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31 band Graphic EQ: Q factor values, Q of Graphic Equalizer designing rules ...
Juha
post Sep 28 2013, 20:05
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I'm preparing a 31 band Graphic EQ for Windows (Vista/7/8/?). It's gonna be based on biquad (peak) filters.

As being new (noob) with EQ design, I was wondering if the Q factor for each band "needs" to be equally set (lets say 4.318 for all 31 bands) and constant ?

There are lots of reading but, looks like I'm a bit lost there.

http://en.wikipedia.org/wiki/Equalization_(audio)
http://en.wikipedia.org/wiki/Filter_design#Digital_filters
http://www.rane.com/note101.html
http://www.sengpielaudio.com/calculator-bandwidth.htm
http://www.dummies.com/how-to/content/how-...or-an-audi.html
http://www.dafx.ca/proceedings/papers/p_037.pdf


Juha


This post has been edited by Juha: Sep 28 2013, 20:07
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saratoga
post Sep 28 2013, 21:03
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Generally the Q factor is a parameter that the user sets. Its not usually constant per band, although it can be if the user wants each band to have the same fractional width.
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Arnold B. Kruege...
post Sep 29 2013, 11:19
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QUOTE (Juha @ Sep 28 2013, 15:05) *
I'm preparing a 31 band Graphic EQ for Windows (Vista/7/8/?). It's gonna be based on biquad (peak) filters.

As being new (noob) with EQ design, I was wondering if the Q factor for each band "needs" to be equally set (lets say 4.318 for all 31 bands) and constant ?

There are lots of reading but, looks like I'm a bit lost there.

http://en.wikipedia.org/wiki/Equalization_(audio)
http://en.wikipedia.org/wiki/Filter_design#Digital_filters
http://www.rane.com/note101.html
http://www.sengpielaudio.com/calculator-bandwidth.htm
http://www.dummies.com/how-to/content/how-...or-an-audi.html
http://www.dafx.ca/proceedings/papers/p_037.pdf


Juha


Traditional Graphic equalizers with 30 +/- bands are always fixed constant Q. Working with real world coils, capacitors, and resistors fixed parameters was the only practical way. This was almost always carried over into digital implementations of the same.

The basic idea was to approximate critical bands, which were not so well understood when the traditions started. The traditions carried over even when we understood critical bands better.

Graphic equalizers with smaller numbers of bands were mostly based on constant Q and constant bandwidth as well but there were some exceptions.

You can check this out with real world pro audio products. Leaders in this field include Behringer, Rane, Ashley, DBX, etc,

http://www.sweetwater.com/c468--Graphic_EQ
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