Equalizer

What it means

An equalizer, often shortened to EQ, is a device or piece of software that lets you selectively boost or cut individual frequency ranges of an audio signal. It thereby changes the tone color without changing the pitches themselves: highs can be made brighter, bass fuller, or disturbing frequencies quieter.

Musical use

Equalizers are standard equipment in mixing desks, studio productions, amplifiers, and playback devices. In recording practice they serve to separate instruments within the overall sound, for instance by giving the bass guitar and the kick drum room in different ranges. There are graphic equalizers with fixed frequency bands and sliders, and parametric equalizers, in which frequency, bandwidth, and boost can be set freely.

An equalizer should be distinguished from a compressor, which processes not the frequency distribution but the dynamics, that is, the difference between loud and quiet passages. It also differs from reverb or echo, since those effects add time-based repetitions, whereas an equalizer changes only the spectral balance.

Performance practice

Be sparing when setting an equalizer: small cuts usually disturb less than large boosts and sound more natural. Compare the processed signal repeatedly with the unprocessed one and check on different playback systems, since a sound that seems balanced on headphones can appear quite different on loudspeakers.