What Makes a Good Center Speaker

The center-channel speaker doesn’t often get the respect it deserves. To keep it slim enough to fit on a shelf, many manufacturers simply offer two-way center designs, laid out in a horizontal woofer-tweeter-woofer arrangement. Every experienced speaker engineer knows that this is the worst way to design any speaker, but cost cutters, marketing departments, and consumers who don’t know better (or don’t care) demand them.

What’s wrong with horizontally arrayed drivers? When a woofer, for example, crosses over to a tweeter, the two drivers overlap over a limited range of frequencies, since loudspeaker crossover filters don’t generally have near-infinite slopes (though there have been a few attempts at this, with the most widely known and successful coming from Joseph Audio designs using a crossover technique patented by Richard Modaferri). If you’re seated at the same distance from the two overlapping, horizontally positioned drivers there’s usually no problem. But if you move off-center in the same plane as the drivers, the arrival times from them will be different. This will produce cancellations, known as comb filtering, at or near the crossover frequency.

In most multi-way speakers the drivers are aligned top to bottom, so these cancellations occur in the vertical. With proper seating height, this will usually not produce noticeable problems, apart from some sensitivity to your seated ear height (which is usually optimum, though not always, on or near the tweeter axis). But if the drivers are arrayed horizontally, and you move off-center, there will be audible cancellations. And these cancellations will occur not only between the woofers and the tweeter, but between the two woofers as well. The frequency and severity in the latter will depend on the woofers’ spacing. The result in either case can be suck outs of several decibels. With the woofers-to-tweeter crossover frequency typically around 2kHz, this can play havoc with dialogue intelligibility.

Have there been two-way centers that minimize this issue? Yes, but the odds are against it.The most successful center-channel speakers are three-way designs. They will still have two woofers at the left and right, but between them there’s a midrange and tweeter, positioned one above the other. At an appropriate ear height there will then be no audible comb filtering between these upper range drivers. There may still be some cancellations between the two woofers, or between the woofers and the midrange, depending on the driver spacing and the crossover frequency to the midrange (in the latter case, the lower the better). But such center speakers tend to be taller than in two-way designs to make room for the vertically stacked midrange and tweeter.

I can’t emphasize enough that the center channel is not just the “dialogue” channel—a persistent misconception. The center is, according to some experts, the most important speaker in a surround setup. It carries not only the dialogue but often a heavy dose of music and effects as well. If it can’t handle that, the system as a whole will be compromised, whether the center is a two- or three-way design.

While we’ve tested some three-way center speakers that don’t measure as well as the theory suggests, if well designed they stand a good chance of being better than your average two-way. The best center speaker, of course, is one that’s identical to the main left and right pair. But unless you plan on a projection system with a perforated screen (which has issues of its own relating to picture quality), or like to crane your neck to look up at a non-perf screen, this isn’t practical for most audio-video setups.

But most home theaters are built around a large flat screen display rather than a projection system. In that case, one practical solution to the center channel dilemma is to allow enough height in the shelf under the TV to accommodate a taller than normal three-way center speaker—something to keep in mind when choosing that audio/video hutch. (Placing a speaker in an enclosed shelf can create other audio issues, but that’s a different subject!)

The only challenge will then be in finding a three-way center that matches the left and right speakers reasonably well. And, of course, that fits your budget. Currently a number of manufacturers do offer such models, including Infinity (the Reference Series, shown in the photo here though not yet available as I write), Revel (Concertas), Aperion, SVS, KEF (a special case with its concentric Uni-Q driver handling the midrange/tweeter chores), the just-announced Pioneer Elite SP-EC73 (also with a concentric mid-tweet) and Paradigm. While none of these are cheap, they won’t demand your firstborn as a down payment.

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COMMENTS
rhirschey's picture

I owned a complete 7-speaker Revel Concerta system for years and the center channel (C12) was amazing, for the reasons you describe in this article. It had great off-axis clarity and blended so well with the floor-standing left and right channels when properly placed. I recently went in-wall and went with Klipsch's top-of-the-line THX in-walls, all matching across the front, all at almost the exact same height. The seamlessness of this setup is amazing, whether it be music or movies...but totally admit there are some things I miss about that great Revel system and that wonderful center channel.

mikem's picture

While I would agree with Mr. Norton wholeheartedly what he did not mention was that movie sound is up to the director and sound engineer - and we are at their mercy. Center channel dialog and sound can range from abysmal to profound. I don't know how many times I've had to amp up my center channel in order to hear precise dialog. And no, my hearing is just fine. If we attribute poor dialog to the center channel why then when I switch to a tv source does the center channel sound just fine. Likewise, when playing well recorded music the center channel sound is just fine. My 7 channel Atlantic Tech system with 2 12" subs, though a bit long in the tooth as it were, can assuredly replicate source material. But, garbage in garbage out. So, what good is a music score mixed for the center channel in which the sound designer primarily emphasizes sound effects rather than dialog?

