The variety of standards used to measure amplifier output power and speaker power can be confusing for anyone. Here is a block amplifier from a reputable company with 35 W per channel, and here is a cheap music center with a 1000 W sticker. Such a comparison will clearly cause confusion among a potential buyer. It's time to turn to standards...

Power standards (DIN,RMS,PMPO)

In Russia, two power parameters are used - nominal and sinusoidal. This is reflected in the names of speaker systems and speaker designations. Moreover, if previously the rated power was mainly used, now more often it is sinusoidal. For example, 35AC speakers were subsequently designated S-90 (nominal power 35 W, sine wave power 90 W)

Rated power - power at the middle position of the amplifier volume control, at which other parameters of the device correspond to those stated in the technical description.

Sine wave power is the power at which an amplifier or speaker can operate for an extended period of time with a real music signal without physical damage. Usually 2 - 3 times higher than nominal.

Western standards are broader, typically using DIN, RMS and PMPO.

DIN- approximately corresponds to sine wave power - the power at which an amplifier or speaker can be operated for an extended period of time with a pink noise signal without physical damage.

RMS(Rated Maxmum Sinusoidal) - Maximum (limit) sinusoidal power - the power at which an amplifier or speaker can operate for one hour with a real music signal without physical damage. Typically 20 - 25 percent higher than DIN.

PMPO(Peek Music Power Output) - Musical power (exorbitant :-)) - the power that the speaker speaker can withstand for 1-2 seconds on a low frequency signal (about 200 Hz) without physical damage. Typically 10 - 20 times higher than DIN.

As a rule, serious Western manufacturers indicate the power of their products in DIN, and manufacturers of cheap music centers and computer speakers in PMPO.

Features of the standards

describing power in audio engineering

Many people have sometimes had to wonder what exactly the power means, which is given in one form or another in the passports of acoustic systems and sound reinforcement equipment. There are surprisingly few materials on this topic on the Internet and in printed publications, and there are also few clear answers to questions.

International standards

RMS(Root Mean Squared)

RMS value of power limited by specified harmonic distortion.

Power is measured with a sine wave at 1 kHz when 10% THD is reached. It is calculated as the product of the rms values ​​of voltage and current with an equivalent amount of heat created by direct current. That is, this power is numerically equal to the square root of the product of the squares of the average voltage and current values.

For a sinusoidal signal, the root mean square value is V2 times less than the amplitude value (x 0.707). In general, this is a virtual quantity; the term “rms”, strictly speaking, can be applied to voltage or current, but not to power. A well-known analogue is the effective value (everyone knows it for the AC power supply network - these are the same 220 V for Russia).

I will try to explain why this concept is not very informative for describing sound characteristics. RMS power is the work that produces work. That is, it makes sense in electrical engineering. And it does not necessarily refer to a sinusoid. In the case of musical signals, we hear loud sounds better than weak ones. And the hearing organs are affected more by amplitude values, rather than by root-mean-square values. That is, volume is not equivalent to power. Therefore, root-mean-square values ​​make sense in an electric meter, but amplitude values ​​make sense in music. An even more populist example is the frequency response. Frequency response dips are less noticeable than peaks. That is, loud sounds are more informative than quiet ones, and the average value will say little.

Thus, the RMS standard was one of the less successful attempts to describe the parameters of audio equipment that do not reflect loudness as a value.

In amplifiers and acoustics, this parameter also, in fact, has a very limited use - an amplifier that produces 10% distortion not at maximum power (when clipping occurs, limiting the amplitude of the amplified signal with specific dynamic distortions arising), still look. Before reaching maximum power, the distortion of transistor amplifiers, for example, often does not exceed hundredths of a percent, and even higher they increase sharply (abnormal mode). Many acoustic systems can already fail if operated for a long time at this level of distortion.

For very cheap equipment, another value is indicated - PMPO, a completely meaningless and not standardized parameter by anyone, which means that our Chinese friends measure it as God pleases. More precisely, in parrots, each in its own way. PMPO values ​​often exceed nominal values ​​by up to a factor of 20.

PMPO

(Peak Music Power Output)

Peak short-term musical power, a value that means the maximum achievable peak value of the signal, regardless of distortion, in general for a minimum period of time (usually 10 mS, but generally not standardized).

