interpretation of more than 2000 concepts that in one way or another relate to sound. We propose to familiarize yourself with only a small part of them, which relates to the subjective description of sound in the translation by Alexander Belkanov (Magazine "Salon AV"):

ah-ax (rhymes with "rah" - Hurray). The coloring of vowels caused by a peak in the frequency response around 1000 Hz.

Airy - airiness. Refers to high frequencies that sound light, gentle, open, with a feeling of unlimited top end. A property of a system that has a very smooth response at high frequencies.

aw - (rhymes with "paw" [po:] - paw). The coloring of vowels caused by a peak in the frequency response around 450 Hz. Strives to emphasize and embellish the sound of large brass instruments (trombone, trumpet).

Boomy - read the word "boom" with a long "m". Characterizes an excess of mid-bass, often with a predominance of a narrow low-frequency band (very close to “one-note-bass” - bass on one note).

Boxy (literally “boxy”): 1) characterized by “oh” - the coloring of the vowels, as if the head is speaking inside the box; 2) used to describe the upper bass/low mids of speakers with excessive cabinet wall resonances.

Bright, brilliant - bright, with shine, sparkling. An often misused term in audio, it describes the degree of hardness of the edge of the sound being reproduced. Luminance refers to the energy contained in the 4-8 kHz band. This does not apply to the highest frequencies. All living sounds have brightness, the problem arises only when there is excess of it.

Buzz is a buzzing low-frequency sound that has a fluffy or sharp character due to some uncertainty.

Chesty - from chest (chest). A pronounced density or heaviness when reproducing a male voice due to excessive energy in the upper bass/lower midrange.

Closed-in (literally - hidden, closed). Needs openness, air and good detail. Closed sound is usually caused by HF roll-off above 10 kHz.

Cold - cold, stronger than cool - cool. Has some excess highs and weakened lows.

Coloration - coloring. An audible "signature" with which the reproducing system colors all signals passing through it.

Cool - cool. Moderately lacking in density and warmth due to monotonic decay starting at 150 Hz.

Crisp - crisp, clearly defined. Precisely localized and detailed, sometimes excessively due to the peak in the mid-HF range.

Cupped-hands - a mouthpiece made of palms. Coloration with a nasal sound or, in extreme cases, sound through a megaphone.

Dark - dark, gloomy (literally). Warm, soft, overly rich sound. It is perceived by ear as a clockwise slope of the frequency response throughout the entire range, so that the output level is attenuated with increasing frequency.

Dip (literally - immersion, failure). A narrow gap in the middle of a flat frequency response.

Discontinuity (literally - gap). Change in timbre or color during the transition of a signal from one head to another in multi-band acoustic systems.

Dished, dished-down - in the form of a saucer, an inverted saucer. Describes the frequency response with a failed middle. The sound has a lot of bass and high frequencies, the depth is exaggerated. Perception is usually lifeless.

Dry (literally - dry). Describes the quality of the bass: lean, lean, usually overdamped.

Dull (literally - dull, dull, boring, lethargic, depressed). Describes a lifeless, veiled sound. Same as “soft” - soft, but to a greater extent. An audible HF roll-off effect after 5 kHz.

her - rhymes with we. Coloration of vowels caused by a peak in the frequency response around 3.5 kHz.

eh - as in "bed". Coloration of vowels caused by a short rise in frequency response in the region of 2 kHz.

Extreme highs - ultra-high. The range of audible frequencies is above 10 kHz.

Fat (literally - plentiful, rich, fatty, oily). An audible effect of moderate redundancy in the mid and upper bass. Excessively warm, more "warm".

Forward, forwardness (literally - brought to the fore, moving forward). A reproduction quality that gives the impression that sound sources are closer than they were when recorded. Typically this is the result of a hump in the midrange plus the narrow directivity of the speakers.

Glare (literally - dazzling, sparkling). An unpleasant quality of hardness or brightness due to excessive low or mid-high energy.

Golden (literally - golden). A euphonious color, characterized by roundness, richness, and melody.

Hard (literally - hard, hard). Aspiring to steel, but not so piercing. This is often the result of a moderate hump around 6 kHz, sometimes caused by slight distortion.

Horn sound - a horn sound made through a horn. "aw" coloring, characteristic of many acoustic systems that have a mid-frequency horn driver.

