POWER... WHO IS THIS?
“I have 200W speakers and a 4 x 50 radio. Will they play together?” Yes, they will, don't worry. But it will be even better if you still understand what is meant by both power and watts. "Power", according to the school definition - the work produced per unit of time, for our purposes the definition is almost useless. We are more comfortable in a different, albeit unusual way: power is the amount of energy converted into the form we need in the same unit of time. It's always about transformation, the energy doesn't go anywhere, that's her habit. The amplifier (albeit in the radio) receives electrical energy ready for use in the form of direct current from the on-board network of the car and converts it into electrical, but in the form of alternating current, representing a sound signal. All? No, about half, the rest goes into the heat given off to the air by small radiators on the back of the radio or large ones, “throughout the body” of a separate, external amplifier.

The speaker (albeit pretending to be a "speaker") receives electrical energy in the form of alternating current and converts it into mechanical energy, now in the form of long-awaited sound vibrations. All? How can I say ... Not really. The efficiency of the speaker (since we went the school way: the ratio of the produced sound power to the received electrical power) almost never exceeds 0.5%. Where do the other 99.5% go? And there, in the heat, in general, any device created by the human mind (as well as the will of the Almighty) produces heat plus something else. In terms of energy conversion, the speaker is 99 percent identical to a soldering iron with a penny. And in the remaining half of a percent - everything: basses, highs, detail, and brilliant musicians. It's a shame? Yes, but nothing better somehow came up with.

And here it is, the main difference between the power of the amplifier and the power of the speaker: the amplifier can be considered to produce it. And the speaker - consumes, not producing in exchange, as we just found out, almost nothing.

And when we talk about the power of the amplifier, then we are talking about what HE GIVES. And when about the power of the speaker - then about what HE TAKES. How much does one give and how much does the other take? In order of arrival:
HOW MUCH GIVES?
Here is the amplifier. Let the one in the radio do not give a damn, then you will feel the difference. What is his power? Yes, whatever, it all depends on what level of the signal is at the input, roughly speaking - in what position the volume control. The output might be 1 watt, maybe 10, maybe 50, maybe... Wait, there must be a limit. Of course, but we did not ask what is the MAXIMUM power. And everyone has their own maximum. It is determined by what the highest AC voltage the amplifier can produce at its output when a load is connected to the output, in the form of a speaker with some kind of resistance. The output power is simply determined: as the value of this voltage squared and divided by the load resistance. We connected a voltmeter and a load to the output, an alternating voltage was applied to the input, for the convenience of measuring power - at any one frequency, and we look. The output is 2V when a 4 ohm load is connected to it. With such measurements, of course, not acoustics are connected to the output, but its equivalent in the form of a resistor, otherwise the ears will wilt. They raised it, divided it and got: the output power is exactly 1 watt. There is a small ambush here, due to the fact that we are talking about alternating voltage, the value of which can be measured in different ways. The most commonly used scale is RMS. In Russian, this word is long, so the English abbreviation RMS (root mean square) has taken root, meaning the same. In order not to go into details, it is enough to remember: for a sinusoid, the RMS voltage value is 1.41 times less than the amplitude value, that is, the root of two. The power indicated in RMS watts is the one that was obtained when the voltage was taken in RMS during the calculation, which is logical. And if we take the voltage amplitude, then the power, firstly, will be called peak, and secondly, it will become exactly twice as much as RMS.

We return to the amplifier. One watt is not serious, we add it at the input. How long will the output voltage rise and what will stop it? Will stop its signal limiting. The amplifier is powered by a constant voltage, and what appears as a variable at its output cannot be greater than the supply voltage in amplitude. There is no more. And if we observe the signal at the output, then at some point the tops of the previously graceful wave will be cut off, there the half-wave wanted to go through the upper limit, the supply voltage. And broke off. We roll back the signal at the input until the restriction disappears, and look at the signal range. It is slightly less than the full supply voltage, because something is lost in the output stages of the amplifier. If the amplifier is powered (as in the notorious "radio tape recorder") from the car's on-board network, then the lower half-wave will come close to zero, and the upper one - to the level of 12 V. What happens? The amplitude, we will assume, is 6 V in each direction, we raise-divide and get a fabulous figure of 4.5 watts. Check if you're not lazy. It turns out that in all science this is the maximum value of the output power of a radio tape recorder powered by 12 V? And that was twenty years ago. And so it is now, if you buy some Vitek or Eurotec for 400 rubles, our colleagues from the Kyiv magazine "FOR Z" conducted a series of such experiments not so long ago, saving us from this sad need. Fortunately, a solution has recently been found that made it possible, if not to reach the formidable 4 x 50, then in any case, to get away from the mournful 2 x 4.5. This is the bridging of amplifiers, which is now used in all car head units, with the exception of the sound sediment like the one mentioned (for example, nothing personal).

When bridged, two amplifiers operate on one load, connected so that the amplitude of the sinusoid at the output doubles. According to the method already told you to calculate the output power, this will be four times more than 4.5 W, because the voltage is squared, therefore - 18. Approximately this value has the maximum output power of all the head units we have ever tested (in each of the four channels, of course).

Where do the famous 4 x 40 W come from, then turned into 4 x 45, 4 x 50 and so on? What is this, pure lies? Somehow it does not fit with the image of eminent and more than respectable manufacturers of equipment, but these numbers adorn the front panels of all brands: Alpine, Blaupunkt, Clarion and so on in Latin alphabetical order. After all, when it comes to individual amplifiers of the same companies, everything becomes honest and correct, there were enough opportunities to make sure over the years. There are two tricks here, the first is technical, and only the second is marketing. The technical trick lies in the fact that in modern "heads" amplifiers of the so-called "class H" are used, there is a special circuit that can give the output stages an increased supply voltage for a short time. There is a capacitor and, while everything is quiet, it is charging. And at loudness peaks, it turns out to be connected in series with the power supply of the output stage, and the peak jumps without distortion, without touching the top of the 12 V ceiling. But this is if the peak of the signal level is very short, for example, the first moment of hitting the drum. Further, of course, the energy supply dries up, but the deed has already been done, even two things: indeed, for a brief moment, the maximum power became much more possible during continuous operation, and secondly, it became possible to mention this. Without focusing too much on the conditions under which the maximum output power became such. To the credit of respectable companies (see the alphabetical list above), it must be said: often in the table of technical characteristics on the last page of the instructions, continuous power is also given, indicating that this is in watts RMS, and indicating what the supply voltage was, as a rule , 14.4 V, because in this case the "ceiling" for the output sinusoid rises, and then exactly 18 - 20 W per channel appear in this line, the cases of entering the third ten are rare.

