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From: rmd@hpfcla.UUCP
Newsgroups: net.audio
Subject: Re: More Magnapan info
Message-ID: <13100008@hpfcla.UUCP>
Date: Mon, 12-Mar-84 15:13:00 EST
Article-I.D.: hpfcla.13100008
Posted: Mon Mar 12 15:13:00 1984
Date-Received: Wed, 14-Mar-84 19:24:42 EST
References: <333@dual.UUCP>
Organization: Hewlett-Packard Fort Collins Systems Division - Fort Collins, CO
Lines: 35
Nf-ID: #R:dual:-33300:hpfcla:13100008:000:2033
Nf-From: hpfcla!rmd    Mar 11 12:13:00 1984

I think that the low end rollof of the Magnaplanar  MG-IIBs (the model I
bought) is  actually  worse than the numbers you give -- at least for my
listening  room.  However,  I don't  think that the effect on music is a
significant as you seem to imply.  The bass response of the Magnaplanars
is deep enough to be quite  enjoyable for most rock music and it is much
more  accurate  and  uncolored  than most  speakers.  I think  that most
people  who object to  Magnaplanars  are used to  response  peaks in the
80-100 Hz and 10-12 Khz regions (typical of many conventional speakers).

I spent a lot of time  measuring the room  response of my MG-IIBs with a
flat  microphone  and a  signal  generator.  My  goal  was  to  match  a
subwoofer  to the MGs.  I found that the base  response  was  relatively
independent of speaker placement (contrary to Magnepan's literature) and
that the MGs peaked slightly at about 65 Hz and then rolled off at about
35db per octave, becoming essentially unmeasurable below 40 Hz.  I would
consider  them  'flat'  to  about  57  or  58  Hz.  I  didn't  make  any
measurements at high frequencies.

I finally came up with a crossover  that cuts off the  subwoofer at 30db
per  octave  above  50  Hz.  This  high  crossover  rate  results  in  a
combination  that is within .5db of the original MG response above 65 Hz
and adds about 6db at 50 Hz.

It turns out that with this  crossover, much pop music is almost totally
unnaffected by the  subwoofer.  Even songs like the  Eurythmics'  "Sweet
Dreams" or the Beatles' "Come  Together" with  apparently  loud and deep
bass  really  don't  have  much  below  about 60 Hz.  There are many pop
recordings with bass content down to about 48 to 50 Hz and for these the
subwoofer makes a noticeable (but relatively  subtle)  improvement.  The
only really striking difference is for classical music with a bass drum.
This  kind  of  music  goes  down to  under  25 Hz.  However,  very  few
conventional speakers go down this low.

Rick Dow
inhp4!hpfcla!rmd