Mid-range hi-fi shelf acoustics test. Detailed explanation of some characteristics of acoustics Impedance of speakers

Even during periods of economic crisis, the stream of true connoisseurs of music does not dry up, for whom it is important not only to listen, but also to hear their favorite compositions as they sounded "live" from the stage. Of course, such a need today is not difficult to satisfy - there would be money! Well, if the finances are tense, and you still want to listen to music in Hi-Fi performance, what can you do? For this, we decided to test such shelf acoustic systemsthat successfully combine Hi-Fi sound quality and affordable price corresponding to the mid-range price category. Of course, these are not "fancy" acoustics, but if we compare the floor-standing acoustics with the shelf units according to the criterion "price / quality", then the latter even win. The only thing you want to warn about in advance. Shelving monitors do not always have ideal bass depth, but this drawback is more than compensated for by the excellent sound of the speakers at low volume. Why, after all, for whom do we listen to music - for our neighbors or for ourselves? Well, choosing the right speaker from the twelve models tested 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. Frequency response and nonlinear distortion factor will objectively show to what extent the monitor design corresponds to acoustic parameters. At the same time, the design features of each model will be studied, and the overall design estimate will be derived. The testing will simultaneously consider the sound character of each speaker. As a rule, good bass depth and high reproduction quality are rarely combined in the shelf format, so this indicator, although it will be mentioned in testing, is kind of 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 character of the sound at low volume will also be indicated separately, which indicates the even (almost linear) dynamics of the speaker systems. The timbre accuracy of the musical scene will not be ignored either. Taken together, all this will make up the sound score.

Acoustic Energy 301

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

Benefits:

• great detail
• timbre accuracy

Disadvantages:

• there is a lack of air

When developing the 300 series, British designers managed to embody exquisite laconicism. Coated with white or black lacquer, the speakers look neutral and strict. Panel joints, as well as other elements of the case, are made filigree, without any "frills" like fasteners or protruding screws - in all respects, this shelf model is made in the classic style of "professional" Hi-Fi acoustics. The Acoustic Energy 301's front panel, which is finished in a black rubber-like finish, houses a proprietary 28mm fabric dome tweeter and a proprietary 110mm bent anodized aluminum woofer. By the way, the legendary AE1 monitors, recognized by experts as the standard, once had such a head.

In the lower part of the front panel there is also the slotted phase inverter outlet. This ingenious 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 phase inverter on the front panel does not distort the frequency response in the mid-bass region, and at the same time allows better matching of the lowest frequencies with the room parameters. And such a detail: the solid internal volume of the speaker (at 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 provides excellent bass sound. With such capabilities, this shelf model of the monitor is practically not inferior to more expensive floor-standing "brothers", especially when working in small rooms.

Sound

And if we are talking about the quality of sound, it should be noted the absence of even a subtle color in almost the entire range. Even the smallest nuances of music are clearly audible on the Acoustic Energy 301 speakers, the tones are almost natural. This indicates that the frequency scale of the monitor is balanced in both level and dynamics, and these speakers reproduce a holistic 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 lightest rise slips, which is especially noticeable on complex musical material, when its perception is somewhat reduced. This picture is typical for both high and low volume.

Measurements

With a flat amplitude-frequency response at the highest frequencies, it starts to go up a little. The drop to the low-frequency region is uniform. The bass is of high quality, of medium depth. THD is low enough to be virtually independent of the volume level. The impedance is unstable.

Bowers & Wilkins 685

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

Benefits:

• good sound
• design

Disadvantages:

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

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

Sound

This model is characterized by an open and light sound with a good level of detail. The bass is accurate, fast, but it could be more focused, but the noises make themselves felt. However, the sound localization is very clear. Music lover will not be pleased with the low dynamic range. In the midrange, the timbres of the instruments are greatly simplified, and the area high frequencies it is not auditioned as well as desired and does not give the impression of airiness and spaciousness.

Measurements

In the ranges of 2.5 kHz and 6-7 kHz, unevenness appears, which can be eliminated by turning the speaker through 30 °. At the same time, the frequency balance goes slightly into the low-frequency range. It is characterized by extremely low SOI. The impedance is very unstable.

Canton Chrono 503.2

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

Benefits:

• clear high frequencies
• meticulous reproduction of timbres

Disadvantages:

• low-frequency range is weak at low volume

The German Chrono 503.2 is characterized by excellent sound reproduction and traditionally high quality control. Although the manufacturer announced a glossy finish, the speaker case is covered with a film, and only the front panel is glossy. A relatively compact speaker is equipped with an impressive speaker (diameter 180 mm) with a traditional aluminum cone for this company. To ensure the longest possible linear and long piston stroke of the diffuser, the suspension is made in the form of a wave. The tweeter is equipped with a lightweight 25mm 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 is also thought out: so that they can be fixed on a stand or bracket, there are two threaded holes in the bottom of the speaker.

Sound

The speakers reproduce almost all genres of music quite cleanly, with an almost ideal frequency balance. Therefore, it is not surprising that the timbres of the instruments sound practically without distortion, even subtle nuances. Although there is no heightened emotionality expected with such parameters, the wide and even dynamic range of the speakers very reliably conveys the musical idea of \u200b\u200bany genre - in this, the speakers can be recognized as universal. The lower frequencies are collected and well distinguishable, but the bass is still not deep enough, and when the volume is lowered, it begins to barely noticeably "leave". When you get to know 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 quantity, without any frills. It is worth noting that the upper register of the speaker is crystal clear and will be appreciated by music fans.

Measurements

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

Chario Syntar 516

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

Benefits:

• emotional and bright presentation
• precise localization

Disadvantages:

• simplifying tones

The classic style of the Italian monitor is primarily given 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 done manually, which again increases the impeccable quality. Then the finished products are necessarily tested - without this, the columns do not go on sale. The tweeter diaphragm (Silversoft Neodium model) is coated with a silvery aluminum powder - the same technology is used in monitors of the leading brand line. It should be noted that the tweeter also reproduces a significant part of the mid-frequency range (starting from about 1 kHz). The double-curved shape of the midrange / woofer cone is 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 the sound nuances are veiled. Despite this, the speakers still accurately and emotionally reproduce musical compositions of different genres. The bass is so deep that it even stands out in the overall sound picture. The localization of the soundstage is good, but it lacks transparency, which is especially evident when listening to complex compositions. As the volume is lowered, the bass starts to weaken, but the sound remains emotional and dynamic.