As follows from the description, the parameter is even more virtual and meaningless in practical use. I advise you not to take these values ​​seriously and not rely on them. If you happen to buy equipment with power parameters indicated only as PMPO, then the only advice is to listen for yourself and determine whether it suits you or not.

DIN 45500

A set of generally accepted IEEE standards that describe various sound reinforcement characteristics of equipment in a more reliable manner.

DIN POWER

The value of power supplied to the actual load (for an amplifier) ​​or supplied (to speakers), limited by nonlinear distortions.

It is measured by applying a signal with a frequency of 1 kHz to the device input for 10 minutes. Power is measured when it reaches 1% THD (non-linear distortion).

Strictly speaking, there are other types of measurements, for example, DIN MUSIC POWER, which describes the power of a musical signal. Typically the value quoted as DIN music is higher than that quoted as DIN.

EIAJ(Electronic Industries Association of Japan) - Japanese association of electronic industries.

Domestic standards

Rated power

(GOST 23262-88)

The value is artificial, it leaves freedom of choice to the manufacturer. The designer is free to specify the rated power value that corresponds to the most advantageous value of nonlinear distortion. Typically, the indicated power was adjusted to the GOST requirements for the complexity class with the best combination of measured characteristics. Indicated for both speakers and amplifiers.

Sometimes this led to paradoxes - with step-type distortion occurring in class AB amplifiers at low volume levels, the level of distortion could decrease as the output signal power increased to the nominal one. In this way, record rated characteristics were achieved in the amplifier data sheets, with an extremely low level of distortion at a high rated power of the amplifier. Whereas the highest statistical density of a musical signal lies in the amplitude range of 5-15% of the maximum power of the amplifier. This is probably why Russian amplifiers were noticeably inferior in hearing to Western amplifiers, whose optimum distortion could be at medium volume levels, while in the USSR there was a race for a minimum of harmonic and sometimes intermodulation distortion at any cost at one nominal (almost maximum) power level.

Noise power rating

Electrical power limited solely by thermal and mechanical damage (for example: slipping of the voice coil turns due to overheating, burnout of conductors in places of bending or soldering, breakage of flexible wires, etc.) when pink noise is supplied through the correction circuit for 100 hours.

Maximum short-term power

The electrical power that the speakers can withstand without damage (checked by the absence of rattling) for a short period of time. Pink noise is used as a test signal. The signal is sent to the speaker for 2 seconds. Tests are carried out 60 times at intervals of 1 minute. This type of power makes it possible to judge the short-term overloads that a loudspeaker can withstand in situations that arise during operation.

Maximum long-term power

The electrical power that the speakers can withstand without damage for 1 minute. The tests are repeated 10 times with an interval of 2 minutes. The test signal is the same.

The maximum long-term power is determined by a violation of the thermal strength of the speakers (sliding of the turns of the voice coil, etc.).

General terminology

Pink noise

A group of signals with a random nature and a uniform spectral density of frequency distribution, decreasing with increasing frequency with a drop of 3 dB per octave over the entire measurement range, with the dependence of the average level on frequency in the form of 1/f. Pink noise has constant (over time) energy in any part of the frequency band.

White noise

A group of signals with a random nature and a uniform and constant spectral frequency distribution density. White noise has the same energy at any frequency range.

Octave

A musical frequency band whose extreme frequency ratio is 2.

Electric power

Power dissipated by an ohmic equivalent resistance equal in value to the nominal electrical resistance of the AC, at a voltage equal to the voltage at the AC terminals. That is, at a resistance that emulates a real load under the same conditions.

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

To effectively sound a small room, sometimes two high-quality speakers are 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 at the required price level and sound quality? Read more about this and its operating features.

Speaker systems | History of multichannel sound reproduction

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

According to 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. In this case, a subwoofer is added to the two front speakers, designed exclusively for reproducing low-frequency sounds.

The fact is that achieving high-quality sound output from front speakers at low frequencies (LF) is quite a difficult task, while the acoustics turn out to be significantly increased in size and price. It is much easier and cheaper to make a separate low-frequency speaker - a subwoofer. The subwoofer signal is separated from the left and right channel signals. This has virtually no effect on 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) regions of the range, for which the 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 did not become widespread. It did not provide a significant increase in sound quality and three-dimensionality effect, but required very expensive analog equipment for recording and playing sound phonograms. However, the digital version of the 4.1 system has been successfully used in some computer games.