CinemaDude's picture

Not for nuthin as we say here in Brooklyn, but the problem with movie dialogue being abysmal in many cases isn't exactly the problem with the mix that the studio engineers designed, it most often is the fact that the home theatre system does abysmally with what passes for a center channel speaker system in the first place.

Cinema sound is mixed with the assumption that the center channel will be identical in design, acoustic power output and specifications as the left and right channel. The three are always EXACTLY the same systems. Not only that, it's also assumed that the center channel will be placed in, you guessed it, the CENTER of the screen. Not above it; not below it, and not some wimpy version of the left and right channels.

Get yourself a video projector and an acoustically transparant screen and then get a center channel that is identical to the left and right speakers systems in response and acoustic power profile and place it BEHIND and in the CENTER of that screen and 9 times out of 10, dialogue which is most often handled by the center channel will sound just fine.

Thinking you can get away with some half-fast center channel and expect dialog to be as rich and full and robust as in the cinema is vodo acoustics.

ahuesjp's picture

Hello Thomas,

I have been actively considering upgrading all my speakers. A lot of what I value is related to music reproduction, but home theater performance is also important. The system will perform double duty as most everyone I know.

I am fairly convinced that I'll go with the Golden Ear Triton Two or Triton One towers as mains, and before this article I was planning to stick to their line for the rest of the speakers.

What Center Speaker would you recommend with the Golden Ear Tritons? My concern is matching the voicing of the High Velocity Ribbon Tweeter the Tritons use. I understand the Golden Ear SuperCenter to be a 2 way design + radiators for low frequency extension, and hence could have the problems described here.

Any thoughts?

Thanks,

Juan Pablo

savage's picture

Don't forget the ADAM Audio GTC 77. Amazing speakers particularly for the price:

Adam Audio GTC77 Speaker System
By Michael Fremer • Posted: Dec 27, 2011

Thomas J. Norton's picture
Based on our review (which I did not do) and a personal but brief audition at the 2014 CES, the new GoldenEar Triton One appears to be a terrific speaker. But we have no ears-on experience with the GoldenEar SuperCenters. Their configuration appears to suggest at least some off the off-axis issues mentioned in the blog, but we certainly can't say for certain.

I'd recommend first borrowing the SuperCenter of your choice from your dealer (or buying it on-line with full return privileges) to try out at home. But to make a possible return easier, don't buy the rest of the system just yet. You might also run the following tests at your dealer if the speakers are set up there, if he or she is patient and cooperative, and if the setup allows you to move off-center as far as you might at home.

Set up the center where you plan to use it, disconnect any other speakers (except possibly a properly balanced subwoofer) and feed it the center channel track from a movie with well recorded dialogue. At your normal listening distance and with your ears at seated ear height, move off-center to the left and right as far as you might expect any frequent listener to sit. If the dialogue becomes more difficult to hear, garbled, nasal-sounding, or boxy as you move around, that could be a deal breaker. Do the same using a scene with a heavy dose of sound effects in the center channel; make sure they don't sound recessed or lose too much punch and dynamics as you move from the center to an off-center seat.

If it passes those tests satisfactorily, play one channel of stereo music through the SuperCenter and note how it sounds using the same left-to-right listening seat approach. As noted in the blog, often the center channel carries some of the music score and you want the music to sound good at various listening seats as well. Keep in mind that in this test you're not hearing the other channel, so familiar stereo recordings might sound a bit odd for that reason. You could try combining the recording to mono if your AVR allows it, but that can sometimes produce strange results.

You can also run the test by instead feeding pink noise into the SuperCenter. No center speaker will pass any of these tests flawlessly, and pink noise is the most difficult, but the less the tonal balance changes as you move off-center the better, particularly in the midrange where dialogue intelligibility is most important.

biaubill's picture

Would anyone know if the M&K S300 speakers, with their horizontal driver orientation with the mid-bass and tweeters would cause a comb filtering issue? Thank you.

coolbrit82's picture

Would you say best center speaker would be the matching brand? I am looking for the center speaker for my triton three. Would it be bad if I use different brand? Sorry if I sound like an idiot.

Bob Ankosko's picture
Going with a center-channel speaker from the same speaker line/company is always the best way to proceed because its voicing will be matched to the front left and right speakers. In your case, GoldenEar recommends the SuperCenter X or SuperCenter XL center speaker.

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