How to Use a Compressor

Audio compression is a method of reducing the dynamic range of a signal.
You will need:

• A compressor with manual controls.
• An audio source to be compressed (eg. microphone, musical instrument, output of sound desk, etc).
• A destination device with which to feed the compressed output (eg. tape deck, sound desk, amplifier, etc).
  

1. Connect the source to the compressor's input, and the compressor's output to the destination device.
2. Adjust the compressor's input and output gains to appropriate levels.
3. Set the threshold level to the point at which you wish compression to take effect. Signals below this level will not be affected. Signal levels above the threshold will be reduced according to the compression ratio.
4. Set the compression ratio. Ratios of 5:1 or less will produce fairly smooth compression; ratios of 10:1 or more will produce more severe cutting off.
5. Set the attack time. This is the delay between detection of a signal above the threshold, and the commencement of compression (ie. the time it takes to "attack" the signal).
6. Set the decay time. This is the time taken to release the signal from compression.
7. Adjust any other settings on the compressor. If you don't know what they are, try to put them on automatic, or disable them.

Example:
Set the compressor to a threshold of 0db, and a compression ratio of 3:1. In this case, all signals below 0db will be unaffected, and all signals above 0db will be reduced by 3db to 1 (ie. for every 1db input over 0db, 1/3db will be output).

See also:

• Expanders
• Limiters