Path: utzoo!attcan!uunet!ogicse!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: hull%janus.Berkeley.EDU@ucbvax.Berkeley.EDU (Christopher Hull)
Newsgroups: rec.audio.high-end
Subject: Re: crossover design
Message-ID: <9135@uwm.edu>
Date: 25 Jan 91 13:54:29 GMT
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Approved: tjk@csd4.csd.uwm.edu
Originator: tjk@csd4.csd.uwm.edu



In a x-over design it is neccessary that the vector sum of the acoustic
pressures from the drivers be equal to 1.   If the drivers are in phase 
than that implies that they are 6db down each (as in Linkwitz 2nd & 4th
order x-overs).  However for 1st & 3rd order butterworth x-overs, the
drivers are in phase quadrature (90 degrees out of phase) and thus each
driver is only 3db down at the x-over frequency.  For x-over designs with
even more phase difference it may be necessary for each driver to have full
output at the x-over frequency (e.g. the "Quasi" second order filter).

There are a number of design considerations that must go into choosing the
x-over.  For example, driver quality, actual x-over freuquncy, power level
required, cost etc.  Each x-over has a different set of trade offs.  First
order x-ovvers will only work with widenband drivers and are best for 
multi-way systems.  Higher slope x-overs are expensive, tricky to build,
but will allow use of fewer drivers over a wider bandwidth /driver.

For two way sytems you may want to use 3rd or 4th order networks. 
For three way sytems first or second order networks will suffice.
For four way sytems generally use first order networks.

Also, their is the Bessel type network used in the Spica Tc-50 , which
I have used myself.  It is 4th order on low pass, and only first order
on high pass.

Chris Hull
< hull@janus.berkeley.edu>