Hot (literally - hot). Sharp resonant surge in high frequencies.

Hum (literally - buzzing). Continuous "itching" at frequencies that are multiples of 50 Hz. Caused by the penetration of the main frequency of the power supply or its harmonics into the playback path.

Humped (literally - hunched over). Characterizes the sound pushed forward (in terms of spatial characteristics). The overall sound is sluggish and meager. Caused by a broad rise in the mid frequencies and a fairly early fall in the lows and highs.

ih - as in the word "bit". Coloration of vowels caused by a peak in the frequency response around 3.5 kHz.

Laid-back (literally - pushed back, pushed back). Depressed, distant sounding, with exaggerated depth, usually due to a saucer-shaped midrange.

Lean - thin, skinny, frail. The effect of a slight downward decline in frequency response, starting from 500 Hz. Less pronounced than “cool” - cool.

Light - light. The audible effect of tilting the frequency response counterclockwise relative to the middle. Compare with "dark" - dark.

Loose - loose, loose, unstable. Refers to poorly defined/washed out and poorly controlled bass. Problems with damping of the amplifier or dynamic drivers/acoustic design of speakers.

Lumpy (literally - lumpy). A sound characterized by some discontinuity in the frequency response in the lower part, starting from 1 kHz. Some areas appear bulging, others appear weakened.

Muffled - muted. It sounds very sluggish, dull, and has no high frequencies in the spectrum at all. The result is a roll-off of high frequencies above 2 kHz.

Nasal (literally - nasal, nasal). It sounds similar to talking with a stuffy or pinched nose. Similar to the coloring of the vowel "eh". In loudspeaker systems, this is often caused by a measured pressure peak in the upper midrange followed by a dip.

oh - pronunciation as in "toe". The coloring of a vowel caused by a wide spike in the frequency response in the region of 250 Hz.

One-note-bass - bass on one note. The predominance of one low note is a consequence of a sharp peak in the lower range. Usually caused by poor damping of the woofer head, room resonances can also appear.

oo - pronunciation as in the word "gloom". The coloring of the vowel is caused by a wide surge in the frequency response in the region of 120 Hz.

Power range - maximum energy range. The frequency range of approximately 200-500 Hz corresponds to the range of powerful orchestral instruments - brass.

Presence range (literally - range of presence). The lower part of the upper range is approximately 1-3 kHz, creating a sense of presence.

Reticent (literally - restrained). Moderately set back. Describes the sound of a system whose frequency response is saucer-shaped in the midrange. Opposite of forward.

Ringing (literally - ringing). Audible resonance effect: coloration, smeared/fuzzy sound, shrillness, buzzing. It has the nature of a narrow surge in the frequency response.

Seamless (literally - without a seam, from a single/solid piece). There are no noticeable discontinuities throughout the entire audible range.

Seismic - seismic. Describes the reproduction of low frequencies that makes the floor seem to vibrate.

Sibilance (literally - whistling, hissing). Coloration emphasizing the vocal sound "s". It may be associated with a monotonic rise in the frequency response from 4-5 kHz or with a wide surge in the 4-8 kHz band.

Silvery - silvery. Somewhat harsh, but clear sound. It gives the flute, clarinet, and violas an edge, but the gong, bells, and triangles can be obtrusive and excessively sharp.

Sizzly - hissing, whistling. The frequency response rises in the region of 8 kHz, adding hissing (whistle) to all sounds, especially to the sound of cymbals and hissing in vocal parts.

Sodden, soggy (literally - wet, swollen with water). Describes loose and poorly defined bass. Creates a feeling of vagueness and illegibility in the lower range.

Solid-state sound - transistor sound, semiconductor sound. A combination of sonic qualities common to most solid-state amplifiers: deep, tight bass, slightly offset bright stage character and clearly defined, detailed treble.

Spitty (literally - spitting, snorting, hissing). A sharp “ts” is a coloring that overemphasizes musical overtones and sibilants. Similar to the surface noise of a vinyl record. Usually, the result is a sharp peak in the frequency response in the extreme HF region.

Steely - steely, steely. Describes shrillness, harshness, importunity. Similar to "hard", but to a greater extent.

Thick - fat, thick, dull. Describes a wet/dull or bulky, heavy bass sound.

Thin - liquid, frail, thinned. Very lacking in bass. The result is a strong, monotonous downward decay starting at 500 Hz.

