Speaker Types

Tower (floorstanding)
Basically, a tall speaker designed to rest on the floor. Because they have relatively large enclosures, tower speakers can typically play louder without distortion than other types and produce deeper bass without sacrificing sensitivity to achieve it.

Power Tower
For even beefier bass, consider a power tower, which usually looks like a regular floorstanding speaker and connects to your receiver or amplifier in the same way. The twist is that these speakers have built-in amplifiers to drive their woofers. Hookup is very simple because the woofer amp simply taps into the signal feeding the rest of the speaker, while the main amp or receiver now has an easier job, as it needs to drive only the upper-range driver or drivers. Some power towers even allow you to connect a line-level signal from a receiver or surround processor’s subwoofer output to their bass sections, which means that the receiver or processor handles the low-frequency crossover.

Bookshelf
Just about any speaker designed primarily for placement on a shelf or stand may be included in this category. They typically have less deep-bass output capability than tower speakers.

Subwoofer
A subwoofer is a special-purpose speaker whose sole function is to reproduce bass, usually below 100 Hz or so. It operates below the range of the woofers in the system, hence the name. The role of subwoofers has changed significantly in the last few years, and in many systems we are asking this anonymous-looking box to handle more of the sonic load than ever before. There was a time when you could assume that almost any good speakers could be used by themselves — adding a subwoofer was simply a way to give more deep-bass punch and kick to what was already essentially a full-range system.

The arrival of the satellite/subwoofer system changed that, however, and now many small satellite speakers skip the bottom two or three octaves completely, making them essentially unusable without a sub. In such cases, the “subwoofer” is more accurately characterized as a common woofer for the system — or simply a “bass module.” A small bass module used in this role might go down to only 40 or 50 Hz, whereas a true subwoofer, designed to plumb the depths, will get down to 20 or 30 Hz. You’ll appreciate such deep, rumbling bass on action-movie soundtracks laden with high-impact effects as well as on recordings of pipe organs or electronic music.

Most subwoofers today are self-powered, with built-in amplifiers carefully matched to their drivers. These amplifiers tend to be pretty similar from sub to sub — often high-efficiency Class D (“digital”) designs or conventional amps with switching power supplies to get a lot of power from a relatively compact and cool-running unit. In many ways, a really big subwoofer is actually easier to drive than a small one, as a big driver has to move in and out only a short distance to vibrate a lot of air.

The current trend toward tiny subwoofers revolves around the use of extremely high-power amplifiers, as the smaller drivers used in these subs need to move much farther in order to play deep and loud. These drivers also need to be exceptionally strong so that they can withstand the high forces involved in such long “excursions” and the heat generated by the power flowing through them.

Powered subwoofers typically accept either a line-level or speaker-level signal from the receiver or amplifier, and making the correct choice usually depends on the type of system being used. Many digital surround receivers and most preamp/processors incorporate a comprehensive digital crossover, and getting the best possible blend between the satellite speakers and the subwoofer in a home theater system is often easiest to do if you set up this crossover so that it combines the bass from each main channel with the low-frequency effects (LFE, or “.1”) channel common to multichannel Dolby Digital and DTS soundtracks. Then a single line-level signal is sent to the subwoofer, bypassing the subwoofer’s internal crossover if that is possible.

Subwoofer/Satellite (Sub/Sat) System
These systems have been around for years, but it is only with more recent developments in surround sound processing that they’ve surged in popularity. In a conventional (large) full-range speaker, most of the physical volume is used to give it the ability to play deep bass. Humans, however, find it almost impossible to determine the direction of a sound below about 100 Hz, so subwoofer/satellite systems take advantage of this phenomenon by combining the deep-bass information from all channels and diverting it to a standalone subwoofer that can be positioned just about anywhere in the room. Now, freed from deep-bass duty, the main speakers can be dramatically smaller — “satellites” that are less conspicuous visually and much easier to position for optimum sound.

