<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=windows-1252">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<p>Bernard,</p>
<p><br>
</p>
<p>I think you mix up my comments and misses my point.</p>
<p>I know what order of filter and Q of the pole-pairs do.</p>
<p><br>
</p>
<p>For speech clarity, you want the group-delay to be flat, and
essentially no ringing. This moves you away from high-Q solutions.
Some have used high-Q solutions to make simple filters with enough
slopes, but they miss out on the properties of the filters and
what it does in the application. For maximum flat group-delay,
Bessel-Thompson is the ideal to look for. The selectivity you get
by degree of the filter to have slopes from that rather than Q.<br>
</p>
<p><br>
</p>
<p>Cheers,<br>
Magnus<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2019-09-04 05:40, Bernard Arthur
Hutchins, Jr wrote:<br>
</div>
<blockquote type="cite"
cite="mid:BN8PR04MB6036C0A583110B460F91D16ABCB80@BN8PR04MB6036.namprd04.prod.outlook.com">
<meta http-equiv="Content-Type" content="text/html;
charset=windows-1252">
<style type="text/css" style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} --></style>
<div id="divtagdefaultwrapper"
style="font-size:10pt;color:#000000;font-family:Arial,Helvetica,sans-serif;"
dir="ltr">
<div
style="mso-element:para-border-div;border:none;border-top:solid
#CCCCCC 1.0pt;
mso-border-top-alt:solid #CCCCCC .75pt;padding:11.0pt 0in 0in
0in;background:
white;margin-left:34.5pt;margin-right:7.5pt">
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:10.5pt;
font-family:"Helvetica",sans-serif;color:#333333"><o:p> </o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;tab-stops:.5in
49.5pt;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;
padding:0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:10.5pt;
font-family:"Helvetica",sans-serif;color:#333333"><o:p><span
style="font-size: 12pt;"> </span></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size: 12pt; font-family: Helvetica,
sans-serif; color: rgb(51, 51, 51);">Magnus –<o:p></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:18.0pt;
font-family:"Helvetica",sans-serif;color:#333333"><span
style="font-size: 12pt;">I think we would agree that
there may be reasons for considering bandpass responses
of order greater than 2 – but getting a higher Q
(sharper peak) is</span><span style="font-size: 12pt;"> </span><span
style="font-size: 12pt;">not likely to be one of them.</span><span
style="font-size: 12pt;">
</span><span style="font-size: 12pt;">Usually the sharper
Q is obtainable just by increasing the performance Q of
the second-order.</span><span style="font-size: 12pt;">
</span><span style="font-size: 12pt;">It’s not like the
case with low-pass where extra poles give you a sharper
roll-off rate JUST BEYOND the corner (like 24 db instead
of 12).</span><span style="font-size: 12pt;">
</span><span style="font-size: 12pt;">With a high-Q BP,
the “skirts” begin well after the response is well below
the peak.
</span><o:p></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:18.0pt;
font-family:"Helvetica",sans-serif;color:#333333"><span
style="font-size: 12pt;">If you DO want sharper “skirts”
(say 12 db on each side of the peak instead of the 2</span><sup><span
style="font-size: 12pt;">nd</span></sup><span
style="font-size: 12pt;">-order 6db on each side), then
a cascading of identical BPs is the ticket. The Q
increases in such cases, but distressingly slowly- if I
recall. So it is probably not even a good way to sharpen
a BP.</span><o:p></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:18.0pt;
font-family:"Helvetica",sans-serif;color:#333333"><span
style="font-size: 12pt;">The real use of (and meanings
of) higher-order BP is to achieve a flatter passband.</span><span
style="font-size: 12pt;">
</span><span style="font-size: 12pt;">The poles are
slightly offsets so that when we move away from one,
with a declining gain, the next pole takes over.</span><span
style="font-size: 12pt;">
</span><span style="font-size: 12pt;">This is so-called
“stagger-tuning” - a difficult design.</span><o:p></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size: 12pt; font-family: Helvetica,
sans-serif; color: rgb(51, 51, 51);"> </span></p>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size: 12pt; font-family: Helvetica,
sans-serif; color: rgb(51, 51, 51);">But the design is
easy if one uses a lowpass-to-bandpass transformation for
Butterworth or Chebyshev:
<o:p></o:p></span></p>
<span style="font-size: 12pt;"></span>
<p
style="margin-top:0in;margin-right:0in;margin-bottom:7.5pt;margin-left:0in;background:white;border:none;mso-border-top-alt:solid
#CCCCCC .75pt;padding:
0in;mso-padding-alt:11.0pt 0in 0in 0in">
<span style="font-size:18.0pt;
font-family:"Helvetica",sans-serif;color:#333333"><span
style="font-size: 12pt;"> </span></span><span
style="color:black;mso-color-alt:
windowtext"><span style="font-size: 12pt;"> </span><a
href="http://electronotes.netfirms.com/AN336.pdf"
id="LPlnk802802" class="OWAAutoLink"
previewremoved="true" moz-do-not-send="true"><span
style="font-size: 12pt;">http://electronotes.netfirms.com/AN336.pdf</span></a></span><span
style="font-size:18.0pt;font-family:"Helvetica",sans-serif;color:#333333"><o:p></o:p></span></p>
</div>
<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
Synth-diy mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a>
<a class="moz-txt-link-freetext" href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a>
</pre>
</blockquote>
</body>
</html>