[sdiy] Multi-output comb filter?
Corey K
coreyker at gmail.com
Mon May 21 20:30:38 CEST 2018
Sure. You can implement a comb filter using a parallel bank of 1 or 2-pole
filters. However, the spacing between the filters is inversely proportional
to the delay time. For a 1 second delay time you'd need upwards of 20,000
filters to cover the audible spectrum (which is not exactly practical).
On Sun, May 20, 2018, 20:11 cheater00 cheater00 <cheater00 at gmail.com> wrote:
> Note I'm not adhering to any specific definition of comb filter. I just
> wonder if there's a medium between a typical, delay based comb filter
> (you get all outputs mixed together, but work is very little) and a
> bank of filters (you get each output separately, but a lot of work is
> duplicated).
>
> On Tue, 15 May 2018 04:06 , <[1]rsdio at audiobanshee.com> wrote:
>
> On May 14, 2018, at 11:02 AM, Gordonjcp <[2]gordonjcp at gjcp.net>
> wrote:
> > On Mon, May 14, 2018 at 02:03:13PM +0200, cheater00 cheater00
> wrote:
> >> Hi, I was wondering if anyone knew of a (digital? analog?) comb
> filter
> >> where the computation is done once, but you get separate outputs
> out of
> >> each peak. It's fine if it's just "present" or "not present"
> according to
> >> some threshold. I am looking for implementations in the time
> domain, not
> >> FFT based.
> >
> > You don't get separate outputs of each peak. A "comb filter"
> isn't
> > really a filter in the sense that say a bandpass filter is. It's
> a very
> > short delay line, in which frequencies that are delayed by an odd
> number
> > of half-cycles cancel out and frequencies that are delayed by a
> whole
> > number of half-cycles add, giving the "comb teeth" response.
> What Gordon said!
> The beauty of the comb filter is that itâs cheap to implement
> (âjustâ a delay) and you get all of those peaks from one process.
> Creating what you ask for - separate outputs for each peak - would
> be a totally different process. Most importantly, it wouldnât be
> cheap at all.
> Brian
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> Synth-diy mailing list
> [3]Synth-diy at synth-diy.org
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>
> References
>
> 1. mailto:rsdio at audiobanshee.com
> 2. mailto:gordonjcp at gjcp.net
> 3. mailto:Synth-diy at synth-diy.org
> 4. http://synth-diy.org/mailman/listinfo/synth-diy
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>
-------------- next part --------------
Sure. You can implement a comb filter using a parallel bank of 1 or
2-pole filters. However, the spacing between the filters is inversely
proportional to the delay time. For a 1 second delay time you'd need
upwards of 20,000 filters to cover the audible spectrum (which is not
exactly practical).
On Sun, May 20, 2018, 20:11 cheater00 cheater00
<[1]cheater00 at gmail.com> wrote:
  Note I'm not adhering to any specific definition of comb
filter. I just
  wonder if there's a medium between a typical, delay based comb
filter
  (you get all outputs mixed together, but work is very little)
and a
  bank of filters (you get each output separately, but a lot of
work is
  duplicated).
  On Tue, 15 May 2018 04:06 , <[1][2]rsdio at audiobanshee.com>
wrote:
   On May 14, 2018, at 11:02 AM, Gordonjcp
<[2][3]gordonjcp at gjcp.net>
   wrote:
   > On Mon, May 14, 2018 at 02:03:13PM +0200, cheater00
cheater00
   wrote:
   >> Hi, I was wondering if anyone knew of a (digital?
analog?) comb
   filter
   >> where the computation is done once, but you get separate
outputs
   out of
   >> each peak. It's fine if it's just "present" or "not
present"
   according to
   >> some threshold. I am looking for implementations in the
time
   domain, not
   >> FFT based.
   >
   > You don't get separate outputs of each peak.àA "comb
filter"
   isn't
   > really a filter in the sense that say a bandpass filter
is.ÃÂ It's
   a very
   > short delay line, in which frequencies that are delayed by
an odd
   number
   > of half-cycles cancel out and frequencies that are delayed
by a
   whole
   > number of half-cycles add, giving the "comb teeth"
response.
   What Gordon said!
   The beauty of the comb filter is that itâs cheap to
implement
   (âjustâ a delay) and you get all of those peaks from one
process.
   Creating what you ask for - separate outputs for each peak -
would
   be a totally different process. Most importantly, it
wouldnât be
   cheap at all.
   Brian
   _______________________________________________
   Synth-diy mailing list
   [3][4]Synth-diy at synth-diy.org
   [4][5]http://synth-diy.org/mailman/listinfo/synth-diy
References
  1. mailto:[6]rsdio at audiobanshee.com
  2. mailto:[7]gordonjcp at gjcp.net
  3. mailto:[8]Synth-diy at synth-diy.org
  4. [9]http://synth-diy.org/mailman/listinfo/synth-diy
_______________________________________________
Synth-diy mailing list
[10]Synth-diy at synth-diy.org
[11]http://synth-diy.org/mailman/listinfo/synth-diy
References
1. mailto:cheater00 at gmail.com
2. mailto:rsdio at audiobanshee.com
3. mailto:gordonjcp at gjcp.net
4. mailto:Synth-diy at synth-diy.org
5. http://synth-diy.org/mailman/listinfo/synth-diy
6. mailto:rsdio at audiobanshee.com
7. mailto:gordonjcp at gjcp.net
8. mailto:Synth-diy at synth-diy.org
9. http://synth-diy.org/mailman/listinfo/synth-diy
10. mailto:Synth-diy at synth-diy.org
11. http://synth-diy.org/mailman/listinfo/synth-diy
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