| Video Noise May 2009
Getting the Most from
Room-Correction Software
 More and
more audio/video receivers (AVRs) and surround processors now come equipped with automated
setup and room-correction software made by Audyssey and other companies, often the AVR
manufacturers themselves. However, some aspects of these programs are explained poorly by
the owner’s manuals, if at all.
Should you use it?
If your AVR or processor already has Audyssey or its
equivalent built in, at least try it. These programs, however, don’t seem to work
well for some systems in some rooms, sometimes because the measurements weren’t done
properly, and sometimes for no obvious reason at all. Still, examples of the latter are
rare. Programs like Audyssey can adjust much more than sound levels and delays for speaker
distances. Those capabilities, and the ability to process and correlate measurement data
separately for each channel, as well as in combination with other channels, mean that the
user can do much more than with measurements taken with a handheld sound-pressure-level
meter.
Should you follow the instructions in the manual?
For the most part, yes, especially the explanations of
which steps to take first and which later. But the instructions may mislead you about how
many microphone positions you should take measurements from to get the best results. With
Audyssey MultEQ, which is found in many mid- and higher-priced AVRs, you usually have a
choice of taking measurements from one to eight or three to eight mike positions; however,
your AVR’s manual may not be specific about which number of measurements will produce
the best results. Audyssey recommends six to eight positions.
The manual may also give little or no guidance as to where
to place the mike, other than "measure the next seat" or "measure the next
listening position." That’s not necessarily what you want to do. Many
people’s listening rooms contain seats that are in inappropriate locations for
measurements. If measurements taken at those positions are included with measurements
taken at more typical seating positions (such as in front of the TV), the results can be
unpredictable, and quite possibly bad. All Audyssey measurements should be taken toward
the center of the listening area, even if the room includes seats outside that area. Other
measurements that might be counterproductive would be those taken:
- too close to walls
- behind rear surround speakers
- behind front speakers
- less than about 3’ from any speaker (unless the speaker
is very small)
- too close to a high seat back
Audyssey recommends you begin measuring at the main
listening position. If you don’t, you may as well not bother taking any other
readings. This "best seat in the house" should be somewhere near the center of
the room, and very near the center of the speaker array. The next sets of measurements
should be taken about 2’ to the left and right of the main position. Next, measure
two or three locations 2’ or so (more if the room is large) in front of the
measurements you’ve just made. Finally, measure two or three positions behind the
first three measurement points, again 2’, and more space for larger rooms. But avoid
getting too close to walls: 2’ away from a wall is about as close as you should ever
get; whenever possible, 3’ or more is even better.
No matter what you may have read in the past, Audyssey now
recommends some semblance of this measurement pattern, whether you have one or 20 seats,
and regardless of how or where they’re positioned.
That said, there have been times when I’ve gotten an
odd result with the full complement of Audyssey measurements. In those cases, taking a
smaller number of measurements closer to the main listening position produced better
sound, both subjectively and via measurements. There are no guarantees that Audyssey
MultEQ will work perfectly for every system in every room. Experimentation may be
necessary.
What can I use to hold the measuring microphone?
It’s important to have the microphone at the same
height as your ears when you’re seated, of course, but readings can also be affected
by what the microphone sits on. Using a stack of books, for example, can cause sound
reflections that skew the readings; instead, you want something small. You can tape or
rubber-band the mike to the mount of a camera tripod. If you don’t have a tripod, you
can fashion a support from a cardboard tube from a roll of wrapping paper, a candlestick,
or even a lamp base without the shade. If you use a cardboard tube, punch a random pattern
of holes in the tube up and down its length, to break up any resonances that might form if
the tube is fully enclosed. And when taking measurements, don’t tilt the mike toward
the speakers -- every measurement mike I’ve ever seen has been designed to be aimed
straight up at the ceiling.
Any other things to keep in mind?
When you’ve finished taking your measurements and have
told the room-correction software to calculate the results, it may seem safe to unplug the
microphone and put it away. Don’t do it -- some products will abort the calculation
process altogether if the mike is disconnected. You’ll lose the measurements
you’ve just made and will have to start over. And if, later, you move furniture
and/or speakers and/or the listening seat(s), you’ll need to take a new set of mike
readings and run the calculations again.
. . . Doug Blackburn
db@hometheatersound.com |
