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Lost in the Middle

The center channel loudspeaker is the most important one in any surround system. Failure to use it properly is holding back the development of surround sound as a music medium. It?s not the only thing inhibiting music in surround?record-company apathy and stereo?s dominance in downloads are bigger problems. But it worries me that a listener getting his first taste of music in a 5.1-channel format might not hear it at its best.

Why is the center so crucial? Doesn?t that seem counterintuitive? After all, stereo systems get along without any center channel at all. However, movie mixes depend heavily on the center channel to deliver both dialogue and the leading edge of those action-movie surround effects that make our hearts beat faster. That?s why many speaker makers design the center with a higher efficiency rating?they know it needs to play loud.

In music, as well as movies, the center channel serves a second function?to fill that hole in the middle that undercuts the soundstage in stereo (or in quad for that matter). True, high-end two-channel gear set up in a good room by someone who knows what he?s doing can produce swooningly realistic imaging. But how often does that happen in the real world?

All other things being equal, it?s better to have a center-channel speaker than not to have one. Besides lending greater clarity to dialogue and lead singers, it also produces a seamless front soundstage that anchors the soundfield. That becomes a major advantage in any kind of music playback, whether you?re listening to a 5.1-channel DVD-Audio or SACD release, or playing your CDs in the 5.1-channel Dolby Pro Logic II music mode.

DPLII is a relatively new surround format that I can?t praise highly enough. Not only does it derive center, surround, and subwoofer channels from two-channel sources like CDs and LPs?it actually does the job well. In better surround gear offering the full array of DPLII adjustments, you can alter the balance between the center and sides, either concentrating sound in the center or redistributing it toward the left and right. You can also adjust the front-to-back balance. All this can be done without messing with the overall channel levels in the speaker setup menu.

If I listened to nothing but DPLII-enhanced CDs I?d be well content. It?s the high-res DVD-Audio and SACD releases in my listening diet that worry me. Too many multi-channel music mixes either underuse the center channel or don?t use it at all.

When I?m listening to older surround material, I don?t get too worked up about this. My collection includes a lot of orchestral music recorded in quad during the 1970s and ?80s, everything from DVD-Video titles with Dolby Digital soundtracks to SACD releases. Dolby Digital and SACD are 5.1-channel media, but since the source recordings have only four channels, that?s what comes out of my speakers. Fair enough. I?ll listen in quad if that?s the only way I?ll ever get to see and hear Herbert von Karajan conduct the Berlin Philharmonic in surround?he didn?t survive long enough to record in 5.1. (And I can always finagle my receiver?s bass management settings to route bass to the subwoofer, turning four channels into 4.1.)

What annoys me are the new SACD and DVD-Audio recordings that underuse the center channel. One example is Mongo Santamaria?s Live from Jazz Alley, an SACD release on the Concord label. It?s great music and well-recorded in every way but one: the congas, which are really the lead instrument here, only come out of the front left and right channels, leaving the center virtually unused. As a result, the congas waver from left to right as you move your head from side to side, and the old hole in the middle is baaaack. What could have been a seamlessly tight soundfield collapses as soon as you move out of the sweet spot?and the spell is broken.

On the other hand, mixing surround properly can pay big dividends. If you?re looking for a perfect music-in-surround mix, look no further than another Concord SACD, Gary Burton?s Like Minds. Burton?s vibes come out of every channel, placing him just where the bandleader belongs?smack in the center of an arc formed by his band?with the rhythm section just behind him and the guitarist and pianist on either side of him. This logical shaping of the soundfield serves to make fine music even better.

Why would anyone mixing music in surround avoid using the center? Surely a collapsed soundfield is not a desirable artistic goal. The culprit is not the center channel itself but the center-channel speaker. In many home systems it?s often mismatched and just as often poorly placed.

In the best of all possible worlds the center speaker would always be an identical clone of the left and right. In the real world, manufacturers are hawking horizontal center designs in a popular but usually nonmatching woofer-tweeter-woofer configuration?and the consumers who unwittingly buy these things compound the error by setting them up badly. The cumulative result is a center speaker that?s way out of whack with the others.

There?s a second underlying culprit here, and that?s the hulking video display, which makes correct placement harder. If you?re using a rear-projection or direct-view set, the logical place for the center speaker is atop the set, which puts the center tweeter higher than the left and right tweeters, and may even be too high for a direct hit on the listening position. Few consumers bother raising the left and right speakers to the same level?and if they did, all the front speakers might be too high.

Front-projection systems are better in this respect. It?s easy to keep all speakers at the same level when you?re putting them below the screen. Better yet, you might even use an acoustically transparent perforated screen and have the center speaker directly behind the center of the image.

As a practical matter, what can you do? If you?re in the market for surround speakers, don?t buy anything with a nonmatching center. The center speaker should be identical to the left and right (except maybe for video shielding). Avoid those horizontal woofer-tweeter-woofer designs?they?re prone to acoustic problems that result from one woofer?s output canceling the other. Don?t buy any speaker package that condemns you to living with a horizontal center speaker.

Then there?s placement. Regardless of what kind of center speaker you use, proper placement always helps. If the speaker must sit on the TV, angle it downward so that its output hits the listening position, as opposed to the wall over your head. If you?re setting up a flat panel display, put all the front speakers below the screen at the same level.

A lot of the people who engineer surround recordings simply think that you?re an idiot and always will be. They assume you haven?t got the sense to buy a matching center speaker?or the gumption to set it up correctly?and believe they are protecting the artist by acting defensively.

There are two flaws in their reasoning: One, someday you might wise up, if you haven?t already. Two, once your system is working right, your music library would still be compromised by expensive but badly mixed software that prevents you from getting the best out of your equipment.

By optimizing multi-channel mixes for systems that are set up wrong, mixing engineers are punishing consumers who do things right and favoring those who do things wrong. All those manufacturers selling horizontal center speakers?even though they and their engineers know better?are just as bad. It?s a cynical, pessimistic way of doing business.

Me, I?m an optimist. As surround continues to penetrate more households, I firmly believe that the number of people doing things right will increase, as consumers gain experience in the surround medium, learn how to use it better, and take their first steps on the upgrade path.

OK, I?m sure I?ve annoyed those of you who are stuck with horizontal center speakers. Feel free to retaliate in your postings. I?m a grownup, I can take it, and if I?ve coaxed a few of you to improve your systems?or to avoid making a terrible mistake in the future?then I?ll have earned my paycheck today.

Spare the center?spoil the surround. Multi-channel audio, done right, is one of the greatest pleasures on earth. Don?t settle for a collapsed soundfield. It just doesn?t have to be that way.


Mark Fleischmann is the author of Practical Home Theater (http://www.quietriverpress.com/).

The views expressed here are solely those of the author and do not reflect the beliefs of Digital Trends.

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