The output power of the power amplifier is too large, causing damage to the tweeter, but it is not. In professional occasions, speakers can generally withstand a large signal impact of 3 times the rated power, and instantaneously withstand a peak impact of 5 times the rated power without problems. Therefore, it is not rare that the tweeter is burned by the power of the power amplifier because of unexpected strong impact or long-term howling of the microphone.
As we all know, there are multiple speakers in the speaker, and the power that the speakers bear is distributed differently according to the frequency division point.
The rated power of the speaker, the general professional speakers indicate the maximum pink noise power, that is to say, 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 frequency of 1.6kHz and a rated power of 100W. At rated power, the woofer can be allocated to 78W of output power, while the tweeter is only allocated to 22W. Therefore, when 100W of pink noise power or ordinary program signal power is applied to the speaker, it can withstand; and when using a 100W single frequency signal to test, no matter the treble and bass units may be damaged.
If a three-way loudspeaker has a mid-range and high-frequency crossover point of 4kHz, then the withstand power of the tweeter unit is only 5% of the nominal power. If the power is not properly distributed, it will easily cause damage to the tweeter.
Under normal circumstances, if the signal input to the speaker is doubled, the power of the tweeter is only increased by 5W; but if the power of the power amplifier is insufficient, resulting in clipping of the signal overload, the higher harmonic components will increase dramatically. The original 1kHz sine signal, when the overload amplitude is close to the square wave, will generate a large number of odd harmonics outside the 1kHz sine wave, such as 3kHz, 5kHz and other sine wave energy, so that the proportion of treble components in the signal It is greatly increased, which in turn causes the treble spectrum energy in the signal to far exceed the power that the tweeter can withstand. Even though the total signal power at this time has not yet reached the rated power of the speaker, the tweeter has been overloaded and caused damage. This situation is more dangerous than short-term overloading of the signal, but without clipping. When the signal is not distorted, the short-term overloaded 1kHz signal, the power energy falls on the bass unit with higher power, which does not necessarily exceed the short-term maximum power of the speaker, and generally does not cause deviation of the speaker power distribution and damage the speaker unit. Therefore, under normal use conditions, the rated output power of the power amplifier should be 2-3 times the rated power of the speaker, in order to ensure that the power amplifier does not cause distortion at the maximum power of the speaker.
2. Improper use of frequency divider
Improper use of the crossover point at the input, or the unreasonable operating frequency range of the speaker, is also a cause of damage to the tweeter. When using a frequency divider, the frequency division point should be selected in accordance with the operating frequency range of the speaker provided by the manufacturer. If the crossover point of the tweeter is selected to be low, and the power burden is too heavy, it is easy to burn the tweeter, as is the midrange horn.
3. Improper equalizer debugging
The adjustment of the equalizer is also crucial. The frequency equalizer is set to compensate for various defects of the indoor sound field and the uneven frequency 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 sound knowledge are free to debug, and even a considerable number of people raise the high-frequency and low-frequency parts of the equalizer too high, forming a "V" shape. If these frequencies are increased by more than 10dB compared to the midrange frequency (the equalizer adjustment is generally 12dB), not only the phase distortion caused by the equalizer will seriously stain the music sound, but also easily cause audio tweeters. Burning, this type of situation is also the main reason for burning the speaker. Of course, the design of the sound system should be based on the actual situation, such as the size of the venue, the use, and the sound construction conditions. The maximum continuous sound pressure level should be determined according to the actual use conditions, and then the maximum SPL value of the speaker.
4. Volume adjustment
Many users put the attenuator of the post-amplifier at -6dB, -10dB, which is 70% -80% of the volume knob, or even the general position, by increasing the input of the mixer to achieve the appropriate volume, thinking the power The amplifier is safe, 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 the pre-stage must output 6dB more, and the voltage should be doubled. The dynamic headroom, commonly known as "headspace", will be cut in half. At this time, if there is a sudden large signal, the output of the mixer will be overloaded by 6dB earlier, and the amplitude of the waveform will appear. Although the power amplifier is not overloaded, the input is a clipped waveform, and the treble component is too heavy. Not only is the treble distortion, but the treble unit may also burn out.
The above analysis can make us clearly understand that an important reason for the speaker to burn the tweeter is that the power of the power amplifier is too small, not too large. The signal originally sent by the power amplifier is the amplitude-amplified signal, causing damage to the speaker. Therefore, when configuring the sound, we must establish a correct understanding, we must use the "large horse cart" program to prevent the power amplifier from sending the amplitude signal to damage the high and midrange speaker units. In the design of the audio system, the power amplifier and the design power of the audio should be matched with the above principles, and the equipment in each link of the actual operation must be used reasonably to protect the equipment and achieve the best results for the audio system.
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