MM Productions Ltd - Questions and Answers

Questions and Answers

processor questions

PROCESSORS

(cont)
If a very high compression ratio is used (some compressors have an infinity setting on the ratio control) then the compressor acts as a limiter. This means that however much the input signal increases, the output signal stays fixed. Limiters are used to protect speakers from potentially damaging 'spikes' of power which could damage them.

The controls you see on a compressor are:-

Threshold	Sets the level above which compression takes place
Ratio	Sets the amount of compression
Attack	Sets the amount of time the compressor waits after the signal rises above the threshold level before applying compression. This can be used to let the initial sound through, a technique that preserves the power of some sounds, particularly drums.
Release	Sets the amount of time the compressor keeps applying the compression after the input level has fallen below the threshold. Too fast a release time gives audible 'pumping' as the level fluctuates rapidly, too slow, and soft passages may be lost.
Output Gain	Compression will tend to make the output signal sound quieter. This control increases the overall output level to compensate for this.

Click here to see a picture of a compressor front panel

If you are using a compressor for musical dynamic control, I would start with soft-knee settings at ratios of 2 or 4:1 and the threshold at 0dB and then adjust the attack and release settings by ear. If the unit has meters showing the amount of gain reduction and output level, these can be a useful guide to further ratio and threshold adjustments.