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Gain Structure - 9 - Compressing the mix

As mentioned earlier, if the dynamic range of your performance is greater than the dynamic range of your system, then you will need to compress the signal to make sure that you do not loose the softest sounds in the noise floor or clip the loudest sounds. the following diagram shows what you are trying to achieve -

In this situation, if we assume clipping takes place after 130dB, then the system has 90dB of dynamic range compared to the signals 100dB. Therefore, at least 10dB of compression needs to be applied to the signal, and in the example, 20dB is applied. It is then necessary to increase the overall gain of this 80dB Dynamic range to raise it above the noise floor. (Most compressors have an output gain adjustment to achieve this)
In a real live situation, where this compression takes place will depend on where the range is most limited. If your range is limited by your speaker system, then the compression would best be applied between the mixer outputs and the amplifiers. If your range is limited at your mixer inputs, then you will need to compress the input signals, or at least those giving the maximum input, e.g. a drum kit.

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