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Parametric FIR audio equalizer

Started by Roman Rumian October 14, 2004
Hello,

maybe my question is stupid, but does such a device/algorithm exist in 
practice ?

Regards

Roman Rumian
Roman Rumian wrote:

> Hello, > > maybe my question is stupid, but does such a device/algorithm exist in > practice ? > > Regards > > Roman Rumian
I know what a parametric amplifier is, but not a parametric equalizer. There is such a thing, but I'm not familiar with its specs. Matlab code: http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=1963 How would one change the equalization parameters in an FIR? jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Yes:
http://www.weiss.ch/eq1/images/brochureEQ1-LP.PDF

FYI for Jerry and others, in audio terminology, a parametric equalizer is a
"peaking filter" where the user can adjust 1) the center frequency 2) the amount
of peaking/gain (boost or cut) and 3) the bandwidth or Q of the peak.  It is
always a second order filter AFAIK.  Sometimes equalizers that only allow
adjusting the first 2 parameters are called parametric (or even
semi-parametric).  This same type of peaking filter is also used in graphic EQs,
but only #2 is adjustable in that implementation.

When first invented, these devices were always analog, so IIR implementation are
the most common.  However, as the link explains, an FIR version is possible, but
quite a bit more difficult.

"Roman Rumian" <usun_torumian@agh.edu.pl> wrote in message
news:ckm8dl$qvd$1@galaxy.uci.agh.edu.pl...
> Hello, > > maybe my question is stupid, but does such a device/algorithm exist in > practice ? > > Regards > > Roman Rumian
Hi Jerry,

U&#2013266111;ytkownik Jerry Avins napisa&#2013266099;:

(...)
> I know what a parametric amplifier is, but not a parametric equalizer.
"[...] Many applications require the use of 'equalizing' filters which provide full control over their frequency, characteristics: these are known as parametric equalizers. Parametric EQ can typically be tuned in terms of their center frequency, level of boost or cut at this frequency, and bandwith or Q." Its from Andrew Bateman DSP handbook. Typically, first or second-order allpass filters are used to implement PEQ, since mentioned above params are easily controlled by one-two constants in equations describing them. This implementation is an IIR structure actually. The obvious drawback is a nonlinear phase. FIR implementations would eliminate it, but redesign of several FIR filters by DSP in run-time is much more complicated task. I am about to design DSP audio device, and 9-point PEQ with linear phase is a very desired future.
> There is such a thing, but I'm not familiar with its specs. Matlab code: > http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=1963 > > How would one change the equalization parameters in an FIR?
There exist a FIR design methods/algorithms, so its possible, but the trick is to maximise effort/effect ratio. ;-) Regards Roman Rumian
U&#2013266111;ytkownik Jon Harris napisa&#2013266099;:

> Yes: > http://www.weiss.ch/eq1/images/brochureEQ1-LP.PDF
thank you John, but do you know how they realise the main task ? Best regards Roman Rumian
U&#2013266111;ytkownik Roman Rumian napisa&#2013266099;:

(...)
> There exist a FIR design methods/algorithms, so its possible, but the > trick is to maximise effort/effect ratio. ;-)
minimise, of course. :-D Roman
"Roman Rumian" <usun_torumian@agh.edu.pl> wrote in message
news:ckmkp3$s3t$1@galaxy.uci.agh.edu.pl...
> > Typically, first or second-order allpass filters are used to implement > PEQ, since mentioned above params are easily controlled by one-two > constants in equations describing them. This implementation is an IIR > structure actually. The obvious drawback is a nonlinear phase. > FIR implementations would eliminate it, but redesign of several FIR > filters by DSP in run-time is much more complicated task.
I'm aware of how to make a parametric EQ out of a 2nd order all-pass (combining filtered and unfiltered), but not a first order all-pass. Is that possible? A first order all-pass phase shifts to 180 degrees and then stays there, so I don't see how to make that into a filter that only effects a middle band of frequencies.
All I know is the information on their web site.

"Roman Rumian" <usun_torumian@agh.edu.pl> wrote in message
news:ckmlgh$1r5$1@galaxy.uci.agh.edu.pl...
> U&#2013266111;ytkownik Jon Harris napisa&#2013266099;: > > > Yes: > > http://www.weiss.ch/eq1/images/brochureEQ1-LP.PDF > > thank you John, but do you know how they realise the main task ? > > Best regards > > Roman Rumian
Roman Rumian wrote:

> Hi Jerry, > > U&#380;ytkownik Jerry Avins napisa&#322;: > > (...) > >> I know what a parametric amplifier is, but not a parametric equalizer. > > > "[...] Many applications require the use of 'equalizing' filters which > provide full control over their frequency, characteristics: these are > known as parametric equalizers. Parametric EQ can typically be tuned in > terms of their center frequency, level of boost or cut at this > frequency, and bandwith or Q." > Its from Andrew Bateman DSP handbook. > > Typically, first or second-order allpass filters are used to implement > PEQ, since mentioned above params are easily controlled by one-two > constants in equations describing them. This implementation is an IIR > structure actually. The obvious drawback is a nonlinear phase. > FIR implementations would eliminate it, but redesign of several FIR > filters by DSP in run-time is much more complicated task. > > I am about to design DSP audio device, and 9-point PEQ with linear > phase is a very desired future. > >> There is such a thing, but I'm not familiar with its specs. Matlab code: >> http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=1963 >> >> >> How would one change the equalization parameters in an FIR? > > > There exist a FIR design methods/algorithms, so its possible, but the > trick is to maximise effort/effect ratio. ;-) > > Regards > > Roman Rumian
Thank you, Roman. I hope "u&#380;ytkownik" isn't too derogatory. :-p Jerry -- Engineering is the art of making what you want from things you can get. &macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;&macr;
Jon Harris wrote:

> "Roman Rumian" <usun_torumian@agh.edu.pl> wrote in message > news:ckmkp3$s3t$1@galaxy.uci.agh.edu.pl... > >>Typically, first or second-order allpass filters are used to implement >>PEQ, since mentioned above params are easily controlled by one-two >>constants in equations describing them. This implementation is an IIR >>structure actually. The obvious drawback is a nonlinear phase. >>FIR implementations would eliminate it, but redesign of several FIR >>filters by DSP in run-time is much more complicated task. > > > I'm aware of how to make a parametric EQ out of a 2nd order all-pass (combining > filtered and unfiltered), but not a first order all-pass. Is that possible? A > first order all-pass phase shifts to 180 degrees and then stays there, so I > don't see how to make that into a filter that only effects a middle band of > frequencies. > >
I suppose the first and last sections to cover the band could be made that way. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;