How to understand the reasons for the speaker's tweeter burning

Friends who often pay attention to speakers should know that the mid- and high-pitched units in speakers are easy to burn out, especially in places such as studios, theaters, dance halls, conference rooms, etc. What is going on? I believe some friends know the reason, and some understand but are not clear. Below, Baibaocheng Audio and Video will give you a detailed introduction to the reasons why professional speakers burn out the high-pitched units. Let's take a look.

Reasonable configuration of speakers and power amplifiers

When seeing the title, some friends may think that the damage to the tweeter unit of the speaker is caused by the excessive power of the amplifier. In fact, this is not the case. Professional speakers can generally withstand a large signal impact of 3 times the rated power, and can instantly withstand a peak impact of 5 times the rated power without being damaged. Therefore, there will be no problem if the power of the amplifier is twice the rated power of the speaker. Therefore, as long as there is no unexpected strong impact or the tweeter howls for a long time, it is very rare for the tweeter to be burned out by the high power of the amplifier.

As we all know, there are multiple speakers in a sound box, and the power borne by the speakers is distributed differently according to different crossover points.

Generally, professional speakers will indicate the maximum pink noise power, while the labels for audiophiles and civilian speakers are more vague, but they are all the total power of each unit. In other words, the rated power of the speaker refers to the analog signal power that pink noise or broadband can withstand. A two-way speaker with a crossover point of 1.6kHz and a rated power of 100W, at rated power, the woofer can be allocated 78W of output power, while the tweeter is only allocated 22W. Therefore, if 100W of pink noise power or ordinary program signal power is applied to the speaker, it can withstand it; but when tested with a 100W single-frequency signal, both the tweeter and the woofer may be damaged.

If the crossover frequency of the mid-range and high-frequency of a three-way speaker is 4kHz, the power that the tweeter can bear is only 5% of the nominal power. If the power is not distributed properly, it will easily cause damage to the tweeter.

We know that there are not many treble components in general human voice and music signals, while there are more treble components in metal instruments and string music. Taking a three-way speaker as an example, under normal circumstances, if the signal input to the speaker is doubled, the power of the tweeter will only increase by 5W; but if the power of the power amplifier is insufficient, the signal will be overloaded and clipped, and the high-order harmonic components will increase dramatically. In addition to the original 1kHz sine wave, a large number of odd harmonics are generated, such as 3kHz, 5kHz and other sine wave energy, which greatly increases the proportion of treble components in the signal, and then causes the treble spectrum energy in the signal to far exceed the power that the tweeter can withstand. 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 a short-term overload of the signal without clipping. When the signal is not distorted, the power energy of the short-term overloaded 1kHz signal falls on the woofer with a larger power, which does not necessarily exceed the short-term maximum power of the speaker, and generally does not cause a deviation in the speaker power distribution and damage the speaker unit. Therefore, under normal use conditions, the rated output power of the power amplifier is 2-3 times the rated power of the speaker to ensure that the power amplifier does not cause distortion at the maximum power of the speaker.

Improper use of crossover

Improper use of the input frequency division point or unreasonable working frequency range of the speaker is also a reason for the damage of the tweeter. When using the crossover, the crossover point should be reasonably selected according to the working frequency range of the speaker provided by the manufacturer. If the crossover point of the tweeter is selected too low, the power burden is too heavy, which will easily burn the tweeter, and the same is true for the midrange horn.

Improper equalizer tuning

The adjustment of the equalizer is also crucial. The frequency equalizer is set to compensate for various defects in the indoor sound field and the unevenness of the frequencies of the speakers. It should be debugged with an actual spectrum analyzer or other instruments. The transmission frequency characteristics after debugging should be relatively flat within a certain range. Many tuners who do not have audio knowledge perform debugging at will, and even quite a few people raise the high and low frequency parts of the equalizer too high, forming a "V" shape. If these frequencies are raised by more than 10dB compared with the mid-range frequency (the adjustment amount of the equalizer is generally ±12dB), their electrical power will be more than 3 times higher than that of the mid-range part. In this case, not only will the phase distortion caused by the equalizer seriously color the sound of the music, but it will also easily cause the speaker tweeter to burn out. This type of situation is also the main reason for burning out the speaker. Of course, the design of the sound system should be based on the actual situation, such as the size of the venue, purpose, building acoustic conditions, etc., and the maximum continuous sound pressure level should be determined according to the actual conditions of use, and then the maximum SPL value of the speaker should be determined.

Volume adjustment

Many users set the attenuator of the power amplifier to -6dB, -10dB, which is 70%-80% or even half of the volume knob, and increase the input of the mixer to achieve the appropriate volume, thinking that the power amplifier has a margin and the speaker is 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 pre-stage must output 6dB more, the voltage must be 1 times higher, and the upper dynamic margin of the input, commonly known as the "head space", will be cut in half. At this time, if there is a sudden large signal, it will overload the mixer output by 6dB earlier, resulting in a clipping waveform. Although the power amplifier is not overloaded, the input is a clipping waveform, and the treble component is too heavy, not only the treble is distorted, but the tweeter unit may also burn out.

The above analysis allows us to clearly understand that an important reason for the speaker to burn out the tweeter is that the power of the power amplifier is too small, not too large. The signal sent by the power amplifier is itself a clipping signal, which causes damage to the speaker. Therefore, when configuring the audio, we must establish a correct understanding and use the "big horse pulling a small cart" solution to prevent the power amplifier from sending out clipping signals and damaging the tweeter and midrange speaker units. When designing the audio system, the design power of the power amplifier and the speaker should be matched according to the above principles. In actual operation, the equipment in each link should be used reasonably to protect the equipment and achieve the best effect of the audio system.