In the field of professional sound reinforcement, the equipment of audio equipment is very important. Among them, the equipment of power amplifier and speaker is the most important. The equipment of power amplifier and speaker touches many aspects, such as power amplifier brand, selection of power tube type and low frequency. What kind of amplifier should the sensitivity speaker be equipped with, etc. We all know that after the acoustic design of the hall, the speaker power needs to be confirmed according to a series of calculations, and then the power amplifier power is confirmed by the speaker power, but how to choose the power of the two to achieve the best match?

Inexperienced tuners may think that the output power of the power amplifier is too high, which will cause damage to the tweeter, but it is not. In professional occasions, the loudspeaker can generally withstand a large signal shock of 3 times the rated power, and can instantly accept a peak shock of 5 times the rated power without damage. Therefore, under normal circumstances, there is no problem with the rated power of the speaker taking 1/2 of the power amplifier. Therefore, it is rarely assumed that the tweeter is burned by the high power of the power amplifier, not due to unexpected strong impact or long-term howling of the microphone. As we all know, there are multiple speaker units in most sound boxes, and the power received by each speaker unit is distributed differently according to the different frequency division points. Figure 1 is a diagram of dynamic energy distribution in nature. Under normal conditions, the percentage of power distribution of each speaker unit is shown in Figure 1. In the figure, the frequency band assigned to a speaker is read out from the abscissa, and the percentage difference corresponding to the ordinate is the assigned power. For example: a two-way speaker with a crossover point of 1.6kHz (point A in the picture), the tweeter accepts power 100%-78%=22%, and the bass unit accepts power 78%-0%= 78%.

The rated power of the speakers, the general professional speakers indicate the maximum pink noise power, while the fever and civilian professional speakers are more vague, but they are basically the total power of each unit. In other words, the power rating of the speaker refers to the analog signal power that pink noise or broadband can accept. As shown in Figure 1, a two-way speaker with a crossover point of 1.6kHz and a rated power of 100W, at the rated power, the woofer unit can be assigned an output power of 78W, while the tweeter unit can only be assigned to 22W. Therefore, it is acceptable to apply 100W of pink noise power or general program signal power to the speaker; but when using a 100W single-frequency signal to check, both the tweeter and the bass unit may be damaged. Another example is a three-way speaker, the frequency division point of the mid and treble is 4kHz, then the power received by the tweeter only needs to be 5% of the nominal power. If the power distribution is improper, it will easily cause damage to the tweeter.

We know that in the 20Hz to 20kHz range of the human ear, music signals that actually meet a lot of energy are generally in the middle and low frequency bands, while the high frequency band energy is only equivalent to 1/10 of the energy in the middle and low frequency bands. Generally speaking, there is not much weight in high-pitched voices and music signals, and metal musical instruments and silk-stringed songs have more high-pitched voices. Therefore, the power lost in the treble of general speakers is much lower than that of low-pitched speakers, in order to balance the high and low voices; and the power amplifier is such as a current The modulator, under the control of the input audio signal, outputs currents of different sizes to the speakers, so that they can announce different dynamics. Under certain impedance conditions, it is necessary to make the power amplifier with a nominal power of 200W reach 400W or several times. The output is actually very simple, but the distortion (THD) of the power amplifier will be greatly increased. This distortion mainly occurs in the high-frequency harmonics in the mid- and low-frequency signals. The greater the distortion, the greater the high-frequency harmonic energy. These high-frequency distortion signals will enter the tweeter together with the high-frequency music signal. What effect will this have? The power distribution ratio of the general speaker is based on the rules shown in the attached picture.

Taking a three-way speaker as an example, under normal conditions, if the signal input to the speaker is doubled, the power of the tweeter will only increase by 5W; but assuming that the power of the power amplifier is short, the signal overload will be clipped, and high harmonics will appear. The wave weight will increase dramatically. In addition to the original 1kHz sine wave, there will also be many odd harmonics, such as 3kHz, 5kHz, etc. sine wave energy, which greatly increases the proportion of high-pitched components in the signal, which will cause the high-frequency spectral energy in the signal to be far across the power that the tweeter can accept. Even if the total signal power at this time has not reached the rated power of the speaker, the tweeter has been overloaded and damaged. This condition is more risky than short-term overloading of the signal, but without clipping. When the signal is not distorted, the power energy of the short-term overloaded 1kHz signal falls on the woofer unit with higher power, which does not necessarily exceed the short-term maximum power of the speaker. Generally, it will not constitute a fault in the power distribution of the speaker and damage the speaker unit. . Therefore, in normal use, under certain impedance conditions, the power of the power amplifier should be greater than the power of the speaker, but not too large. In general application places, the undistortion rate of the power amplifier should be about 1.2 to 1.5 times the rated power of the speaker; in large dynamic situations, it should be about 1.5 to 2 times. In this way, the adjustment ensures that the power amplifier does not cause distortion at the maximum power of the professional speaker.