Sound Mixers: Channel EqualizationMost mixers have some of sort equalization controls for each channel. Channel equalizers use knobs (rather than sliders), and can be anything from simple tone controls to multiple parametric controls.
Note: For more general information about equalization see Audio Equalizers.
The first example on the right is a simple 2-way equalizer, sometimes referred to as bass/treble or low/high. The upper knob adjusts high frequencies (treble) and the lower knob adjusts low frequencies (bass). This is a fairly coarse type of equalization, suitable for making rough adjustments to the overall tone but is not much use for fine control.
The middle controls consist of two pairs of knobs. These pairs are parametric equalizers — each pair works together to adjust a frequency range chosen by the operator. The brown knob selects the frequency range to adjust and the green knob makes the adjustment.
The top pair works in the high-mid frequency range (0.6KHz to 10KHz), the lower pair works in the low-mid range (0.15 to 2.4KHz).
The "EQ" button below the controls turns the equalization on and off for this channel. This lets you easily compare the treated and untreated sound.
It is common for mixers with parametric equalizers to combine each pair of knobs into a single 2-stage knob with one on top of the other. This saves space which is always a bonus for mixing consoles.
Notes About Channel EqualizationIf the mixer provides good parametric equalization you will usually find that these controls are more than adequate for equalizing individual sources. If the mixer is limited to very simple equalization, you may want to use external equalizers. For example, you could add a graphic equalizer to a channel using the insert feature.
In many situations you will use additional equalization outside the mixer. In live sound situations, for example, you will probably have at least one stereo graphic equalizer on the master output.