Creating a Media Room,
Part 2 -- Audio
One of the hallmarks of a home theater system, of course,
is multiple channels of audio. Few homes can easily accommodate five full-sized speakers
for surround, however, so satellite/subwoofer combinations are often the best solution.
That may be necessary in smaller rooms, but not appropriate
in all cases. A very large viewing room may not be well served by the tiny speakers, for
instance, although many systems do in fact put out excellent sound and lots of it.
One increasingly popular alternative is the in-wall
speaker. In-wall units take up virtually no space in the listening area, using the gaps in
the walls as their enclosures and presenting just a flat grille to the room. These
speakers can be made to be more or less invisible, but are very difficult to change or
upgrade after the fact. Often, the best solution is simply to use full-range speakers in
all positions; if these are identical, or at least very close, the sound will be
consistent throughout the room.
Whatever speaker complement you choose, where you put the
individual reproducers is of crucial importance. As a general rule, you should start with
the main left and right speakers, which should be positioned at equal distances from the
television monitor, and at about the same distance from each other and from the main
listening seat. If you are currently listening to conventional stereo in the room and are
satisfied with it, it makes sense to place the left and right speakers where your present
speakers are, even if they are in fact different models -- why mess with success? This
will yield the best imaging both for video material and conventional audio.
PSB Image 2B speakers
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One thing to be very careful about is the
positioning of the speakers with regard to nearby wall surfaces, which have the tendency
to emphasize a speaker's bass and sometimes cause interference at higher frequencies as
well. Some models are designed to take advantage of this and are meant to be placed next
to walls, in which case they can live on shelves either side of the TV, if it's against a
wall. Other speakers require some distance from room boundaries, which may or may not
disqualify them in your particular room.
If you can accommodate them, most -- especially small
speakers -- have optional stands that place them at the right height both to deal with the
acoustic effects of the floor and to position them at proper listening height (all front
speakers should either be at ear height or angled slightly toward the prime viewing area).
The one thing to avoid absolutely is speakers in widely
varying acoustic environments -- one out from the wall, the other in a corner, for
instance. The sound quality of any speaker is at least as much a product of its
environment as its inherent sonic character, so speakers should be placed in a similar
locations as you can manage. If a mono signal changes character dramatically as you turn
the balance control back and forth, you have some repositioning ahead of you.
The center speaker should, of course, be midway between the
main speakers and as close to the screen itself as possible. Some authorities feel that
the three front speakers should be at the same vertical height, to avoid a "roller
coaster" effect as sounds move about the "stage", but this is not always
practical. Nor is it really necessary, as we have very little perception of vertical
positioning.
More important is that the three front speakers be placed
in acoustic environments that give very similar tonal balances, so the sounds don't change
in spectral character as they move.
Also, the distance of all three to the main listening area
should be identical, or much of the dramatic movement of the sound could be lost. If the
speakers are in a straight line, the center one is likely to be slightly closer to the
listening seat, and any sound that is common to the center and either side will appear to
come from the middle. Pushing the center back a bit, or moving the others forward can
prevent this. One simple technique for making sure things are right is to pin a bit of
string to the middle of the main seat and stretch it to the center speaker. When you move
it left or right, it should just reach the other speakers.
Paradigm's ADP/Studio surround speakers
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Surround speakers pose a different
challenge. Most of us think of these as "rear" speakers (and most surround
decoders and receivers label them as such), but Dolby Laboratories, who should know,
prefers that they be positioned beside the main listening position, rather than
behind it. This doesn't work well in many rooms, and is less preferable when you are using
the ambience-enhancing modes offered by many decoders for use with conventional stereo
material.
In fact, positioning of the rear/surround speakers is quite
uncritical in my experience, and can largely be dictated by the requirements of the
listening room. The rear center speaker in a 6.1-channel setup should, of course, be
directly behind you.
Where the rest of the equipment is placed is important too:
it should be in one place to keep cable lengths short, it should be in clear view of the
main viewing position (not so you can see its glowing lights, but so that it can
"see" the remote control you will be using to run it), and it should ideally be
fairly unobtrusive. Placing the electronics in a compact area means that fairly ordinary
cables can be used to connect them together; longer runs place greater demands on wiring.
If that doesn't work in your room, it may be preferable to
place the source and control components in one spot near the viewing position, where the
cables between most components can still be short. Speaker cables will inevitably be
longer in this arrangement, but as long as they are heavy enough, that shouldn't be a
problem. Any speaker wire that has to be more than about 15 feet should be 12-gauge
minimum, but beyond that, the wire isn't really very critical.
When it comes to connecting command central to your TV
display, high-quality cables should be used because the run may be fairly long. It's
almost never wise to feed the RF output of your VCR to the antenna terminals of your
television; direct video connection is always preferable, and this demands decent cables.
One of the best solutions is to use ordinary 75-ohm video cable with standard RCA plugs at
each end. This may require a bit of soldering, but it's worth it.
Both video and speaker wiring are reasonably impervious to
external interference as long as you keep the runs as short as possible. Tacking them to
baseboards is often practical, or threading them over dropped ceilings. Avoid trailing
them across the floor, however; this may be dangerous for you and your guests, to be sure,
but it may also cause damage to your equipment if repeated disruption loosens the
connections at either end and causes short circuits. And running them under the carpets is
almost never a good idea (and hazardous if they carry AC current).
The media room or home theater may well have become the rec
room of the '90s, but its technological nature demands it be planned and executed with
considerable care.
...Ian G. Masters
ian@mastersonaudio.com
For video installation considerations, see "Creating a Media Room, Part 1 -- Video" also posted
January 1, 2001.
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