[PD] butterworth/chebyshev/etc in biquad?
Alexandre Torres Porres
porres at gmail.com
Mon Dec 15 18:00:43 CET 2014
"I'm not sure how much difference it makes for low-order filters (biquad
has 2 poles and 2 zeros). The differences really matter more for higher
order filters, say 8 poles or more..."
That's really relevant information, thanks :)
> I'd just use the ones already made in iemlib...
Sure, but it's more of theoretical doubt and concern. I just wanna learn
more about it, even if I just use what's there in iemlib.
> There's also a 3rd order BW in the docs
Sure, I know about them and I'm studying it. And I'm also now checking
I assume it's a matter of how to calculate the coefficients for you to get
filters that are butterworth/chebyshev/etc, and the text from miller point
to how to get butterworth coeficients. But it doesn't point to how to get
Chebyshev 1 pr 2, Eliptic, Bessel and whatever. Any hints?
And I still wonder what's the kind of filter from objects like [lop~],
[hip~], [bp~], [lores~] and [reson~] for instance (cause I know how to get
those with biquad coefficients). And also about the filters described at
"Cookbook formulae for audio EQ biquad filter coefficients"
Do any of you know what kind of filter it is?
2014-12-15 13:59 GMT-02:00 Frank Barknecht <fbar at footils.org>:
> On Mon, Dec 15, 2014 at 03:41:45PM +0000, Claude Heiland-Allen wrote:
> > On 15/12/14 14:49, Alexandre Torres Porres wrote:
> > >Do any of you know if they're Butterworth or what?
> > I'm not sure how much difference it makes for low-order filters
> > (biquad has 2 poles and 2 zeros). The differences really matter
> > more for higher order filters, say 8 poles or more...
> > You could waste time calculating coefficients for a biquad cascade
> > (the process is quite involved - see the mkfilter package online),
> > but I'd just use the ones already made in iemlib...
> There's also a 3rd order BW in the docs, if you're interested in the inner
> workings: 3.audio.examples/H13.butterworth.pd
> Frank Barknecht _ ______footils.org__
> Pd-list at lists.iem.at mailing list
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