Nearfield Loudspeaker Placement
GUIDELINES FOR
SETTING UP SPEAKERS
(is the rule of thirds dead?)
by
Leo Massi
Sound
II, North Dartmouth, Massachusetts
(reprinted with permission)
The following is an attempt to provide a guide for setting up
speakers for those of you who may feel you need suggestions.
It is intended to take some of the randomness (and insecurity)
out of speaker placement. It is not intended as absolute "gospel".
The need to be sensitive to the issue of decor is an individual
matter, and if that applies to you, our hope is for you to use
whatever out of this that works for you.
I have compiled this system by decades of (sometimes) objective
observation, the enlightened teachings of Michael Green, room
treatment expert (? The next audio Messiah?), and from Joaquim
Gerhardt, who has extensively published on this issue, and may
be bordering on genius and regarding sound wave behavior in a
room, and particular sensitivity behaviors of the human ear.
Joaquim lives in Germany and is also the designer of Audio Physics
speakers.
Leo
The following comments
apply to truly phase coherent speakers, the majority of which
tend to have simple (or no) crossovers. This type of speakers,
if well designed, will generally display better timbral accuracy,
harmonic integrity, and a natural seamlessness. It is hard to put into words just how
much even the simplest crossover, or variance in driver material
adds to a sense of UNREALITY. Conversely, this method may not
apply to speakers with complex crossovers (i.e. some Thiels,
and many others) because, as you will see later, if you sit too
close to these speakers, you WILL HEAR THE CROSSOVER. Here we
go:
STEP #l ESTABLISH PROPER BASS RESPONSE
It is NOT absolutely true that one gets the best bass near the
wall. For example, corner positioning may substantially enhance
bass response below 40 to 50 hz, yet may drastically reduce mid-bass
output at the listening position. Panels, or rear firing ports
may elicit adverse peaks and "suck-outs". If the positioning
causes standing waves or "suck-outs" you can bet the
whole tonality of the presentation will be off, and trying to
fix this problem by changing cables or amps is like trying to
hold on to a fist full of wind. So, finding the "bass"
is the first step, and hopefully, you have a choice on which
wall you position the speakers. If you position them along the
wider wall you will get a better (read wider) stage presentation.
If they are placed along the shorter wall, it is more unlikely
that you will get as wide a stage, yet, if you can thusly accommodate
their placement closer to you, the listener, you will experience
a vastly improved sense of depth. In any case, the presentation
of stage width should always go out well beyond the two speakers.
There are three positions suggested
in Figure A: good, better and best. While your room may vary,
do try to apply, or at least experiment with, these rules. The
listener should be probably within a couple, three, feet from
the rear wall to minimize de-focusing reflections from the rear
wall. It wouldn't hurt to have some sort of sound dissipating
material on the wall part directly in back of the listeners head.
Somewhere within a foot to an
inch of the exact middle of the room will give you the best OVERALL
bass response
Front or rear quarter positions will be close seconds. These
distances should be measured with a tape and, while slight deviations
could be beneficial, being a foot or more off is likely to mean
your bass response (and overall tonality) will
be off.
FIGURE A
The front quarter position takes most of the back of the room
out of play and will give you the most holographic sense of depth
and is therefore my favorite. It is referred to as "nearfield
listening", and it is a never ending surprise to me how
many people have never been exposed to the effect this placement
generates. Middle positioning is second in depth, and most often
extremely acceptable, indeed some speakers with crossover complexity
(or errors) will actually benefit from this positioning. Rear
quarter placement is a most acceptable compromise where decor
demands. Having taken time to ponder and execute the positioning
in step one that suits your life style, while still giving you
proper bass response, it's on to step two. Please be sure you
have taken your time to explore step one to it's fullest, without
impatience or hurry, or else, don't blame me if it doesn't work.
STEP #2 ESTABLISH `STAGE WIDTH'
Take the speakers along the axis you have chosen in step l and,
ONE AT A TIME, have someone move them distally (toward the side
walls) WHILE LISTENING. You will notice that the "stage"
gets wider. At a certain point you will experience a "center
stage weakening" and then you have gone too far. Move it,
or them, proximally (or toward center) a hair to re-achieve good
balance.
STEP #3 ESTABLISH EXACT `FOCUS'
By focus I mean exactly like with a camera, the performers will
come into focus. And this definitely takes two people.
FIGURE B
Have the other person rotate the speaker, ONE AT A TIME, in a
rapid fashion (like tuning a guitar), on the axis indicated by
the arrows in figure B, while the listener checks for focus.
After a small amount of practice the listener will say "right
there, right there!" Then do it on the other side. Have
faith in yourself, you WILL hear it.
STEP #4 ESTABLISH STAGE `BALANCE'
We have all experienced some rooms that seem to impart a great
stage presentation on one side, but a smaller and less dominant
one on the other side. To correct this phenomenon, the (other
person) FIGURE C would
FIGURE C
move that speaker which is on the weaker side of the stage forward
along the axis chosen in figure B, the "focus" step,
in 1/16" to 1/8" increments until "stage balance"
is achieved. By the way, there is a rumor going around that Audio
Physics speakers must be set up in this fashion. This is absolutely
not true. They, as well as many other brands, will benefit from
this procedure (actually the listener benefits, not the speaker).
They will be affected neither more nor less than any other well
designed brand speaker.
Again, some of the steps in this method will probably not work
on loudspeakers with phase problems, or with complicated crossovers,
and that's life. Back to the rule of thirds??
To briefly touch on some other room problems, I would say the
biggest culprits of defocusing the musical images are the four
corners between the walls and the ceiling, as well as the corners
themselves. These are a good place to start treating with Michael
Green's "Room Tunes". If you want literature on the
subject of "Room Tunes" you can ask, fax, or write
Sound II for it.
"DOTS" from Marigo work very, very well to tweak the
room with finishing touches, particularly on windows, but on
equipment as well.
Leo
Notes:
(1) In a subsequent conversation,
Leo noted the different effects different setups have on bass
response: the 1/4 and 1/2 positions improve low bass performance
(under 50 Hz.), while the 1/3 position improves mid bass performance.
(2) See "Basic Stereo Loudspeaker
Placement," for a basic placement recommendation, if
you do not have a dedicated listening room. See "Surround
Loudspeaker Placement," for recommendations for surround
and home theater loudspeaker placement.
(3)The opinions expressed in the above article are those of the
author, Leo Massi. |