Why aren't they written on the front panel? Consider it a tradition, like the price of oil in dollars per barrel, and for gold - per troy ounce. Moreover, as we found out, formally they have the right. Now quickly answer the security question: when was the last time you saw car speakers that were labeled LESS than 18 watts? Therefore, any talk about “selecting” acoustics for a radio or CD receiver in terms of power by comparing what is written on the boxes with one and the other does not make any sense. “But how,” you might ask, “did my garage neighbor’s 100-watt mugs wheeze and burn out?” And this, my dears, happened not because there was a lot of power of the head unit, but because there was little MAXIMUM power.
WHERE THE POWER ENDS
Everyone sees, but few people pay attention: where, seriously, and not for beauty, in troy ounces, the maximum output power is indicated (for example, on the last page of the instructions), next to it is the value of the coefficient of non-linear distortion corresponding to the given value. With us, this is abbreviated in kn, and in the English-language instructions it will look like THD and some number with a percent sign. We recall (or learn) what non-linear distortions are. They are sometimes called harmonic (THD and stands for Total Harmonic Distortion - total harmonic distortion), which is more correct. The bottom line: when the amplifier works perfectly, the output signal will differ from the input signal only in amplitude, and in direct proportion. Let's add coke. The output voltage increased by a little over a volt, when suddenly a whole fence of harmonics grew on the spectrogram, which means that the output signal came dangerously close to the maximum possible amplitude. The amplitude of the harmonics seems to be small (the upper scale is strongly stretched vertically), and in total they add up to a small total: less than half a percent. But: this fence was not in the sound before, but now it is. We add more - and now, we have sailed: on the sinusoid, the distortions of the form became clearly visible, exactly those that we expected - you can’t jump above the power supply. And the output signal has become monstrous, in real life we ​​will hear, in addition to the pure tone of 250 Hz, a lot of new things: both 500 and (especially) 750 Hz, and further to the most impossible frequencies, the consolation that they are all multiples of 250 Hz is rather weak, for hearing, this is either a creak or a wheeze, depending on the fundamental frequency. Now a question from an ancient anecdote: where will we make the waist? What is the maximum output power? If there was still very little distortion, then it will be 13.5 watts. RMS, as you now understand, having seen what the output voltage is indicated in. If there, where under half a percent, then it will be almost 19 watts. And if we agree with 10%, then we get a fabulous value for such amplifiers of 23 watts. But it’s better not to agree: do you see what lies behind this inconspicuous figure?

The result of our analysis is paradoxical at first glance: on the one hand, the amplifier has only one maximum achievable output power, depending on the supply voltage and load resistance. But at the same time, you can specify it as you like, the question is what level of distortion is considered acceptable. Traditionally, for really powerful, external amplifiers, the maximum power value is indicated at a k.n.i. equal to 1%. For head units, manufacturers prefer 10%, for reasons that no longer need comment.
AND EVERYTHING, WHY?
Why, with such, in general, miserable values ​​​​of the maximum power of the head unit amplifiers, the “200-watt” 6 x 9 attached to them begin to wheeze, or even burn? Why wheeze, you have already seen: wheezing is the harmonics that appeared at the output of the amplifier when it was overloaded. A person thinks that his mighty radio tape recorder has overloaded the speaker, but in fact he plays the “burdock” that he was given, thinking with his burdock brains that this is how it should be. And why do they burn if they have such power - like a pellet for an elephant? And let's take another look at the results of previous experiments with distortions, and then even continue them. I added something there: conditional curves showing which part of the frequency spectrum falls on the low-frequency head (actually "burdock"), and which part - on the block of high-frequency heads in its center. Naturally, this fully applies to any multi-band acoustics, and we have no other. Something is playing, and there is a powerful component with a frequency of 250 Hz. The tweeter is still on vacation: on the blue field depicting its operating range, there is almost no signal, and rightly so, this is not its frequency. When the distortion becomes half a percent, something already appears, but so far it's okay, the amplitudes are small, and most of them fall into the area where the tweeter filter is already starting to cut off the unnecessary. At 10% it's already not good: the tweeter is put to rest, and a lot of harmonics fall on it, and even with a level higher than the content of the high frequencies in a normal phonogram. Let's go further, to the limit: we unscrew the input signal so that after cutting off the tops of the half-waves, the quiet sinusoid turns into an almost rectangular signal, in which the harmonics are forty percent of the main signal. Here is the squeaker, most likely, Khan. But we have the same amplifier, and the frequency is still “not beeping”. With some natural gift, such a signal can also spoil the midbass. Rectangular pulses carry much more energy at the output than a sine wave, and the electrical power that is supplied to the speaker in this case will be more than 50 watts. Imagine a 50-watt soldering iron, then remember that the speaker is a 99.5% soldering iron, and the fate of the voice coil, which, unlike the soldering iron winding, is made not from nichrome, mica and asbestos, but from much more delicate materials, will cease look cloudless.

Does all this mean that you can not look at the power of acoustics at all? Not really. You just have to look a little differently. This view of power "from the other end" will be the theme of the second issue of Total Recall.

Dealing with power in the end
Andrey ELYUTIN
Those who started methodically “remembering everything” together with us in the last issue, it seems to me, had enough time to grieve that “4 x 45 W” inscribed on the radio tape recorder is not the most direct road to happiness. It's time to choose a path, and at the same time dispel some of the myths that have taken root in our environment cleaner than that of saxaul. And at the same time, remember some properties of our body (with some parts of which we listen to music) and how these properties influenced the system of measures in acoustics.
EVERYTHING, SUCCESSED
Clearly, without an amplifier - not life. We begin to choose and, of course, the first thing we look at is the maximum (we already know what it is) power, what are we fighting for? About how to choose it, the conversation will be separate and unexpectedly short for you. But first, let's define where this power comes from. What makes a separate amplifier such a qualitatively different device compared to the inherited amplifier channels built into the head unit? From the previous issue of "V.V." It became clear that it was all about nutrition. The amplifier creates an alternating voltage at the output with a swing, from top to bottom, no more than the supply voltage of the output stages. For the radio amplifier, this is the voltage on board, 12 V on a muffled car, about 14 V - on the go. The main component of the external amplifier is the power supply. It receives a constant voltage from the on-board network, turns it into an alternating one of a rather high frequency (tens of kilohertz), the alternating one can already be increased using a transformer, which the power supply of the amplifier does, and then, already increased, is rectified again and fed to the amplifier itself. Up to how many volts the voltage was inflated during this activity, at such a height the ceiling of the output voltage range will pass. What follows is simple arithmetic. Let's assume that out of 12 V on-board power supply created 50. In reality, it will be two voltages of different polarity, 25 V each, it's more convenient. This means that the output voltage range will be (in each direction) no more than 25 V minus some pennies lost in transistors. The maximum output power is 25 squared divided by the load impedance. This is according to Ohm's law, he is relentless. It comes out a little over 150 watts. Only this is the peak value, on the RMS scale - exactly half as much, about 75 watts. The figures are quite real, such amplifiers - in bulk. Can you get more out of this amp? The first stage of "afterburner" for many models will happen by itself, it is worth starting the engine. For many amplifiers, the output voltage of the power supply is not stabilized and is in proportion to the input. And when, with the engine running and the generator running, the voltage on board becomes not 12, but, on a well-adjusted machine, 14.4 V, the voltage at the output of the power source will increase from 50 to 60 V, and the “ceiling” for the output voltage of the amplifier will also rise , and the maximum power will increase to 108 watts. Wow increase, right? Just don't get too excited just yet. Will this make the amp play louder? And what is it from, exactly? The overall gain, from the signal source to the output, remained the same, it does not depend on the power supply (and if it suddenly depended, the component responsible for this would urgently request permanent registration in the trash can), which means that it will be as it played. It’s another matter that if earlier distortions appeared at some volume, this is when at the peaks of the signal the output voltage tried to jump over the bar set by the power source, now this moment will move to the area of ​​\u200b\u200bhigher volume. How far will it move? Let's guess. One and a half decibels. One click of the volume, or even none, it depends on the step of the regulator.

And what have we gained in comparison with the “past life”, when there was no amplifier at all? There seems to be a lot in watts. And in decibels, the maximum undistorted volume, again, seems to be not very: 5.4 dB. But this is only “seemingly”, as we will see later, happiness is not in just clicks of the volume control. We still need to organize some kind of harmony between the capacities. See, for example, what power the acoustics have, and choose an amplifier based on it, right?
WRONG

I did it on purpose, for the purpose of provocation. About how you can ruin the acoustics with insufficient power, it was in the last issue, now let's try to do it with the help of excess. It will be much more difficult, I warn you.

