From looking at the helpfile for [phaseshift~], this sounds very much like
the all-pass filter from Robert Bristow-Johnson's EQ Cookbook. You can calculate the biquad coefficients for it like this:
w0 = 2*pi*frequency_in_Hz / sample_rate alpha = sin(w0)*sinh(ln(2)/2*Q*w0/sin(w0))
fb1 = 2*cos(w0) / (1+alpha) fb2 = (-1+alpha) / (1+alpha) ff1 = -fb2 ff2 = -fb1 ff3 = 1
.mmb
On Sat, Oct 5, 2013 at 12:31 PM, Alexandre Torres Porres porres@gmail.comwrote:
the phase response given in phaseshift's help file suggest otherwise.
it's more like the response from miller's H14 example...
So I guess you can have a 2nd order one (lie phaseshift) by putting two of these together, right? And I suspect it doesn't really need to have anything to do biquad just for being "2nd order", huh?
cheers
2013/10/5 Alexandre Torres Porres porres@gmail.com
Anyway, next on my list is finding out how to implement max's [phaseshift~], which is also an allpass filter. There's no Pd clone for it so it seems, right?
Well, it doesn't really what it is other than a 2nd order filter. From that I could think you can generate it with [biquad~], but the phase response given in phaseshift's help file suggest otherwise.
any contributions welcome
thanks a lot
2013/10/5 Alexandre Torres Porres porres@gmail.com
but this way it won't be the same as cyclone's [allpass~], the way I did it is equivalent to it (and max's).
cheers
2013/10/3 Chris Clepper cgclepper@gmail.com
You only need one delay line for the allpass.
feedforward = input * -gain feedback = delayout * gain delayin = input + feedback output = delayout + feedforward
http://www.spinsemi.com/knowledge_base/effects.html#Reverberation
On Thu, Oct 3, 2013 at 11:29 AM, Alexandre Torres Porres < porres@gmail.com> wrote:
i hope i guess i figured it out on how to implement it with delay lines. see attachment. And I realize you can't do this with [fexpr~] or [biquad~] because the sample delay length is kinda big for that, right?
cheers
2013/10/3 Alexandre Torres Porres porres@gmail.com
cool, but do you know how to implement cyclone's [allpass~] with it?
It's really unclear to me what is the relation of this pass filter with the one you can generate with biquad coefficients, or with raw poles/zeros objects for that matter.
Well, one way or another, it's also unclear to me how to do it with delay lines.
seems that it is related to a comb filter, right?
cheers
2013/10/2 Chris Clepper cgclepper@gmail.com
> Allpass for reverb is easy to do with delwrite~ and vd~. I used 32 > of them today to recreate a famous 'deep space' reverb. > > > On Wed, Oct 2, 2013 at 1:53 AM, Alexandre Torres Porres < > porres@gmail.com> wrote: > >> hi there, i see the biquad's coefficients can be set as an allpass >> filter, generated by frequency and "Q" parameters. But can it do the same >> as cyclone's [allpass~] filer? If yes, them how since the parameters for >> [allpass~] are different (delaytime and such). >> >> One way or another, I guess that my real question is: how to >> implement [allpass~] from vanilla objects? >> >> thanks >> >> _______________________________________________ >> Pd-list@iem.at mailing list >> UNSUBSCRIBE and account-management -> >> http://lists.puredata.info/listinfo/pd-list >> >> >
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