Friends who often pay close attention to the speaker should know that the middle and high pitch units in the speaker box are easy to burn down, especially in places such as studio, theater, singing and dancing hall and conference room. What’s going on? This reason I believe some friends know, there are also some understanding but not clear, the following baibaocheng audio and video for you to detailed introduction to the cause of professional speaker burning high pitch unit, let’s have a look.
Reasonable configuration of sound box and power amplifier
When some friends see the title, they may think that the power of the amplifier is too high, which leads to the damage of the speaker tweeter. In fact, it is not. Professional speakers, speakers can generally withstand 3 times of the rated power of the large signal impact, instantaneous can withstand 5 times the rated power peak impact without damage. Therefore, the power of the amplifier is twice as high as the rated power of the speaker. As a result, as long as it is not accidental strong impact or the high pitched unit howls for a long time, it is very rare that the high power amplifier will burn down the high pitch unit.
As we all know, there are many loudspeakers in the loudspeaker box, and the power borne by the loudspeakers is distributed according to different frequency division points.
Generally, professional speakers will be marked with the maximum pink noise power, fever and civil audio marks are vague, but are the total power of each unit. In other words, the rated power of the speaker refers to the pink noise or analog signal power that the broadband can bear. A 2-way loudspeaker with 1.6kHz frequency division point and 100W rated power can allocate 78W output power to the bass unit and 22W to the treble unit at the rated power. Therefore, if 100W pink noise power or ordinary program signal power is applied to the speaker, it can bear it; when 100W single frequency signal is used to test, both the high and low pitch units may be damaged.
If a three-way speaker has a frequency division point of 4kHz for medium and treble, then the bearing power of the treble unit is only 5% of the nominal power. If the power distribution is not proper, it will easily cause damage to the treble unit.
We know that in general, the treble component of voice and music signal is not much, while that of metal musical instrument and silk string music is higher. Taking the three frequency loudspeaker as an example, under normal circumstances, if the input signal to the speaker is doubled, the power of the treble head will only increase by 5W; however, if the power of the power amplifier is insufficient, resulting in signal overload and clipping, the higher harmonic component will increase sharply. The original 1kHz sine wave generates a large number of odd harmonics, such as 3kHz, 5KHz and other sine wave energy, which greatly increases the proportion of treble components in the signal, and then causes the high frequency spectrum energy in the signal far exceeds the power that the treble unit can bear. Even if the total signal power at this time has not reached the rated power of the speaker. But the tweeter has been overloaded and damaged. This situation is more dangerous than short-term overload of signal without clipping. When the signal is not distorted, the power energy of 1kHz signal overloaded for a short time falls on the bass unit with larger power, which does not necessarily exceed the short-term maximum power of the speaker. Generally speaking, the deviation of power distribution of the speaker will not cause damage to the loudspeaker unit. Therefore, under normal use conditions, the rated output power of the power amplifier is 2-3 times of the rated power of the speaker, so as to ensure that the power amplifier does not cause distortion at the maximum power of the speaker.
Improper use of frequency divider
The improper use of the input frequency divider or the unreasonable working frequency range of the loudspeaker is also one of the reasons for the damage of the treble unit. When using the frequency divider, the frequency division point should be selected reasonably according to the working frequency range of the loudspeaker provided by the manufacturer. If the frequency division point of the tweeter is low and the power load is too heavy, it is easy to burn the tweeter, and so is the midrange horn.
Improper adjustment of equalizer
The adjustment of equalizer is also very important. Frequency equalizer is set up to compensate for various defects of indoor sound field and frequency unevenness of loudspeakers. It should be debugged with actual spectrum analyzer or other instruments. The transmission frequency characteristics after debugging should be relatively flat in a certain range. Many tuners who do not have sound knowledge can debug at will, and even quite a few people raise the high and low frequency parts of equalizer too high, forming a “V” shape. If these frequencies are increased by more than 10dB compared with the mid tone frequency (the adjustment of equalizer is generally within ± 12dB), the electric power will be increased by more than 3 times than that of the mid tone part. In this case, not only the phase distortion caused by the equalizer will seriously stain the music sound, but also it is very easy to cause the speaker high pitch unit to burn out, which is also the main reason for the speaker burning. Of course, the design of the sound system should be based on the actual situation, such as the size of the site, the use of the building sound conditions, etc., and the maximum continuous sound pressure level should be determined according to the actual use conditions, and then the maximum SPL value of the speaker should be determined.
Many users set the attenuator of the back stage power amplifier at – 6dB, – 10dB, that is, 70% – 80% of the volume knob, or even half of the volume knob. They increase the input of the mixer to achieve the appropriate volume. They think that if the power amplifier has a margin, the speaker will be safe. In fact, this is also wrong. The attenuation knob of the power amplifier attenuates the input signal. If the input of the power amplifier is attenuated by – 6dB, it means that to maintain the same volume, the mixer or front stage must output 6dB more, the voltage should be doubled, and the upper dynamic margin of input, commonly known as “overhead space”, should be cut off by half. At this time, if there is a sudden big signal, the mixer output will be overloaded by 6dB earlier, and amplitude clipping waveform will appear. Although the amplifier is not overloaded, the input is clipping waveform. If the treble component is too heavy, not only the treble is distorted, but also the treble unit may be burnt out.
From the above analysis, we can clearly understand that one of the important reasons for the loudspeaker burning the treble unit is that the power of the power amplifier is too small, not too large. The signal from the power amplifier itself is the clipping signal, which leads to damage to the speaker. Therefore, in the configuration of audio, we must establish a correct understanding, and use the “big horse pulling the car” scheme to prevent the power amplifier from sending out the clipping signal and damaging the high and medium tone speaker units. In the design of sound system, the design power of power amplifier and sound box should be matched according to the above principles. In practice, the equipment in each link should be used reasonably, so as to protect the equipment and achieve the best effect of the sound system.