Speaker systems | Multichannel sound and Dolby technology

Specialists from the American company made a significant contribution to the subsequent improvement of multi-channel sound systems Dolby Laboratories, who developed digital coding algorithms at the end of the last century that make it possible to obtain concert hall-level sound at home. Format Dolby Digital, often used for film scoring, especially on DVDs. It provides three-dimensionality of acoustic scenes, clearer detail, natural movement of sound sources, and stereophonic 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 videotapes and television broadcasts.

The minimum audio system required for a home theater should 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 responsible for “soundtracking” in musical compositions and creating 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 in the space of sound sources.

For full playback of multi-channel recordings in Dolby Digital and Dolby Pro Logic formats using only two speaker systems, a processing algorithm is used Dolby Virtual Speaker.

Speaker systems | Characteristics

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

• reproducible frequency range;
• amplitude-frequency response (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 between the two acoustic systems, not every ear will be able to catch it. In general, the maximum required band of reproducible frequencies is 20...20,000 Hz. However, for many, lowering the upper limit to 16 kHz may be quite sufficient. As for the lower threshold of reproduced frequencies (especially revered by many music lovers), for systems in the mid-price range 30-40 Hz is a completely 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 troughs, demonstrating an overestimated and underestimated level of sound reproduction at certain frequencies and actually characterizing the sound quality of an acoustic speaker or speaker. The quality of the frequency response is assessed by the unevenness of the curve, in decibels. Unfortunately, many manufacturers do not provide this graph in the technical description of the acoustics.

Speaker power

It is by this parameter that many people choose acoustics for themselves, since they consider it the equivalent of volume. However, for acoustics this is not entirely true. The power of a speaker or speaker system is measured in watts (W) and determines the maximum possible power of the electrical signal supplied to it. If the nominal value for a given acoustic system is exceeded, the level of distortion increases sharply, and if it is excessively exceeded, the speaker may fail due to damage to the coil winding.

Acoustic manufacturers, knowing that for many listeners this is the main characteristic, are often disingenuous, wishful thinking. The fact is that there are different types, methods and units of measuring the power of speaker systems. For example, some manufacturers indicate the so-called peak short-term power (PMPO), while others indicate the average electrical power (RMS), there is also musical power. All this leads to a fairly 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 audibility in silence at a sound frequency of 1 kHz. The zero level is taken to be a pressure of 20 µPa.

Sound pressure in acoustics is the difference between the instantaneous pressure value at the measurement point caused by a sound wave and 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 energy 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 with a power of 1 W is applied to its input. However, it is necessary to take into account that the measurement conditions (distance, power input) may differ between different acoustic manufacturers.

Dynamic range of the speaker system

Dynamic range acoustic system determines the possibility of reliable reproduction of sound phonograms with significantly varying volume levels. The greatest dynamic range is required for the reproduction of classical music, where the roar of timpani and the muted singing of a flute may 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 the acoustics in 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 precisely this parameter that must be taken into account when connecting the speaker system to the amplifier. If the speaker impedance value is lower than the output impedance of the amplifier, there will be some (minor to the ear) distortion in the sound, but if the volume is excessively high, such a connection may damage the amplifier; If the impedance of the acoustics is higher than the output impedance of the amplifier, then the sound will be much quieter.

For active speaker systems, important parameters are harmonic distortion factor, caused by nonlinear distortions of the amplifier and the relationship between the level of the useful signal and the level of the “noise” signal introduced by the amplifier.

Speaker harmonic distortion (THD)

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

Signal-to-noise ratio of the speaker system

All of the above parameters significantly simplify the selection 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 purchasing, you should not forget about the individual characteristics of sound perception, and carefully listen and compare several types of acoustics.

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

Power

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

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

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

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

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

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

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

Sensitivity

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

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

frequency response

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

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

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

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

Nonlinear distortion, harmonic distortion

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

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

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

Total electrical resistance, impedance

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

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

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

Speaker housing, acoustic design

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

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

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

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

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

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

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

Many people have sometimes had to wonder what exactly the power means, which is given in one form or another in the passports of acoustic systems and sound reinforcement equipment. There are surprisingly few materials on this topic on the Internet and in printed publications, and there are also few clear answers to questions. I'll try to somehow reduce the number of white spots in this area. Some more precise descriptions of definitions arose in my dialogue, while trying to better explain their meaning to my interlocutor.

