13.1 How should I place speakers in my room? What size room is best?
Description
This article is from the rec.audio.* FAQ, by with numerous contributions by Bob Neidorff others.
13.1 How should I place speakers in my room? What size room is best?
You are after two important, distinct goals: flat frequency
response and good three-dimensional image. At your disposal is
the room size, the room shape, speaker height, speaker
placement, listening position, and room treatments. Even though
good speakers are essential to good sound, room effects are also
extremely important. In many cases, the differences in room
effects will be more noticeable than spending twice as much on
speakers!
Here are some generally-accepted-as-good guidelines for good
sound. If you use these as a starting point, you will be far
ahead in terms of getting good sound from your speakers and
room. But these are just a guide. Each room and each speaker
is a little different. Experiment to see if a change will
help. Also, if the manufacturer recommends something
different, give that a try, too. Then use what sounds best to
you.
For smoothest bass response, a listening room should be as large
as possible, have dimensions as unrelated as possible, and
should be optimally damped. Although nothing is ever ideal,
there are a few room dimension ratios that are better for
listening rooms:
Height Width Length
1 1.14 1.39
1 1.28 1.54
1 1.6 2.33
If your room isn't shaped like that, don't worry. These
effects are not major.
Also for smooth bass response, woofers should be at distances
from the nearest three room boundaries that are as different as
possible. In some cases, the line dividing the listening room
into left and right halves must be considered a room boundary.
Also, for smooth bass response, the listener's ears should be
at distances from the nearest three room boundaries that are
as different as possible.
All of this is essential because a wall near a speaker boosts
the bass from that speaker at some frequencies. If a speaker
is the same distance from three walls, then some frequencies
will be emphasized much more than others, rather than slightly
more.
For best three-dimensional image, a listening room should have
good symmetry about the plane between the two speakers. This
means that if one speaker is in a corner, the other speaker
must be in a corner. If this symmetry is not right, the first
reflection from the wall behind one speaker will be different
from the first reflection from the wall behind the other speaker
and critical parts of the stereo signal will be damaged.
Also, no large object should block the path from speakers to
listener or from speaker to speaker. Speakers should be
elevated so that tweeters are at listener ear height. The
distance between speakers should be no greater than the distance
from each speaker to the listener. Finally, the tweeters should
be aimed at the listeners.
A normal box-shaped listening room with bare walls will have
"slap echo" which will reduce intelligibility. A good cure is
randomly-placed wall hangings consisting of small rugs spaced
an inch or so away from the wall to increase sound absorption.
Another cure is convex-shaped art objects on the walls to
disperse harmful reflections. If money is available, commercial
room treatments such as "Tube Traps" and "RPG Diffusers" are
also valuable, but many of the benefits of these exotic devices
are available with simpler techniques.
As a general rule, in a good room, speakers and listener can be
close to room boundaries with minimal adverse effects. In a bad
room, a good strategy is to place both speakers and listener as
far away from room boundaries as possible.
An excellent starting point for speaker placement is to measure
the listening room diagonal dimensions. Divide that measurement
by three. Put each speaker that distance from a corner, on the
room diagonals.
I----------------------------------I I I I L I I I I S S I I I I----------------------------------I
Place your listening position midway between the two speakers
and approximately half way from the speakers to the wall. Be
sure that there is nothing in the "triangle" formed by the
listening position and the speakers.
Try this and then move things 12" (30cm) at a time to see if
you can improve the sound. Your ears will be a better guide
than any commonly-available instruments. To keep track of
what you are doing, take notes. To remember exactly where
you put the speaker on the floor, a practical trick is to
mark the floor with a sewing needle and thread.
Some speakers want to be aimed right at the listener (toed in)
while others work best pointed straight ahead. Experiment.
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