Friends who are always concerned about speakers should know that the mid and tweeters in speakers are easy to burn, especially in places such as studios, theaters, dance halls, meeting rooms, etc. What is going on? I believe some friends know this reason, and some understand but don’t know it. Below, Baibaocheng Audio and Video will introduce the reasons why professional speakers burn tweeters in detail. Let’s take a look.
Reasonable configuration of speakers and power amplifiers
When some friends see the title, they may think that the power amplifier is too powerful, which causes the damage to the speaker tweeter, but it is not. Professional speakers, speakers generally can withstand a large signal impact of 3 times the rated power, and can withstand a peak impact of 5 times the rated power instantaneously without being damaged. Therefore, the power of the power amplifier is twice as high as the rated power of the speaker, and there is no problem. Therefore, as long as it is not an accidental strong impact or long-term howling of the tweeter, it is very rare that the tweeter is burned due to the high power of the power amplifier.
As we all know, there are multiple speakers in a speaker, and the power of the speakers is allocated differently according to the different crossover points.
In general, professional speakers will indicate the maximum pink noise power, while fever and civilian audio tags 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 can withstand pink noise or a wide frequency band. For 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 can only be allocated to 22W. Therefore, applying 100W pink noise power or ordinary program signal power to the speaker can withstand it; and when using a 100W single-frequency signal to test, both the treble and woofer may be damaged.
If a three-way loudspeaker has the crossover point of the mid-range and high-range frequencies at 4kHz, then the withstand power of the tweeter is only 5% of the nominal power. If the power distribution is improper, it will easily cause damage to the tweeter.
We know that there are not many high-pitched components in general vocal and music signals, and there are more high-pitches in metal musical instruments and silk string music. Take a three-way speaker as an example. 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 a clipping of the signal overload, the high-order harmonic components will increase sharply. In addition to the original 1kHz sine wave, a large number of odd harmonics are generated, such as 3kHz, 5kHz, etc. sine wave energy, which greatly increases the proportion of high-pitched components in the signal, and causes the high-frequency spectrum energy in the signal to far exceed the tweeter The power that 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 the short-term overload of the signal, but no clipping occurs. When the signal is not distorted, the short-term overload of the 1kHz signal, the power energy falls on the woofer with larger power, which does not necessarily exceed the short-term maximum power of the speaker, and generally will not cause the deviation of 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, so as to ensure that the power amplifier does not cause distortion at the maximum power of the speaker.
Improper use of divider
Improper use of the input crossover point or the unreasonable working frequency range of the loudspeaker is also a cause of damage to the tweeter. When using a frequency divider, you should choose a reasonable crossover point in strict accordance with the working frequency range of the speaker provided by the manufacturer. If the crossover point of the tweeter is chosen to be too low and the power burden is too heavy, it is easy to burn the tweeter, as is the midrange horn.
Improper tuning of the equalizer
The adjustment of the equalizer is also crucial. The frequency equalizer is set up to compensate for the various defects of the indoor sound field and the unevenness of each frequency of the loudspeaker. 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 make adjustments at will. There are even quite a few people who raise the high frequency and low frequency parts of the equalizer too high to form a "V" shape. If these frequencies are increased by more than 10dB compared with the midrange frequency (the equalizer adjustment is generally ±12dB), the electric power will be more than 3 times higher than the midrange frequency. In this case, not only the phase distortion caused by the equalizer will seriously stain the music sound, but it is also very easy to cause the tweeter of the speaker to be burned. This type of situation is also the main reason for the burning of the speaker. Of course, the design of the sound system should be based on the actual situation, such as the size of the venue, use, sound construction conditions, etc., to determine the maximum continuous sound pressure level according to the actual use conditions, and then determine the maximum SPL value of the speaker.
Many users put the attenuator of the power amplifier at -6dB, -10dB, which is 70%-80%, or even half of the volume knob, and rely on increasing the mixer input to achieve the appropriate volume, which is the power If the amplifier has a margin, the speakers are 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 should be doubled, and the input The upper headroom, commonly known as "head space", is about to be cut in half. At this time, if there is a sudden large signal, the output of the mixer will be overloaded 6dB earlier, and a clipping 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 the treble is distorted, but the tweeter may also be burned out.
The above analysis can make us clearly understand: an important reason why the speaker burns 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 clipped signal, causing damage to the speaker. Therefore, when configuring the audio, you must establish a correct understanding and use the "big horse-drawn trolley" scheme to prevent the power amplifier from sending out a clipped signal and damaging the high and mid-range speaker units. When designing the sound 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, so that the equipment can be protected and the sound system can achieve the best effect. .