Output power. Sound power standards RMS, AES, Program power, Peak power What is speaker output power

Often our customers, seeing numbers in the name of the stabilizer, mistake them for power in Watts. In fact, as a rule, the manufacturer indicates full power device in Volt-Amps, which is not always equal to the power in Watts. Because of this nuance, regular power overloads of the stabilizer are possible, which in turn will lead to its premature failure.

Electrical power includes several concepts, of which we will consider the most important for us:

Apparent Power (VA)- a value equal to the product of current (Ampere) and voltage in the circuit (Volts). Measured in Volt-Amps.

Active power (W)- a value equal to the product of current (Ampere) and voltage in the circuit (Volts) and load factor (cos φ). Measured in Watts.

Power factor (cos φ)- value characterizing the current consumer. Speaking in simple language, this coefficient shows how much total power (Volt-Ampere) is needed to “push” the required useful work power (Watt) to current consumer. This coefficient can be found in technical specifications current consuming devices. In practice, it can take values ​​from 0.6 (for example, a hammer drill) to 1 (heating devices). Cos φ can be close to unity in the case when the current consumers are thermal (heating elements, etc.) and lighting loads. In other cases, its value will vary. For simplicity, this value is considered to be 0.8.

Active Power (Watts) = Apparent Power (Volt-Amps) * Power Factor (Cos φ)

Those. when choosing a voltage stabilizer for a home or country house as a whole, its total power in Volt-Amps (VA) should be multiplied by the power factor Cos φ = 0.8. As a result we get approximate power in Watts (W) for which this stabilizer is designed. Do not forget to take into account in your calculations starting currents electric motors. At the moment of start-up, their power consumption can exceed the nominal capacity from three to seven times.

With active load resistance output power amplifier is equal to

Where Uout- active, and Um out – amplitude value of the output voltage.

Output power is the useful power developed by the amplifier into the load resistance.

The increase in the output power of the amplifier is limited by distortions that arise due to the nonlinearity of the characteristics of the amplifying elements at large signal amplitudes. Therefore, most often an amplifier is characterized by the maximum power that can be obtained at the output, provided that the distortion does not exceed a given (permissible) value.

This power is called nominal amplifier output power.

Efficiency

This indicator is especially important to consider for medium and high power amplifiers, as it allows you to evaluate their efficiency. Numerically efficient equals

Where R o – power consumed by the amplifier from the power source.

Rated input voltage (sensitivity)

The rated input voltage is the voltage that must be applied to the input of the amplifier in order to obtain the specified output power. The input voltage depends on the type of source of amplified oscillations. The lower the input voltage that provides the required output power, the higher the sensitivity of the amplifier. Applying a voltage higher than the rated voltage to the input of the amplifier leads to significant signal distortion and is called input-side overload.

If an amplifier is designed to operate from several sources, then its input is usually calculated at the lowest voltage provided by one of the sources, and other signal sources are connected through voltage dividers.

Amplified frequency range

The range of amplified frequencies, or bandwidth, is the frequency region in which the gain does not change more than is permissible according to technical conditions.

Allowable changes in gain factors within the passband depend on the purpose and operating conditions of the amplifier.

Amplifier self-noise level

The causes of interference at the amplifier output can be divided into three main groups:

1) thermal noise, 2) noise of amplifying elements, 3) interference due to supply voltage ripples and interference from external electromagnetic fields.

It is known that in conductors and semiconductors at normal room temperature (about
C) electrons move chaotically, and in each at the moment the number of electrons moving in any one direction exceeds the number of electrons moving in other directions. The preferential movement of electrons in any direction is an electric current and, therefore, a voltage is created on the conductor or semiconductor that does not obey any specific law.

Noise voltages, due to their randomness, have very different frequencies and phases and therefore practically cover the entire frequency band of the amplifier. Therefore, as the amplifier bandwidth increases, the noise level increases. In addition, the higher the temperature and the greater the resistance of the circuit, which creates the thermal noise voltage, the greater the noise.

At a temperature of 20 - 25°C, the noise voltage can be found using the formula

U t.sh
,

Where U t.sh – thermal noise voltage, µV; f in and f n - the highest and lowest frequencies transmitted by the circuit, kHz;

R– active component of the circuit resistance in the frequency band from f in to f n, kOhm.

