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<p>Dear David,</p>
<p>Many other vocoders used higher Q setups, and Jürgen and I agreed
that you need to avoid that. The reason is that higher Q gets you
into higher group delay, making the filter more sluggish to
respond and rings longer after the end of a sound. It also causes
different time-shifts between bands to become bigger than if you
use low Q.</p>
<p>Jürgen was inspired by the EMS3000 vocoder until I sent him the
EMS5000 manual and schematic, which derailed the project a little.
:)</p>
<p>So, it is not recommended to go for higher Q, and I think you get
why.</p>
<p>Cheers,<br>
Magnus<br>
</p>
<div class="moz-cite-prefix">On 2019-08-31 06:05, David G Dixon
wrote:<br>
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<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">Hey SDIY Team!<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">I’m thinking about building a vocoder,
and I have a
general question about the bandpass filters.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">I’ve looked at Jurgen Haible’s Living
Vocoder,
and he used 8-pole filters with low Q. These give a
reasonably broad band
with fairly steep slopes. He makes the filters from two
pairs of LP and
HP.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">I was thinking about using BP filter
sections, but just
4-pole, and with higher Q (around 10). This gives a
somewhat narrower
band, and the slope is steep near the corner, but fairly
shallow around the
skirt. This idea uses a lot fewer components (about half
as many).<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">What I’m asking is, does anybody here
have any insight
into what the “proper” approach to vocoder filters would
be? What
is the design goal? Do you want significant overlap from
one band to the
next, or should they be fairly distinct? I guess I’m just
looking
for some general guidelines and conventional wisdom.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">Cheers,<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span
style="font-size:10.0pt;
font-family:Arial">Dave Dixon<o:p></o:p></span></font></p>
</div>
<br>
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