1. Unreasonable configuration of speaker box and power amplifier
Inexperienced tuners may think that the output power of the power amplifier is too high, causing damage to the high pitch unit, but it is not. In professional situations, the loudspeaker can generally withstand a large signal shock of three times of the rated power, and instantaneously a peak shock of five times of the rated power without any problem. Thus, it is rare to see high pitch units being burned by a high power amplifier, rather than an accidental blast or a long-time microphone squealing.
It is well known that there are several loudspeakers in the speaker box. The power the loudspeaker withstands can be distributed by the different crossover frequencies.
Generally, the rated power of the professional speaker is labeled as the maximum pink noise power. In other words, the rated power of the speaker refers to the analog signal power that the pink noise or broadband can bear. For example, a half frequency speaker with a frequency point of 1.6kHz and rated power of 100W can be assigned to the low pitch unit at the rated power of 78W, while the high pitch unit is only allocated to 22W. Therefore, it can withstand 100W of pink noise power or common program signal power. When tested with a 100W single frequency signal, both high pitch and low pitch units may be damaged.
2. Improper use of frequency divider
Improper use of the crossover point at the input end or improper operating frequency range of the speaker is also a cause of damage to the high pitch unit. When using the frequency divider, the crossover point should be selected according to the operating frequency range of the loudspeaker provided by the manufacturer. If the pitch of the loudspeaker is low and the power loaded is too high, it will easily burn down the high pitch unit, so does the alto horn.
3. Improper adjustment of equalizer
Equalizer adjustment is also crucial. The frequency equalizer is designed to compensate for the defects of the indoor sound field and the inhomogeneity of the frequency of the loudspeaker. The adjusted transmission frequency characteristic should be relatively flat within a certain range. Many tuners without any knowledge about speaker box perform tuning at will, and even a considerable number of people lift the high 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 mediant frequency (the equalizer is normally adjusted at 12dB), not only the phase distortion caused by the equalizer will be heavily colored to the music sound, but also the sound high pitch unit will be easily burnt. Of course, the design of the sound system should be based on the actual situation, such as site size, use, sound conditions and other comprehensive considerations, according to the actual use of the conditions to determine the maximum continuous sound pressure level, and then determine the maximum SPL value of the speaker.
4. Adjust the volume
Many users put the attenuator of the post power amplifier at -6db, -10db, that is, 70% -80% of the volume knob, or even half of the position, by increasing the input of the sound console to achieve the appropriate volume, so that the power amplifier left some space to protect the sound box. In fact, it is also wrong. The attenuation knob of the power amplifier attenuates the input signal. If the input attenuation of the power amplifier is 6dB, it means that to maintain the same volume, the tuning table or front level must output 6dB more, the voltage must be 1 times higher, and the input upper dynamic margin, commonly known as “overhead space” will be cut in half. At this time, if there is a sudden large signal, 6dB will overload the output of the tuning table, resulting in clipping waveform. Although the amplifier is not overloaded, with the clipped waveform input, the high pitch unit is overbalance, not only the high pitch distortion, the high pitch unit may also burn out.