Equalisation or EQ is generally considered to be the most important section of a mixing console, which is where you will most commonly encounter it. Usually, EQ is used for one of two purposes - to cut part of the frequency range we want to hear less of, or to boost an area we want more of. In normal circumstances, an engineer will use EQ liberally at the recording and mixing stages, whereas in the mastering suite, the use EQ is much more restrained, the goal being to try to achieve a satisfying overall tonal balance.
Highs, Mids and Lows
The frequency range of EQ is traditionally broken up into separate groups - highs, mids and lows, and these are often represented on a console with each frequency group having a separate set of controls. The most basic type of EQ is the shelving EQ, which cuts or boosts all frequencies above or below a specific point. There are usually two controls one for the amount of cut or boost measured in decibels or dB, and one for the frequency above or below which will be affected. Peaking EQs on the other hand, affect a range of frequencies either side of a specified centre frequency standard controls are for cut/boost and frequency (although as with shelving EQs, some operate only at fixed frequencies), and some parametric EQs add a third for Q which controls the width of the frequency range affected. Check out our separate online guide to EQ if you would like to learn more about this topic.