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Regarding the power matching between the power amplifier and the speakers

2021-05-09 17
Regarding the power matching between the power amplifier and the speakers, this is a problem that many people are concerned about, and there are many opinions in the industry. For this problem, if you just look for the answer instead of looking at it from a system perspective, there are problems with how to match.

First of all, we have to figure out the concept of speaker power. This concept is wrong. All discussions about power matching are wrong. For example, it is often heard that this speaker has a lot of power and no power amplifier can push it.

But this is a wrong perception!

The concept of speaker power is different from ordinary electrical appliances. The general electrical concept of electrical power is "need". It needs to be supplied with nominal power to work effectively. For example, a 1000 watt rice cooker needs to provide it with 1000 watts of power. The speaker power is "withstand", the concept is completely different, the nominal 1000 watts means that the speaker can withstand 1000 watts of power, instead of having to give it 1000 watts to work, you give it 1 watt of power and it will emit Corresponding to a sound pressure of 1 watt, this is an essential difference.

Sometimes, there will be a phenomenon. When a speaker with a low power amplifier is used to drive a speaker with a large nominal power, it will feel that it is not strong enough and the sound cannot be produced. This situation cannot be simply understood as the speaker power is too large. Can't push; problems with speakers or amplifiers themselves will cause this phenomenon, not the size of their respective power problems.

When we have figured out the concept of speaker power, then we will discuss the matching of power amplifier and speaker.

Of course, we can't look at the matching problem of power amplifier speaker power in isolation, but must closely follow the scene application to get the correct result.

You can't just look at the power matching problem of the power amplifier speaker, you must combine the specific application to get the correct result.

First of all, we need to know what kind of scene application this is. For example, a quiet conference hall and an electronic music bar have completely different requirements for sound pressure, and this difference will cause the required power to be very different.

Regarding the power matching between the power amplifier and the speakers

Assuming that a place with gentle sound pressure requirements needs to generate 100db sound pressure at 8 meters, we can first randomly set a speaker with a sensitivity of 98db/1m, and calculate the required power according to the physical rules of distance and sound pressure. .

Every time the distance is doubled, the sound pressure decreases by 6db. The law of physics can tell that the sound pressure of a speaker with a sensitivity of 98db/1m at 8 meters drops to 80db, and the sound pressure increases by 3db for every doubling of the power. According to the law, it is calculated that adding 128w of power to the speaker can produce a sound pressure of 101db. The conclusion is that in this place, a speaker with a sensitivity of 98db and a power of 130 watts can meet the application needs of the scene. .

However, according to actual application experience, due to the dynamic factors of music, it is necessary to add a power margin of 20db, which is 10 times, 1280 watts, to ensure that the power amplifier itself is not easily overloaded; once the power amplifier is overloaded, it will output a large amount of high-frequency distortion components. Thereby causing serious impact on the horn, especially the tweeter.
The smaller the power amplifier power, the more likely it is to be overloaded and distorted, and the easier it is to burn the speaker.

Some people may ask, the power of the amplifier is ten times that of the speaker, will the speaker not burn out?

The answer is no!

Because, according to the application requirements, as long as 100db sound pressure at 8 meters is enough, the power amplifier power only needs 128w to meet the needs; no matter how large the power is, it will exceed the demand, and it will be unbearable for people to listen. Will continue to push up. Therefore, although the power amplifier is much more powerful, it is not normally used. The excess part is only used to meet the needs of instant peaks, to ensure that the amplifier itself is not overloaded, rather than dumping all the power. On the speakers! The speaker is a high-power signal that can withstand no overload distortion for a short time, as long as it is not continuous.

A power amplifier without power headroom will produce clipping and distortion due to overload when the music peak comes, which will cause the sound to deteriorate at a minimum, and will burn the treble until the woofer is also burned out.

In addition, if the user feels that the sound pressure is sufficient, he will no longer continue to push the volume up, and if the sound pressure is too high, he will not be able to stand it.
Next, we look at how to choose the power of the speakers.

In theory, 128-watt speakers can meet the needs, but there is no power margin.

The diaphragm of the speaker is a moving part. The greater the amplitude, the greater the distortion. The distortion will become large when it is close to full load. Therefore, in order to maintain good sound quality, try to make the speaker work at low power and light load. , Stay away from full load. If the application is not very intense and not very dynamic, consider that the power does not exceed one-third of the rated power when the speaker is working normally; according to this principle, we should choose a speaker with a power of 400 watts or more. But if it is an intense application of large dynamics, it is best to leave a margin of 10 times.

Frequent full-load work, the speaker is also easy to damage.

In this example, selecting a speaker with a sensitivity of 98db/1m and a power of 400 watts, combined with a 1300 watt power amplifier, can well meet the application needs of generating a sound pressure of 100 db at 8 meters.

The above is an example of a speaker. In actual applications, it is usually a combination of many speakers, but the principle is the same.

in conclusion

The matching problem of the speaker and the power amplifier must be considered in conjunction with the specific application project, otherwise, how to match may be wrong, as long as the matching is reasonable, even if the power of the power amplifier is more than ten times larger than the speaker, it will not burn the speaker!
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