| Video Noise November 2005
Doug's Rules for Home
Theater: Part Three -- More on Speakers
Space, Alignment, Distance
This month, my rules cover the spaces and distances needed
to make loudspeakers sound their best. These general rules will be applicable to many, but
not all, speakers. The better manufacturers will include information covering various
aspects of setting up the speakers to achieve the best sound. Rather than say, "Read
and follow the manufacturer’s information" ten times, I will say it just this
once -- and once again at the end.
Vertical listening height: Many speaker designs work
best when the listener’s ears are within a specific vertical window -- sit too high
or too low and the sound will be compromised. This is usually specified as the distance in
inches the listener’s ears should be above the floor. Sit in your listening chair and
measure the distance from your ears to the floor -- don’t guess or estimate.
(When I tried to estimate how high my ears were from the floor when sitting on our
listening sofa, I was off by half a foot.) If there is nothing in the speaker
documentation about vertical listening height, you can hope that the speakers will sound
pretty good over a fairly large vertical window, but use common sense. If you sit very
high, aim or position the speakers a little high; if you sit lower, aim or position the
speakers accordingly. Surround speakers are almost always intended to be placed slightly
higher than the listener’s ears. Center-channel speakers, of necessity, often must be
higher or lower than the ears. If recommended to by the manufacturer, aim the
center-channel to compensate for low or high speaker positioning.
Listener-to-speaker distance: To get the best
possible sound from your speakers, you need to sit a specific distance from them for the
sounds from their individual drive-units to blend properly. If you’re too close,
you’ll hear the drivers’ outputs separately rather than as a single source of
sound; if you’re too far from the speakers, you’ll hear more of the reflected
room sound and less of the direct sound from the speakers themselves. The size of the
speaker has a lot to do with listening distance: most smaller speakers will sound better
if you’re not too far away; most larger speakers will want more breathing room.
Toe-in: Some speakers sound best aimed straight
forward. Others sound best when aimed right at the listener(s). Many speakers will want to
be somewhere between those two extremes. Usually, the manufacturer supplies specific
information about this.
Speaker separation: The distance between two
speakers is usually measured from the centers of the speakers’ front panels. Most
often, the ideal distance between the speakers will be 10% to 20% less than the distance
from the listener to the speaker. If you have a large video display between your speakers,
you might need a bit more space between the speakers to keep them from being too close to
the display. Rear surround speakers often must be much farther apart due to living
considerations; that’s OK, especially if a center surround speaker(s) is used.
General rules: Small speakers can get lost in big
rooms, and big speakers can overpower small rooms. Freestanding speakers need open space
around them to sound their best: 2’ to 5’ behind them and to the sides. The
larger the speaker, the more room it needs. On-wall and in-wall speakers will sound best
when surrounded by expanses of uninterrupted wall. Some speakers are specifically designed
to have very large "windows" of good sound, while others may have design
features that make the listening window, or "sweet spot," relatively small.
Obviously, larger windows of good sound will be desirable for home theaters designed to
seat more than two or three people, especially if you want the sound to be good whether
the listeners are on the floor or sitting in a second or third row of seats on raised
platforms. If you prefer the sound of speakers that have a smaller listening window, they
will perform well as long as the window is large enough to cover the intended listening
area.
If you want all the loudspeaker performance you’ve
paid for, follow the placement instructions provided by the manufacturer. It’s
critical for good home-theater sound.
...Doug Blackburn
db@hometheatersound.com |