Measurements

The optimal frequency response is recorded when the speaker is turned by 30 °. The model is characterized by relatively good unevenness with a smooth and smooth roll-off to low frequencies. The THD is fairly even - from the high to the lowest frequencies. The impedance is fairly stable.

Dynaudio DM 2/7

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

Benefits:

• authenticity of tones
• clean high frequencies

Disadvantages:

• excessive rigor in sound presentation

In the group of shelf monitors, the Danish company Dynaudio is represented by the DM line. As you might expect, the company has designed the speakers in its own corporate style: the massive front gray panel is slightly thicker than the side walls in order to more effectively dampen unwanted resonances. The same applies to the body as a whole: it is filigreely muted and impeccably finished with classic veneer. The 28-mm silk dome of the branded tweeter is treated with a special impregnation, while the midrange / woofer cone is made of magnesium-silicate polymer, which has proven itself in the world of acoustics. The voice coils are wound on a Kapton frame with a lightweight aluminum wire and are paired with a powerful magnet system to create excellent dynamics and sensitivity. The designers of these loudspeakers have paid great attention to maximizing impedance equalization to minimize the dependence of the speakers on the amplifier.

Sound

The speakers reproduce music freely and naturally, and the beautiful sounding of timbres transforms the soundstage into a natural one, delivering an expressive and balanced sound. Indeed, one gets the impression that you are at a "live" concert and clearly hear where which instrument is. Low frequencies are dense, energetic and distinct. The upper case is subtle, clean and expressive. All the details are well worked out in the sound and there is no color. It is worth noting that the speakers play equally confidently at both low and high volumes.

Measurements

The frequency response is a flat line with a slightly noticeable drift into the HF range. The model is characterized by a broad focus. Total Harmonic Distortion is stable and low, as well as impedance. All in all, excellent results.

Magnat Quantum 753

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

Benefits:

• precise timbres
• clean sound stage

Disadvantages:

This shelf monitor from the German company Magnat Audio-Produkte from the Quantum 750 line is perhaps one of the most impressive speakers in question. To minimize cabinet resonance, the front of the speaker is made of 40mm double-layer slab with a 30mm podium thickness. The legendary German solidity is also emphasized by the subdued, austere matte surface of the case, and only the podium with the front panel playfully shine with careful polishing. The Fmax tweeter (by the way, a proprietary development of Magnat) has a dual fabric compound dome that provides an extended working area. 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 is also thought out - so that the air flow passes freely and reduces potential resonances. The large bass reflex output is located on the back of the monitor. The crossover, assembled from high-quality elements, is almost perfectly "sharpened" for the phase and amplitude of the signal, due to which the resolution of this model is much higher than average.

Sound

Emotional and dynamic performance is characteristic of the monitor sound, with excellent reproduction of the entire spectrum of instrumental timbres - the localization of sound sources is simply excellent. The sound stage is clean, large-scale and deep, the details are worked out as much as possible 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 through" a little. Decreasing the volume decreases the emotionality of the speakers.

Measurements

With minimal frequency response unevenness, 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 THD varies by less than 1% depending on loudness, there is no noticeable resonance. It should be noted that the THD margin is good for low frequencies. The impedance is stable.

Martin Logan Motion 15

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

Benefits:

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

Disadvantages:

• pass a little at low volume

The design of this monitor is pleasing to the eye with its filigree finish and a beautiful protective steel grill on the front panel. And underneath, the highlight is the expensive, ultra-high-resolution ribbon tweeter that delivers crisp, precise and dynamic sound. The column case is assembled from 19 mm MDF plates, and only the aluminum front panel of the monitor is anodized in black, which gives it solemnity and rigor. The diffuser of the midrange / woofer with a long stroke is made in the same color scheme - the appearance of the column is laconic and strict. As for the speakers, their work is coordinated by a crossover with improved characteristics - the manufacturer achieved this effect thanks to the use of polypropylene capacitors and electrolytes with a low loss factor. On back panel the speaker port is brought out.

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

Sound

These speakers have one feature: they do not like working at medium and low volumes - in such cases, only the middle frequencies remain in the range, and the dynamics becomes boring and sluggish. But as the volume increases, elastic and fast basses “cut through” more and more clearly, the upper range becomes clearer. And although the lower middle continues to dominate and does not yield to position, the music is served more energetically and more bitingly. It must be admitted that when the speakers work in any volume mode, no extraneous sounds are heard. Moreover, the overshoot sometimes disappears even where they could be. It should be noted that although this model of "shelf speakers" simplifies the timbres of instruments, a ribbon tweeter with increased sound feed helps the situation and gives the middle-upper range a particularly delicate drawing. Therefore, despite the insignificant listed monitor errors, music lovers appreciate the work of this speaker.

Measurements

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

MK Sound LCR 750

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

Benefits:

• sound focused, clear
• good tone reproduction

Disadvantages:

• truly reflect the shortcomings of studio recording

The laconic design of the M&K Sound speakers 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 an excellent result - today, among professionals, these speakers have rightfully won a reputation as the standard of control acoustics. The 750 Series for home theater meets this flattering characteristic, in which the 750 LCR shelf monitor stands out for its solid dimensions. The column is quite original and stands out favorably even among the models we are considering. Among its main features, we will name a closed case, due to which the bass response is minimized, as well as the installation of two radiators at once - a mid-frequency and a low-frequency one, which significantly increases the dynamic range of the monitor. Another manufacturer's know-how is that a 25 mm silk tweeter mounted at 4.7 ° to the front plane optimizes the dispersion of various frequencies.

Mineral filled polypropylene diffusers combined with the installed phase-focused crossover significantly improved the acoustics of the monitor. For ease of use, threaded holes are prepared on the rear panel of the speaker for one or another monitor mounting option.

Sound

With a 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 audible clearly. And since the 750 LCR does not add the slightest emotional color, this sound may even seem a little dry to an untrained listener. However, it should be so.

Measurements

The deviations of the frequency response of the monitor are so small that there can be no talk of any distortion of the tonal balance. Optimal results are obtained when the column is rotated 30 °. The vanishingly low THD grows very smoothly towards low frequencies, and only at low volume reaches 5%. The impedance is stable. In general, we can state quite a good result.

