A Summary of the Eight Causes of Loudspeaker Burnout

- Aug 20, 2018-

1. The configuration of speaker and power amplifier is not reasonable.

Many people think that the power output 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 twice the rated power, and can withstand a peak impact of 4 times the rated power without any problem. Therefore, it is not the case that the power amplifier has a large power and the tweeter is burned due to an unexpected strong impact or a long whistle of the microphone, and the case where the tweeter is burned is extremely rare. However, if the power output of the amplifier is too large, both the treble and the woofer may be damaged. If the power of the power amplifier is insufficient, the signal overload will be cut, and the higher harmonic components will increase sharply.

The original sinusoidal signal generates a large number of odd harmonics when the amplitude is close to the square wave, which greatly increases the proportion of the high-frequency component in the signal, causing the high-frequency energy in the signal to exceed the high-pitched unit the power to withstand. Even if the total power of the signal at this time has not reached the rated power of the speaker, the tweeter has been overloaded and damaged. This situation is overloaded for a short period of time, but it is more dangerous without clipping. When the signal is not distorted, the short-time overload signal, the power energy falls on the high-powered woofer, does not necessarily exceed the short-term maximum power of the speaker, and generally does not cause the deviation of the speaker power distribution and damages the speaker unit. Therefore, under normal use conditions, 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 maximum power of the speaker.

2. Improper use of frequency division.

Improper use of the crossover point of the input terminal during external crossover or unreasonable operating frequency range of the speaker is also a cause of damage to the tweeter. When using the crossover, the crossover point should be reasonably selected according to the operating frequency range provided by the manufacturer. If the crossover point of the tweeter is too low and the power load is too heavy, it is easy to burn the tweeter.

3. Equalizer debugging is not proper.

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 uneven frequency of the speakers. It should be debugged with an actual spectrum analyzer or with other instruments. The transmission frequency characteristics after debugging should be relatively flat within a certain range. Many tuners who do not have audio knowledge are free to debug, and even quite a few people raise the high-frequency and low-frequency parts of the equalizer too high to form a "V" shape. If these frequencies are raised by more than 10 dB compared to the mid-range frequency (the equalizer adjustment is generally 12 dB), not only the phase distortion caused by the equalizer will seriously stain the music sound, but also the acoustic tweeter. Burned, this kind of situation is also the main reason for burning the speaker.

4. Volume adjustment.

Many users set the attenuator of the power amplifier to -6dB, -10dB, that is, 70%-80% of the volume knob. Even in the general position, increase the input of the front stage to reach the appropriate volume, so that the power amplifier is left. With a margin, the speaker is safe; in fact it 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 front stage must output 6dB more, the voltage is 1 times higher, and the input dynamic headroom It will be cut in half. At this time, if there is a sudden large signal, the output will be overloaded 6dB earlier, and the clipping waveform will appear. Although the amplifier is not overloaded, the input is a clipped waveform, and the high-pitched component is too heavy. Not only the high-pitched distortion, but also the tweeter may burn out.

5. Poor selection of low cut causes damage to the woofer.

Many tuners don't pay much attention to low-cutting problems. In fact, this low cut is the biggest hidden danger of woofer damage. Many woofer horns can't restore some ultra-low frequencies, such as frequencies below 40 Hz, but they can't. The frequency component that is reduced to sound energy still exists, he converts it into heat energy, and our horn is glued by many parts with glue. When the high-powered horn input into the ultra-low frequency component signal that cannot be converted, due to the volume of the box is limited, the heat is not timely, and a large amount of heat is collected. Once the glue cannot withstand, it will melt, causing the elastic waves to fall off, the voice coil to be scattered, and the horn to be damaged. For low cuts, the damage to the woofer at very low frequencies can be greatly reduced.

6. Difference in input sensitivity when different power amplifiers are used at the same time.

In engineering, there is often a situation in which different brands and models of power amplifiers are mixed. There is a problem that is easily overlooked. This is the problem of amplifier input sensitivity. This problem is often overlooked, that is, the same power, different models. The power amplifier may have the problem that the sensitivity voltage is not uniform. For example, two power amplifiers have an output power of 300 watts, the A power amplifier input sensitivity is 0.775V, and the B power amplifier input sensitivity 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 A power amplifier output reaches 300W, but the output of the B power amplifier only reaches 150W, and the signal level continues to be increased. When the signal strength reaches 1.0V, the A power amplifier is overloaded, and the B power amplifier has just reached the rated 300W output power.

In such a case, the speaker unit to which the overload signal is connected must be damaged. When the power of the same power and different sensitivity voltages is mixed, the input level of the amplifier with high sensitivity is attenuated. It can be unified by adjusting the output level of the preamplifier or by reducing the amplifier input potentiometer with high sensitivity. For example, the two units mentioned above are 300W output power amplifiers. The sensitivity voltage is 1.0V and the other is 0.775V. At this time, the level of the input to the 0.775V power amplifier is reduced by 3dB or the power discharge is turned on the knob. In the -3dB position, when the two power amplifiers input the same signal, the output power is the same.

7. The large signal is disconnected instantaneously, causing the woofer to be stuck.

In KTV, many times, guests or DJs have a very bad habit of cutting songs or muting in a state of loud pressure. The audio signal is input to the horn through the current mode. The horn pushes the paper cone back and forth by the electromagnetic force to make the air vibrate into a sound. When the motion is greatly exercised, the signal input is suddenly broken, which is easy to cause the motion to the extreme and the recovery ability is lost.

8. Preamp, the components of the amplifier are self-excited.

The circuit of the output stage of the front stage is broken down, resulting in a sine wave pure tone rate output, similar to some frequency whistling, and the output power is very large, which can directly cause the woofer to burn out due to power overload. The amplifier becomes a DC output due to current breakdown, which causes the speaker's high and low sound units to be damaged.



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