Holding the Center: The Misunderstood
Center-Channel Speaker
Based on the letters I receive, the most puzzling aspect of
building a home-theater system is the center-channel. That's not surprising -- after all,
stereo held center stage for about 50 years, so people are used to having left and
right channels. And, let's face it, rear-channel speakers are pretty much
self-explanatory. But that channel in the center is both new and alarming.
Here's a typical letter:
Wes,
I'm trying to decide which center speaker to buy. I have
a pair of largish MB Quart 490 speakers that I would say are very good. They're 4-ohm
speakers with a 130W max capacity. I'm buying a new Yamaha 5550 75W receiver to replace my
very old one and now, I've become convinced that a center speaker is the way to go. But
which one?
My living room is about 18' x 24'. Would I hear a
noticeable difference in sound quality blindfolded between the Polk CSi130 and the LSiC? A
significant difference or a slight difference? Also, how important is it that I match the
4-ohm impedance of the Quarts?
Just look at how many issues it raises -- no wonder some
people never take the plunge to a 5.1-channel system!
There's nothing all that tricky to understand about the
center-channel speaker, but there's a whole bunch of gray area between understanding
it and making the right choice.
Think of the front three channels of a surround system as a
team. For movie dialogue, the center is the most important speaker in the system -- that's
because almost all film dialogue is mixed to come out of it. This anchors the dialogue
solidly to the screen. There will be some spoken material coming from the left and right
speakers, but most will come from the center.
This means the center-channel speaker needs to do a lot of
work -- unlike the surround channels -- so it needs to be a substantial unit that can
output at least as much sound as the left and right front speakers.
But, in addition to reproducing dialogue, the
center-channel has to reproduce the musical and environmental sounds, which are also
reproduced by the front left and right speakers. Since that's everything from the sound of
the wind ruffling the grass to huge explosions, the center-channel needs to be every bit
as accurate and rugged as the front left and right speakers.
More importantly, it has to be a tonal match for
those other two front speakers or you'll hear sounds change tonal character as they move
around in space.
This is why many people, when buying a surround-sound
speaker system from scratch, purchase three identical loudspeakers for the front speakers.
However, this isn't always practical -- and besides, many people are happy with the left
and right speakers they already have. That's when you have to be careful about matching
the center to the other two front channels.
You'd think the simple answer would be to buy a center
speaker from the same manufacturer that produced the other two, but life just doesn't
always favor the simple solution, worse luck.
You may have space or budget constraints, or the
manufacturer that made your left and right speakers might not even make a
center-channel -- or not one that you feel really mates well with the two you already own.
That's when you have to go shopping for the perfect center speaker for your system.
The first thing to do is to consider how you'll use the
center-channel speaker. Where will it be placed? If the answer is above or below your
monitor, you'll want a speaker that's wider than it is tall. If you'll be stand-mounting
it below a projection screen or in front of a rear-projection TV, those choices will also
influence the speaker's size and shape.
Another consideration is room size, but presumably your
other front loudspeakers have also been chosen based on your listening space, so this is
less important than matching the other two speakers.
But definitely give some thought to how you will drive the
center speaker. The power output of your receiver or amplifier is the important number
here -- not the "wattage" of your right and left speakers. Normally, you'd
choose an amplifier's power based on a speaker's sensitivity, but when you're building a
surround system incorporating existing components, you don't have that luxury.
What you want to do is choose a center-channel speaker that
can be powered by the same amp that powers your front left and right speakers. You don't
have to match sensitivity ratings precisely, since most surround processors let you
adjust individual channel volume levels, but you need to at least determine that the power
you already have is adequate to power your new speaker.
These are just general rules, but that's okay. Basically,
if you have large, efficient, front left and right speakers, you'll probably do better
with a large, efficient, center speaker, too. If you've chosen small, power-hungry
stand-mounted mini-monitors for the left and right, you should strongly consider something
similar for the middle.
Ultimately, you'll have to audition a few -- and
that means hearing them with your front left and right speakers. Play a variety of
music and films -- and use the set-up menu to navigate the individual channels in checking
how closely the center matches its mates.
A test I find particularly revealing is listening to Noah
Adams on NPR's All Things Considered -- his deep, resonant voice is perfect for
determining whether or not a speaker adds extra "chestiness" to the sound.
Unfortunately, Adams has taken a leave of absence to write a book, so you won't be able to
use him again until March 2003. Any male spoken-word recording will do in a pinch,
however.
Obviously, there are no easy answers to choosing a
center-channel speaker. There are literally thousands to choose from -- and there are
probably almost as many really good ones as there are choices. The trick is discovering
which among them work with the front-channel speakers you already own. Get it right,
however, and you're in for a grand old time listening to multichannel music and home
theater as it was meant to be heard.
...Wes Phillips
wes@onhometheater.com
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