Speaker Types

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Surround sound didn't happen overnight. It grew out of stereo and evolved into today's state-of-the-art discrete digital multi-channel formats. Before building your dream system, you'll need to know the differences.

Dolby Pro-Logic
Squeezing all those extra channels onto a piece of film or recording tape isn't easy. In fact, before the advent of digital sound, it was impossible. To accommodate surround information, Dolby Laboratories developed Pro-Logic, which "piggybacked" the center and rear channels onto the analog stereo tracks. The Dolby Pro Logic surround system is found on nearly all movies made in the past twenty years, but it suffers two major limitations. First, the rear channel is monaural: whether you use one, two or twenty speakers at the back of your theater, they all receive exactly the same signal. What's more, that signal has extremely limited frequency range, with no high treble or deep bass. Second, there is little separation between any two adjacent channels, which significantly compromises the "surround" effect. For watching videotapes (which cannot accommodate digital multi-channel formats), Pro-Logic is all you need. If, however, you'd like to hear your DVDs, Laserdiscs or Mini-Dish satellite broadcasts at their very best, you'll also want digital surround sound capability that is described in the next section.

Dolby Digital
The most popular of the digital surround formats, Dolby Digital® (a.k.a. AC-3) features five full-frequency-range channels-left, center and right front, plus left and right rear-and a sixth channel for Low Frequency Effects (bass). Digital surround sound is often referred to as "5.1"; 5 main channels plus the Low Frequency Effects (LFE) channel. The advantages of digital 5.1 surround are more exciting surround effects and imaging with life-like impact and dynamic range. The difference in sound quality between Dolby Digital surround and Pro Logic surround is similar to the difference between CD and LP records.

Loudspeakers have the toughest job in the home entertainment system. While source, processing and amplifier components like players, receivers and amps simply have electrical signals with which to contend, speakers are transducers-devices which convert electrical energy (the audio signal supplied by the amp) into mechanical energy (the music and sounds we hear). A good speaker will accurately do this job; reproducing sounds precisely as they were recorded, and efficiently; squeezing the most volume from the least power. What's more, there's no single way to build a fine loudspeaker. Unlike amps, pre-amps and processors, which all employ the same basic circuits but differ in terms of features and construction quality, the diversity of speaker designs is nearly as limit-less as the speaker designer's imagination.

All loudspeakers make sound by moving air. Your amplifier powers the speaker's drivers-woofers for bass, tweeters for treble, and midrange for everything in between-which vibrate at frequencies and volumes to match the original recording. Since they all work the same, why don't all speakers look the same? Because everyone's needs are different. Do you want to make your home theater the focal point of your living room, or do you believe that speakers should be heard and not seen? Are thunderous bass and life-like volumes important, or is softer better? No matter: there's a perfect speaker for your room, budget and listening taste, once you know how to find it.

In addition to playing music, the left and right "main" channels of a soundtrack carry most of a motion picture's special effects and orchestral score. In order to excel at these tasks, the stereo pair must encompass wide frequency and broad volume swings (dynamic range), reproduce subtle recorded details, and be able to create a convincing "sound-stage" (the impression of three dimensions). When choosing main channel loudspeakers, play a handful of music and movie selections you know well. Listen to a solo vocalist. Does the "image" of that performer seem to float at the center of the soundstage (good), or can you trace the singer to the speakers (bad)? Next, try an acoustic guitar, violin or cello. You should hear natural, detailed string tone, as well as the resonance of the instrument's wooden body. Finish with an action flick. Are the effects-gunshots, explosions, etc-clearly reproduced, or do they become hard, flat and generally unpleasant as the volume increases? A good pair of loudspeakers should never sound "fatiguing."

Although listening is the ultimate test of a loudspeaker, there are other clues to quality. Rap your knuckles on the sides of the cabinet: a hollow thud indicates a poorly made enclosure that will probably degrade the sound. The weight of a speaker will give you a clue as to the materials and construction quality. The best speakers offer 5-way binding posts that offer the best possible connection with any type of cable.

Loudspeaker Types
Floor-standing Speakers
Floor-standing or "tower" loudspeakers are audio's equivalent of a big-block V-8 engine. Thanks to their large enclosures and increased size or number of drivers, floor-standers move enormous quantities of air, enabling them to have greater dynamic range (to play louder and cleaner) and produce deeper bass than other designs.

Polk RTi12

Advantages - Extremely wide frequency response and dynamic range make floor-standers the choice where performance is the primary purchasing criteria. And while they tend to be large, many current models feature slender cabinets with small footprints, minimizing placement difficulties and visual impact. Also, since most of the world's best loudspeakers are towers, their manufacturers often lavish better parts or build quality on these "flagship" products.

Disadvantages - When space is at a premium, such as in a small apartment or smartly decorated room, towers simply might not fit. What's more, the prodigious output capabilities of such speakers means that placement can be more critical-floor-standers should be located 2-3 feet from nearby walls for best performance. Finally, beware of "bargains": large cabinets are expensive to build. Unusually low pricing is often the result of construction shortcuts. Browse Polk Floor-standing Speakers

Powered Towers-Floor-standing with Built-in Subwoofers
A new and increasingly popular approach to loudspeaker design, "powered towers" are floor-standing speakers with the powered subwoofers built right in. Expect this product category to boom in the future (we could not resist the pun).

