Path: utzoo!attcan!uunet!ogicse!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: jj@alice.att.com (jj, like it or not)
Newsgroups: rec.audio.high-end
Subject: Re: bi-amping
Message-ID: <9137@uwm.edu>
Date: 25 Jan 91 13:55:01 GMT
Sender: news@uwm.edu
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Approved: tjk@csd4.csd.uwm.edu
Originator: tjk@csd4.csd.uwm.edu


	Anyone seriously considering "real" bi-amping
(which means a low-level crossover in front of the amps)
should probably look into various asymetric designs for
crossovers.

	Why?  Because you wind up with (for instance)

	a low pass of           and a high pass of

	2s+1                         s*s
      ________                     _________
     s*s+2s+1                      s*s+2s+1

Which, you note, adds up to 1, with no phase-problems,
and no amplitude problems.

This does have a problem, in general you wind up with slower
crossover points somewhere, usually at low freq's.

I have done this with a machine-optimized 5th order
transfer function, where the highpass looked like third order
and the low pass like second order.  The q of all the
sections was quite low, because of the design, so I think
you COULD even build it with valves for that IM distortion
warmth, if you'd insist.

You just have to do the math, and then figure out the 
parts values for ONE of the filters.

You get the other one by direct subtraction, thus taking care
of any significant parameter problems around the crossover
point.
-----
You can make this an article if you want.  I don't have
time.

jj
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