The variety of standards used to measure amplifier output power and speaker power can be confusing for anyone. Here is a block amplifier from a reputable company with 35 W per channel, and here is a cheap music center with a 1000 W sticker. Such a comparison will clearly cause confusion among a potential buyer. It's time to turn to standards...

Foreign and international standards and definitions

SPL(Sound Pressure Level) - the level of sound pressure developed by the speaker. SPL is the product of the relative sensitivity of the speaker system (sound system) and the supplied electrical power. It should be borne in mind that hearing is a non-linear instrument, and to estimate subjective loudness, corrections must be made to the weighting curves, which in practice differ not only for different signal levels, but also for each individual.

A-weighting(weighting curve) - weighting curve. A relationship describing sound pressure levels at different frequencies that are perceived by the ear as equally loud. Amplitude-frequency response of a weighting filter used in sound pressure level measurements and taking into account the frequency properties of human hearing.

RMS(Root Mean Squared) - root mean square value of electrical power limited by specified nonlinear distortions. Or in another way - the maximum (limit) sinusoidal power - the power at which an amplifier or speaker can operate for one hour with a real music signal without physical damage. Typically 20 - 25 percent higher than DIN.

Power is measured with a sine wave at 1 kHz when 10% THD is reached. It is calculated as the product of the rms values ​​of voltage and current with an equivalent amount of heat created by direct current.

For a sinusoidal signal, the root mean square value is V2 times less than the amplitude value (x 0.707). In general, this is a virtual quantity; the term “rms”, strictly speaking, can be applied to voltage or current, but not to power. A well-known analogue is the effective value (everyone knows it for the AC power supply network - these are the same 220 V for Russia).

I will try to explain why this concept is not very informative for describing sound characteristics. RMS power is the work that produces work. That is, it makes sense in electrical engineering. And it does not necessarily refer to a sinusoid. In the case of musical signals, we hear loud sounds better than weak ones. And the hearing organs are affected more by amplitude values, rather than by root-mean-square values. That is, volume is not equivalent to power. Therefore, root-mean-square values ​​make sense in an electric meter, but amplitude values ​​make sense in music. An even more populist example is the frequency response. Frequency response dips are less noticeable than peaks. That is, loud sounds are more informative than quiet ones, and the average value will say little.

Thus, the RMS standard was one attempt to describe the electrical parameters of audio equipment as a consumer of electricity.

In amplifiers and acoustics, this parameter also, in fact, has a very limited use - an amplifier that produces 10% distortion not at maximum power (when clipping occurs - limiting the amplitude of the amplified signal with specific dynamic distortions arising), still look. Before reaching maximum power, the distortion of transistor amplifiers, for example, often does not exceed hundredths of a percent, and already above it increases sharply (abnormal mode). Many acoustic systems can already fail if operated for a long time at this level of distortion.

For very cheap equipment, another value is indicated - PMPO, a completely meaningless and not standardized parameter by anyone, which means that our Chinese friends measure it as God pleases. More precisely, in parrots, each in its own way. PMPO values ​​often exceed nominal values ​​by up to a factor of 20.

PMPO(Peak Music Power Output) - peak short-term musical power, a value that means the maximum achievable peak value of the signal, regardless of distortion in general, in a minimum period of time (usually 10 mS, but, in general, not standardized), the power that the speaker speaker can withstand for 1-2 seconds on a low frequency signal (about 200 Hz) without physical damage. Typically 10 - 20 times higher than DIN
As follows from the description, the parameter is even more virtual and meaningless in practical use. I advise you not to take these values ​​seriously and not rely on them. If you happen to buy equipment with power parameters indicated only as PMPO, then the only advice is to listen for yourself and determine whether it suits you or not.

100 W (PMPO) = 2 x 3 W (DIN)

DIN is an abbreviation for Deutsches Institut fur Normung.