PSB Imagine B

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

Benefits:

• faithful reproduction of timbres
• smooth dynamics

Disadvantages:

• limited high frequency range

The basis of why the Canadian company PSB has been successfully selling the Imagine line for several years now is the original design development of the monitors, which allowed them to achieve outstanding acoustic parameters of these speakers. And although the originality and elegance of the speakers were duly awarded the prestigious design award RedDot, the sympathies of music lovers around the world were won by the magnificent specifications... Judge for yourself. You will not find right angles in the speaker case, finished with natural veneer - the curved walls of the monitors of the line resemble a bizarre intersection of several cylinders at once, which gives rise to the impression of "cosmic". However, at the same time, the structure looks solid and solid, and all the bends "work" exclusively to achieve the perfect sound, eliminating the appearance of standing waves and the birth of internal resonances. However, the latest technical developments embodied in the PSB speakers contribute to the achievement of this goal. Take a 25mm tweeter, for example. Its titanium dome is equipped with an acoustic lens and is cooled by a magnetic fluid, and a powerful neodymium magnet is used in the column. Another effective engineering solution: the polypropylene midrange / woofer cone 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 constructive solutions, the speakers deliver collected and perfectly balanced sound. The 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 volume, the monitors play in a relaxed and natural way. True, the high frequency range is a little limited, which is why the airiness suffers a little. Speaking of detailing, it should be noted that sometimes monitors lose the smallest nuances, however, even in such cases they please with the expressiveness and richness of the music. The bass is not very deep, but bright enough. Good and medium range - 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 high frequencies will begin to pass. The total harmonic distortion is low over the entire range and shows stability - down to the lower frequency limit. The impedance is stable.

Rega RS1

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

Benefits:

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

Disadvantages:

• the sound is slightly 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 incorporates the most interesting premium solutions, while remaining quite affordable in terms of price. Despite the compactness and small thickness of the panels, the speakers look elegant and rich - primarily due to the careful veneer finishing and strict classic design. The emitters designed and assembled within the walls of 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 optimum damping of acoustic waves. The midbass diffuser is made of paper.

Due to the smooth frequency response of the speaker, it can be integrated with a tweeter. This requires a crossover that has good phase matching. On the rear panel there is a bass reflex port.

Sound

Although the Rega RS1 speaker fairly accurately conveys timbre shades, due to the barely noticeable color, the sound stage loses a little transparency. Again, the upper case is slightly missing, although it is completely clean. All the details are heard, but they are a little hidden. In general, reproducible material is presented clearly and sweepingly. Although the bass is reproduced neatly, it does not always have enough weight. In addition, the localization of sound in the RS1 speakers is a little blurry. But as for complex symphonic music, the monitor does not do so well here, and the sound material becomes more difficult to make out. However, if you listen to music at low volume, the speaker reproduces almost perfectly.

Measurements

In the range of the upper middle and high frequencies, the speakers sound somewhat differently due to the uneven frequency response. This can be corrected by rotating the speaker 30 °. Although the total harmonic distortion is unstable, this indicator has practically no effect on the sound quality - it is less than one percent. The impedance is unstable.

Triangle Color Bookshelf

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

Benefits:

• live open sound
• crisp tone reproduction

Disadvantages:

• some excess bass

As is typical of the French, in the production of loudspeakers, Triangle has combined the highest quality with grace and elegance. This is most vividly confirmed by the stylish Color line, the columns of which delight music lovers with an impeccable lacquered finish. The choice of the buyer is offered monitors in colors of red, black and white. Speaking of the Bookshelf shelf unit, first of all, it should be noted its tweeter with a titanium membrane and a paper cone of the midrange / woofer covered with a special composition. The speaker's originality is complemented by a cloth and wide corrugated suspension, as well as a dust-proof cap made in the form of a bullet. The crossover uses effective technologies, which at one time delighted in the top-end Magellan line - now this know-how is also in the shelf operator. Let's add that the bass reflex output is located on the back of the speaker.

Sound

The monitor produces a very lively and natural sound with very high timbre accuracy. Reproduction of sound material is easy and natural.

The power of the musical sound is incredibly accurate to recreate a live performance. The bass is well designed and pleasantly deep. Sometimes it seems that there is even too much of it. The sound is very clean 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 volume the sound quality does not deteriorate.

Measurements

The frequency response imbalance detected in the high-frequency range is eliminated traditionally - it is enough to turn the column by 30 °. The THD is quite low, but at midrange it becomes higher, although it does not exceed 1%. Distortion in the upper bass is noticeable at high volumes. The impedance is unstable.

Wharfedale jade 3

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

Benefits:

• good attention to detail

Disadvantages:

• dynamics is slightly weakened
• inaccurate localization

What distinguishes the British company Wharfedale is its scrupulous approach to the production of budget lines. For example, to the Jade 3 model - the only three-band monitor in our test. But if other manufacturers consider large and heavy monitors with curved panels to be top brands, the British chose this shape for a shelf speaker solely for pragmatic reasons - auxiliary bulkheads dampen unwanted resonance inside the sealed case and minimize harmful sound coloration. At the 3 kHz border, the aluminum dome tweeter neatly yields to the midrange, whose cone is made of aluminum-cellulose composite. And already in the range of 350 Hz, the main dynamic load is transferred to the woofer, which is equipped with a woven cone made of a reinforced fabric consisting of carbon threads and fiberglass. It is pertinent to note here that this combination of materials turns the diffuser into a flawless piston, which eliminates the unwanted resonance phenomena typical of metal diffusers. We add that the speaker speakers work in a sealed volume, and the ideal linearity phase signal the crossover is the result of computer optimization.

Sound

According to the well-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 bass, as well as the upper register, the speakers give out 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 should be noted that the monitor behaves very well at low volume.

Measurements

The frequency response of the speaker is almost perfectly flat, but in the upper range it behaves unusually: after an unexpected drop, a sharp rise is immediately recorded. The bass range is deep enough. The coefficient of nonlinear distortion pleases: in all ranges it is almost extremely flat and as low as possible. The bass range shows a solid headroom. The impedance is fairly stable.

conclusions

Comparing the measurement results of the speakers in our test laboratory, we came to the conclusion that it is not as interesting to compare bookshelf acoustics as in the old days. All monitors tested showed almost the same flat frequency response with minor deviations that do not affect perception, as well as a very low total harmonic distortion, again not going into the critical zone even in the bass region. It is 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, whatever the body shape of the tested speakers, we did not notice any serious distortions, because every manufacturer now has the opportunity to correctly calculate the damping elements. As a result, the design of all the tested speakers was rated quite high.