Let's go back to the phrase that I uttered (and wrote) on various occasions so many times, the last time - in the last issue. Here it is: “And when we talk about the power of the amplifier, then we are talking about what HE GIVES. And when it’s about the power of the speaker, then about what HE TAKES. The maximum power of the amplifier is the one that it cannot give more than, because it starts to distort the signal, and we did not buy it for this. The maximum power of acoustics, therefore, is the one that it cannot take more than, because WHAT? Also starts to distort the signal? And she begins to do this immediately and little by little, not at all like an amplifier, acoustics do not have a hard limit bar. In ancient times, there was a Soviet standard, according to which the so-called nominal power of speakers was normalized. Special conditions were stipulated there, the frequency band, and so on, in general, the power was considered such that the non-linear distortion did not exceed 10%. The best bass speaker of that time was called 6GD2, the first digit is just the rated power. There were 4 more HDs, 3 HDs, and so on, then they adopted the definition of nameplate power, which no longer depends on distortion, but on survivability, and all these HDs at once got fatter to 10, 20, 75 and the like. These GOSTs ordered us all to live long, and now power is defined differently, and it is very important to understand this in order to experience the attitude that it deserves towards this indicator.

I'll ask you to type it in red, if I forget - you yourself then in pencil, okay?

The power indicated on the acoustics is not the one at which it should work, but the one that destroys it.

Of course, there must be a relationship between the capabilities of acoustics and the resources of the source of this probable destruction, but this is a relationship, not an identity. Imagine: you bought a car with a top speed of 200 km/h. And you turned up tires with a speed index T (190 km / h). What can't you drive? At 191 km / h, all four wheels are in tatters? Or vice versa, tires have a Z speed index (240 or more), and you get knocked off your feet, choosing a suitable car for such rubber. Unreal.

Nevertheless, quite often one has to hear (and even read) how the acoustics to the amplifier (and vice versa) are selected, looking first of all at the power, and then at everything else.

So let's go for the last time, so as not to return to the question. The numbers on the acoustics, accompanied by the words Power, without indicating what is meant by this, do not mean anything, this is part of a modern, but rooted tradition. If the speaker manufacturer is at least relatively correct in the numbers he gives, then he can indicate the long-term power, and this is the maximum non-destructive (or minimally destructive, do not forget about this) power supplied to the speaker for half an hour according to the scheme: a minute works - two resting. At the same time, a noise signal is supplied, passed through a filter that cuts off everything below 40 Hz and everything above 4 kHz, so this is almost irrelevant to the tweeter. Now, if the acoustics survived these most difficult half an hour in their life, the used power value is recorded. If it died, it is taken from previous experience with less power. Short-term power is one that will not destroy the speaker (or destroy it, but at the last moment) after 60 cycles of “a second orem - a minute we rest”. All the described procedures involve bringing the tested sample of acoustics as close as possible to the edge of the grave, so it is somehow not very reasonable to focus on them as a normative indicator for someone who paid for the acoustics out of their own pocket. The only type of indicator that even slightly resembles the possible real use of its legitimate property is rated noise power according to the IEC 268-5 standard, when the acoustics must remain alive after 8 hours of continuous operation on the already mentioned noise signal. It is almost never indicated.

Landmarks here should be different, you should not look for them on boxes with acoustics.
REFERENCES, WHERE ARE YOU?

Our staff experts in acoustics tests repeatedly recommended (when the manufacturers completely lost their shame and it was unthinkable to keep silent) to be equal to indicators that at least roughly indicate the range of possible values. For 6-inch component acoustics, the limits of reasonable risk lie somewhere between 40 and 90 W (this is wide, inside you already have to look at the design features), for a 5-inch speaker it is naturally lower, 30 - 70 W. We consider these values ​​to be rated noise power. You can disagree, but refuting experiments - at your own expense, please.

The numbers, in principle, resemble the common values ​​​​of the maximum output power of widespread amplifiers, so the simplest, on the verge of primitivism, answer to the question of matching the power of an amplifier with the power of acoustics is already ready: a typical amplifier is suitable for working with typical acoustics. Anyone - with anyone. In principle, if you do not want to bathe, you can take it into service. But the answer is too simple to somehow claim to be exhaustive, that's clear.

A slightly more common answer can be found in the experience of superbison in the world of acoustics. The undoubted superbison is JBL, which has equally succeeded in acoustics for home, stage, automotive and designed for sounding rooms and open spaces. The company's technical circular contains the following recommendation: in the case when the volume level is under control (it explains: it means a house or a studio, but not a word about a car), the maximum amplifier power (RMS) can be twice the rated noise power. In the case when the control is not perfect (this is about sound systems), parity must be observed.

Next, you need to look at the realities of life. In real life, I have reason to believe, both the amplifier and acoustics will be used to reproduce music, and not test signals that only very approximately resemble music. A musical signal is not a sine or even noise, it is a signal with a large difference between the average value and the peak. Short-term signal peaks, with rare exceptions, do not threaten the health of acoustics, which mainly have to resist thermal stress, and the heat generated on the voice coil is a function of the average level of the supplied signal. I had to see in the documentation of the most serious manufacturers of acoustics, how, next to quite real (and indicating all the regulatory data) figures for long-term power, the values ​​\u200b\u200bof withstanding power for short (say,

10 ms) peaks. The numbers sometimes reached hundreds of watts, and this is no longer marketing, this is a fact, even a very powerful one, but a very short burst of signal will not destroy the speaker. And the amplifier has a fundamentally different view of the level peaks. At least for a millisecond it will exceed the signal level of the maximum power bar - and it will be mercilessly decapitated, that is, it will go further along the wires to the acoustics already in a distorted form compared to the original source. This cannot be allowed. And here it already makes sense to look at your musical tastes.

TASTES ARE NOT MEASURED

Why so? You can also try. I passed a number of musical fragments through the computer and chose quite significant in terms of the ratio of average (dangerous for acoustics) and peak (which should be feasible for the amplifier) ​​power. The signal level was measured in decibels relative to the maximum recorded on the disk, but for clarity, I converted everything into a percentage of the maximum power. The first picture is 60 seconds of "Procession of the Dwarves" (6th track "Let's Test!"). If the system is set up so that the largest peaks of the signal do not go beyond the output power of the amplifier, then in general for this minute the acoustics will get about one and a half percent of this power. Even in those 12 seconds, when the orchestra is completely unbelted, the thermal load will be no more than half the power.

A minute of activity of Yamato drummers (remember, you came to Moscow?). The signal level is chosen so as to easily miss the peak of activity at 21 seconds. As a result, the average power of the entire fragment is less than a percent of the maximum, and its most intense part is one tenth of the maximum.

Third example: "In the Pocket" (Kai Eckhardt, "NAIM Sampler", track 8). The average power is 13% of the maximum, and turning up the volume in a sincere attempt to ruin the acoustics will mean cutting off the numerous peaks caused by the skillful work of the drummer.

Don't listen to audiophile delights? We will not force. Here is a fragment of the soundtrack of the punk rock band Kurban (Turkish and, by the way, quite curious). Here already - yes, the guys on the stage do not rest, and the average power for a long time is about 40, or even more percent of the maximum. But the guidelines, in principle, remain the same as those proposed by the bright heads from JBL, God bless them. It's just that rock music falls into the category of "faulty control", which is logical.