Tizzy (literally - excitement, anxiety), “zz” and “ff” are the coloration of the sound of cymbals and vocal hisses, caused by an increase in the frequency response above 10 kHz. Similar to "wiry", but at higher frequencies.

Tonal quality - tonal quality. The accuracy/correctness with which the reproduced sound reproduces the timbres of the original instruments. (It seems to me that this term would be a good replacement for timbral resolution - A.B.).

Tube sound, tubey - sound due to the presence of tubes in the recording/playback path. A combination of sound qualities: richness (richness, liveliness, brightness of colors) and warmth, an excess of midrange and a lack of deep bass. Protruding image of the scene. The tops are smooth and thin.

Wiry - hard, tense. Causes irritation with distorted high frequencies. Similar to brushes hitting cymbals, but capable of coloring all sounds produced by the system.

Wooly - lethargic, vague, shaggy. Refers to loose, loose, poorly defined bass.

Zippy - lively, fast, energetic. Slight emphasis in the upper octaves.

So, now, looking at the given frequency response, you can characterize the sound in one or more terms from this list. The main thing is that the terms are systemic, and even an inexperienced reader can, by looking at their meaning, understand what the author wanted to say.

What material is the acoustics tested on? When choosing test material, we were guided by the principle of diversity (after all, everyone uses acoustics in completely different applications - cinema, music, games, not to mention different tastes in music) and the quality of the material. In this regard, the set of test disks traditionally includes:

DVDs with films and concert recordings in DTS and DD 5.1 formats;

discs with games for PC and Xbox 360 with high-quality soundtracks;

high-quality recorded CDs with music of various genres and genres;

MP3 discs with compressed music, material that is mainly listened to on MM acoustics;

special test CDs and HDCDs of audiophile quality.

Let's take a closer look at the test discs. Their purpose is to identify shortcomings in acoustic systems. There are test discs with a test signal and with musical material. Test signals are generated reference frequencies (allowing you to determine by ear the boundary values ​​of the reproduced range), white and pink noise, a signal in phase and antiphase, and so on. The popular test disk seems to us the most interesting F.S.Q. (Fast Sound Quality) and Prime Test CD . Both of these discs, in addition to artificial signals, contain fragments of musical compositions.

The second category includes audiophile discs containing entire compositions, recorded in studios of the highest quality and mixed with precision. We use two licensed HDCD discs (recorded at 24-bit and 88 kHz sampling frequency) - Audiophile Reference II (First Impression Music) and HDCD Sampler (Reference Recordings), as well as a CD sampler of classical music, Reference Classic, from the same label, Reference Recordings .

AudiophileReference II(the disc allows you to evaluate such subjective characteristics as musical resolution, involvement, emotionality and presence, the depth of the nuances of the sound of various instruments. The musical material of the disc is classical, jazz and folk works, recorded with the highest quality and produced by the famous sound wizard Winston Ma. On the recording You can find magnificent vocals, powerful Chinese drums, deep string bass, and on a truly high-quality system you can get real listening pleasure.

HDCDSampler from Reference Recordings contains symphonic, chamber and jazz music. Using the example of his compositions, one can trace the ability of acoustic systems to build a musical stage, convey macro- and microdynamics, and the naturalness of the timbres of various instruments.

ReferenceClassic shows us the real strong point of Reference Recordings - chamber music recordings. The main purpose of the disc is to test the system for faithful reproduction of various timbres and the ability to create the correct stereo effect.

Z-characteristic. Measurement technique and interpretation

Surely even the most inexperienced reader knows that any dynamic head, and, consequently, the speaker system as a whole, has a constant resistance. This resistance can be regarded as direct current resistance. For household equipment, the most common numbers are 4 and 8 ohms. In automotive technology, speakers with a resistance of 2 ohms are often found. The resistance of good monitor headphones can reach hundreds of ohms. From a physics point of view, this resistance is determined by the properties of the conductor from which the coil is wound. However, speakers, like headphones, are designed to operate with audio frequency alternating current. It is clear that as the frequency changes, the complex resistance also changes. The dependence characterizing this change is called the Z-characteristic. The Z-characteristic is quite important to study because... It is with the help of it that one can draw unambiguous conclusions about the correct matching of the speaker and amplifier, the correct calculation of the filter, etc. To remove this dependence, we use the LSPCad 5.25 software package, or more precisely, the JustMLS measuring module. Its capabilities are:

MLS Size (Maximum-Length Sequence): 32764,16384,8192 and 4096

FFT (Fast Fourier Transform) size: 8192, 1024 and 256 points used in different frequency bands

Sampling rates: 96000, 88200, 64000, 48000, 44100, 32000, 22050, 16000, 1025, 8000 Hz and user selectable Custom.