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

And if we are talking about a beautiful and comfortable sound, we note that most of the monitors tested meet these criteria as well as possible. For most of the speakers under test, such features are inherent as accurate sound localization, accuracy in the reproduction of timbres, well-discernible bass - everything that is so appreciated by true music lovers. According to the test results, the main advantages of the shelf units should be noted: dense, rich sound in PSB Imagine B, accurate presentation of material in Canton Chrono 503.2, open airy image in Rega RS1, defiantly aggressive pressure in MartinLogan Motion 15. However, there are no winners. Therefore, we give the palm of our test &

If you find impedance minima around 3 ohms, don't fret. Some speaker models from well-known brands have a minimum of 2.6 ohms. One - two models even 2 ohms! On the other hand, there is nothing good about such impedance "dips". Amplifiers get overheated with this kind of load if you listen to music loudly. Distortion of the amplifier grows in the region of the minima of the speaker impedance.

For tube triode amplifiers, low and mid-low frequencies are especially dangerous. Moreover, if the impedance drops below 3 ohms, the output lamps may fail. Output pentodes do not break in such cases.

It is important to remember that the output impedance of the amplifier is involved in setting the speaker filter. For example, if you provide afterburner by 1 dB of the Fc region, tuning speakers with a transistor amplifier, which has almost zero output impedance, then when these speakers are connected to a tube amplifier (typical output impedance ~ 2 Ohm), there will be no trace of the afterburner. The frequency response will be different. To repeat the characteristics achieved with a transistor amplifier, in the case of working with a tube apparatus, you will have to create another filter.

The listener who is capable of developing his own personality eventually comes to understand the value of good tube amplifiers. For this reason, I usually set up an AC with a tube amplifier, and when connected to a transistor amplifier, in series with the AC, I put a 10 W low-induction (no more than 4-8 uH) resistor with a resistance of 2 Ohm.

If you have a transistor amplifier, but do not exclude the possibility of acquiring lamp technology in the future, then connect your speakers during setup and subsequent operation to the amplifier output through the above resistors. Then, when switching to a tube amplifier, you do not need to tune the speaker again, just connect to it directly, without resistors.

For those who cannot get hold of a generator, I recommend finding a test CD with tracks containing test signals for evaluating frequency response. In this case, you will not be able to smoothly change the frequency of the test signal and miss the point of the deepest drop in impedance in the region of its drop. However, even a rough estimate of the impedance frequency response will be helpful. For a rough estimate, pseudo-noise signals in one-third-octave bands are even more convenient than sinusoidal ones. Such signals are on the test CD of the "Salon AV" magazine (# 07 of 2002).

As a last resort, you can do without impedance measurements by limiting the afterburner recoil at the filter cutoff frequency to 1 dB. Under this condition, the impedance is unlikely to drop more than 20%. For example, for a 4 ohm speaker this corresponds to a minimum of 3.2 ohms, which is acceptable.

Please note that you will have to "catch" the parameters of the filter elements required for the desired frequency response correction yourself. A preliminary calculation of test filters is needed to initially not miss "by a kilometer".

Resistors can be added to a simple low-midrange filter head for some frequency response manipulations that may be required when tuning your speakers.

If the average sound pressure level of this speaker is higher than the corresponding parameter of the tweeter head, a resistor must be connected in series with the speaker. Switching options are shown in Fig. 6a and 6b.

The value of the required decrease in the recoil of the LF-MF head, expressed in dB, is denoted by the symbol N. Then:

Where Rd is the average value of the speaker impedance.

You can use the following information instead of calculations:

Table 1

Where V us is the effective value of the voltage at the amplifier output. V d - the same on the dynamics. V d is less than V c, due to the attenuation of the signal by the resistor R 1. In addition, N \u003d N HF - N LF, where N LF and N HF are the sound pressure levels developed by the LF and HF heads, respectively. These levels are averaged over the bands reproduced by the bass and treble drivers. Naturally, N LF and N HF are measured in dB.

An example of a quick estimate of the required value of R1:

For N \u003d 1 dB; R1 \u003d Rd (1.1 - 1) \u003d 0.1 Rd.

For N \u003d 2 dB; R1 \u003d Rd (1.25 - 1) \u003d 0.25 Rd.

For N \u003d 6 dB; R1 \u003d Rd (2 - 1) \u003d Rd.

A more specific example:

Rd \u003d 8 Ohm, N \u003d 4 dB.
R1 \u003d 8 ohms (1.6 - 1) \u003d 4.8 ohms.

How to calculate the power of R1?

Let R d be the rated power of the LF-MF loudspeaker, PR 1 - the allowable power dissipated by R 1. Then:

It is not necessary to impede the removal of heat from R 1, that is, it is not necessary to wrap it with electrical tape, fill it with hot glue, etc.

Features of preliminary filter calculation with R1:

For the circuit in Fig. 6b, the values \u200b\u200bof L 1 and C 1 are calculated for an imaginary speaker, the total resistance of which is R Σ \u003d R 1 + R d. In this case, L 1 is greater and C 1 is less than that of a filter without R 1.

For the circuit in Fig. 6a - the opposite is true: the introduction of R 1 into the circuit requires a decrease in L 1 and an increase in C 1. It is easier to calculate the filter according to the scheme Fig. 6b. Use this particular scheme.

Additional correction of the frequency response using a resistor:

If, in order to improve the frequency response uniformity, it is necessary to reduce the filter suppression of signals above the cutoff frequency, you can apply the circuit shown in Fig. 7.

The use of R 2 in this case leads to a decrease in recoil in F with. Above F c, the recoil, on the contrary, increases in comparison with the filter without R 2. If you need to restore close to the original frequency response (measured without R 2), you should reduce L 1 and increase C 1 in the same proportion. In practice, the range of R 2 is in the range: R 2 ~ \u003d (0.1-1) * R d.

Frequency response correction:

The simplest case: on a fairly uniform characteristic, there is a zone of overestimated recoil ("presence") in the midrange. You can apply a corrector in the form of a resonant circuit (Fig. 8).

At resonance frequency

The circuit has a certain impedance value, in accordance with the value of which the signal on the speaker is attenuated. Outside the resonant frequency, attenuation is reduced, so the circuit can selectively suppress "presence". It is possible to roughly calculate the values \u200b\u200bof L 2 and C 2 depending on F p and the degree of suppression of N 2 (in dB) as follows:

It is convenient to use Table 1. I will draw it differently:

Example. It is necessary to suppress "presence" with a center frequency of 1600 Hz. The speaker impedance is 8 ohms. Suppression level: 4 dB.

The specific shape of the frequency response of the loudspeaker may require more complex correction. Examples in Fig. nine.

The case in Fig. 9a is the simplest. It is easy to select the parameters of the correction contour, since the "presence" has a "mirror image" shape of the possible filter characteristic.