One way to greatly simplify the shopping process is to go with a prepackaged speaker system from a single manufacturer. This will avoid many of the potential pitfalls of trying to put together a system à la carte, as you can be pretty confident that the various parts have been designed to work well together. Many of these systems use very small satellite speakers, which can sometimes make the transition from them to the subwoofer less than ideal, as it struggles to reach up far enough and they struggle to reach down. You should, however, get an accurate timbre match across the front channels, while the style conscious will appreciate a system in which every element looks cut from the same cloth.

The main downside of a prepackaged system is its lack of flexibility. Most don’t give you any speaker options, so you couldn’t get, say, a really topnotch pair of front left and right speakers for stereo music listening along with more modest center and surround speakers for occasional movie watching. Also, most prepackaged systems are either 2.1-channel setups for stereo listening or 5.1-channel surround systems, with very few 6.1- or 7.1-channel jobs for people who want the whole enchilada.

Teensy-weensy satellite speakers obviously can’t offer much in the way of bass, so these systems hand off a large measure of the sound to the subwoofer. If the subwoofer has its own amplifier, that should make the system pretty easy to drive without needing a lot of power. Some have passive subs, however, which are driven by the same amplifier or receiver as the satellites. Either way, make sure the system as a whole will play loud enough in your space. Movie soundtracks often have wide dynamic ranges and can get shockingly loud — with a set of tiny satellites in a big room, you might occasionally run up against the speakers’ limits, which can mean awful-sounding distortion.

Center
When we experience a movie at home through a surround sound system, much of what we hear is actually coming from the center-channel speaker. In most movie soundtracks, the center channel contains not only all of the dialogue but also many sound effects and some of the music. Typically, about 60% of the total sound energy will be in the center channel.

Given the center speaker’s critical role, there are two key buying considerations. Most important, the center speaker’s sound has to match that of the front left and right speakers very closely, a characteristic that’s often called timbre matching. Otherwise, sounds panned from one side of the screen to the other will seem to change as they pass through the middle. Most speaker companies design their center speakers to match the other speakers in the same product line, and many will develop a line of speakers using different combinations of the same drivers to maximize compatibility.

The other thing to check out with a center speaker is its “off-axis” performance. That is, how does it sound as you move from directly in front of it to one side or the other? Most center speakers have the drivers mounted in a horizontal line, often with a pair of woofers flanking a central tweeter. Sometimes the sound radiating from the different drivers in such designs interferes in ways that cause the tonal balance to change substantially off to the sides. If a center speaker starts to sound hollow or not quite right as you move to the side, it could be a problem if your room has a wide seating area. This issue usually doesn’t arise for three-way center speakers, however, and good engineering can minimize it in two-way designs.

Surround
Surround speakers come in a couple of different flavors: direct-radiating and diffuse-radiating. The latter typically have drivers mounted on opposing sides of the box so that they project sound forward and backward along the side walls rather than directly into the listening area. In the dipole version of this approach, the rear-firing drivers are wired out of phase with the front ones, and the overall effect is a nondirectional wash of sound that gives the listener a good sense of envelopment. While this is great for generating a rich ambience, it’s less effective for precisely locating sound effects. The benefits and drawbacks swap places for direct-radiating, or monopole, speakers. A popular compromise is embodied in bipole surround speakers, which are built like dipole surrounds except with all the drivers wired in phase. That yields more direct sound while still providing more diffusion than conventional speakers. Some models even allow switching between dipolar and bipolar operation.

The introduction of 6.1-channel surround formats, or 7.1-channel with two back surround speakers, along with surround music formats like DVD-Audio and SACD, have prompted more people to opt for direct-radiating surround speakers, especially for the back surrounds. Often the speakers used are simply small bookshelf models. Some manufacturers do make special low-profile versions of their bookshelf speakers for surround use that hug the wall better than the standard models. Another popular approach is to use regular floorstanding speakers for the front channels and one or two pairs of in-walls for the surround channels.

In-Wall
The ultimate in stealth speaker technology is undoubtedly the in-wall speaker. Once this meant a buzzy “pie plate” ceiling speaker like the ones playing background music in an elevator or at the mall, but thankfully those days are far behind us. Today’s best in-walls are downright high-tech, with features like pivoting tweeters and adjustable crossovers.

