Recycle Your Stereo for Surround Sound

You may not have to replace all your equipment to assemble a great home theater system. Here's how to get started.

Michael Riggs, Special to PC World

Writer Michael Riggs has been reviewing A/V gear for more years than he likes to admit.

You like your stereo system, but now you want a surround-sound home theater as well. Does that mean you have to throw out your existing receiver and speakers and start over from scratch? Or can you somehow use that equipment as a base to build on?

Maybe you can start with what you've got.

Whether the incentive is to hold on to a pair of speakers you love or simply to save money, there is hope. It depends on the kind of equipment you have now, your plans, and the room in which the system will reside.

In this story, we'll discuss some surround-sound strategies (see "Four Scenarios for Surround Sound"), but before that, we'll give you the lowdown on the essential components you need for a surround-sound setup, along with some important things to consider, depending on how far you want to go with your system. We explain how surround-sound technology works, and we also provide some tips on how to evaluate the equipment you already own.

Getting Started: Basic Surround Sound

Surround sound involves four key elements: A source, a receiver, amplifiers, and speakers.

Source: Your source can be anything that carries a surround-encoded sound track, which would include DVDs and videotapes of just about any movie made in the last 20 years and many television programs. Taking advantage of these sources--DVD movies, videos, and TV programs--requires a DVD player, a hi-fi VCR, or a TV with line-level stereo audio outputs.

Receiver: Your standard audio/video receiver typically has a number of inputs--AM/FM, CD, DVD, and so on. The decoder, which can extract the four, five, or six audio channels that comprise a surround-sound sound track, is usually embedded in an audio/video receiver, though you can also have it as a separate component. The least common denominator for surround decoding is Dolby Pro Logic, or the more modern and superior Dolby Pro Logic II; any recent surround processor or receiver will also provide Dolby Digital decoding, which is better for sources such as DVD and HDTV.

Amplifiers: These are needed to power the speakers. As with the decoder, amps are usually built into an A/V receiver. The minimum number of amplifier channels is four, but current A/V receivers have five to seven. If the surround processor is a separate component, the amplifiers will be too.

Speakers: Your speaker system will include at least two more units than in a regular stereo system. You can have as few as four speakers or as many as seven, supplemented by a subwoofer or two. A four-speaker setup, for example--where you have left and right speakers at the front, along with left and right surround-sound speakers--can give a very pleasing result. In this case, the two additional speakers are placed at the sides or somewhat behind the listening area to generate the ambience and sonic envelopment that make surround sound so much more realistic than plain old stereo.

That's your basic setup, but if you want to go a step or two further, you may want to think about including a center speaker. You might also want to look at some possibilities for more advanced speaker positioning. For these situations, it helps to look at how surround-sound technology works.

The Great Center Speaker

If you add a center speaker between the front left and right speakers, you'll notice a big improvement in sound quality. Here's why: All surround-sound tracks for movies include a center channel, which normally is the most important one, carrying about 60 percent of the total sound energy. Including a center speaker should always be at least a long-range goal, even if you can't get one right away.

When there is no center speaker, the center channel is split equally across the left and right front speakers to create a "phantom center" image, just like in regular stereo, but this is never as good as if you were using a proper, dedicated center speaker. It is critical, however, that the center speaker's tonal balance (or timbre) closely matches that of the front left and right speakers. In fact, the more alike all the speakers in your setup sound, the better; but the blend across the front is most important.

That almost invariably means that the center speaker must be from the same manufacturer as the front left and right speakers, and preferably designed specifically to match them. In general, you can expect all the speakers in a given line from the manufacturer to work well together, and companies often provide specific match-up recommendations on their Web sites.

If you have a pair of speakers made within the last few years by a big-name speaker manufacturer, such as Infinity, JBL, Paradigm, Boston Acoustics, Polk Audio, or Klipsch, for example, chances are very good that you can go out today and buy a center speaker that will match them very well. But if you have AR speakers from 1975, say, that's going to be nearly impossible.

Get Surrounded

Today's movies normally are made with 5.0- or 5.1-channel digital sound tracks that are carried over directly to DVD. That's five full-frequency-range channels--left, center, and right front and left and right surround--plus in many cases a bass-only low-frequency effects (LFE) channel that helps create certain intense sound effects, such as explosions.

Some recent movie sound tracks--ones that use Dolby Digital EX or DTS ES encoding--also have an additional back surround channel that can be reproduced by one or two speakers directly behind the listening area or split to the left and right surround speakers in systems that don't have the extra back speakers. (Dolby Digital EX was initially developed for Star Wars Episode I: The Phantom Menace, and it also was used for Episode II and the upcoming Episode III.) The main left and right surround speakers should be positioned more to the sides of the listening area whenever possible, either directly or pulled a few feet toward the back when there's enough space.