In Fig. 9b shows another possible option. It can be seen that the simplest contour allows one to "exchange" one big "hump" into two small ones with a small dip in the frequency response in addition. In such cases, you must first increase L 2 and decrease C 2. This will expand the suppression band to the desired limits. Then you should bypass the circuit with a resistor R 3, as shown in Fig. 10. The value of R3 is selected based on the required degree of suppression of the signal supplied to the speaker in the band determined by the parameters of the circuit. R 3 \u003d R d (Δ - 1)

Example: It is necessary to suppress the signal by 2 dB. Speaker - 8 ohms. Refer to Table 1. R 3 \u003d 8 ohms (1.25 - 1) \u003d 2 ohms.

How the correction occurs in this case is shown in Fig. 9c.

A combination of two problems is quite typical for modern loudspeakers: "presence" in the 1000-2000 Hz region and some excess of the upper mids. A possible view of the frequency response is shown in Fig. 11a.

The method of correction that is most free from harmful "side" effects requires a slight complication of the contour. The corrector is shown in Fig. 12.

The resonance of the L 2, C 2 circuit is needed, as usual, to suppress the "presence". Below Fp, the signal passes almost losslessly to the speaker through L 2. Above F p, the signal goes through C 2 and is attenuated by resistor R 4.

The corrector is optimized in several stages. Since the introduction of R 4 weakens the resonance of the circuit L 2, C 2, then initially you should choose L 2 more and C 2 less. This will provide excessive suppression on F p, which is normalized after the introduction of R 4. R 3 \u003d R d (Δ - 1), where "Δ" is the amount of suppression of signals above F p. "Δ" is selected in accordance with the excess of the upper middle, referring to Table 1. The stages of correction are conventionally illustrated in Fig. 11b.

In rare cases, a reverse effect on the frequency response slope is required using a correction circuit. It is clear that for this R 4 must move to the chain L 2. The diagram in Fig. thirteen.

The problematic frequency response and its correction for this case is shown in Fig. fourteen.

With a certain combination of L2, C2 and R4 values, the corrector may not have much suppression at Fp. An example of when exactly such a correction is needed is shown in Fig. fifteen.

If necessary, you can use the second order filter and the correction contour together. Switching options are shown in Fig. sixteen.

with the same element ratings, option a) provides a greater return at medium frequencies and at the cutoff frequency. In principle, by selecting the values \u200b\u200bof the elements, you can almost level the frequency response of the speaker for both filter options. For some reason, about which to talk for a long time, I advise you to use option a) more often. Sometimes a very pronounced "presence" requires the use of option b). The joint work of the filter and the corrector is illustrated in Fig. 17.

Let's consider filters for high-frequency speakers.

For high-frequency drivers much more often than for low-frequency speakers, we apply a first-order filter, that is, just a capacitor connected in series with the loudspeaker. The fact that such a simple filter introduces a noticeable slope in the frequency response of the speaker does not have such a detrimental effect on the sound as in the case of the woofer. First, this slope is often partially compensated by a smooth complementary (complementary) slope of the frequency response of the woofer in the same frequency range. Secondly, some "dip" in the area of \u200b\u200bthe lower top (3-6 kHz) is quite acceptable according to the results of subjective examinations. The possible course of the frequency response of the high-frequency speaker without a filter, with a filter and together with a low-frequency speaker is shown in Fig. eighteen.

You should not be afraid of experimenting with the connection of the HF speaker in antiphase with the LF loudspeaker. Sometimes this is one of the few ways to get good sound. The most likely results of reversing the polarity of the RF head are shown in Fig. 19

Acoustic system (General concepts and frequently asked questions)

1. What is a speaker system (AC)?

This is a device for efficient sound emission into the surrounding space in an air environment, containing one or more loudspeaker heads (GG), 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 (LH)?

It is a passive electro-acoustic transducer designed to convert audio signals from electrical to acoustic form.

3. What is a passive converter?

It is such a transducer 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 emission of HG sound. In other words, in most cases, AO is a speaker cabinet, which can have the form of an acoustic screen, box, horn, etc.

5. What is a single-way speaker?

In fact the same as broadband. This is an AC, all of whose GGs (usually one) operate in the same frequency range (i.e., filtering the input voltage using a PF, as well as the filters themselves are absent).

6. What is a multi-way speaker?

This is an AU, the GG of which (depending on their number) operate in two or more different frequency ranges. However, a direct calculation of the number of GGs in the AU (especially the release of previous years) may not say anything about the real number of bands, since several GGs can be allocated to the same band.

7. What is an open speaker?

This is an AS in which the effect of air elasticity in the AO volume is negligible, and the radiations of the front and rear sides of the HG mobile system are not isolated from each other in the LF region. It is a flat screen or a box, in which the back wall is either completely absent, or has a number of through holes. The front wall (in which the GG is mounted) and its dimensions have the greatest influence on the frequency response of the AC with an open-type AO. Contrary to popular belief, the open-type AO side walls have very little effect on the characteristics of the AO. Thus, it is not the internal volume that is important, but the area of \u200b\u200bthe front wall. Even with its relatively small size, bass reproduction is significantly improved. At the same time, in the area of \u200b\u200bthe midrange and, especially, the high-frequency screen no longer has a significant effect. A significant drawback of such systems is their susceptibility to acoustic "short circuit", which leads to a sharp deterioration in the reproduction of low frequencies.

8. What is a closed type speaker?

This is an AC in which the elasticity of the air in the volume of the AO is commensurate with the elasticity of the mobile system of the GS, and the radiation of the front and rear sides of the mobile system of the GS are isolated from each other in the entire frequency range. In other words, this is a speaker with a hermetically sealed housing. 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 the fact that the resonant frequency of the HG mobile system increases, as a result of which the reproduction of frequencies below this frequency deteriorates.

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

The desire to obtain a fairly good reproduction of low frequencies with a moderate volume of AO is quite well achieved in the 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 air volume in the AO resonates at some frequency with the air mass in the hole or tube. This frequency is called the resonant frequency of the FI. Thus, the AS as a whole becomes, as it were, consisting of two resonant systems - a mobile system of the GG and an AO with a hole. With a correctly selected ratio of the resonant frequencies of these systems, the reproduction of low frequencies is significantly improved in comparison with closed-type AO with the same AO volume. Despite the obvious advantages of AC 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 required effect, the FI must be correctly calculated and adjusted.

10. What is bass-reflex?

The same as FI.

11. What is a crossover?

The same as a crossover or crossover filter.

