>> The real part may be used as a resonant >> bandpass filter and the imaginary as a >> resonant low-pass filter, but they can be >> combined to make other possibilities."
> what sort of possibilities??? I wouldn't expect much about this. I guess it's like any other filters that can be combined in many ways. Another thing I wanted to inquire is about bp~ having a frequency response that is not symmetric. The lower part of the spectrum has more energy. Could one consider it more of a "resonant low-pass filter", similar to [vcf~]'s second outlet? By the way, while we're at it, I'd like to share something that may not be too important, but it's related. I was able to implement [cpole~] in [fexpr~]. Here it goes: expr 1: [fexpr~ $x1 + ($x3 * $y1) - ($x4 * $y2); $x2 + ($x4 * $y1) + ($x3 * $y2)] if we consider $x3 and $x4 as variables named, respectively, coefr (coeficient for the real part) and coefi (coeficient for the imaginary part), we then have: expr 2: *[fexpr~ $x1 + (coefr * $y1) - (coefi * $y2);* *$x2** + (*coefi * $y1) + (coefr * $y2)] Now, by checking the code of [vcf~] I was able to narrow down to its core formula, which is something like this expr 3: *ampcorrect * oneminusr* * *f1 + (coefr * re2) - (coefi * im)*; *(coefi * re2) + (coefr * im)* the bolded letters in "expr 3" seem to match perfectly to "expr 2". The differences are underlined ($x2 in expr 2 and ampcorrect/oneminusr in expr 3). That gets me closer to being able to implement [vcf~] with a [cpole~] I guess, but I find it weird that the imaginary output does not have the $x2 signal input to be added to the rest of the expression. I worry that actually prevents it from being successfully implemented with [cpole~]. Am I missing something? Anyway, the thing is that I'm still really curious to learn wether vcf~ is a "two pole" filter or a "one complex pole" filter, and the reason behind it is because I believe we could make a biquad~ version of [vcf~] (at least for its real output). That's the bottom line. cheers 2014-07-24 6:45 GMT-03:00 i go bananas <hard....@gmail.com>: > just chipping in with my 2 cents that it would be fantastic to get more > documented info on all this. > > especially curious about: "but they can be combined to make other > possibilities." > > what sort of possibilities??? > > > On Thu, Jul 24, 2014 at 5:07 PM, Alexandre Torres Porres <por...@gmail.com > > wrote: > >> Hi Miller, still trying to get my head around this. But anyway, one thing >> I have to note is that the source code of [vcf~] says it is a "two pole >> filter", not a "one complex pole" filter. >> >> Should that description be changed? If not, why? >> >> thanks >> >> >> 2014-04-12 14:13 GMT-03:00 Miller Puckette <m...@ucsd.edu>: >> >> Yep - vcf~ is essentially a wrapper for cpole~. >>> >>> cheers >>> M >>> >>> On Sat, Apr 12, 2014 at 02:10:19PM -0300, Alexandre Torres Porres wrote: >>> > that's great to know, thanks! >>> > >>> > Let me just see if I get a bit of the theory. Can I get [vcf~] with >>> just >>> > one [cpole~] object and the right coeficients? >>> > >>> > Cheers >>> > >>> > >>> > 2014-04-12 13:36 GMT-03:00 Miller Puckette <m...@ucsd.edu>: >>> > >>> > > They're quite different. bp~ is the cheapest possible bandpass >>> filter >>> > > (as far as I know). vcf~ is a one-pole complex filter whose outputs >>> are >>> > > the real and imaginry parts. The real part may be used as a resonant >>> > > bandpass filter and the imaginary as a resonant low-pass filter, but >>> > > they can be combined to make other possibilities. >>> > > >>> > > It's possible to graph their frequency responses using the help patch >>> > > "H10.measurement.pd' in 3.audio.examples. >>> > > >>> > > cheers >>> > > Miller >>> > > >>> > > On Sat, Apr 12, 2014 at 04:28:11AM -0300, Alexandre Torres Porres >>> wrote: >>> > > > Hi there, who can confirm that both [bp~] and [vcf~] are exactly >>> the >>> > > really >>> > > > same thingy? The code looks quite different... >>> > > > >>> > > > Moreover, why the two outlets for vcf~? Help doesn't say anything. >>> > > > >>> > > > Thanks >>> > > >>> > > > _______________________________________________ >>> > > > pd-l...@iem.at mailing list >>> > > > UNSUBSCRIBE and account-management -> >>> > > http://lists.puredata.info/listinfo/pd-list >>> > > >>> > > >>> >> >> >> _______________________________________________ >> Pd-list@lists.iem.at mailing list >> >> UNSUBSCRIBE and account-management -> >> http://lists.puredata.info/listinfo/pd-list >> >> >
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