An attentive reader may be puzzled here: “Wait a minute, it turns out that we listen to music on one or two, a lot - ten watts connected to the acoustics? Why is it loud then? You yourself have heard: loudly. I will answer: why shouldn't she play loudly? After all, you are easy to manage with decibels (even those who did not know how before). We take any acoustics from any of our past tests and look at the sensitivity indicator. Well, let's say 87 dB, that's right, average-typical value. Such sound pressure will be created by these acoustics at a distance of 1 m with a power of 1 (one and only) W supplied to it. It's not quiet anymore, by the way. In order for this acoustic to create a sound pressure level of 90 dB, which is standard for control listening in sound recordings, it only needs 2 watts. Apply 10 watts - get 97 dB. It's quite loud. Moreover, please note that we have at least two such speakers, and they do not sound in a muffled room, but in the cabin, where there are much less losses, and the reflected sounds come to us. What then, you ask, will the speaker do when those very peak hundred, say, watts come to it? Exactly what it should: for a short time, within a fraction of a second, it will scream at 107 dB. Give him that 100 watts continuously, in the form of noise or, worse, a tone, and the scream will be death. And so - everything is under control, do not worry.

What will be discussed next? Now about acoustics. About what characterizes it, in addition to power, this topic, I hope, we have closed.
In acoustics, everything is measured differently than in the ordinary world. There are several reasons for this, explanations of others can lead to the paradise of science, we will not touch them. Others lend themselves to simple interpretations. Or they can simply be taken for granted, whichever you prefer.

The human ear cannot add and subtract. Just multiply and divide. Evolution (or the Creator, choose according to your taste) arranged it in such a way, as it seems to me, guided by technical expediency. Hearing works in a huge range of volumes. The sound pressure (measurable, as you know) corresponding to the pain threshold exceeds the sound pressure of the hearing threshold by ten million times (in words, so as not to count zeros). Hearing adapted to this by becoming (by the will of evolution or the Creator) logarithmic. People came up with logarithms later, but in our head they sit by nature. The logarithmic nature of hearing is that it evaluates the difference in loudness not by how much more sound pressure is, but by how many times it has become more. So (if we remove now all the intermediate chapters of the story) a unit of measurement was invented, on which absolutely everything is based in acoustics and electroacoustics - the decibel. Whoever knows everything about this, do not read further, however, I asked about this when I opened this series of publications.

I give the rest, no matter how many of them, the opportunity to master operations with decibels in five minutes and subsequently do it easily and gracefully. So: a decibel is a unit, which, if added, means “multiply”, and if subtracted, it means “divide”. For example: sound pressure is 3dB higher. It means double. Another 3 dB? Double more. More than 1 dB is 1.25 times, approximately. More than 10 dB - ten times. And vice versa: subtract 3 dB from the sound pressure, and this will mean that it has halved.

Sent by MitrAlex from the forum

"I can't help it," said Lord Darlington to Lady Windermere. “I can resist anything but temptation.” This is one of Oscar Wilde's sharpest and most honest maxims; and although it does not apply directly to the world of Hi-Fi, it can be assumed that a wiser person than Lord Darlington is needed to create an optimal system.

Having recently discovered new Award winners, we decided that now is the time to clarify an important question: how to choose the right speakers? It would seem that it could be simpler: buy the most expensive Award-winning model that you can afford. If it is a winner in the price category, then it will be the best for you too?

Bring to the point of absurdity

We don't compare ourselves to car or real estate sellers, but in many ways, investing in AS is just as treacherous. Following their investment approach, each of us would spend 15 hours in our Lamborghini on our way to work from a mansion in the Hebrides. It is necessary to clearly define the difference between the most expensive and what will be the best for you.

Glossary

bass Low frequency sound is often difficult to reproduce. It is less directional than midrange and treble.

Tue Always look for numbers marked "RMS" (root mean square).

top The highest sounds. Unlike bass, the treble is strongly directed, so precise speaker placement is very important.

Two cable connection Speakers with separate crossovers and two sets of terminals can be connected with two cables for better sound quality.

2 way speakers Most speakers have two speakers and a crossover to separate the signal. Some speakers have three or more speakers; if the crossover divides the input signal into three frequency ranges, such models should be called three-band.

Speakers Sound emitters. Midrange / woofers are responsible for low or medium frequencies, tweeters - for the top.

Permissible power The highest power safe for speakers. When overloaded, the speaker is more likely to be damaged by an amplifier with a lower output power than with a high one.

AC terminal The connector has a threaded washer for clamping bare wires and sometimes a banana plug connector.

crossover The circuitry inside the speaker that divides the input signal into high and low frequency components and sends the first to the tweeter and the second to the mid/bass driver.

middle The frequency range in which most instruments and the human voice radiate sound.

Resistance The higher this figure, the easier it is for the amplifier to control the speakers.

Phase inverter This design element provides more powerful low frequencies due to the air flow from the port to the cabinet.

Frequency The frequency of sound is measured in hertz (Hz). A 1 Hz signal travels one cycle per second. Highs are high, bass is low. A healthy human ear on average hears sounds with a frequency of 20 Hz (low) to 20 kHz (high).

Sensitivity An indicator of the ratio between the power of the electrical signal applied to the speaker and the sound emitted by it. Speakers with high sensitivity are easier for the amplifier to “pump”. It is usually expressed in dB/W/m (the sound pressure level in decibels generated by an input power of 1 W, measured at 1 meter from the speaker). Most speakers have a sensitivity of 86-91 dB/W/m.

Setting

AC location
WALLS
Resist the temptation to place speakers in the corners of the room. The bass level may increase, but the rhythm, transparency of the sound and detail in the low range deteriorate.
ANGLE OF ROTATION
Experiment with reversal. It depends on the model, but for most speakers a small inward turn will stabilize the stereo image. Do not overdo it - otherwise the sound stage will decrease.
DISTANCE
Much depends on the room, but ideally speakers should be placed no closer than a couple of meters from each other and a meter from the side and rear walls.
OTHER COMPONENTS
Keep speakers as far away from other system components as possible. Any vibrations have a bad effect on the sound.

Need preparation

The first and most important thing you should do before you start your search is to decide on the size of the budget. We are not going to act as your accountant and will not advise you to sell children into slavery to pay for the purchase, but there are certain considerations that need to be taken into account - and not all of them are obvious.

What should be kept in mind?

If you set a budget before you start looking at models, you can narrow down your search considerably. In addition, you need to understand where you can give up strict budget requirements. If you're buying all the components of a new system, it makes no sense to spend 90% on speakers and then be upset that they highlight all the imperfections of the previous links in the chain. In the same way, the owners of a system bought “somewhere outside the city, very inexpensively” should not spend a hundred thousand on a pair of floorstanding speakers - all you get is a visit from the district police officer on the complaint of neighbors.

However, this sword (like most others) turns out to be double-edged. Prudence and frugality are valuable in themselves, but in this case an element of foresight is added to them. If, for example, you are planning an early upgrade of other components of the system, then it is quite possible to choose speakers with the expectation of future upgrades. By spending a little more today, you can avoid much higher costs in the near future.

Another boring but necessary task is measuring the dimensions of the room. The characteristics of your room may limit your options to a certain type of speaker (more on that in a moment); in addition, it will reduce the number of locations. Most models require a certain free space to work; if you can only allocate them an area against the wall, consider this when choosing speakers.

This won't necessarily affect the sound quality: there are plenty of great-sounding models on the market that don't mind mounting flush against the wall behind. Just keep in mind that you are dealing with sound waves, the propagation of which depends on what they meet on their way. If the manufacturer advises to install speakers at least two meters from the walls, it is better not to ignore these recommendations.

Give it some gas

Put down the tape measure; it's time to think about what type of speakers you're going to target. As we mentioned earlier, this is partly determined by the size of the room: a cow cannot fit in a rabbit hole. You can choose floorstanding or bookshelf speakers (the name itself speaks of their intended location) or a triphonic of satellites and a subwoofer, in which the latter will be responsible for the bass, and it will be easier to find a suitable place for a pair of main speakers.