Polk LSi25

Advantages - Powered towers offer the ultimate in dynamic range and frequency response. For 5.1 channel digital systems, the chore of selecting and placing the sub-woofer disappears. Also, since the sub-woofer and main speaker drivers are designed together, they can be optimized with each other for better performance and better "blending." There is no sense of dis-continuity between midrange and bass as there often is with separate main/sub-woofer speaker systems. While not cheap, powered towers are often less expensive than purchasing separate speakers and subwoofers of comparable quality.

Disadvantages - Assuming your room can accommodate a pair of floor-standing models, there are few. Just make sure you have AC outlets near each speaker position. In very large rooms or those that have bass "suck-out" problems (see section on room acoustics and speaker placement, page 23), powered towers may need to be augmented with a separate subwoofer.
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Bookshelf Speakers
With their compact cabinets, bookshelf speakers work where towers won't. Actually, the name "bookshelf" is unfortunate, since most such designs perform best when placed upon rigid stands, rather than tucked inside pieces of furniture. These speakers are not only more placement-friendly but, since small enclosures are more rigid, they produce less sonically degrading "box resonance" than all but the best towers.

Polk RTi6

Advantages - Usually modest in price as well as size, bookshelf speakers fit rooms and budgets that cannot accommodate a pair of towers. The small, solid cabinets are both versatile-able to excel in bookcases, atop shelves or hung on walls-and feature excellent midrange clarity. Caution: Many speakers use air tunnels or "ports" to improve efficiency and bass output. If you plan to place your speakers against a wall or inside a cabinet, choose a model whose port is located on the front panel, with the drivers. The exceptions to this caution are the Polk RT Series bookshelf models that feature a rear mounted Power Port. The Power Port's unique design permits proper operation under these conditions. (Couldn't resist the plug here!)

Disadvantages - Reduced cabinet volume and driver surface area limit the dynamic and bass frequency range of bookshelf speakers, and can also compromise power handling and efficiency. Fortunately, the addition of a subwoofer can overcome these problems.
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Subwoofer/Satellite Systems
When even the smallest bookshelf speakers are too visible to fit your lifestyle, a sub-woofer/satellite (sub/sat) system is the answer. By combining palm-sized satellites with a subwoofer designed specifically to work with them, sub/sat systems have become one of the most popular categories in home audio.

Polk RM6700

Advantages - The big advantages here are size, placement flexibility and cosmetics. The satellites can be placed just about anywhere, on a shelf, on the wall, in a cabinet or on a table. Most are small enough to fit in the palm of your hand and are hard to spot when placed alongside books and bric-a-brac. Some of this genre are very handsomely styled so that even when they are seen, they complement rather than detract from the look of the room. The subwoofer section can be placed out of sight - in a corner, behind furniture or under a table. Sub/sats also have certain performance advantages over more traditional designs. The slender front baffles cannot interfere with the drivers' dispersion, so imaging is absolutely first rate. The best of the genre produce a wide, deep soundstage that is in some ways superior to larger speakers. The subwoofer cabinet can be placed where bass performance is best (near wall or corner), so bass response is often awe-some. Most folks are agog when they hear such loud bass apparently coming from two tiny speakers.

Disadvantages - Those little satellites cannot reproduce bass of their own, making it tough to achieve a seamless blend between satellite and sub. There is often a "hole" or weak response in the lower midrange area (bottom range of a male voice) where the satellite's response leaves off and the subwoofer takes over. When evaluating sub/sat systems listen closely to male voices, if they sound "thin" the system suffers from this midrange suck-out problem. These systems' small drivers and enclosures compromise dynamic range and power handling. If you have a very large room to fill with sound, a sub/sat system may not be right for you. The other issue is bass response. Some of the so-called "subwoofers" in these systems are passive (not amplified) and should really be called "woofers" because they don't reproduce the truly deep bass with authority. If the system is to be used for only music, that may not be a problem. But if the primary use is home theater, you may later find the need for an additional powered subwoofer. Many sub/sat systems now come with powered woofers that are worthy of the name sub-woofer. As always, listen before you buy and trust your ears.
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In-Wall Speakers
For environments where box-type (tower or bookshelf) loudspeakers are unacceptable, in-wall speakers flush-mount in holes cut into the sheet-rock of your walls. Most models feature paintable grilles so you can disguise them, enabling them to virtually disappear.

Polk LC265i

Advantages - Since they consume no floor or bookshelf space and can be easily concealed, in-walls work when and where other speakers will not. If you plan to expand your system throughout your home, in-walls are a wonderful way to bring sound to additional rooms. They are also useful as rear surround speakers when the room configuration makes it impossible to properly place box speakers.

Disadvantages - In-walls cannot deliver the dynamic range and bass response of an equivalently priced box-type loudspeaker, and are less capable of great stereo imaging. Performance is inconsistent due to differences in-wall construction quality. Unless you are a do-it-yourselfer, professional installation will add to the cost of the system.
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