Parametric equalizer

I have never had a graphic equalizer on my home stereo system,
and never missed one.  I now saw an article referencing an article
by Bob Pease (a name that should sound familiar to some here):

http://electronicdesign.com/article/analog-and-mixed-signal/what_s_all_this_absurd_filter_stuff_anyhow.aspx

reminding me of the Parametric equalizer.

With a graphic equalizer, you have some number of adjustable gain
filters with fixed center frequency and bandwidth.  Usually the
number is fairly small, maybe five or six.

The other possibility, which never got popular for home stereo
use, is the parametric equalizer.  You have a smaller number,
maybe three, filters with adjustable gain, center frequency,
and bandwidth (or maybe Q instead).    You can probably do many
more filtering solutions with the parametric equalizer, but it
lacks the graphic quality, the ability to see the response
function in the knobs.

-- glen

glen herrmannsfeldt wrote:


> With a graphic equalizer, you have some number of adjustable gain
> filters with fixed center frequency and bandwidth.  Usually the
> number is fairly small, maybe five or six.

The standard options are 10 octave bands or 31 bands of 1/3 octave.

> The other possibility, which never got popular for home stereo
> use, is the parametric equalizer.

In the DSP land, graphic or parametric is just a way of representation 
of the user settings. There is a number of biquads in a row. You can 
approximate any response whether it is defined as "graphic" or 
"parametric" or some other way.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com