<html><body><font face="Helvetica">Oh sorry, I thought we were discussing string filters.<br><br>Ian<br><br><br>Sent from XFINITY Connect Mobile App<br><br><br>------ Original Message ------<br><br>From: rburnett@richieburnett.co.uk<br>To: ijfritz@comcast.net<br>Cc: Tom Wiltshire, Mattias Rickardsson, Synth DIY<br>Sent: July 3, 2017 at 6:35 AM<br>Subject: Re: [sdiy] Resonator type filters<br><br>I think vocoder bands must be a lot more sharp (higher order) than a <br>"string filter" so the effect is a lot more pronounced with a vocoder as <br>Mattias Rickardsson originally said. When I passed an impulse through <br>my vocoder consisting of a bank of thirty 1/4 octave bandpass filters <br>all set to the same level it yielded a very definite chirp. Clearly <br>audible, and you could also clearly identify the change in direct of the <br>"sweep" if that sound was recorded and played back in reverse.<br><br>My point... If you pass a signal through a bank of bandpass filters and <br>then re-combine the outputs, the signal undergoes dispersion. If <br>there's lots of filters with very narrow passbands (high-Q) then that <br>dispersion can become quite extreme and very noticeable as MR had <br>stated.<br><br>-Richie,<br><br><br><br>On 2017-07-03 09:36, ijfritz@comcast.net wrote:<br>> Richie --<br>> <br>> All true enough, but I'm not clear on what your point is. I don't<br>> hear any chirp when a note is attacked on a violin. I just tried<br>> pulsing my string filter: I can see the output is dispered, taking 100<br>> ms or so to totally die out, but I don't perceive anything like a<br>> chirp. It just sounds like someone beating on a drum. Perhaps at a<br>> much higher Q setting you could perceive the chirp, but nothing when<br>> in normal operation, as far as I can tell. And why would you call it<br>> all effed up when it is emulating a violin? :-)<br>> <br>> Ian<br>> <br>> Sent from XFINITY Connect Mobile App<br>> <br>> ------ Original Message ------<br>> <br>> From: Richie Burnett<br>> To: Mattias Rickardsson, Tom Wiltshire<br>> Cc: Synth DIY<br>> Sent: June 30, 2017 at 9:41 AM<br>> Subject: Re: [sdiy] Resonator type filters<br>> <br>> If you pass a transient through a whole bank of high-Q analogue<br>> bandpass<br>> filters in parallel and then recombine their outputs what you end up<br>> doing<br>> is dispersing the energy. Even if their responses combine in equal<br>> proportions to give a more or less flat magnitude response, different<br>> frequency components incur different delays unless some measures are<br>> taken<br>> to compensate for this. As you said the more bands you have in your<br>> vocoder, for example, the high the Q-factors, and the more rapidly the<br>> phase<br>> changes across the bandwidth of each individual filter, and therefore<br>> the<br>> more severe the dispersion you get when you feed transients through<br>> the<br>> parallel filter bank as a whole. For example, a click gets<br>> transformed into<br>> a chirp... Or f####d up as you put it.<br>> <br>> -Richie,<br>> <br>> -----Original Message-----<br>> From: Mattias Rickardsson<br>> Sent: Friday, June 30, 2017 2:48 PM<br>> To: Tom Wiltshire<br>> Cc: Synth DIY<br>> Subject: Re: [sdiy] Resonator type filters<br>> <br>> On 30 June 2017 at 10:46, Tom Wiltshire <tom@electricdruid.net> wrote:<br>>> Is there some reason why string filters use a large number of fixed<br>> bands,<br>>> rather than fewer variable ones?<br>> <br>> Isn't the goal also to make the phase as messy as possible?<br>> <br>> I always think it seems to sound more wooden the higher the number of<br>> resonant bands you have in a vocoder-type filter... even if all the<br>> bands are set to middle position. And I guess the phases of the sound<br>> is what's mostly modified then. Steady-state sounds are not as<br>> spectacular, but every sudden transient will be fücked up.<br>> <br>> /mr<br>> <br>> _______________________________________________<br>> Synth-diy mailing list<br>> Synth-diy@synth-diy.org<br>> http://synth-diy.org/mailman/listinfo/synth-diy<br>> <br>> ---<br>> This email has been checked for viruses by AVG.<br>> http://www.avg.com<br>> <br>> _______________________________________________<br>> Synth-diy mailing list<br>> Synth-diy@synth-diy.org<br>> http://synth-diy.org/mailman/listinfo/synth-diy<br></font></body></html>