The Basics: Compression

Compression:

Basics of compression: Compression is another essential tool for studio work. A compressor can be used to achieve a number of results. Compressors can be used to tame any comparatively loud transients in a track. They can be used tame rogue instances of relative loudness, thicken sounds, or add punch to drums and vocals. Compressors various uses become more and more apparent the better we understand the functions of a compressors various parameters. 

Threshold: A compressor functions by measuring an audio signal in dB (Decibels) the Threshold is a level we set within the compressor. With the threshold set, we begin attenuating the signal whenever it exceeds the threshold we've set. In this fashion, the louder the signal, the greater the attenuation is.

Waves API-2500 Compressor

Ratio: The Ratio sets the ratio of attenuation. At a ratio of 2:1, our signal will be compressed by 2  dB for every 1 dB that is crossing above our set threshold. 

Knee: A knee is an optional parameter on many compressors. With no knee, we may think of our threshold as a singular point, with our compressor squashing the signal as much as our ratio will allow, as soon as that signal crosses the threshold. With a knee, things are different. The knee turns our threshold from a singular point, and turns it into a range of attenuation.

Lets say we have a threshold of -20 dB with a knee of 5 dB. Our signal will undergo light compression at -25 dB and reach the fully allowed compression ratio at -15. In this sense, we have turned our threshold from a singular location, into a range of decibels.

Attack: Attack controls how responsive our compressor is to a signal in milliseconds.

Release: Release controls how long it takes for our compressor to stop attenuating the signal after it has dipped back below the threshold. 

Gain (output): This effects the levels of your compressors output after compression. Many use the output gain as a sort of "makeup gain" 

We'll discuss proper applications of makeup gain and other advanced compression techniques in our post: Compression Part: II