As a rule, larger speakers are able to provide higher volume, better dynamics and more abundant bass - although this pattern is not absolute and largely depends on the specific model. Also, think about how loud you are going to listen to music. Your mighty floorstanders may never get a chance to spread their wings; and cute little bookshelf speakers are unlikely to spice up a party.

One or two

Many speakers today are equipped with four terminals, which makes it possible to organize a two-cable or two-amp connection. When using one set of cables, each of them transmits a complete signal with all its frequencies; By connecting two cables to each speaker, the speaker can receive high and low frequencies separately, allowing it to produce clearer and more accurate sound.

Perhaps your amplifier does not support two-cable connection, or you are not interested in it. That's not to say that four-terminal models won't work for you: most of them come with jumpers that connect pairs of terminals, so that the music will sound full. But keep in mind that speakers with two terminals preclude the possibility of switching to a two-cable or two-amp connection in the future.

Another criterion for choosing speakers is passive or active. Most models on the market are passive; a powerful signal from the amplifier is fed to their inputs and then sent to the speakers through a crossover. In active speakers, the low-current signal is divided into frequency bands even before it enters the amplifiers located inside the case, and for their operation, the speakers need a separate connection to the network.

Active lifestyle

However, not all active speakers function this way. Some models are equipped with a built-in amplifier that drives the signal through a passive crossover. This means that the signal is amplified even before it is divided into frequency bands. At first glance, this is akin to the question of what should be poured into a cup first - milk or tea, but the difference is fundamental.

There are many operations going on inside active ASs. If the crossovers are operated at line level rather than speaker level, then better components can be used and a more accurate separation can be achieved. In addition, each speaker is controlled by its own amplifier. They are connected directly, not by cable, which also increases the degree of control.

The main disadvantage of this approach is not even the price (although active speakers are expensive, but if you take into account the cost of a component amplifier, they often provide the best value for money), but the fact that if you want to upgrade the system, you will have to replace all its components. which may end up costing you more in the long run.

We've seen time and time again that it's easier to get the best sound by choosing separate components - source, amplifier, quality interconnects and speaker cables, and a pair of speakers - but cleverly made active speakers are a rare exception.

Of course, this solution is not for everyone; if you don't have the space or desire to clutter up your living room with a multitude of devices, a wide range of active speakers are at your service.

A few words about power. Today, this problem is not as acute as in warm tube days, but if your speakers are too capricious, you will need a powerful enough amplifier to "pump" them. Don't just go by the top number on the stats list; look at the power rating at a load of 4 ohms - if it is about twice as high (than 8 ohms), then this amplifier provides good current and will cope with demanding speakers.

We keep reminding you that our magazine's rankings are based primarily on value for money; however, it would be absurd to say that everything else is irrelevant. Our goal is that after reading the reviews you can take home a pair of speakers that will delight you until old age. Let's just say, no matter how good the sound is, if you don't like the looks of the speakers, you won't want to spend long evenings in their company. Listening to music does not disable other senses; we had to deal with components that were so unattractive to the eye that we tried to quickly finish testing and get them out of sight.

paw prints

Chances are your room will be used for more than just listening, so it's worth considering whether the new speakers will look like gargoyles at a beauty pageant, and in general how they will fit into the interior.

In particular, you should pay attention to the protection of the tweeter - especially if you have small children or an inquisitive cat. Metal domes, like a magnet, attract the prints of small fingers or paws, quickly becoming covered with dents. We don't want to be held responsible if your investment goes to waste within an hour of installing your speakers.

Time to shop

Grab your bus pass - we're almost ready to go shopping. Since you are reading this material, you are probably aware of the high authority of our magazine and website. Believe me, you really should study the reviews of all interesting models before visiting the seller, and we are not saying this to increase sales or traffic on the site.

We do not urge you to immediately agree with our opinions on the selected speakers. We simply help to exclude from the list those models that do not meet your requirements, and also suggest what to look for when listening. Let's say we noted the tendency of the treble to harshness and that it becomes annoying with prolonged listening, but you may not hear it during a short run on the sales floor.

Make sure the speakers you are listening to are warm enough. Different models require different time to reach the optimal level of sound quality.

A simple conclusion from this follows: if you are not too impressed with the sound of the speakers, from which we were delighted, they may not have warmed up enough.

We often note in reviews that the nature of such-and-such speakers has changed radically after a few hours of operation; this is worth paying attention to.

Bring your songs

If you're the bad guy who likes to turn off the sounding selection at a party and put on a rare Animal Collective record that no one in this company likes, your finest hour has come: grab a collection of records with you to the store. This is the most efficient and easiest way to evaluate speaker quality. A good component will sound good anyway, but the more familiar a song is to you, the better you remember its arrangement, composition, and dynamics. This will allow you to evaluate the sound fidelity of the selected pair of speakers.

For the same reason, it is worth asking the seller to assemble a system similar to the one you have at home. If you have an old or obscure amp, call the dealer ahead of time and make sure the store has something similar. If not, bring your own copy; in the long run, this will bring you less inconvenience than the unfortunate discovery that the new speakers in the home system play completely differently than yesterday in the store.

During check

In essence, you will be doing the same thing in the store as we are doing in our test labs, and you should follow the same tactics. Despite the fact that each review is usually written by one person (we do not mention the invaluable contribution of colleagues and editors who work with the texts before they are published - and even manage to take all the jokes to the public before they catch your eye ), the testing process itself is performed collectively.

It's not that we don't trust our own ears, it's just that the perception is basically very subjective: a bad mood due to a morning traffic jam can affect the assessment, or some aspect of the speaker sound can delight you so much that you don't pay attention to the shortcomings.

It is important to be open to alternative options. A missed review in our magazine, a new speaker model we haven't tested yet, speakers you initially rejected because of a four-star rating - any of these models may be more suitable for you than an Award winner.

A good salesperson knows their products (which is why they have them in their store) and can offer something that you didn't originally consider that might work better for your system. Do not take any words for granted - after all, you will have to listen to these speakers for many years, not the seller - but also do not tune in in advance that the store owner will certainly want to sell you illiquid assets.

However, this is a bilateral relationship; if you're serious about your music system, you're sure to become a regular customer. That is why the store employees pay a lot of attention to you (although, of course, you are a very nice and pleasant person, with whom it is a pleasure to talk), so reciprocate them. This means that it would be indecent to choose speakers in a store and then go home and start looking for the same model cheaper on the Internet.

Listen to the seller

It's not that we stand up for our industry peers, but if you don't want to completely ruin your relationship with someone who sincerely wants to help you, you should not think about the benefits (especially since they are usually small) in the first place. Imagine that the girl you are in love with tells you that she would like to find someone like you. Someone like you is standing right in front of her!

However, don't be tempted to make a decision immediately and don't think that buying online is somehow bad from a moral point of view. If you don't have a salesperson ready to help you choose, don't worry; just take a couple more tips into service. Buying online means that you will have fewer opportunities to audition than in a store. Therefore, carefully study the points regarding the selection of the system, and not just the ratings.

The main advantage, which is also the main disadvantage of shopping on the Internet, is that it is the largest store in the world, surpassing any shopping malls. Therefore, do not discount last year's models. Even the best speakers are discontinued from time to time, after which they can be bought at deep discounts. Follow our reviews and you will know when the old model began to seem less successful. If it's still for sale, it's likely that it's doing well.

In addition, when buying online, you should follow the usual precautions: buy from a trusted online store and make sure that the goods can be returned if necessary.

