The center channel speaker and its unique horizontal cabinet is an eye-catching centerpiece of most any home theater system. Designed to fit in space restricted areas above or below a television or projector screen, it’s estimated that modern surround sound presentations ask center channels to handle nearly 70-percent of a 
film’s key audio presentation (including dialog, music, and sound effects). In addition, a center channel acts as a bridge between the left and right channels, making sure sound pans and motion appear seamless across the front soundstage. Today, we’ll take a closer look at center channel speakers, evaluate design benefits and limitations, review how center channels should be properly integrated into a multi-channel system, and suggest several alternatives that home theater owners should consider.
Functionality by Design
The most obvious differentiating factor between a center channel and typical floorstanding and bookshelf speakers is its size and horizontal cabinet design. At first look, one might assume its unique physical characteristics and overall width allow for superior dispersion of dialog and sound across a large seating area.
That would be a misnomer, however, as its cabinet and chosen driver array are purely intended to allow for placement where traditional speakers simply won’t fit (for example, on a table top with little space between the table’s surface and the bottom of a screen). Placement flexibility is the name of the game and most manufacturers do their best to minimize cabinet height and depth to make placement as easy and convenient as possible.
The challenge all center channels face is accurate and even reproduction of sonic material across a wide listening space. Unfortunately, the very nature of aligning similar drivers on a horizontal plane can cause off-axis listeners to hear something entirely different than a listener sitting in the middle listening position. Some frequencies become inaudible while others become enhanced, and imaging can appear to shift away from the center of the room. The resulting audio can sound distractingly shallow and unbalanced, giving listeners in the same room a completely different experience depending on their seating position.
Almost a decade ago, I ran a rather poorly designed center channel in my dedicated theater room. The audio experience was perfectly fine when sitting in the middle of the listening space, but any movement off-axis led to noticeable audio deficits, particularly when sitting on the right side of the room. While sound pans and motion across the front sound stage were semi-passable (despite sounding warped and bubbled toward the seating area), off-axis viewers were delivered dialog that sounded nasally, shallow, and completely detached from the middle of the screen. It was almost as if the speaker was damaged, leading me down a path of endless hours of useless trouble shooting; frustration was certainly abound!
Proper Center Channel Design Can Improve Performance
Speaker manufacturers have attacked the problems described above by implementing various designs that stray from the standard M-T-M horizontal driver array that features two identical midrange drivers flanking a single tweeter. That particular design is best avoided if possible, however some manufacturers have found better performance success with MTM designs that pull the midrange drivers closer to the middle of the cabinet (so make sure you research MTM center speakers carefully).
The most popular alternative is a three-way design that adds a midrange driver underneath a single center mounted tweeter.
Take a look at Aperion Audio’s Verus II Grand Center Channel and you’ll see a great example of this W-T/M-W (woofer-tweeter/midrange-woofer) design. This particular layout sounds better across a wide seating area because the addition of a single midrange driver allows the dual woofers to operate in a lower frequency range that’s less influenced by horizontal alignment issues.
Getting The Most From Your Center Channel
There are a few easy steps enthusiasts can take to get the most from their center channel. A lways use the same brand and series of speakers across the front soundstage of a room. No compromises. In doing so, you’ll ensure those speakers share the same tweeters and crossover components for perfectly matched voicing and seamless blending. You should also strive to align all tweeters, height-wise, across the front soundstage. If perfect alignment is impossible, make sure your left and right channels are aligned and then do what you can to get the center channel tweeter height as close as possible. Placement is also a factor. Generally speaking, try to avoid housing your center channel inside a cabinet cubby, jamming it up against a wall, or placing it directly on a hard surface (such as a cabinet top or counter top). Try to give the speaker some breathing room from boundaries and surfaces in immediate proximity. Finally, run your AV receiver’s room calibration software. While not the ultimate answer to creating perfect sound, room calibration software can improve overall sound quality quite noticeably.
For true perfection, use three identical speakers across your front soundstage. This means dumping a horizontal center channel in favor of a matching tower or book shelf speaker. Here’s where the real world might bare its teeth, because that kind of speaker arrangement requires significant amounts of free space under your television or projector screen (or the use of an acoustically transparent projector screen). If you have the space, go for it, because vertically arranged drivers offer better overall performance, not to mention a full-range tower speaker can typically play deeper into low frequencies as compared to a horizontal center channel. If you have some spare space in the middle of your front soundstage (but not enough for a full-range speaker), get creative and turn your center channel on its side. This will allow the speaker to reap the benefits of vertical driver alignment and deliver better results across a seating area.
Not a believer? Perform some center channel listening tests with your own speaker by alternating between horizontal and vertical orientations. You’ll undoubtedly hear a more even and uniform response while sitting in off-axis seating. Several years ago, I rebuilt my theater room and made design decisions that allow for the use of three matching tower speakers across the front soundstage. The results have been absolutely remarkable.
The Phantom Center
One last option to consider is ditching a physical center channel and allowing the front left and right channels to handle full front soundstage duty. In this scenario the two front speakers work together to create a “phantom center.”
There are lots of reasons to run a phantom center. For one, it completely eliminates the need for a speaker in the middle of the soundstage, making it a perfect option for rooms that lack the space for three speakers up front. It also allows a system to benefit from the low frequency playback capabilities of the left and right channels. Finally, there’s the financial aspect, as it completely eliminates the need to spend money on an additional speaker, allowing more funds to be allocated to better stereo speakers or upgraded equipment and components.
Setting up a phantom center is rather easy. Simply enter your receiver’s menu system, find the center channel setting, and turn it to “off.” Some receivers may offer a phantom mode, but most will only allow you to add or subtract the center channel. This step is important because it tells your receiver to route all center channel information to the left and right channel speakers. Next, you’ll need to properly align and space your left and right speakers. Typically, speakers perform better in this configuration when spaced further apart and toed-in toward the central seat in the room.
Phantom center channel arrangements do have one significant Achilles’ heel: off-axis listening. As a general rule of thumb, a phantom center should only be used in cases where the majority of listeners sit in the middle of the room. Imaging and the centrality of dialog shifts as listeners move away from the center listening position, which completely defeats the purpose of the configuration from a sound quality perspective.
The Wrap
The center channel is often referred to as the most important speaker in a surround sound system. Considering the amount of work its asked to do, that kind of a statement is hard to argue. While its best to deploy three matching speakers across the front soundstage, that kind of configuration requires loads of space and design sacrifices. If a phantom center won’t work for your particular seating spread, then incorporate a horizontal center channel design. Be sure to invest in a quality, well-designed, center channel that sonically matches your left and right channels. Then follow the rest of the integration tips detailed above. Follow those steps and you’ll be well on your way to a better home theater experience.