| Video Noise December 2004
Home Theater Setup:
Performance Considerations, Part Two
Consider AC power
conditioning
An AC power conditioner is more likely to be thought of as
an inexpensive "surge suppressor" of dubious value than as a sophisticated
home-theater component that’s as important as a monitor or surround processor. Power
conditioning can’t improve a bad video source, but it can make good-performing
low-to-mid-priced components look and sound far better than A/V critics expect. In fact,
the less expensive your home-theater equipment, the larger the potential payback for
improving the power delivered to the system.
Let’s say you have a balanced $3600 system of monitor,
receiver, speakers, DVD player, and cables. In this case, "balanced" means that
you don’t have a $3000 monitor hooked up to $600 worth of electronics and
speakers -- your investment is more or less evenly divided among all the components. It
would be about right to spend 20% of this investment, or $720, on power conditioning to
get better audio and video. This will buy a good-quality, handmade conditioner with few
bells and whistles, but with good surge and spike protection along with passive filtering
of the AC power. You could also get a Monster Power or Belkin power conditioner with LEDs,
a built-in line voltmeter, a guarantee covering the replacement cost of equipment damaged
by surges or spikes, and loads of convenience features. The higher-volume products in that
category give up a little in sound quality to the handmade products, but give up nothing
in video quality.
 With a $10,000
system, you could justify a $1995 ExactPower EP15A (shown right), which actively regulates
the AC voltage to 120VAC and removes distortions from the power line. This device is a
significant step up in performance compared to passive-filtering products that sell for
less than $1000.
If you have a $15,000 system, one ExactPower SP15A used in
conjunction with an EP15A could run all of your source components with lower noise and
better video and audio performance.
Consider room acoustics
One of the best ways to tell if your room has acoustic
problems is to clap your hands and listen for echoes. You should be sitting or squatting
at your listening height when you do this -- if you clap only while walking around the
room, you might hear echoes that seated listeners won’t, and/or miss problems that
seated listeners would hear. You’ll find areas in the room with very strong echoes,
and areas with little or no audible echo. You can improve the sound of your system
considerably if none of the speakers or listeners are in locations with a lot of echo. You
could move the speakers and/or listeners a foot or two, out of the areas where echoes are
most severe.
Adding products to improve room acoustics are the next
step. Michael Green’s Pressure Zone Controllers mount on walls and have an adjustable
tuning bolt in the center of a wooden panel. If someone turns this bolt while you’re
listening to high-quality music, you’ll hear the acoustics change as the bolt is
turned. It’s quite surprising to hear this effect for the first time. I don’t
favor devices that trap, absorb, or damp sound, as these tend to make the sound too dead
and boring. I prefer products that remove reflection and echo problems and tune out
unwanted resonances to products that absorb sound in any way. Anything that can be done to
break up large, unbroken expanses of wall or ceiling will improve the acoustics of the
room.
Consider room dimensions and placement of speakers
Room dimensions have a big effect on sound quality. A
cubical room measuring, say, 14’ x 14’ x 14’ will sound awful because all
three dimensions are the same. Bass resonances, for example, will be three times stronger
than they would be if the room had three different dimensions. A room 24’ x 16’
x 8’ is almost as bad because all its dimensions are divisible by 8, 4, and 2. This
means that there will be tripling of room modes for some frequencies. A room 23.5’ x
19.5’ x 10.5’ spreads the room modes out enough that they won’t double and
triple themselves. A 10.5’ ceiling will keep away from listeners many reflections
that they would hear in a room with an 8’ ceiling.
If your room has a cathedral ceiling 8’ high at one
end and 15’ high at the other, place the speakers along the wall where the ceiling
height is a constant 8’. The listening position would be toward the wall where the
ceiling is 15’ high. This prevents uneven reflection delays from the speakers, and
the sloped ceiling will actually help keep unwanted reflected sounds from reaching
listeners.
Consider room surfaces
Framed pictures and windows can impart a hard, annoying
quality to your sound due to the reflection of sound off the glass surfaces. You’ll
find the sound more enjoyable if such surfaces are "softened" with light
draperies or shades. The harsh sound reflected off of glass is especially noticeable if it
reaches listeners directly. Other hard, flat surfaces, such as tile or polished stone, can
also sound very annoying. Reflections from plastic surfaces are also detrimental to
getting the best sound. Breaking up these reflections will improve your sound to a
noticeable degree and will make for better home theater.
...Doug Blackburn
db@hometheatersound.com |