As always, if an offer seems too good to be true, then it probably is, and you are unlikely to get your money back.

Finally, the most important rule of online shopping - do not buy anything without first listening. If you don't have a suitable store nearby, take the time to visit a Hi-Fi trade show, or just ask a friend for a loan of speakers you've always loved to hear how they play with your components. If you buy something without listening, you are a very brave (or reckless) person.

welcome home

So, you are back at home, upset that you spent twice as much as planned, and are wondering how you will eat only canned food for the next six months - but with a couple of new beautiful speakers, whom you have already loved more than all your uncles and aunts. Unfortunately, just like your relatives, they will not offer you anything until you do everything necessary for them.

We've already mentioned how important warm-up is to speakers, so don't judge them immediately after unpacking, installing, and connecting cables. Some models require almost 100 hours, although for most speakers a day of idling will be enough. All you have to do is turn them on and let them play, allowing the components to warm up, stretch, and return to normal working order. It is unlikely that you will do this at maximum volume, but in any case, do not load them too hard right away. Let them walk before they run.

The main thing is the place

In addition to connecting the speakers and waiting for the necessary time, another important problem for you is to find the right place and position for them. Take the time to do this: small changes in the geometry of the arrangement can seriously change the sound balance.

By placing speakers close to the back wall, you will get more powerful bass; if you move them away from the walls, the stereo panorama will become more convincing.

You need to find a balance, not a compromise, with speakers with a bass reflex port (i.e. radiating sound out the back) more sensitive to rear-wall installation. But in no case do not put them in a corner, even if this option seems more convenient: plump and uneven bass will spoil the whole impression.

The stereo panorama is strongly affected by the turn angle of the speakers. Most require a slight inward orientation towards the position of the listener, who must be placed at the same distance from the speakers in order to achieve the best focus. Models from some manufacturers (such as DALI) do not need to turn around. Check your owner's manual for recommended distances from each other and from walls for your speaker model, but don't be afraid to experiment - they may behave slightly differently in your room than elsewhere.

Stand one's ground

Are you comfortable sitting? Your speakers want it too. Even if you buy a model that says “shelf” in the description, a reliable foundation is extremely important for its quality work. Buy good racks: The sound of bookshelf speakers depends to a large extent on the quality of the racks on which they are installed - compromises in this case are unacceptable.

Likewise, if you choose floorstanding speakers, make sure the spikes are securely fastened. Owners of wooden floors will need metal circles, which are supplied with some models; if yours doesn't come with them, use regular coins - that's all you have left after buying speakers (just kidding).

Another important, though obvious, note is that the speakers should stand on a perfectly horizontal surface, and they should not wobble. Stable speakers = quality sound.

Do not forget about cables (yes, this is another remark from a series known to everyone for a long time).

Some buyers do not think about the importance of quality conductors or try to save at least something. But try, for example, eating soup with a knife - you are more likely to remain hungry because of inappropriate cutlery than because of tasteless food.

Happy listening!

Most importantly, your new speakers should bring you joy. That is what all our advice is aimed at. Treat your speakers with respect and they will serve you faithfully for years to come. That means no Webber musicals, no X-Factor Christmas specials - and, for heaven's sake, no Th e Eagles songs!

Speaker Power
​

Maximum noise power of the speaker, maximum long-term power of the speaker, maximum short-term power of the speaker.

Noise Power Limit (PHC)- the power that the dynamic head can withstand for a long time without thermal and mechanical damage. The duration of continuous tests is indicated by the manufacturer in hours and on which signal.

Ultimate Continuous Power (RMS)- the power that the dynamic head can withstand without thermal and mechanical damage for 1 min with an interval of 2 min for 10 cycles in a row.

Short Term Power Limit (PMPO)- the power that the dynamic head can withstand without thermal and mechanical damage for 1 second with an interval of 60 seconds for 60 cycles in a row.

Under the word power in colloquial speech, many mean "power", "strength". So it's natural for consumers to associate power with loudness: "The more power, the better and louder the speakers will sound." However, this popular belief is fundamentally wrong! It is far from always that a 100W speaker will play louder or better than one that has a power of “only” 50W. The power value rather speaks not about the volume, but about the mechanical reliability of the acoustics. The same 50 or 100 watts is not at all the volume of the sound emitted by the speaker. Even the best dynamic heads themselves have low efficiency and convert only 2-3% of the power of the electrical signal supplied to them into sound vibrations, and most speakers have even less (although the sound produced is quite enough to create sound accompaniment).
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 applied, 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 hangers of the system, etc.).

Thus, the power of the speaker system is a technical parameter, the value of which is not directly related to the loudness of the acoustics, although it is associated with some dependence. The nominal power values ​​of dynamic heads, amplifying path, acoustic system can be different. They are indicated rather for orientation and optimal pairing between components. For example, an amplifier of much less or much more power can disable 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 in various ways and under various test conditions. There are generally accepted standards for these measurements. Let us consider in more detail some of them, which are most often used in the characteristics of products of Western firms:

RMS(Root Mean Squared - root mean square value). Power is measured by applying a sinusoidal signal with a frequency of 1000 Hz until a certain level of non-linear distortion is reached. Usually in the passport for the product it is written like this: 15 W (RMS). This value indicates that the speaker system, when a 15 W signal is applied to it, can work for a long time without mechanical damage to the dynamic heads. For inexpensive acoustics, higher power values ​​in W (RMS) compared to Hi-Fi speakers are obtained due to measurements at very high harmonic distortions, often up to 10%. With such distortions, it is almost impossible to listen to the soundtrack due to strong wheezing and overtones in the dynamic head.

PMPO(Peak Music Power Output - peak musical power). In this case, the power is measured by applying a short-term sinusoidal signal with a duration of less than 1 second and a frequency below 250 Hz (typically 100 Hz). This does not take into account the level of non-linear distortion. For example, the speaker power is 500W (PMPO). This fact indicates that the speaker system, after reproducing a short-term low-frequency signal, did not have mechanical damage to the dynamic heads. Popularly, the units of power measurement W (PMPO) are called "Chinese watts" due to the fact that power values ​​with this measurement technique reach thousands of watts! Imagine - small speakers with a diameter of 10 cm playing from a cheap balalaika (radio tape recorder) with an electrical power of 15 V * A and at the same time develop a peak musical power of 1500 W (PMPO).

PHC The maximum (limiting) noise (passport) power (English power handling capacity), which characterizes the stability of the acoustic system to thermal and mechanical damage during long-term (for 100 hours) work with a noise signal of the "pink noise" type, the spectrum of which approaches the spectrum of real musical signals;

Along with Western standards, there are also Soviet standards for various types of power. They are regulated by the current GOST 16122-87 and GOST 23262-88. 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.

Drawing conclusions: The most important in practice is the power value given in W (RMS) at harmonic distortion (THD) values ​​of 1% or less. However, comparing products even by this indicator is very approximate and may not have anything to do with reality, because the sound volume is characterized by the sound pressure level. Therefore, the information content of the indicator "power of the acoustic system" is zero.

SENSITIVITY

Sensitivity (SPL)- one of the parameters specified by the manufacturer in the characteristics of acoustic systems. The value characterizes the intensity of the sound pressure developed by the column at a distance of 1 meter when a signal with a frequency of 1000 Hz and a power of 1 W is applied. Sensitivity is measured in decibels (dB) relative to the hearing threshold (zero sound pressure level is 2*10^-5 Pa). Sometimes the designation level of characteristic sensitivity (SPL, Sound Pressure Level) is used. At the same time, for brevity, dB / W * m or dB / W ^ 1 / 2 * m (or 2.83V) is indicated in the column with units of measurement.
It is important to understand, however, that sensitivity is not a linear proportionality factor between sound pressure level, signal strength and distance to the source. Many companies list the sensitivity characteristics of dynamic heads, measured under non-standard conditions.

