| Video Noise March 2005
Getting Stereo and Surround
Sound to Coexist
It is amazingly expensive to assemble a
surround-sound system that has all the performance and sound quality of a good high-end
two-channel system. In fact, it might be impossible. In all but a few fortunate
situations, the big floorstanding speakers you might use in a high-end system won’t
be practical to use as center-channel or surround speakers. If the great stereo speakers
you have cost $3500/pair and you hook them up with $800 speaker cables, duplicating that
setup for three more channels will cost you another $6450. Already you’re over
$10,000 and you haven’t spent a dime on the rest of the system.
Because of practical limitations of cost and physical size,
most people use less expensive speakers for the center-channel and surround duties. The
center and surround speakers may be really good, but they’re not usually as capable
as those big stereo beauties, which were honed to perfection by years of fanatical design.
What you end up with is a system that can reveal more of the nuances of recordings when
playing music in two-channel stereo than it can in surround sound.
Nonetheless, you may find yourself wanting to enjoy both
stereo and surround sound with a single system. The problem is how to best accomplish that
without compromising the stereo sound.
If you were a high-end audio aficionado before you were a
home-theater enthusiast, you probably know about stereo preamplifiers. You’ll need
one of these to make stereo really sing in your surround system. As much as I’d like
to say that there are surround processors that are as good in stereo mode as some of the
better stereo preamps, in my experience it hasn’t happened yet at a price that would
be considered reasonable.
A really primo stereo preamp can solve one of the stickiest
problems about combining stereo and surround sound in a single system: each of your power
amplifiers has just one set of inputs. If you connect the output of the surround processor
to a power amp, you’d have to unplug the surround processor and plug in your stereo
preamp to listen to stereo music. Not only is that inconvenient, you’ll eventually
wear the gold plating off the connectors. A better solution is to connect the surround
processor’s left and right front outputs to the stereo preamp’s Video inputs. If
there are no Video inputs, Aux or CD should also work fine. This means the preamp must be
set to Video for movies or surround music, but now you’ve got a whole new set of
connections available on the preamp for high-quality stereo sources such as a turntable or
CD player, without using the surround processor.
Having the preamp inserted in the main front channels can
cause surround-sound balance problems, because the preamp’s volume control will
affect only the front two channels. When you’re playing movies, only one
setting of the preamp’s volume control will be at the correct level to match the
levels in all the other channels. The obvious exception to this would be a preamp with a
home-theater bypass function. Let’s assume that’s not what you have.
Setting your preamp for HT operation
You’ll need your SPL meter to set the preamp volume
level for movies. The first step is to activate your surround processor’s pink-noise
generator -- the one that’s used to set speaker levels. When adjusting the front left
and front right levels, use the volume and balance controls on the preamplifier --
don’t make adjustments to those settings in the surround processor. Once you have the
correct level selected for the front left and right channels using the preamp volume and
balance controls, you need to be able to reproduce that level easily every time you play a
movie or listen to surround music. If your preamp has detent steps or a numeric display,
you’re all set. Just remember the detent number, or the number from the display on
the preamp, and set the stereo preamp to that number each time you watch movies or listen
to surround music. If your preamp has no such references, make yourself some sort of
pointer. You can cut masking tape in the shape of a small pointer and stick that to the
preamp’s faceplate. You could also use some of the widely available chewing-gum-like
adhesive to stick the point of a toothpick to the preamp’s front panel. The pointer
then becomes your reference for where you set the stereo preamp for movies or surround
music.
When you listen to stereo music, switch the stereo preamp
to the input you’re using for your high-quality stereo source. You can then adjust
the stereo preamp’s volume control at will to set the stereo music at the correct
level for your listening pleasure. You’ll have a signal path from the stereo source
to the stereo preamp, and from the stereo preamp to the amplifier for the main speakers.
Lastly . . .
Worried about that big video monitor between the speakers?
Don’t be. You can achieve remarkable soundstage width and depth despite a large box
in the middle. Just make sure the main speakers are either forward of the monitor or no
more than a couple of inches behind it. That will minimize reflections. If you still find
that the sound reflecting off the monitor is degrading the imaging and/or soundstaging, a
lightweight blanket tossed over the monitor can be a big help -- anything too heavy will
deaden the room too much.
...Doug Blackburn
db@hometheatersound.com |
