NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/rec/audio/car/4895

Internet Message Format | 1992-11-17 | 1.8 KB

Path: sparky!uunet!cis.ohio-state.edu!zaphod.mps.ohio-state.edu!wupost!spool.mu.edu!olivea!decwrl!access.usask.ca!kakwa.ucs.ualberta.ca!news
From: [e-mail] (Andrew Gilchrist)
Newsgroups: rec.audio.car
Subject: Xover points, Brian Gentry
Message-ID: <[e-mail]>
Date: 17 Nov 92 05:19:22 GMT
Sender: [e-mail]
Reply-To: [e-mail] (Andrew Gilchrist)
Organization: University of Alberta Electrical Engineering
Lines: 32
Nntp-Posting-Host: eigen.ee.ualberta.ca


Okay.  I figured out what I was thinking.

In a previous post about crossover slopes, etc. I stated that using
a passive crossover for slopes greater than 6dB/octave was a poor
idea.  Brian responded by explaining that there is significant
empirical evidence to suggest that passive crossovers with 12 and 18dB/octave
slopes can yield perfectly acceptable results, and are used in many high
end speaker systems.

He is correct, of course.

I was thinking in terms of DoItYerself circuitry.  The tendency for
inexperienced DIYers is to try to make a second order filter by cascading
two first-order sections.  This is not the way to do it. It is this
method of generating 12 and 18 dB/octave slopes I was thinking of.

With the proper reference, there's no reason you couldn't build a
perfectly feasible second or third order chebychev, butterworth, or
whatever. (I would recommend going for Legendre-Papoulis)

The bad part is, for passive crossovers, you need big coils.  I hate
coils.  You also need unpolarized capacitors.  Usually pretty big ones.

You get much better control over the poles in an active design.
Besides, active crossovers are cheap nowadays.  Why torture yourself
winding coils? (I suppose you could go by an xover from Rad-Shak)

Anyways, I appologize to everyone for this misunderstanding, and I hope the
flamefest can end.

Andrew