Window: Half Offset

Internal representation: From 5 Hz to 50000 Hz, 1000 frequency points with logarithmic periodicity.

To measure, you need to assemble a simple circuit: a reference resistor (in our case C2-29V-1) is connected in series from the speakers, and the signal from this divider is fed to the input of the sound card. The entire system (speaker/AC+resistor) is connected via an AF power amplifier to the output of the same sound card. We use the ESI Juli@ interface for these purposes. The program is very convenient because it does not require careful and lengthy setup. Just calibrate the sound levels and press the "Measure" button. In a split second we see the finished graph. Next comes its analysis; in each specific case we pursue different goals. So, when studying a low-frequency speaker, we are interested in the resonant frequency to check the correct choice of acoustic design. Knowing the resonant frequency of the high-frequency head allows you to analyze the correctness of the isolation filter solution. In the case of passive acoustics, we are interested in the characteristic as a whole: it should be as linear as possible, without sharp peaks and dips. So, for example, acoustics whose impedance sags below 2 ohms will not be to the taste of almost any amplifier. These things should be known and taken into account.

Nonlinear distortions. Measurement technique and interpretation

Total Harmonic Distortion (THD) is a critical factor when evaluating speakers, amplifiers, etc. This factor is due to the nonlinearity of the path, as a result of which additional harmonics appear in the signal spectrum. The nonlinear distortion factor (THD) is calculated as the ratio of the square of the fundamental harmonic to the square root of the sum of the squares of the additional harmonics. Typically, only the second and third harmonics are taken into account in calculations, although accuracy can be improved by taking into account all additional harmonics. For modern acoustic systems, the nonlinear distortion factor is normalized in several frequency bands. For example, for the zero complexity group according to GOST 23262-88, the requirements of which significantly exceed minimum requirements IEC Hi-Fi class, the coefficient should not exceed 1.5% in the frequency band 250-2000 Hz and 1% in the band 2-6.3 kHz. Dry numbers, of course, characterize the system as a whole, but the phrase “THE = 1%” still says little. A striking example: tube amplifier with a non-linear distortion coefficient of about 10% can sound much better than a transistor amplifier with the same coefficient of less than 1%. The fact is that lamp distortion is mainly caused by those harmonics that are screened by auditory adaptation thresholds. Therefore, it is very important to analyze the spectrum of the signal as a whole, describing the values ​​of certain harmonics.

This is what the signal spectrum of a specific acoustic looks like at a reference frequency of 5 kHz

In principle, you can look at the distribution of harmonics across the spectrum using any analyzer, both hardware and software. The same programs RMAA or TrueRTA do this without any problems. As a rule, we use the first one. The test signal is generated using a simple generator; several test points are used. For example, nonlinear distortions that increase at high frequencies significantly reduce the microdynamics of the musical image, and a system with high distortions as a whole can simply greatly distort the timbral balance, wheeze, have extraneous sounds, etc. Also, these measurements make it possible to evaluate the acoustics in more detail in combination with other measurements, and check the correctness of the calculation of the separation filters, because the nonlinear distortions of the speaker increase greatly outside its operating range.

Article structure

Here we will describe the structure of the article on acoustic systems. Despite the fact that we try to make reading as pleasant as possible and do not squeeze ourselves into a certain framework, articles are compiled taking into account this plan, so that the structure is clear and understandable.

1. Introduction

Here it is written general information about the company (if we are getting to know it for the first time), general information about the product line (if we are taking it for a test for the first time), we give an outline of the current state of the market. If the previous options are not suitable, we write about trends in the acoustics market, in design, etc. - so that 2-3 thousand characters are written (hereinafter - k). The type of acoustics is indicated (stereo, surround sound, triphonic, 5.1, etc.) and positioning on the market - as a multimedia gaming for a computer, universal, for listening to music for an entry-level home theater, passive for a home theater, etc.

