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From: seifert@ihuxl.UUCP
Newsgroups: net.audio
Subject: Re: Speakers
Message-ID: <434@ihuxl.UUCP>
Date: Wed, 13-Jul-83 09:33:46 EDT
Article-I.D.: ihuxl.434
Posted: Wed Jul 13 09:33:46 1983
Date-Received: Thu, 14-Jul-83 21:29:59 EDT
References: <1392@iedl02.UUCP>
Organization: BTL Naperville, Il.
Lines: 38

"British" speakers intentionally "beam" the high  frequencies  at
you,  as opposed the the "American" school of thought which tries
for as wide a pattern of dispersion as possible  (remember  omni-
directional speakers?).

The idea is to avoid early reflections which mess up the sound.

My view is that low frequencies are going to be  omni-directional
(or  close  to  it)  no  matter  what  you do, so build the high-
frequency drivers to match.     Also, I  don't  like  having  the
sound  change drastically when I walk around the room. Which also
explains why I haven't gotten Carver's sonic-holography toy.

There is the alternate method of eliminating  early  reflections:
cover  the  'speaker'  half  of  the  room  with  sound absorbing
material, carpet, ceiling tile, rugs on the walls, etc. Put sound
reflecting  material  on  the  other  end  for  balance.  Put the
listening chair/sofa/whatever in  the  middle.  I  haven't  tried
this,  but  would  like to some day. Has anyone experimented with
this?  It was in "Absolute sound" or "Sensible sound" a couple of
years ago.

An interesting side-effect of building speakers with  'wide-angle
tweeters'  is  that,  in  the  old  days,  when  tweeters  beamed
horribly, they were also much more efficient than the woofer, and
would  have  a  resistor in series to decrease the power to them.
Now they are building 180-degree tweeters and gee, it takes  more
power  to  cover more area!  To get enough power into the tweeter
of my AR-11s, they made the impedance at 10 kHz about  1.5  Ohms,
the  max impedance is about 16 Ohms somewhere in the bass region.
The speakers are rated at 4 Ohms, but your amp  better  not  mind
driving  under  2  Ohms!  And  whatever  you  do,  don't parallel
anything with them!  (assuming solid state, tranformerless output
power amps.)


                        Dave Seifert
                        ihnp4!ihuxl!seifert