Sensitivity - a characteristic that is more important when designing your own acoustic systems. If you do not fully understand what this parameter means, then when choosing acoustics, you can not pay special attention to sensitivity (since it is not often indicated), if there is an external power amplifier.

The speaker system is an integral part of any audio system, from cinema and concert equipment to a home theater or a conventional computer multimedia system. The acoustic system includes several sound (acoustic) speakers (AS), their number and purpose can vary greatly.

For effective sounding of a small room, two solid speakers are sometimes enough to enjoy all the nuances of the sound picture of modern films or the most advanced computer games, you will need a multi-channel active speaker system.

What exactly do you need to know to purchase acoustics of the required price level and sound quality? Read more about this and the features of operation.

Acoustic systems | History of multichannel audio

Historically, the first multi-channel sound reproduction system was stereophony. Two audio speakers located in front of the listener provide a spatial distribution of the sound sources of the audio track being listened to. Naturally, the sound recording must be made in stereo format and listened to through a two-channel amplifier having a right and left channel (PC and LC).

According to the modern classification, such acoustics are designated - 2.0, which means two front side speakers in the absence of a subwoofer. The modern version of the stereo system is 2.1 format. This adds a subwoofer to the two front speakers, designed exclusively for reproducing low-frequency sounds.

The fact is that to achieve high-quality sound output from the front speakers at low frequencies (LF) is a rather difficult task, while the acoustics are significantly increased in size and price. It is much easier and cheaper to make a separate woofer - a subwoofer. The subwoofer signal is extracted from the left and right channel signals. This practically does not affect the quality of the stereo effect, since the human ear almost does not perceive the location of the source of low-frequency sounds. The main information about the localization of sound sources is in the mid-frequency (MF) and high-frequency (HF) parts of the range, for which two front speakers are responsible.

A further improvement in audio systems was four-channel sound reproduction. The analog version of such systems was called quadraphony. In this case, two rear speakers are added to the two front speakers. The 4.1 system also has a subwoofer to simplify the front speakers. However, quadraphony was not widely used. It did not give a significant increase in sound quality and the effect of three-dimensionality, but it required very expensive analog equipment for recording and playing sound tracks. However, the digital version of the 4.1 system has been successfully used in some computer games.

Acoustic systems | Multi-channel audio and Dolby technologies

Specialists from the American company made a significant contribution to the subsequent improvement of multichannel sound systems. Dolby Laboratories, who developed at the end of the last century digital coding algorithms that make it possible to receive sound at the level of a cinema and concert hall at home. Format Dolby Digital, often used for film scoring, especially on DVDs. It provides three-dimensional acoustic scenes, clearer detail, natural sound source movement, stereo sound in the rear space.

Today, the most advanced active acoustics are equipped with digital decoders. Dolby Theater System(DTS) and Dolby Pro Logic(DPL) is an analog surround sound system used on HI-Fi VHS tapes and broadcast television.

The minimum audio system required for a home theater system must be 5.1. In this system, in addition to the subwoofer, there are five so-called. satellites (smaller speakers). Two front speakers, a center speaker and a subwoofer are placed in front of the listeners and reproduce the main sound picture. The two rear speakers play a less important role. They are used for "sub-sounding" in musical compositions, creation of three-dimensional effects in games.

advanced system Dolby Digital EX allows, by introducing additional rear surround channels (acoustics 6.1, 7.1), to obtain an even higher degree of localization of sound sources in space.

To fully reproduce Dolby Digital and Dolby Pro Logic multi-channel recordings using only two speakers, the Dolby Virtual Speaker.

Acoustic systems | Characteristics

Objectively, the quality of a speaker system can be judged by a set of characteristics. The main parameters of the speakers and the loudspeakers used in them include:

• reproducible frequency range;
• amplitude-frequency characteristic (AFC);
• power;
• sound pressure level;
• sensitivity;
• dynamic range;

Speaker frequency range

The wider the frequency range, the better the audio system can sound. True, with a slight difference in this characteristic for two acoustic systems, not every ear will be able to catch it. And, in general, the band of reproducible frequencies of 20 ... 20,000 Hz is considered the most necessary. However, for many it may be quite sufficient to lower the upper limit to 16 kHz. As for the lower threshold of reproducible frequencies (especially revered by many music lovers), then for systems of the middle price range 30-40 Hz is quite an acceptable limit, provided that the frequency response is of high quality.

Amplitude-frequency response (AFC) of the acoustic system

frequency response- graphical dependence of the output signal level (voltage, power or sound pressure) on frequency. Ideally, the frequency response should be a straight horizontal line. Alas, the real frequency response has many peaks and dips, demonstrating an overestimated and underestimated level of sound reproduction at certain frequencies and really characterizes the sound quality of an acoustic speaker or speaker. The quality of the frequency response is estimated by the unevenness of the curve, in decibels. Unfortunately, many manufacturers do not provide this graph in the technical description of acoustics.

Speaker power

It is by this parameter that many choose acoustics for themselves, since they consider it the equivalent of loudness. However, for acoustics this is not entirely true. The power of a speaker or loudspeaker is measured in watts (W) and determines the maximum amount of electrical power that can be delivered to it. If the passport value for this acoustics is exceeded, the level of distortion increases sharply, and if it is exceeded excessively, the speaker may fail due to damage to the coil winding.

Acoustic manufacturers, knowing that this characteristic is the main one for many listeners, are often cunning, wishful thinking. The fact is that there are various types, methods and units for measuring the power of acoustic systems. For example, some manufacturers indicate the so-called short-term peak power (PMPO), while others indicate the average electrical power (RMS), there is also musical power (Music Power). All this leads to a rather significant difference in numbers with approximately the same real power.

Speaker sound pressure level

It is this parameter that determines the possible volume level from your acoustics, measured in dB relative to the zero level corresponding to the threshold of human hearing in silence at a sound frequency of 1 kHz. A pressure of 20 µPa is taken as the zero level.

Sound pressure in acoustics is the difference between the instantaneous pressure at the measurement point caused by the sound wave and the normal atmospheric pressure in the absence of sound. Pressure is often measured in pascals (Pa).

Speaker sensitivity

This parameter of the acoustic system determines the efficiency of converting electrical energy into sound and is one of the most important. From acoustics with less power, but with greater sensitivity, you can often get a louder sound.

Sensitivity is usually characterized by the sound pressure level (in decibels), measured at a certain distance from the audio speaker when an electrical signal of 1 W is applied to its input. It is necessary, however, to take into account that the measurement conditions (distance, input power) may differ for different manufacturers of acoustics.

Speaker Dynamic Range

Dynamic Range of the acoustic system determines the possibility of reliable reproduction of sound tracks with a significantly changing volume level. The greatest dynamic range requires the reproduction of classical music, where the roar of the timpani and the muffled singing of the flute can coexist.

Numerically, the parameter is measured in decibels and is determined by the ratio between the loudest and quietest sound. The wider the dynamic range, the richer the acoustic capabilities of the audio system.

Speaker Impedance

Or resistance - the total electrical resistance of acoustics to alternating current. For speakers and speakers, it is usually 4, 6, 8 or 16 ohms. In general, impedance is not directly related to the sound quality of a particular speaker system. However, it is this parameter that must be taken into account when connecting a speaker system to an amplifier. If the speaker impedance is lower than the output impedance of the amplifier, there will be some (minor audible) distortion in the sound, but at an excessively high volume, such a connection may damage the amplifier; if the speaker impedance is higher than the output impedance of the amplifier, then the sound will be much quieter.

