Compression is one of the most important tools for mixing and mastering engineers. You can use it for many different purposes. For example, to fatten drums, to level vocals and so on. In some situations heavy compression is needed and in other situations only a slight gain reduction does the trick.

In this article I’m going to explain the basic parameters of the compressor: threshold, ratio, attack, release & make-up gain. 

 
Threshold:

What a compressor basically does is automatically control the volume of a sound source when it exceeds a certain level. That certain level is called the threshold. If you set the threshold at -10Db, than the compressor will compress the signal that’s louder than that level. 

Ratio: 

A ratio of (for example) 3:1 simply means that for every 3 Db’s louder than the threshold, 1 passes, and 2 get reduced. Another example, a ratio of 6:1 lets the compressor reduce 5 of every 6 Db’s that pass the threshold.

The ratio should be set in relation to the threshold. It all depends on what you want to achieve. If you want to compress harder you can use a higher ratio and a lower threshold, and vice versa for slight compression. 

Attack & Release: 

The attack time sets how quickly the compressor reacts when the level passes the threshold, and the release time sets how fast the compressor will “release” the signal from the compression.

The picture below shows you how the compressor responds to the attack and release.

 
Make-up Gain: 

The make-up gain is a knob to boost the volume of the signal you compressed. If you compress 5Db’s you’re going to want to boost that same amount to keep the overall level the same.

The settings below are some good starting points when compressing the certain elements. Please do keep in mind that they’re just starting point and you’ll probably need to tweak them to meet the needs of your project.

 
Written by Roy "R-skillz" Wehbe
Producer, Mixing & Mastering Engineer.