Speaker burnout is a very headache for our audio maintenance staff, whether it is in KTV venues, or bars and scenes. In order to let the majority of colleagues and friends try to avoid loudspeaker burnout in the future, we have summarized some common eight reasons for loudspeaker burnout, hoping to help you in your future work.
The speaker and power amplifier configuration is unreasonable
Many audio players think that the output power of the power amplifier is too large, which is the cause of damage to the tweeter. In fact, it is not. In professional situations, the speaker can generally withstand a large signal impact of 2 times the rated power, and can withstand a peak impact of 4 times the rated power instantaneously without any problems. Therefore, it is rare that the tweeter is burnt due to the high power of the power amplifier, not because of unexpected strong impact or long-term microphone whistling. But if the power output of the power amplifier is too large, both the treble and the bass unit may be damaged. If the power of the power amplifier is insufficient, resulting in clipping of the signal overload, the higher harmonic components will increase sharply.
The original sine wave signal, when the overload clipping is close to the square wave, produces a large number of odd harmonics, which greatly increases the proportion of the high frequency components in the signal, causing the high frequency energy in the signal to far exceed what the tweeter unit can The power to withstand. Even if the total signal power at this time has not reached the rated power of the speaker, the tweeter has been overloaded and damaged. This situation is more dangerous than the short-term overload of the signal, but not a small amount. When the signal is not distorted, the power energy of the short-term overload signal falls on the higher-power woofer, which does not necessarily exceed the short-term power of the speaker, and generally will not cause the deviation of the speaker power distribution and damage the speaker unit. Therefore, under normal conditions of use, the rated output power of the power amplifier should be 1-2 times the rated power of the speaker to ensure that the power amplifier does not cause distortion at the power of the speaker.
Improper use of crossover
Improper use of the input crossover point during external crossover, or the unreasonable working frequency range of the speaker is also a cause of damage to the tweeter. When using the frequency divider, the frequency division point should be selected strictly according to 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.
Improper adjustment 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 uneven frequency of the speakers. It should be debugged with an actual spectrum analyzer or other instruments. The transmission frequency characteristic after debugging should be relatively flat within a certain range. Many tuners who do not have sound knowledge are free to make adjustments. There are even quite a few people who 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 with the midrange frequency (the equalizer is generally adjusted at 12dB), not only the phase distortion caused by the equalizer will seriously stain the music sound, but it will also easily cause the sound tweeter. Burning, this kind of situation is also the main reason for burning speakers.
Many users set the attenuation of the power amplifier at -6dB, -10dB, that is, 70%—80% of the volume knob, or even at a general position, increase the input of the front stage to achieve a suitable volume, leaving the power amplifier with With margin, the speakers are safe, which is actually 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 front stage must output 6dB more, the voltage should be doubled, and the input headroom , Will be cut in half. At this time, if there is a sudden large signal, the output will be overloaded 6dB early, 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.
Improper low-cut selection causes damage to the bass unit
Many tuners don’t pay much attention to the low-cut problem. In fact, this low-cut is a hidden danger of woofer damage*. Many woofers cannot well restore some ultra-low frequencies, such as frequencies below 40 Hz. However, they cannot The frequency components that are restored to sound energy still exist. They are converted into heat energy. Our speakers are glued together with many components. When the ultra-low frequency component signals that cannot be converted are input to the speakers for a long time with high power, because The volume of the box is limited, heat dissipation is not timely, and a large amount of heat accumulates. Once the glue can not bear it, it will melt, causing the elastic wave to fall off, the voice coil is scattered, and the speaker is damaged. The use of low-cut can greatly reduce the damage of ultra-low frequencies to the woofer.
The difference of input sensitivity when using different power amplifiers at the same time
In engineering, there is often a situation where power amplifiers of different brands and models are mixed. There is a problem that is easily overlooked, that is, the input sensitivity of the power amplifier. This problem is often ignored, that is, the same power, different models The power amplifier may have the problem of uneven sensitivity and voltage. For example, two power amplifiers, the output power is 300 watts, the input sensitivity of the A power amplifier is 0.775V, and the input sensitivity of the B power amplifier is 1.0V, then if the two power amplifiers receive the same signal at the same time When the signal voltage reaches 0.775V, the output of A power amplifier reaches 300W, but the output of B power amplifier only reaches 150W, continue to increase the signal level, when the signal strength reaches 1.0V, A power amplifier is overloaded, and B power amplifier has just reached the rated 300W Output Power.
In this case, the speaker unit connected to the overload signal will surely be damaged. When power amplifiers with the same power and different sensitivity voltages are mixed, the input level of the power amplifier with high sensitivity should be attenuated. It can be unified by adjusting the output level of the front-end equipment or reducing the input potentiometer of the power amplifier with high sensitivity. For example, the two power amplifiers mentioned above are both power amplifiers with 300W output power, one is 1.0V and the other is 0.775V. At this time, reduce the level of the input to the 0.775V power amplifier by 3 decibels or place the power level knob At the -3dB position, when the two power amplifiers input the same signal, the output power will be the same.
The large signal momentarily disconnects causing the woofer to jam
In KTV, most of the time box guests or DJs have a very bad habit, which is to cut or mute the song under loud pressure. Especially when playing Di tunes, it is easy to cause the voice coil of the woofer to burn out. The audio signal is input to the speaker through the current method. The speaker uses electromagnetic force to push the paper cone back and forth to make the air vibrate into sound. When doing a large amount of movement, the signal input is suddenly cut off, which can easily cause the movement to a certain degree and lose the ability to recover. The unit is damaged.
Pre-stage, the components of the power amplifier are self-excited
After the circuit of the front output part is broken down, a sine wave pure tone frequency output is caused, which is similar to some frequency howling, and the output power is very large, which can directly cause the woofer to burn out the coil due to power overload. The power amplifier turns into a DC output due to current breakdown, which damages both the speaker's treble and bass units.
The eight points summarized above are not only for KTV venues, but also for bars and scenes. Dear friends, please compare your past speaker burnout with the above eight possibilities. The reasons for your speaker burnout are: Not among the above eight points.