German non-governmental organization dedicated to standardization for better integration of the market for goods and services in Germany and on the international market. The products of this organization are a variety of standards covering a wide variety of applications, including those related to the field of sound reproduction, which is what interests us here.

DIN 45500, which describes the requirements for high-fidelity sound equipment (aka Hi-Fi - High Fidelity), includes:

• DIN 45500-1 High fidelity audio equipment and systems; minimum performance requirements.
• DIN 45500-10 High fidelity audio equipment and systems; minimum performance requirements for headphones.
• DIN 45500-2 Hi-Fi technics; requirements for tuner equipment.
• DIN 45500-3 Hi-Fi technics; requirements for disk record reproducing equipments.
• DIN 45500-4 High fidelity audio equipment and systems; minimum performance requirements for magnetic recording and reproducing equipment.
• DIN 45500-5 High fidelity audio equipment and systems; minimum performance requirements for microphones.
• DIN 45500-6 High fidelity audio equipment and systems; minimum performance requirements for amplifiers.
• DIN 45500-7 Hi-Fi-technics; requirements for loudspeakers.
• DIN 45500-8 Hi-Fi technics; requirements for sets and systems.

DIN POWER- the value of the power output at the actual load (for the amplifier) ​​or supplied (to the speaker), limited by the specified nonlinear distortions. It is measured by applying a signal with a frequency of 1 kHz to the device input for 10 minutes. Power is measured when it reaches 1% THD (non-linear distortion). There are other types of measurements, for example, DIN MUSIC POWER, which describes the power of the music (noise) signal. Typically the value quoted as DIN music is higher than that quoted as DIN. Approximately equivalent to sine wave power - the power at which an amplifier or speaker can be operated for an extended period of time with a pink noise signal without physical damage.

Domestic standards

In Russia, two power parameters are used - nominal and sinusoidal. This is reflected in the names of speaker systems and speaker designations. Moreover, if previously the rated power was mainly used, now more often it is sinusoidal. For example, 35AC speakers were subsequently designated S-90 (nominal power 35 W, sine wave power 90 W)

Rated power (GOST 23262-88) is an artificial value; it leaves freedom of choice to the manufacturer. The designer is free to specify the rated power value that corresponds to the most advantageous value of nonlinear distortion. Typically, the indicated power was adjusted to the GOST requirements for the complexity class with the best combination of measured characteristics. Indicated for both speakers and amplifiers. Sometimes this led to paradoxes - with step-type distortion occurring in class AB amplifiers at low volume levels, the level of distortion could decrease as the output signal power increased to the nominal one. In this way, record rated characteristics were achieved in the amplifier data sheets, with an extremely low level of distortion at a high rated power of the amplifier. Whereas the highest statistical density of a musical signal lies in the amplitude range of 5-15% of the maximum power of the amplifier. This is probably why Russian amplifiers were noticeably inferior in hearing to Western amplifiers, whose optimum distortion could be at medium volume levels, while in the USSR there was a race for a minimum of harmonic and sometimes intermodulation distortion at any cost at one nominal (almost maximum) power level.

Nameplate noise power - electrical power limited exclusively by thermal and mechanical damage (for example: slipping of the turns of the voice coil due to overheating, burnout of conductors in places of bending or soldering, breakage of flexible wires, etc.) when pink noise is supplied through the correction circuit for 100 hours.

Sine wave power is the power at which an amplifier or speaker can operate for an extended period of time with a real music signal without physical damage. Usually 2 - 3 times higher than nominal.

Maximum short-term power is the electrical power that the speakers can withstand without damage (checked by the absence of rattling) for a short period of time. Pink noise is used as a test signal. The signal is sent to the speaker for 2 seconds. Tests are carried out 60 times at intervals of 1 minute. This type of power makes it possible to judge the short-term overloads that a loudspeaker can withstand in situations that arise during operation.

Maximum long-term power is the electrical power that the speakers can withstand without damage for 1 minute. The tests are repeated 10 times with an interval of 2 minutes. The test signal is the same.

The maximum long-term power is determined by a violation of the thermal strength of the speakers (sliding of the turns of the voice coil, etc.).

Pink noise (used in these tests) is a group of signals with a random nature and a uniform spectral density of frequency distribution, decreasing with increasing frequency with a drop of 3 dB per octave over the entire measurement range, with the average level depending on frequency in the form 1/f. Pink noise has constant (over time) energy in any part of the frequency band.

