Sound Performance Lab 2595 manual Active EQs, Parametric EQs, Graphic EQs

The Basics of Frequency Filtering

Active EQs

The filters of an active network require external power which allows for an integration of amplifying elements that allow for both boost and cut functions.

Active EQs dominate the market, and perhaps a good part of this is due to their user friendly capacity to combine both boost and cut features into single controls. A very good active filter designs can often offer very responsive characteristics with relatively little signal coloration or alteration. But the operative word here is “can”—the sonic result of filtering comes under the influences of so many parameters that it is almost impossible to fullfill any such claims made categorically.

Parametric EQs

With a fully parametric EQ, all filter parameters are adjustable: The frequency, amplitude and bandwidth of each filter can be adjusted by a user. The fully parametric EQ is therefore ideally suited to working very specific or in very narrow limits at any desired frequency. There is also the case of semi- or half-parametric filters, whose bandwidth is fixed, usually at around two octaves.

Graphic EQs

For working with the entire audible frequency range, there are available certain fixed frequency and bandwidth active filters. One can only alter the amplitude of each filter. Because the designs of such machines originally employed fader controls (and often continue to do so), these adjusted faders represent in a graphic curve the frequencies and amount of alteration, and thus earned the name, graphic EQ.

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