An Overview of Compression

As a newbie to recording, you may have heard of compression or even played around with a compressor. However, at first it is quite difficult to understand exactly what all those knobs do.

First things first... a compressor essentially limits all signals over a certain threshold value. When it limits these peaks or high volumes, it does not simply chop then off like a limiter. It reduces the peak's volume over a certain period governed by the attack and release times. Also, the size of the adjustment to the peak's volume is determined by the compression ratio.

Compression is useful for two things,

1. to reduce high peaks which saturate the output.
2. to louden the quieter bits. By reducing higher volumes and raising the make-up gain, the track volume becomes more constant. i.e. The chorus has loud drums and electric guitar and the verse has acoustic picking - naturally, the verse will be far quieter than the chorus. The solution would be to use a compressor on the master track which limits the chorus but not the verse, and then bump up the volume with the make-up gain.

The following link defines in detail what each knob on a compressor does: Compression Glossary