| Video Noise November 2004
Home Theater Setup:
Performance Considerations, Part One
There’s more to setting up a
home theater than just putting things where they seem to fit. There are setup
techniques that can help to make the home-theater experience more exciting for everyone in
the audience. The tips here include those that make the biggest improvements in
performance.
Speaker setup
An important rule for speakers is Don’t guess,
measure! This applies to distances from the listening position as well as to
volume/loudness, or sound-pressure levels (SPLs). Whenever possible, the speakers should
all be the same distance from the primary listener. At a very minimum, the front left and
right speakers should be the same distance from a listener sitting in the sweet spot. The
center-channel speaker should be the same distance away as the front left and right
speakers. This means that the baffles of the three front speakers will describe not a
straight line, but an arc swept from the central listening position.
Yes, you can compensate for unequal speaker distances in
your surround processor or receiver’s setup menus, but that will add varying amounts
of digital delay to the signal. Your home theater will sound better if no delay
processing is applied. Delay processing for subwoofers and rear surround speakers is not
as obviously audible as delay processing for the front set of speakers, but is still best
avoided.
 Don’t guess at the volume
setting for each channel. Use your surround processor’s built-in calibration test
tones to set individual speaker levels, and measure the SPLs -- don’t
calibrate by ear. RadioShack sells a modest yet effective SPL meter for under $40 (catalog
number 33-4050). You’ll be amazed how much more balanced and integrated your home
theater will sound when you calibrate channel levels with a meter instead of your ears.
To make this measurement, set the SPL meter to "C
Weighting" and "Slow" response. Aim the meter up at a 45-degree angle. The
meter’s built-in microphone should be at a seated listener’s ear height and as
close as possible to the center of that listener’s head position. This usually means
sitting in the center listening position, leaning back farther than usual, and putting the
meter right in front of your neck. Turn the meter toward the speaker reproducing the test
tone, but don’t aim the meter directly at the speaker; maintain the 45-degree angle.
Then adjust each channel’s level until it matches the others.
The subwoofer level commonly needs to be set 4dB or 5dB
higher (per the SPL meter) than the reference level for the other five channels for the
sound to be balanced. Inexpensive SPL meters may read lower for bass frequencies used for
setting the subwoofer level than they do for midrange and high frequencies used to set the
levels for the other speakers. The capabilities of your subwoofer need to be considered,
of course. Some smaller, less expensive subs will distort badly when set to reproduce bass
at levels intended by a film’s sound director. Be careful.
Monitor setup
 Few people can
set up a video monitor by eye. Test and setup images available on test DVDs and
D-VHS/D-Theater HDTV tape are usually needed to help ensure that the video parameters are
set up for the best possible picture quality. Currently there are half a dozen or more
setup DVDs that can help you improve the video quality of your home theater far more than
would ever be possible by eye. If you want only the most basic adjustments and the
greatest ease of use, go for the Sound & Vision Home Theater Tune-Up DVD (under
$20). Of the test DVDs that cover the basics but also get into some of the trickier
problems and setup issues, Digital Video Essentials (under $25) is the best.
Something often overlooked is that a monitor needs to be
calibrated for each video source. It’s common to have three or four video sources,
each requiring different settings for color, tint, contrast, and brightness to look their
best. When you set up your DVD input for optimum quality with a test DVD, you’ll
probably find that standard-definition TV and HDTV now look very different. That properly
set-up DVD source can then become a reference to use to get the other video inputs to look
their best. It’s common for newer TVs, especially HDTVs, to have three or four
different video setups available, allowing you to custom-tune the picture quality for each
source. Some newer monitors automatically select the correct video settings for each
input, but many sets require you to remember to change the video settings with a
remote-control command when you switch to a different source.
Surround processor or A/V receiver setup considerations
Recheck your speaker-level settings periodically,
especially after power outages. Some equipment loses speaker-volume settings and other
setup parameters if the power is interrupted. I had one product that would save settings
just fine if I unplugged it from the wall, but if there was a power failure, which we get
with some regularity, there was a 50/50 chance the settings would be lost.
 If you’re not using a digital
(optical or coaxial) connection between your DVD player and processor, you probably
aren’t getting the best movie sound. There are a number of good optical cables
available for less than $25. Try the Acoustic Research (AR), a no-frills cable with good
performance at a reasonable price, available at many large retailers, including Best Buy.
Digital coaxial cables often provide better sound than
optical cables, but it’s harder to find good-sounding digital coax at low prices.
Some of the better values come from several Internet vendors who sell Belden 1694A or
1695A digital coax cables terminated with Canare RCAP-C53 RCA plugs. The Canares are
closer to being 75-ohm plugs (ideal for video use) than are most RCAs. Because these
connectors sell for around $5 each in small quantities and the Belden coax sells for about
50 cents a foot, you won’t have to pay a lot for a single digital cable -- say, $15
for the parts and $15 for the labor to make a cable. You could make the cable yourself,
but the proper crimping tool to use with these crimp-on 75-ohm RCA plugs sells for about
$150; you might want to settle for soldering the coax center conductor. To find Internet
vendors who sell this type of digital coax, search for the connector name or cable name. A
number of sources will come up.
Tune in next month for Part Two and more setup tips.
...Doug Blackburn
db@hometheatersound.com |