12. What is a transition filter?

This is a passive electrical circuit (usually consisting of inductors and capacitors) that turns on before the input signal and ensures that only the frequencies that they are supposed to reproduce are supplied to each HG in the AC.

13. What are "orders" of transient filters?

Since no filter can provide an absolute cutoff of the voltage at a given frequency, the BPF is calculated at a certain crossover frequency, beyond which the filter provides a selected amount of attenuation, expressed in decibels per octave. The amount of attenuation is called the slope and depends on the PF construction scheme. Without going into too much detail, we can say that the simplest filter - the so-called first-order PF - consists of only one reactive element - a capacitance (cut off the low frequency if necessary) or inductance (cut off the high frequency if necessary) and provides a steepness of 6 dB / oct. Twice the slope - 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, it is a doubling or halving of the frequency.

15. What is a speaker work plane?

This is the plane in which the radiating openings of the HG AC are located. If the HG multiband speakers are located in different planes, then the one in which the radiating holes of the HF GG are located is taken as the working one.

16. What is an AC Work Center?

This is a point on the work plane from which the distance to the AC is measured. In the case of single-sided speakers, it is taken as the geometric center of symmetry of the radiating hole. In the case of multi-lane speakers, it is taken as the geometric center of symmetry of the radiating holes of the HG HF or the projections of these holes onto the working plane.

17. What is the AC working axis?

It is a straight line through the AC work center and perpendicular to the work plane.

18. What is the nominal impedance of the speaker?

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

19. What is speaker impedance?

Without delving into the fundamentals of electrical engineering, we can say that impedance is called the TOTAL electrical resistance of the AC (including crossovers and GG), which, in the form of a rather complex dependence, includes not only the usual resistance R (which can be measured with an ordinary ohmmeter), but also and reactive components in the form of capacitance C (frequency-dependent capacitance) and inductance L (frequency-dependent inductive reactance). 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 AC it often looks like a "pig's tail") in the coordinates "amplitude-phase-frequency". Precisely because of its complexity, when one speaks of impedance as a numerical value, one speaks of its MODULE. Of greatest interest from the point of view of research are the projections of the "pig's tail" on two planes: "amplitude-from-frequency" and "phase-from-frequency". Both of these projections, presented on one graph, are called "Bode graphics". The third projection "amplitude-versus-phase" is called the "Nyquist plot." With the advent and spread 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 hung on it, and what is the need for current. Therefore, if we assume that the amplifier driving the GG AC in motion is a voltage source, then the impedance of the AC will clearly show what the current consumption will be. As already mentioned, the impedance is not only reactive (i.e. characterized by a non-zero phase angle), but also changes with frequency. Negative phase angle, i.e. when the current is ahead of the voltage, it is due to the capacitive properties of the load. The 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 a typical speaker? The DIN standard requires that the speaker impedance does not deviate from the specified rating by more than 20%. However, in practice, things are 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 LAMP amplifier with an output impedance of the order of several ohms (!) Is introduced into the game, the result can be very disastrous - the coloration of the sound is inevitable.
The loudspeaker impedance measurement is one of the most important and powerful diagnostic tools. According to the impedance graph, you can say a lot about what the speaker data is, without even seeing them in your eyes or hearing them. Having an impedance graph in front of your eyes, you can immediately tell what type of speaker data is - closed (one hump in the bass region), bass reflex or transmission (two humps in the bass region) or some kind of horn (a sequence of evenly spaced peaks). It is possible to judge how well the bass (40-80Hz) and the lowest bass (20-40 Hz) will be reproduced by one or another speaker by the shape of the impedance in these areas, as well as by the quality of the humps. The "saddle" formed by two peaks in the low-frequency region, typical for 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 HG drops by 6 dB, i.e. approximately 2 times. From the impedance plot, you can also understand whether there are resonances in the system, and what is their nature. For example, if measurements are taken 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, and 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 be ahead of it by the 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 goes to zero. Therefore, knowing the "passport" 8 (or 4) ohms as the nominal resistance does NOT give absolutely nothing. Depending on the phase angle of the impedance, which will be different at each frequency, one or another speaker 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 cope with the loudspeakers just because at TYPICAL loudness levels acceptable in TYPICAL home conditions, TYPICAL speakers DO NOT require more than a few watts from a TYPICAL amplifier.

20. What is the GH rated power?

This is a given electrical power at which the harmonic distortion of the GG should not exceed the required one.

21. What is GG maximum noise power?

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

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

In general, a speaker with a higher nominal impedance is more preferred, since such a speaker provides 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 a speaker?

This is her response to the “perfect” impulse.

27. What is an “ideal” impulse?

This is an instant (rise time is 0) voltage rise to a certain value, "stuck" at this constant level for a short period of time (say, a fraction of a millisecond) and then an instant drop back to 0V. The width of such a pulse is inversely proportional to the bandwidth of the signal. If we wanted to make the 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 the speaker?

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

29. What is a step signal?

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

30. What is coherence?

This is the coordinated course of several oscillatory or wave processes in time. With regard to the AU, it means the simultaneous arrival of signals from different GGs to the listener, i.e. actually reflects the fact that the phase integrity of information is preserved.

31. What is the polarity of the HS?

This is a certain polarity of the electric voltage at the terminals of the GG, which causes the movement of the mobile system of the GG in a given direction. The polarity of a multiband speaker is determined by the polarity of its LF HG.

32. What is the connection of HS in absolute positive polarity?

This is the connection of 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 gap of the magnet, i.e. air compression takes place.

33. What is the frequency response of the speaker?

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

34. What is the polar characteristic?

This is a graphical dependence in 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 the 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 mids
• 2.56-5.12kHz - mid
• 5.12-10.24kHz - upper mid
• 10.24-20.48kHz - top

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

Attenuators. These are sometimes called acoustic equalizers.