White noise is a group of signals with a random nature and a uniform and constant spectral frequency distribution density. White noise has the same energy at any frequency range.

An octave is a musical frequency band whose extreme frequency ratio is 2.

Electrical power is the power dissipated by an ohmic equivalent resistance equal in value to the nominal electrical resistance of the AC, at a voltage equal to the voltage at the AC terminals. That is, at a resistance that emulates a real load under the same conditions.

Don't forget about speaker impedance. Mostly on the market there are speakers with a resistance of 4, 6, 8 ohms, 2 and 16 ohms are less common. The amplifier power will vary when connecting speakers of different impedances. The amplifier's instructions usually indicate what speaker impedance it is designed for, or the power for different speaker impedances. If the amplifier allows operation with speakers of different impedances, then its power increases as the impedance decreases. If you use speakers with an impedance lower than that specified for the amplifier, this may cause it to overheat and fail; if it is higher, then the specified output power will not be achieved. Of course, the volume of the acoustics is affected not only by the output power of the amplifier, but also by the sensitivity of the speakers, but more on that next time. The main thing is not to forget that power is only one of the parameters, and not the most important one for obtaining good sound.

The physical characteristic of sound volume is the sound pressure level. Measured in decibels (dB). 30 dB - whisper. 50-65 dB - quiet / loud conversation. 70-80 dB - scream. 100 dB - tutti of a symphony orchestra. 140 dB - the plane is at the start.

Amplifier power and speaker impedance

Energy characteristics of the electrical signal produced by the amplifier at the output. The unit of measurement is Watt. The level of electrical power developed by the amplifier at the output depends on the input impedance of the speaker system. 8 ohm speakers tend to be quieter than 4 ohm speakers. The best amplifier models double the electrical power when the load impedance is halved. The power of a standard home audio amplifier (at 4 Ohm load) is 25-150 Watts. The power of professional amplifiers designed for sounding large spaces (halls, open areas) is hundreds and thousands of watts.

AC power

Usually, by power (peak musical power) of speakers we mean the maximum level of electrical signal, at which the acoustics are able to sound without mechanical damage. The value of the musical power of an acoustic system is limited by the mechanical and electrical strength of the loudspeakers of the acoustic system. In some cases, the power calculation also takes into account the acceptable level of distortion. There are different standards and methods for measuring speaker power.

Specifications for passive speakers often indicate the range of recommended power of the amplifier connected to the speaker system (for example, 25-120 W). The upper power value (in this case 120 W) is essentially the musical power of that speaker system, exceeding which may damage it. The lower value indicates the minimum permissible amplifier power (in this case 25 W), together with which this speaker system is still capable of providing acceptable sound quality.

Sensitivity and power

Speaker sensitivity is a characteristic that shows how loud the sound will be when a signal of a certain power is applied to the speaker. Sensitivity is measured in dB/W/m. For example, a sensitivity value of 93 dB/W/m indicates that when 1 W of power is supplied from the amplifier, the speaker creates a sound pressure level of 93 dB at a distance of 1 m on the radiation axis. Typical sensitivity values ​​of modern speakers are in the range of 84-97 dB/W/m.

Calculation of required power

Sound amplification power is calculated based on:
1) desired volume level (in dB)
2) technical parameters of the speakers
3) acoustic features of the space and placement of loudspeakers

The main rule for calculation: an increase of 3 dB is equivalent to a twofold increase in the supplied power. An increase of 1 dB corresponds to an increase in power by 1.25 times, and by 2 dB - by 1.6 times (since “decibel” is a unit of logarithmic nature). Accordingly, a speaker with a sensitivity of 90 dB/W/m at 100 W of power will sound as loud as a speaker with a sensitivity of 87 dB/W/m at 200 W.

To sound a small room (area 14-16 sq. m) using acoustic systems with a characteristic sensitivity of 90 dB/W/m, it is enough to have an amplifier with an output power of 20-30 W per channel. For larger rooms of 18-20 sq. m. optimal results can be achieved using an amplifier with a power of 40-50 W. To sound large spacious halls, power of hundreds of watts is required. For sound recording at concert venues - thousands of watts.