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From: prk@charm.UUCP (Paul Kolodner)
Newsgroups: net.audio
Subject: a new topic
Message-ID: <748@charm.UUCP>
Date: Sun, 15-Sep-85 13:04:59 EDT
Article-I.D.: charm.748
Posted: Sun Sep 15 13:04:59 1985
Date-Received: Mon, 16-Sep-85 03:13:24 EDT
Organization: Physics Research @ AT&T Bell Labs Murray Hill NJ
Lines: 50

new topic
net.audio



I would like to introduce a new topic:  arranging a listening room
for best sound.  Here's an area where hard facts are hard to communicate
because rooms are not sold, but clearly, the biggest thing you can
do to change the sound of equipment you liked in the store is to
take it have and install it there.  Who can communicate general
principles to help me improve the sound of my living room?
My living room is the front third of an open space 15 ft wide
by 50 ft long.  The front wall (15 ft wide ) has two windows covered
by floor-to-ceiling heavy curtains.  The speakers are two ft in
front of this wall, about 5 ft apart.  I sit about 10 ft back.
The wall on my left is plaster in front of me and is blocked by
a large bookshelf behind me.  The wall on my right is brick in front of
me (a fireplace) and is covered by a floor-to-ceiling bookshelf behind me.
Behind me is about 40 ft of empty space.  The floor is wood, with
a 4ft by 6ft area rug right between me and the speakers.  The furnishings
include a heavy sofa on my left but nothing else that absorbs sound.
There are a number of features of this space which might have an effect
on the sound, but I'm not sure about WHAT effect.  First, the space
in front of me is asymmetric from left to right.  Second,  NO  reflections
come from behind me; in fact, the rear wall is actually  at a noticable
angle from the side walls; this is apparently quite common and deliberate
in old houses - keeps the reflections down and the place is quiet.
Third, behind the speakers is a mass of heavy material which presumably
absorbs high-frequency sound.  Fourth, the speakers seem to be coupled well
enough to the floor to let me feel the bass notes in my feet.
This space is acoustically dead, despite the presence of hard, reflective
materials and the absence of absorbers.  When I snap my fingers or clap my
hands, no ringing is heard, presumably due to the large size of the room and
the slightly angled walls.  If I do the same thing in my bedroom, it rings
quite a bit, because the carpenter put in straight, true walls; this despite
heavy carpeting, heavy drapes, a big bed, a chair, and other absorbers.
So now the questions.  Does one want the speakers to be coupled or
decoupled from the floor?  Do large left-right asymmetries have a bad
or good effect on the sound?  Does one want reflections from the side and 
the rear?  In concert halls, reflections are good, but that's not very
relevant here.  Does one want a reflector or absorber behind the speakers?
Suppose I do what my wife wants me to do: put the speakers on either side
of the brick fireplace on the right wall and sit on the sofa on the left wall.
This would put a 40-ft deep empty space on my right and a wall on my left.
Is such an asymmetric arrangement a bad idea? (I'm going to check it out 
this week.) 
I have spent some time describing the details of one room that most of you
will never see.  However, I hope that the specific questions I just asked
will generate some information of GENERAL usefulness to us all.  If this 
results from YOU giving ME advice about MY room, great!


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