1. Unreasonable configuration of speakers and power amplifiers
Many speakers believe that the excessive output power of the power amplifier is the cause of damage to the tweeter unit. Actually, it's not. In professional settings, speakers can generally withstand large signal impacts twice the rated power, and can instantly withstand peak impacts four times the rated power without any problems.
Therefore, it is rare for the high-frequency unit to burn out due to the high power of the power amplifier, rather than accidental strong impact or prolonged microphone whistling. But if the power output of the amplifier is too high, both the high-frequency and low-frequency units may be damaged. If the power of the power amplifier is insufficient, causing signal overload and clipping, the high-order harmonic components will increase dramatically. The original sine wave signal generates a large number of odd harmonics when the overload clipping approaches a square wave, greatly increasing the proportion of high-frequency components in the signal, resulting in the high-frequency energy in the signal far exceeding the power that the high-frequency unit can withstand.
Even though the total signal power at this time has not yet reached the rated power of the speaker, the high-frequency unit has been overloaded and damaged. This situation is more dangerous than short-term signal overload without clipping. When the signal is not distorted, the power energy of a short-term overload signal falls on the high-power bass unit, which may not necessarily exceed the short-term maximum power of the speaker. Generally, it will not cause a deviation in the power allocation of the speaker and damage the speaker unit.
Therefore, under normal usage 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 input crossover point during external crossover, or an unreasonable operating frequency range of the speaker, are also reasons for damage to the tweeter unit. When using a frequency divider, it is necessary to strictly follow the operating frequency range provided by the manufacturer to select the appropriate frequency divider point. If the frequency division point of a tweeter is chosen to be too low and it bears a heavy power burden, it is easy to burn out the tweeter unit.
3. Improper equalizer debugging
The adjustment of the equalizer is also crucial. A frequency equalizer is set up to compensate for various defects in indoor sound fields and uneven frequencies of speakers, and should be calibrated using an actual spectrum analyzer or other instruments.
The transmission frequency characteristics after debugging should be relatively flat within a certain range. Many sound engineers without audio knowledge casually debug, and even quite a few people raise 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 mid-range frequency (the adjustment amount of the equalizer is usually 12dB), not only will the phase distortion caused by the equalizer seriously dye the music sound, but it is also very easy to cause the high-frequency unit of the speaker to burn out, which is also the main reason for burning out the speaker.
4. Volume adjustment
Many users place the attenuator of the rear stage amplifier at -6dB, -10dB, which is 70% -80% of the volume knob, or even at a normal position, and increase the input of the front stage to achieve the appropriate volume, thinking that the power amplifier has enough margin and the speaker is safe. In fact, this is also incorrect. 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 in order to maintain the same volume, the front-end must output 6dB more, the voltage must be doubled, and the input dynamic margin must be cut in half.
At this point, if there is a sudden large signal, it will cause the output to overload 6dB earlier, resulting in a clipped waveform. Although the amplifier is not overloaded, the input is a clipped waveform, which results in excessive high-frequency components. This not only causes distortion of the high-frequency, but also has the potential to burn out the high-frequency unit
5. Improper low cut selection causes damage to the bass unit
Many sound engineers do not pay much attention to the issue of low frequency cuts. In fact, this low frequency cut is the biggest hidden danger that causes damage to the bass unit. Many bass speakers cannot reproduce some ultra-low frequencies well, such as frequencies below 40 Hz. However, frequency components that cannot be restored to sound energy still exist, which are converted into heat energy. Our speakers are made up of many components bonded together with glue. When high-power ultra-low frequency component signals that cannot be converted are input to the speaker for a long time, due to limited space in the box, heat dissipation is not timely, and a large amount of heat accumulates. Once the glue cannot withstand it, it will melt, causing ripples to fall off, voice coils to disperse, and the speaker to be damaged.
The use of low cut can greatly reduce the damage of ultra-low frequency to the subwoofer.
6. Differences in input sensitivity when using different amplifiers simultaneously
In engineering, there is often a situation where different brands and models of power amplifiers are mixed, and there is an easily overlooked issue, which is the input sensitivity of the power amplifier. This issue is also often overlooked, that is, for the same power, different models of power amplifiers may have inconsistent sensitivity voltages. For example, two power amplifiers with output power of 300 watts, A power amplifier input sensitivity is 0.775V, B power amplifier input sensitivity is 1.0V. If these two power amplifiers receive the same signal at the same time, when the signal voltage reaches 0.775V, A power amplifier output reaches 300W, but B power amplifier output only reaches 150W. Continuing to increase the signal level, when the signal strength reaches 1.0V, A power amplifier is overloaded and B power amplifier is 1.0V. Just reached the rated output power of 300W.
In this case, it will inevitably cause damage to the speaker unit connected to the overload signal. When mixing amplifiers with the same power but different sensitivity voltages, the input level of the amplifier with higher sensitivity should be attenuated. Unification can be achieved by adjusting the output level of the front-end equipment or reducing the sensitivity of the amplifier input potentiometer. For example, the two amplifiers mentioned above both have an output power of 300W, with a sensitivity voltage of 1.0V for one and 0.775V for the other. At this point, reduce the input level to the 0.775V amplifier by 3 decibels or place the amplifier level knob at the -3dB position. When the same signal is input, the output power of the two amplifiers will be the same.
7. The sudden disconnection of the large signal caused the low-frequency unit to jam
In KTV, many times guests or DJs in private rooms have a bad habit of cutting songs or muting them when the volume is too loud. Especially when playing Di songs, it is easy to cause the voice coil of the bass unit to jam or burn out.
The audio signal is input to the speaker through electric current, and the speaker uses electromagnetic force to push the paper tray forward and backward, causing air vibration to become sound. When the signal input is suddenly cut off during large movements, it is easy to cause the loss of recovery ability after reaching the extreme motion, resulting in unit damage.
8. Front stage, self-excited components of power amplifier
After the circuit of the front-end output part is broken down, it results in a sine wave pure tone frequency output, similar to some frequencies whistling, and the output power is very high, which can directly cause the coil of the bass unit to burn out due to power overload. The amplifier, due to current breakdown, becomes a DC output, causing damage to both the high and low frequency units of the speaker.
The eight points summarized above are not only for KTV venues, but also for bars and on-site situations. Dear friends, please compare your past cases of speaker burnout with the above eight possibilities. Are there any reasons for your speaker burnout among the above eight points.