All amplifier circuits create thermal noise voltage, but the inherent noise of the first amplifier stages has a particularly large impact, since this noise is subsequently amplified by all subsequent stages. If, for example, the highest and lowest operating frequencies of the amplifier are 10000 and 100 Hz, and the active resistance of the input circuit is 500 Ohms, then the thermal noise voltage will be equal to

U t.sh
≈ 0.27 µV.

The above calculations show that the thermal noise voltage is very small. Therefore, interference from thermal noise in amplifiers affects only at high gain factors.

Noise voltage can also arise due to the uneven movement of electrical charge carriers through the amplifying element. This phenomenon is called shot effect . The noise level of transistors is usually assessed by the noise figure, expressed in decibels and showing how many decibels a transistor connected to the circuit increases the noise level compared to the thermal noise of the circuit.

Great influence on general level Amplifier interference is caused by voltage pulsations of power supplies, as well as interference from external electric and magnetic fields. Reducing this interference can be achieved by using additional smoothing filters at the output of power supplies and careful shielding of the most critical amplifier circuits (mainly input).

The amount of total noise at the output of the amplifier should be significantly less than the voltage of the amplified signal; otherwise, it will be impossible to isolate a useful signal from the chaotically changing interference voltage. It is usually believed that the useful signal must exceed the interference level by at least

2 – 3 times (by 6 – 10 dB).

The ratio of the amplitudes of the strongest and weakest signals at the input of the amplifier is called the dynamic range of amplitudes D. Dynamic range is usually expressed in decibels

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 speakers ( speaker system) to the supplied electrical power. It should be borne in mind that hearing is a nonlinear instrument, and to estimate subjective loudness, corrections should be made to the weighting curves, which in practice differ not only for different levels signal, but also for each individual individually.

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. Well-known analogue - effective value(everyone knows it for the power supply network alternating current- 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. 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 ones. 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 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 very limited use - an amplifier that produces 10% distortion not at maximum power(when clipping occurs - limitation of the amplitude of the amplified signal with specific dynamic distortions arising), look further. 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 application. 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 indicated value of DIN music is higher than that given 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 it was mainly used rated power, then now more often - 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 corresponding to the most advantageous value of nonlinear distortion. Typically, the indicated power was adjusted to the GOST requirements for the complexity class of execution at the best combination 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 in amplifier data sheets were achieved, 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 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.

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 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 the 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 dependence of the average level on frequency in the form 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.

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

Electrical power - power dissipated in an ohmic equivalent resistance, equal in value to the nominal electrical resistance 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 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...

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.

Sinusoidal power- the power at which an amplifier or speaker can operate for a long 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 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.

RMS(Rated Maximum 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(Peak 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.

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

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.

For general development, and "so that it was":

The greatest number of discrepancies when choosing speakers is caused by the power indicated in the passport data. On current moment There are several standards for measuring the power of dynamic drivers. Of course, each standard has its pros and cons, and the values ​​obtained as a result of measurements of the power characteristics of loudspeakers also differ.
It is quite natural that, for commercial reasons, speaker manufacturing companies are interested in indicating the power in those standards that make it possible to deliver great value without going into conflict with your own conscience. The result of all these discrepancies, as a rule, is inconsistency between the power amplifier and the speaker system, which subsequently leads to failure of the latter.
Most amplifier manufacturers quote output power in RMS, while most speaker manufacturers quote power in the more fashionable AES standard.
We present comparative power conversion factors for the two above standards.
AES 1 W= RMS 1 W. x 1.43.
Program power (Music): Program power 1 W = RMS 1 W. x 2.
Peak power is a short-term value, no more than 10 ms, at which the speaker is not destroyed:
Peak power 1 W = RMS 1 W. x 4.
Example: * Let's take the most frequently cited power data for the Eighteen Sound 18LW1400 speaker.
******* 18LW1400 - 1000 W.
We get:
******* RMS = 1000/1.43 = 700 W.
******* Program power* = 700 x 2 = 1400 W.
******* Peak power = 700 x 4 = 2800 W.
Which, by the way, is honestly said in the native Italian catalogue.
ATTENTION: All P.AUDIO speaker power data is in RMS standard.

Taken from P.audio website