For active acoustic systems, important parameters are harmonic coefficient, caused by non-linear distortions of the amplifier and the ratio between the level of the useful signal and the level of the "noise" signal introduced by the amplifier.

Loudspeaker Harmonic Distortion (THD)

At the same time, it should be noted that non-linear distortions are very noticeable only for transistor amplifiers. Tube systems, having much higher harmonic coefficients, subjectively have a very high sound fidelity, for which they are valued by music lovers.

Speaker signal-to-noise ratio

All of the above parameters greatly simplify the choice of the necessary acoustics. Unfortunately, manufacturers do not always allow an objective assessment of the quality of their products, applying a minimum set of parameters with a maximum of advertising statements. At the same time, when buying, do not forget about the individual characteristics of sound perception, and listen in detail and compare several types of acoustics.

The range within which the level of sound pressure developed by the acoustic system is not lower than a certain specified value, in relation to the level averaged over a certain frequency band. The sound pressure level is understood as the ratio of the measured value of the sound pressure module to the value of 2 x 10-5 Pa, expressed in decibels. In IEC 581-7 recommendations, the minimum requirements for this parameter are 50-12500 Hz with an 8 dB roll-off from the level averaged over the 100-8000 Hz frequency band. The characteristic largely determines the naturalness of the sound of acoustics. Speaker manufacturers strive to bring this parameter as close as possible to the maximum range perceived by the human ear (20 - 20,000 Hz). The effective reproducible range is determined by the characteristics of the speakers, the design and dimensions of the speaker system, and the parameters of the built-in crossover filter. At low frequencies, the volume of the speaker cabinet plays a decisive role. The larger it is, the more effectively low frequencies are reproduced.

There are usually no problems with the reproduction of high frequencies; modern tweeters (tweeters) allow even ultrasound to be reproduced. Therefore, the range of reproducible frequencies of some speakers exceeds the upper limit of audibility. It is believed that in this case the timbre coloring of the audible components of the sound program is more accurately transmitted. Typical values: 100 - 18000 Hz for bookshelf speakers and 60 - 20000 Hz for floorstanders. The catalogs provide a graph of the sound pressure developed by the acoustic system, depending on the frequency (graph of the amplitude-frequency characteristic (AFC)), by which it is possible to determine both the effective operating frequency range and the unevenness of the frequency response, discussed below.

Frequency response flatness (sound pressure flatness)

The degree of frequency response unevenness is characterized by the ratio of the maximum value of the sound pressure to the minimum, or by another method, the ratio of the maximum (minimum) value to the average, in a given frequency range, expressed in decibels. The IEC 581 - 7 recommendations, which define the minimum requirements for Hi - Fi equipment, indicate that the frequency response unevenness should not exceed ± 4 dB in the range of 100 - 8000 Hz. The best Hi-Fi speakers achieve a flatness level of ± 2 dB.

Directivity

Allows you to evaluate the spatial distribution of sound vibrations emitted by the acoustic system, and optimally position the acoustic systems in different rooms. This parameter allows you to judge the directional diagram of the speaker, which is the dependence of the sound pressure level on the angle of rotation of the speaker relative to its working axis in polar coordinates, measured at one or more fixed frequencies. Sometimes the decrease in the amplitude-frequency characteristic when the speaker is rotated by some fixed angle is displayed on the main graph, in the form of additional frequency response branches.

Characteristic sensitivity (Sensitivity, Efficiency)

The ratio of the average sound pressure developed by the acoustic system in a given frequency range (usually 100 - 8000 Hz) on the working axis, reduced to a distance of 1 m and an input electrical power of 1 W. In most Hi-Fi speaker models, the characteristic sensitivity level is 86 - 90 dB (in the technical literature, dB / m / W is often indicated instead of dB). In recent years, high-quality broadband speakers with high sensitivity of 93 - 95 dB / m / W and more have appeared. A parameter that determines what dynamic range, that is, the ratio of the maximum sound pressure to the minimum, expressed in decibels, is capable of providing the speaker. A wide dynamic range allows you to reproduce complex musical works, especially jazz, symphonic, chamber music, with great reliability.

THD (Distortion, Total Harmonic, THD)

It characterizes the appearance in the process of conversion of spectral components that were absent in the original signal, distorting its structure, that is, ultimately, the fidelity of reproduction. An important parameter, since the “contribution” of the speakers to the total coefficient of non-linear distortion of the entire audio path is usually the maximum. For example, the coefficient of nonlinear distortion of a modern amplifier is hundredths of a percent, while the typical value of this parameter for acoustics is a few percent. As the signal power increases, the non-linear distortion factor increases.

Electrical (acoustic) power (Power Handling)

Power determines the sound pressure level and dynamic range (including characteristic sensitivity) that a speaker can potentially provide in a particular room. Several types of capacities defined by different standards are used:

characteristic

At which the speaker provides a given level of average sound pressure. The IEC recommendations set this level to 94 dB at a distance of 1 meter.

Maximum (limit) noise or passport (Power Handling Capacity)

At which the acoustic system can work for a long time without mechanical and thermal damage when tested with a special noise signal that is close in spectrum to real music programs (pink noise). According to the measurement technique, it coincides with the nameplate power, determined in domestic standards.

Maximum (limit) sinusoidal (Maximum Sinusoidal Testing Power, Rated Maximum Sinusoidal Power)

The power of a continuous sinusoidal signal in a given frequency range, at which the speaker can operate for a long time without mechanical and thermal damage.

Maximum (limit) long-term (Long Term Maximum Input Power)

The power that acoustics can withstand without mechanical and thermal damage for one minute, with the same test signal as for nameplate power. The tests are repeated 10 times with an interval of 1 minute.

Maximum (limit) short-term (Short Term Maximum Input Power)

The power that the speaker can withstand when tested with a noise signal with the same distribution as for nameplate power for 1 second. The tests are repeated 60 times with an interval of 1 minute.

Peak (maximum) musical power or "musical" (Peak Music Power Output - PMPO)

A favorite parameter of manufacturers who are concerned about the sale of their often not very high quality equipment. The measurement technique, defined by the German standard DIN 45500, is as follows: a short-term (less than 2 seconds) signal with a frequency below 250 Hz is applied to the speakers. Acoustics is considered to have passed the test if there are no noticeable aural (!) distortions. This technique allows the manufacturers mentioned above to supply their products with bright stickers with the following texts: "P.M.P.O. …" (or "Musical Power…") "…100!", "…200!" and even… "…1000 Wt!". It is clear that this parameter poorly characterizes the real quality of sound reproduction.

When choosing an amplifier plus speaker pair, it is desirable that the actual maximum power of the speaker system exceeds the power of the amplifier by approximately 30 percent or more. In this case, you will be insured against the failure of the acoustics, due to the supply of an unacceptably high level signal to it. For example, with an amplifier with a power of 50 watts per channel, you can use speakers with a nameplate power of 75 watts each. What amplifier power is sufficient for high-quality sound reproduction? This is largely determined by the parameters of the room, the characteristics of the acoustic systems, the needs of the listener himself. To a large degree of approximation, it is considered that for modern medium-sized living quarters, the power of the amplifier should be at least 20 watts.

Electrical (input) resistance (impedance)

The most common values ​​are: 4, 8 or 16 ohms. This parameter is important when choosing an amplifier with which the speakers will work. It is optimal to use a speaker system with an impedance corresponding to that specified in the amplifier's passport. Such a solution will provide an ideal match between the characteristics of the acoustics and the amplifier, that is, the maximum sound quality.