Tactical and technical characteristics summarized in the table. Before the table with performance characteristics, we make a short introduction (for example, “we can expect serious YYY parameters from acoustics costing XXX”). The table type and set of parameters are as follows:

For systems2.0

Parameter	Meaning
output power, W (RMS)
External dimensions columns, WxLxH, mm
Gross weight, kg
Net weight, kg
Speaker diameter, mm
Speaker resistance, Ohm
Supply voltage, V
frequency range, Hz
Frequency response unevenness in the operating range, +/- dB
Low frequency adjustment, dB
Crosstalk, dB
Signal to noise ratio, dB
Completeness
Average retail price, $

For systems2.1

Parameter	Meaning
Output power of satellites, W (RMS)
SOI at rated power, %
External dimensions of satellites, WxDxH, mm
Gross weight, kg
Net weight of satellites, kg
Subwoofer net weight, kg
Speaker diameter, mm
Speaker resistance, Ohm
Magnetic shielding, availability
Supply voltage, V
High frequency adjustment, dB
Low frequency adjustment, dB
Crosstalk, dB
Signal to noise ratio, dB
Completeness
Average retail price, $

For 5.1 systems

Parameter	Meaning
Output power of front satellites, W (RMS)
Output power of rear satellites, W (RMS)
Center channel output power, W (RMS)
Subwoofer output power, W (RMS)
Total output power, W (RMS)
SOI at rated power, %
External dimensions of front satellites, WxDxH, mm
External dimensions of rear satellites, WxDxH, mm
External dimensions of the central channel, WxDxH, mm
External dimensions of the subwoofer, WxDxH, mm
Gross weight, kg
Net weight of front satellites, kg
Net weight of rear satellites, kg
Net weight of the central channel, kg
Subwoofer net weight, kg
Speaker diameter, mm
Speaker resistance, Ohm
Magnetic shielding, availability
Supply voltage, V
Frequency range of satellites, Hz
Subwoofer frequency range, Hz
Frequency response unevenness in the full operating range, +/- dB
High frequency adjustment, dB
Low frequency adjustment, dB
Crosstalk, dB
Signal to noise ratio, dB
Completeness
Average retail price, $

We take the tables given as a basis; if additional data is available, we make additional columns; columns for which there is no data, we simply remove them. After the table with performance characteristics, some preliminary conclusions.

3. Packaging and accessories

We describe the delivery package and box, at least two photographs. Here we evaluate the completeness of the kit, describe the nature of the cables included in the kit, and, if possible, estimate their cross-section/diameter. We conclude that the kit corresponds to the price category, convenience and packaging design. We note the presence of a Russian-language operating manual and its completeness.

4. Design, ergonomics and functionality

We describe the first impression of the design. We note the nature of the materials, their thickness, quality factor. We evaluate design decisions in terms of their potential impact on sound (remembering to add the word “allegedly”). We evaluate the quality of workmanship, the presence of legs/spikes, grill/acoustic fabric in front of the diffusers. We are looking for fastenings, the possibility of installation on a stand/shelf/wall.

Describes ergonomics and impressions of working with acoustics (excluding listening). It is noted whether there is a click when turned on, whether the wires are long enough, and whether all controls are convenient to use. Implementation of controls (analog sliders or knobs, digital encoders, toggle switches, etc.) Several photographs of controls, remote control if available, photos of speakers in a setting or in comparison with ordinary objects. Convenience and speed of switching, the need to check phasing, whether the instructions help, etc. We note the effectiveness of magnetic shielding (on a CRT monitor or TV). We pay attention to additional inputs, operating modes (pseudo-surround sound, built-in FM tuner, etc.), service capabilities.

