<div dir="auto"><div><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Den lör 31 aug. 2019 06:46David G Dixon <<a href="mailto:dixon@mail.ubc.ca">dixon@mail.ubc.ca</a>> skrev:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Well, I think I might have answered my own
question. Looking again at the JH Living Vocoder, since Jurgen Haible’s
filter responses overlap at about the 8dB mark, it really should not matter at
all what’s going on around the skirt of the response, and higher-Q filters
with two 2-pole stages should give very similar results to low-Q filters with four
4-pole stages (and be much much cheaper to build).</span></font></p></div></div></blockquote></div></div><div dir="auto"><br></div><div dir="auto">Between those two alternatives I'd expect audible differences due to ringing, and practical differences due to sensitivities to component tolerances.</div><div dir="auto"><br></div><div dir="auto"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div class="m_-3502678896119312643Section1"><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"><u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy"><u></u> I</span></font><span style="color:navy;font-family:Arial;font-size:10pt">’d still appreciate if anyone has
any specific insights into this problem. Cheers. </span></p></div></div></blockquote></div></div><div dir="auto"><br></div><div dir="auto">Paul's viewpoint is one of many when it comes to the filterbank design. Some aspects have conflicting optima. Figuring out these strategic choices is the charm in designing a vocoder, I guess. 8-)</div><div dir="auto"><br></div><div dir="auto">/mr</div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div class="m_-3502678896119312643Section1">
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<p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size:10.0pt;font-family:Tahoma;font-weight:bold">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size:10.0pt;font-family:Tahoma"> Synth-diy
[mailto:<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank" rel="noreferrer">synth-diy-bounces@synth-diy.org</a>] <b><span style="font-weight:bold">On
Behalf Of </span></b>David G Dixon<br>
<b><span style="font-weight:bold">Sent:</span></b> Friday, August 30, 2019 9:05
PM<br>
<b><span style="font-weight:bold">To:</span></b> <a href="mailto:synth-diy@synth-diy.org" target="_blank" rel="noreferrer">synth-diy@synth-diy.org</a><br>
<b><span style="font-weight:bold">Subject:</span></b> [sdiy] vocoder filters</span></font><u></u><u></u></p>
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<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial">Hey SDIY Team!<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial"><u></u> <u></u></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.<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial"><u></u> <u></u></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.<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial"><u></u> <u></u></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).<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial"><u></u> <u></u></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.<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial"><u></u> <u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial">Cheers,<u></u><u></u></span></font></p>
<p class="MsoNormal"><font size="2" face="Arial"><span style="font-size:10.0pt;font-family:Arial">Dave Dixon<u></u><u></u></span></font></p>
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