Evaluate Your Existing Equipment

So, how much of what you need for surround sound do you already have? Many two-channel stereo music systems are built around stereo receivers, but if by chance you already have a surround-capable receiver that happens to feed just a pair of speakers, you only need to add more speakers to get started. Otherwise, you're going to have to buy a surround-capable receiver, in which case you should make sure it provides Dolby Digital and Dolby Pro Logic II decoding, and at least five amplifier channels, plus a line-level output for a powered subwoofer. If you have room for seven loudspeakers, and you think you might eventually want to take full advantage of the most advanced surround technologies, make sure the receiver also incorporates Dolby Digital EX decoding.

Even though you will add speakers to your system, you may be able to make good use of the ones you already own (check out our surround-sound strategies section). Perhaps the most important consideration here is how much bass your current speakers can produce. The deeper and stronger their low-frequency output capability, the easier it will be for you to get by (at least initially) without including a subwoofer in the system. Two or three small and relatively inexpensive speakers might do the trick.

Generally speaking, a speaker's bass output is roughly proportional to its size. A floor-standing speaker with a big woofer (or multiple medium-size woofers) will typically deliver much better bass than a bookshelf or satellite speaker with a smaller woofer. If you'd like to get a good subjective handle on the situation, try listening to a recent action movie on DVD in stereo through your current system. That should give you a fair impression of the bass impact you can expect if you rely on your existing speakers to carry the low-end load when you go to surround sound.

Now let's put some of these ideas to work. Here are a handful of scenarios you can try out. Chances are you can adapt at least one of them to fit the peculiarities of your own situation. You may even be able to use several of them, one after the other, in a kind of rolling upgrade.

Four Scenarios for Surround Sound

Use Your Existing Speakers for the Front Left and Right

Add a center speaker, a pair of small speakers for the surrounds, possibly a subwoofer, and you're ready to rumble. This option is especially appealing if you have relatively large, recent-vintage loudspeakers that you like so much you'd hate to give them up."Recent vintage" means you have a decent shot at finding a matching center speaker, since almost all manufacturers have been making dedicated center speakers for years now.

If your speakers are relatively old, you can still go with just the pair up front until you're ready to spring for a new, matched front threesome. (Upgrading in stages is always an option.) Or, if you're really in love with your current speakers and you expect most of your listening to be to stereo music rather than surround-sound tracks, you may decide that you'd rather live without a center speaker than sacrifice your old favorites.

Use Your Existing Speakers as Surrounds

This will work as long as the speakers will fit where they need to go--which doesn't necessarily mean they have to be small. Even big floor-standing loudspeakers can work as surrounds. In fact, one possibility if you have such speakers is to put small matched speakers across the front and let the bass management in your receiver or processor send all the low frequencies to the big surround speakers, giving you time to save up for a subwoofer and maybe a new set of surrounds. Check out the setup features on your receiver and make sure that it will let you set the front speakers to Small and the surround speakers to Large.

Use Your Existing Speakers and Receiver as a Powered Subwoofer

This is not an option if your current speakers are really small, but if they have at least 8-inch (or even 6.5-inch) woofers, it's worth considering. The beauty of this approach is that it lets you buy small but well-matched, high-performance speakers for the front and surround channels while the old clunkers handle all the grunt work at the bottom end. Essentially any receiver will serve the purpose here, though the higher its power output capability, the better.

Here's how to set things up: Put one or, preferably, both speakers together in a corner of the room, if possible. Two speakers will allow greater maximum output than one, and since they will be receiving the same signal in this situation, there is normally no benefit to separating them. (Corners are usually best, especially when well away from open doors, because that also increases output and typically yields the smoothest, most accurate output as well, but other locations can also work. No matter what, though, try to keep the speaker or speakers close to a wall.) Connect the speaker or speakers to the receiver just as you normally would. Hook the subwoofer output on your surround receiver or processor to your old receiver or amplifier, using a Y-connector if you're using both speakers. (You'll need a Y-connector with one male RCA plug and two female RCA sockets, which attach to a stereo RCA cable leading to the old receiver or amplifier.)

You can use any of the stereo receiver's line-level inputs (that is, any input not designed to connect to a phono cartridge); just make sure the receiver's source selector is set to that input. You will also need to adjust the volume control to a range where you can achieve an appropriate sound level from your makeshift subs, which you can achieve by trial and error in conjunction with your surround receiver's speaker setup function.

One caveat, however: Unless your speakers are fairly large, floor-standing models, they are unlikely to provide the deep-bass extension of a good purpose-built subwoofer. (Not that everything called a subwoofer does, either, but that's another story.) This can still be a good stopgap strategy, though, for taking some of the low-frequency load off your main speakers while ensuring that you don't completely lose the bass from channels served by small speakers.

Use Your Old Stereo Receiver (or Amp) to Drive Back Surround Speakers

Another potential application for your existing stereo receiver (or amp) would allow you to use it as an amplifier to drive back surround speakers. This would work in a system where the surround receiver (or processor) has Dolby Digital EX decoding capability but only a five-channel amplifier section. Such receivers have outputs to drive an external stereo amplifier for the back surround speakers. You hook things up as described in the section above, except that you usually don't need a Y-connector and the speakers, obviously, are not set up and positioned as subwoofers. The amount of energy reproduced by the surround speakers--back surrounds especially--is quite low relative to the front speakers, so even a very low-power receiver will be adequate for this application.