5. Design

We disassemble the speakers, if there is a subwoofer, then that too. We note the following design features:

Type of acoustic design (open, closed box, bass reflex, passive radiating, transmission line, etc.) + general photo of the internal structure;

Dimensions and internal volume of the case, assume the compatibility of the AO with the GG;

Location of loudspeaker heads (SG), method of attachment to the acoustic design;

Quality of internal installation, assembly, fastening + 1-2 photos with internal installation details;

Availability of mechanical damping, quality of its execution and materials used + photo;

The shape and dimensions of the bass reflex (if any), its location (estimated effect on the sound) and the manufacturer’s likely adaptations to eliminate jet noise + photo;

The quality of internal wiring, the presence of overload protection, proposals for modernization;

The GGs used are the type, material of manufacture (paper, impregnated silk, aluminum, plastic, etc.), the nature of the diffuser surface (conical, exponential surface, corrugated, with “stiffening ribs,” etc.) and the protective cap (flat , “acoustic bullet”, etc.), suspension (rubber, paper, etc.), degree of suspension rigidity), coil diameter, tweeter cooling, markings, resistance + photo of each GG;

Type of fastening of the wire to the speakers (detachable, screw clamps, spring clamps, banana clamps, etc.) + photo;

Signal cable connectors - types, quantity, quality.

We illustrate the following with diagrams and graphs:

Amplifier chip(s) - table with key characteristics, their analysis for compliance with performance characteristics and speakers, if possible - provide a graph of power versus SOI and a photo, maybe a photo of the radiator;

Power transformer - table with currents, type of transformer (torus, on W-shaped plates, etc.) indicating the total power in VA, conclusions about the availability of power supply reserve, the presence of a power filter, etc. + photo;

Separation filter - we sketch the circuit, indicate the order of the filter (and, accordingly, the attenuation of the signal), and draw a conclusion about its justification; application (if appropriate measurements are available), we calculate the cutoff frequency if we subsequently measure resonance and/or Z-characteristic;

We calculate the resonant frequency of the bass reflex, present the formula and justify its use.

6. Measurements

We make the following measurements and provide an analysis for each of them, making assumptions about the nature of the sound.

Axial frequency response of the column with detailed analysis;

Frequency response of speakers at angles of 30 and 45 degrees, analysis of the nature of speaker dispersion;

Frequency response of the subwoofer (if any) + total frequency response of systems, quality analysis; trifonic matching, influence of bass reflex resonance;

Axial frequency response depending on tone controls (if any);

Frequency response of the bass reflex, analysis;

Harmonic distortion spectrum;

Frequency response of speakers separately (for example, LF and HF), if necessary.

7. Audition

First, we give the first subjective assessment of the nature of the sound, indicating whether the volume is sufficient for various playback modes. We note the peculiarities of the acoustics in each of the typical applications - cinema (for 5.1 systems we focus on the quality of positioning), music and games. We indicate the type of listening room, its area and volume, as well as the degree of demands of the given acoustics on the room. Next, we analyze the sound of the speakers using the list of characteristics and terminology described above. We try to avoid subjective comments and, at every opportunity, make a reference to the measurement result that confirmed this or that sound feature. In general, all sound analysis is done in conjunction with measurements. Be sure to pay attention to the following parameters:

The nature of the acoustics in each of the key frequency ranges, the extent to which one or another range is emphasized;

The nature and quality of the stereo effect (the width of the stage, the positioning of sound sources and instruments on it); for 5.1 acoustics, a separate assessment of spatial positioning is given. Don’t forget to place the acoustics correctly (the angle to the front pair is 45 degrees, the distance is slightly greater than the stereo base, the rear pair is twice as close to the listener as the front pair, all speakers are at ear level);

Detail, sound transparency, “grain” (post-pulse activity at mid and high frequencies);

The presence of color and its character in different ranges, timbral balance and natural sound;

Clarity of sound attack (impulse response) and separately - subwoofer operation (if any);

Signal saturation with harmonics (warmth or coldness of sound);

Micro- and macrodynamics of sound, detail of background sounds, “openness” or “tightness” of sound (width dynamic range, quality of the transient response of the GG);

Optimal values ​​for tone controls.

Here is given overall rating acoustics, first of all, the compliance of the solutions used in it with the final result and price category. It is assessed whether the acoustics are successful, promising, and suitable as a “blank” for modifications. A list of pros and cons of the system is given.

Conclusion

The assiduous reader, having completed reading this article, probably learned something new and interesting for himself. We did not try to embrace the immensity and cover all possible aspects of the analysis of acoustic systems and, especially, sound theory; we will leave this to specialized publications, each of which has its own view of the line where physics ends and shamanism begins. But now all aspects of acoustics testing by the authors of our portal should be extremely clear. We never tire of repeating that sound is a subjective matter, and you cannot be guided by tests alone when choosing acoustics, but we hope that our reviews will greatly help you. Have a good sound, dear readers!