In-walls are designed to be mounted between the studs of a standard drywall and typically have a mesh grille and frame that can be painted to match. While most use the wall cavity to form a floor-to-ceiling enclosure one stud space wide, many of the best models now have enclosures (or “back boxes”) that fit inside the wall. This approach makes the sound considerably more predictable and reduces sound transmission into the room on the other side of the wall behind the speaker.

There are two basic types of in-wall speakers: rectangular and round. Rectangular models have two or more drivers arranged like a regular bookshelf speaker, while round models typically mount the tweeter coaxially with the woofer — that is, right in front of it. The round types are used more often in ceilings, while the rectangular versions usually end up in walls, but there’s no rule that you can’t do it the other way around. There are even a few in-wall and under-floor subwoofers, making it possible to put together a complete “stealth” surround sound system. Because in-walls are often mounted high above the listener’s ears, a pivoting tweeter can be useful in directing the highs toward your listening position.

On-Wall
The biggest change in speakers over the last couple of years has been the explosion in the selection and quality of models designed for wall mounting. For years people looking for an unobtrusive setup have been directed toward in-wall speakers, yet unless your room has unobstructed drywall exactly where you need it, in-walls are not going to work. When plasma TV hit it big, many of the affluent early adopters wanted better speakers than the cheesy little ones supplied with the sets, yet most of them were unwilling to install floorstanding towers or bookshelf speakers. Sensing a need, several speaker manufacturers scrambled quickly to fill the void, and there is now an excellent range of on-wall speakers for every channel in a home theater setup. (Of course, wall mounting is nothing new for the surround speakers.)

Panel
While the vast majority of speakers use conventional dome tweeters and cone woofers to generate sound, several alternative technologies are highly prized by some enthusiasts. Planar speakers use a paper-thin rectangular membrane that is driven evenly over its entire surface. Most have a large woofer panel and a narrow but tall line-source tweeter (often called a ribbon). Panel speakers are natural dipoles, radiating equally but out of phase front and rear, which gives them a distinctively open sound. Planar-magnetic, electrostatic, and ribbon speakers are in this category.

Because they send just as much sound to the rear as to the front, panel speakers must be placed well out from the wall behind them. Quite a bit of experimentation may be necessary to get the best sound, especially in the bass, where panels tend to be weak. Some models counter this by mating a dipole panel with a conventional woofer, or you can use a subwoofer to handle the low end. Many also have relatively narrow sound dispersion, which restricts the seating area in which the speakers sound their best.

Outdoor
Moving your music outdoors requires a wholesale rethinking of priorities. Propping a pair of bookshelf speakers in the window to blast into the yard might have been fun back at the frat house, but unless you live on a remote farm, trying a similar stunt now will probably get you a ticket for violating some noise ordinance. A much better solution is to install speakers designed for outdoor use much closer to the intended listening area. That way you can get good sound coverage in the desired areas without having to blast it in a way that might raise the hackles of your neighbors.

Many people are particularly sensitive about maintaining a natural look in their gardens, and stealth is an important factor in the design of many outdoor speakers. Some look like boulders that you can position strategically in your flower beds, while others are built into everything from garden lamps to innocuous-looking stone columns.

Whatever form they take, however, outdoor speakers must be built to withstand some pretty hideous conditions. The speakers may be assaulted by everything from termite attacks to snow drifts to driving rain and hail. When you add in temperature extremes from 20° below to 110°, it’s amazing that they can survive at all.

Building in this level of ruggedness makes the choice of construction materials particularly critical, as conventional wooden cabinets and paper driver cones will quickly turn into mush or toast under the harsh conditions. Because of the design limits created by this need for extreme durability, many outdoor speakers in the past have been pretty cruel jokes sonically, but there are now some that manage to combine good sound with ruggedness in a way that requires no apologies.

Listening outdoors without surrounding walls to support the bass is fundamentally different from indoor listening, and speakers that have been designed for indoor use will usually sound thin if you play them outdoors. Good outdoor speakers are specifically voiced for outdoor use, but if you really feel the need for additional low-end kick, you’ll be pleased to hear that subwoofers have also made the move out of the house and into the garden.

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