GAIN11

The Art & Science of Audio & Video

Lifting the Shroud on Graphic EQ’s

Q: I have been told many times that graphic EQ’s are detrimental to the sound quality of your system and can actually be counter productive. If this is true why do they remain so popular?

A: This often a misunderstood topic. Before starting let’s lay a little groundwork to build from. Graphic equalizers have a fixed number of filters set at pre-determined center frequencies. Now earlier graphic EQ’s and some current lower quality units were and are variable “Q”. This is where the problems originate. A filter’s “Q” otherwise known as bandwidth, although not actually the same thing, is a means of determining how wide the filter is. In other words if you have a filter with a center frequency set at 4kHz how many other frequencies on either side of that will have their amplitude effected. In 1/3 octave EQ’s each filter could be easily over an octave wide at its lowest settings. They were only true 1/3 octave filters at its deepest boost or cut settings. In the early eighties Rane developed a new type of graphic EQ that was a true 1/3 octave filter regardless of the position of the boost/cut slider. The Rane units still remain some of the most highly regarded graphic EQ’s on the market. Others have adopted their technology or variations thereof but most come at a much higher price.

So you may ask why not just use all parametric EQ’s where all these parameters can be controlled independently and accurately. In some cases users need quick access to multiple filters without having the time or ability to make finite adjustments to the center frequencies. One of the most common applications is in use with stage monitors. Quick and easy with little fuss. I live situations where setup time is limited and the acoustics are never the same twice the graphic is an invaluable tool and will continue to remain so for years to come.

by Jason Levert

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March 23, 2008 - Posted by | FAQ's | , , , , , , , , ,

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