37. What is the purpose of the attenuators?

Depending on the calibration, increase and / or decrease the voltage applied to one or another HG, which, accordingly, leads to an increase and / or decrease in the sound pressure level in a certain frequency range. Attenuators do not change the shape of the frequency response of individual HGs, but change the GENERAL view 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 delivered by the speaker to the consumed ELECTRIC power. Those. the question is formulated as follows: if I put 100 electric watts in the speaker, how many watts of acoustic (sound) will I get? And the answer to it is "a little, a little." The efficiency of a typical moving coil generator is in the order of 1%.
Efficiency is usually given in the form of the sound pressure level created by the speaker at a given distance from the working center of the speaker at a power input of 1 W, i.e. in decibels per watt per meter (dB / w / m). Nevertheless, knowledge of this value cannot be called useful in any way, since it is extremely difficult to determine what a 1 W input power is for given specific speakers. Why? Because there is a dependence on both impedance and frequency. Feed a speaker with an impedance of 8 ohms at 1 kHz with 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" \u003d "voltage squared" / "resistance "). And here comes a big "BUT" - not only is the speaker impedance is variable and depends on the frequency, at lower frequencies it can drop 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 200Hz, we will thus 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 at 200 Hz.
And why, in fact, does efficiency matter at all? If half a century ago, audio engineers were very concerned with the problem of power transmission (and telecommunications engineers are interested in this to this day!), Then with the advent of semiconductor devices, audio amplifiers began to behave more or less like sources of "constant" voltage - they support the same output voltage, regardless of what load is suspended on it, and what is the consumed current. That is why it is NOT the efficiency that comes to the fore, but the SENSITIVITY for voltage, 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 speaker center at a voltage at the terminals of 2.83 volts (i.e. the voltage required to dissipate 1 watt across an 8 ohm resistor).
The advantage of specifying sensitivity instead of efficiency is that it always remains constant regardless of the AC impedance, since the amplifier is assumed to always be able to supply enough current to maintain 2.83 Volts. The closer the speaker module of impedance approaches to that of a pure 8-ohm resistor, the higher the degree of equivalence of these two criteria. However, in the case when the impedance of the speaker is significantly different from 8 Ohm, the benefit of knowing the efficiency is nullified.
The AC voltage sensitivity is important in particular when selecting a pair "amplifier - AC". If you have a 20W amplifier, you better think about a VERY high gain speaker, as otherwise you will never listen to loud music. And vice versa, 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 you spend $ 10,000 on an amplifier with a power of 600 Watts with these speakers would be a waste of money.
However, while it is quite obvious to everyone that voltage sensitivity is more than an important parameter of the speaker, many people still do not want to adjust it properly. The problem is that the speakers tend to be characterized by an uneven frequency response, and therefore finding the peak value among all its slaves and the statement from the series "Since the speaker plays the loudest at this frequency, then this is the sensitivity!" Is for the marketing departments of companies that produce speakers by the GREAT TEMPTATION.
So what is the real sensitivity of typical speakers? It turns out to be 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 types, 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 is ALWAYS costly. And the overwhelming majority of speaker designers are constrained by the BUDGET framework, which means only that they will ALWAYS seek compromises, saving on the size of magnets, the shape of the 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 the speaker on the spikes?

It is highly desirable.

40. What are thorns for?

In order to maximally reduce the transmission of vibration of the acoustic design of the speaker to objects in contact with it (floor ceilings, shelves, for example). The effect of using thorns is based on a radical reduction in the area of \u200b\u200bcontact surfaces, which is reduced to the area of \u200b\u200bthe tips of the thorns / cones. It is important to understand that installing the speaker on the spikes does NOT eliminate body vibrations, but only reduces the effectiveness of their further propagation.

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

The most unfavorable support for the speaker is its installation on 3 (three) metal spikes / cones, of which one is located in the middle at the back wall, and the other two are at two front corners. This arrangement of the speaker "gives free rein" to almost ALL body resonances.

42. How to minimize speaker cabinet resonances?

The BEST way to REDUCE the speaker cabinet resonances caused by how and on what they are installed is to use a vibration-absorbing material like a dense padding polyester as a pad.

43. When is bi-wiring / bi-amping justified?

Bi-wiring does NOT have a physical basis and, as a result, does NOT have ANY audible effect, and therefore is absolutely meaningless.
Bi-amping is of two types: false and literate. You can see what this means. Despite the existence of a physical validity of the application, the effect of bi-amping is vanishingly small.

44. Does the exterior of the speaker (vinyl, natural veneer, powder paint, etc.) affect the sound?

No, the sound is NOT affected in any way. Only at the PRICE.

45. Does the interior decoration (foam rubber, mineral wool, synthetic winterizer, etc.) affect the sound of the speaker?

The purpose of ANY "stuffing" of a speaker is the desire or need to suppress standing waves that occur within any acoustic design, the presence of which can seriously degrade the performance of the speaker. Therefore, all the "influence" of the interior decoration on the sound comes down to how well the decoration prevents the formation of standing waves. The presence of in-body resonances can be assessed, for example, by measuring impedance with high frequency resolution.

46. \u200b\u200bDo grills and other decorative framing of the front panels of the 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 one's own eyes during measurements. The only question is, can you still hear it? In some cases, when this influence exceeds 1dB, it is quite possible / real to hear it in the form of some "roughness" of the sound, as a rule, in the HF region. The influence of cloth "decorations" is minimal. As the rigidity of the "decorations" increases (especially for metal products), the degree of visibility increases.

47. Are there real benefits to rounded corners?

There are none.

48. Is the special shape of the dust caps on the speakers a necessity or a decoration?

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

49. What is piston mode?

This is a mode in which the entire surface of the GG diffuser moves as a whole.
It is very convenient to explain this concept using the example of a broadband GG. In the LF region, the rate of change in the phase of the signal in the voice coil is less than the rate of propagation of mechanical excitation in the material of the diffuser, and the latter behaves as a 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, the developers of the GG seek to expand the area of \u200b\u200bthe piston action of the diffuser towards the HF by imparting a special shape to the generatrix of the cone. For a properly designed cellulosic cone, the area of \u200b\u200bthe piston action can be roughly defined as the wavelength of sound 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 rate of propagation of mechanical excitation in the material of the diffuser, and bending waves appear in it, the diffuser no longer vibrates as a whole. At these frequencies, the damping index of mechanical vibrations in the material of the diffuser is not yet large enough and the vibrations, reaching the diffuser holder, are reflected from it and propagate along the diffuser back towards the voice coil.
As a result of the interaction of direct and reflected oscillations 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 for an not optimally designed diffuser.
At HF, the attenuation index of mechanical vibrations in the material of the diffuser increases and standing waves are not formed. Due to the weakening of the intensity of mechanical vibrations, the radiation of high frequencies occurs mainly in the area of \u200b\u200bthe diffuser adjacent to the voice coil. Therefore, to increase the reproduction of HF, horns are used, fastened to the mobile system of the GG. To reduce the unevenness of the frequency response, various damping (increasing the damping of mechanical vibrations) additives are introduced into 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 makes too different requirements for the GG, which one single GG (broadband) is not able to fully satisfy even 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 HG with increasing frequency. Ideally, GGs in an AU should not only work in a piston mode each, which, generally speaking, entails a sharp increase in the total number of GGs in the system (and, accordingly, an increase in the number of transient filters, which automatically causes a sharp increase in the complexity and cost of the product), but also to be characterized by the omnidirectionality of radiation, which is possible only 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 show good dispersion.
As long as the frequency is low enough, this condition is met and the HG is omnidirectional. With increasing frequency, the radiation wavelength decreases and, sooner or later, becomes COMPARABLE with the linear dimensions of the GG (diameter). This, in turn, leads to a sharp increase in the directivity of the radiation - the HH eventually begins to radiate like a searchlight, straight ahead, which is completely unacceptable. Take, for example, a 30cm diameter burdock bass. At a frequency of 40Hz, the radiation wavelength is 8.6m, which is 28 times its linear size - in this area such a woofer is omnidirectional. At a frequency of 1.000Hz, the wavelength is already 34cm, which is literally COMPARABLE with the diameter. At this frequency, the dispersion of such a woofer will be radically worse, 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 response of the speaker in the specified region, which has the shape of a dip or gorge. The failure is due to the fact that while the LF GG in this area becomes sharply directed, the buzzer (usually 1.5-2 cm in diameter) in the same area is practically omnidirectional.
In particular, this is why a good 3-way speaker is always BETTER than a good 2-way speaker.

