What is a compressor?
A compressor controls dynamic range. Dynamic range can be defined as the difference in amplitude between the loud parts and the quite parts of a signal.
Let's cover a few key terms:
Threshold is the amplitude at which the compressor will engage
Ratio is the strength of compression at a given threshold
Attack is the time it takes the compressor to react once the threshold has been exceeded
Release is the time it takes the compressor to disengage once the signal falls below the threshold
Output is used to increase the overall volume of a compressed signal
Knee; a soft knee will allow the compressor to engage as the signal approaches the threshold, a hard knee is more reactive
Lookahead; a slow lookahead will allow the compressor to detect an incoming signal before it has arrived. To control transients, a slow lookahead is ideal.
Why do I need a compressor?
1. Create punchiness with drums
Medium ratio, fast attack, medium release
2. Create a more consistent average output
Medium ratio, fast attack, fast release
3. Control excessive spikes in amplitude
High ratio, fast attack, fast release
4. Level out an inconsistent performer (singer, guitarist, etc…)
Low ratio, medium attack, medium release
5. Control dynamic ambience
Low ratio, slow attack, slow release
low (2:1 to 5:1), medium (6:1 to 12:1), high (13:1 to inf:1)
slow (1 to 2 seconds), medium (100ms to 1 second), fast (1ms to 100ms)
slow (1 to 3 seconds), medium (200ms to 1 second), fast (25ms to 200ms)
*use the auto release when unsure of a manual release time, typically, it isn't as reactive*
A fast attack will control transients
A slow attack will maintain dynamic range and definition
A fast release will increase loudness and distortion
A slow release will maintain a natural sound
Tip: Compressors are delicate and they are easy to overdo. Compression offers loudness as a by product and louder is more appealing. Pay attention the dynamic range itself to determine amount of compression instead of overall volume!