51. What is variance?

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

52. What is a radiation pattern?

Same as polar characteristic.

53. What is the frequency response unevenness?

It 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 the peaks and dips of the frequency response already 1/8 octave are not taken into account. However, this approach is not progressive, since the presence of serious peaks and dips (albeit narrow ones) on the frequency response indicates poor performance of the diffuser, the presence of standing waves in it, i.e. about the defect of GG.

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

Since transient filters in ANY case change (or, as they say, rotate) the phase of the input signal - the higher the filter order, the greater the phase shift - then in some cases the situation develops in such a way that in the transition zone signals from different HGs "meet" in antiphase, which leads to serious distortion of the frequency response, bearing the form of steep dips. Turning 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 the equalization of the frequency response in the transition zone.

55. What is cumulative spectrum attenuation (CLC)?

This is a set of axial frequency response of the speaker, obtained with a certain time interval with the attenuation of a single pulse applied to it, and displayed on one three-dimensional graph. Since, being an electromechanical system, the AC is an "inertial" device, the oscillatory processes continue for some time even after the termination of the impulse, gradually damping in time. Thus, the graph of the cumulative spectrum attenuation clearly shows which areas of the spectrum are distinguished by increased post-pulse activity, i.e. allows you to identify the so-called delayed resonances of the speaker.
The "cleaner" the graph of the loudspeaker GLC looks in the region above 1 kHz, the higher the chance that such loudspeakers will be subjectively assessed by listeners as having "great transparency", "no graininess" and "sound purity". Conversely, speakers that are said to sound "grainy" or "harsh" are almost 100% likely to be characterized by strong "ridging" of the KZS graphs (although, of course, factors such as nonlinear distortion and frequency imbalance can also play his role).

56. What are the names of the peculiar dividers of bizarre shape or geometry, which are placed on top of some GG?

Phase shifters, deflectors, acoustic lenses.

57. Why are phase shifters used?

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

58. Does the material from which the GG cone 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 so on, 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, then, is the point of using DIFFERENT materials in the manufacture of diffusers? The point is that any competent developer seeks, in fact, only one goal: to use for the production of diffusers such a material that would simultaneously satisfy the following requirements: it would be tough, lightweight, durable, well-damping, 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 on approaches to reducing the audible coloration of the sound that appears due to resonances arising in the diaphragms.

59. Is it true that good, "real" bass can be obtained only on speakers with large bass-mugs about 30 centimeters in diameter?

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

60. What, then, is the meaning of big bass-mugs?

A large woofer has a larger surface area and therefore drives more air than a smaller woofer. Consequently, the sound pressure developed by such a woofer is also higher, which directly affects the sensitivity - speakers with large woofers, as a rule, have a very high sensitivity (usually above 93dB / W / m).

12/25/2005 Globalaudio

I myself faced this topic for a long time, but decided to figure it out when I began to seriously engage in acoustic measurements. I dug a little on the internet, talked a little with friends and in the end this article was drawn, which I hope will help in our difficult business.

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

Example of speaker impedance:

Unlike a resistor, the electrical resistance of which characterizes the ratio of voltage to current across it, an attempt to use 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 - to infinity ...

Resistance correctly describes the properties of the coil and capacitor only in 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 equal to zero. This behavior is no longer described by the resistance, since the 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 a certain characteristic for reactive elements, which, under any conditions, would 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 turn out to be connected by a certain 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 representation that allows simultaneously taking into account both the amplitude and phase characteristics of signals and systems.

In general, the value of the total electrical resistance (impedance) of the speaker system will not tell the buyer about anything related to the sound quality of this or that 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 is lower than the recommended amp load, the sound may be distorted or short circuit; if higher, the sound will be much quieter than with the recommended impedance.

If you imagine a speaker system as a four-port device to the input terminals of which a signal generator is connected, then depending on the frequency of the applied 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 the other. The more complex the filter on your speaker system, the more more changes in impedance.

The speaker impedance is frequency dependent. But when using an amplifier with current feedback - ITUN (voltage controlled current source) or semi-ITUN (popularly such an amplifier is widely known asMF 1), such an indicator as dependence on frequency, by itself disappears... Because there is no longer any dependence on resistance at different frequencies, which means that the current passing through the coil no longer changes so much. It works only if the current does not exceed certain values... But I will add that ITUN and MF1 (semi-ITUN) are not the same thing, since ITUN does not have only current feedback, and MF1 has a combined current and voltage coupling. Therefore, the MF1 can be called "semi-ITUN", as it combines combined feedback.

I would like to draw your attention to the fact that ITUN has slight boost at high frequencies, and this is due precisely to the fact that the current that passes through the HF speaker coil no longer "falls through" and the speaker seems to play more evenly. Exactly the same effect (raising high frequencies) is present in MF1 for the same reason, but it already affects the low frequencies less, thus,MF 1 is more versatile in terms of AU and complex load, relatively pure ITUN.

And in the case of INUN (voltage controlled voltage source), which are the vast majority of amplifiers, at the moment of low resistance, it can create such a current that will damage the output stage due to overcurrent. Otherwise, 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 distortion, and several times.

Once again, a memo to 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 a little knowledge in electrical engineering.

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

I want to make a special thanks DTSy, in help writing an article and solving some of the nuances. Well, as usual, the article was prepared by LDS , which is specially written for the site website.