Adding Surround Sound to Your Home Theater
A surround system includes at least five speakers (front left and right, center channel, rear left and right surrounds), an optional subwoofer and a receiver (or decoder/processor, amps and tuner). All components have to be wired through the receiver, and the speakers installed in the best positions for the room in which you will be watching movies.
The Receiver
While some people choose to purchase separate components (such as a decoder/sound processor, preamp, and multiple power amps) for processing surround sound, a receiver integrates a processor, amplifier and tuner into one chassis. Pick a receiver that has Dolby Digital and DTS, about 85-100 watts per channel, and expect to pay anywhere from $300 to $3,000.
Components connect to a receiver through audio and video inputs. Make sure your receiver has enough; look for a receiver with a few more inputs than you need. Because video components must be wired through the receiver as well, make sure some inputs are dedicated to S-video. S-video provides better picture quality than coaxial connectors. S-video inputs are used on satellite receivers, Super VHS, DVD players, and most new high-quality large-screen televisions.
Sound Formats
While all surround-sound formats-Dolby Surround, Dolby Pro Logic, Dolby Digital 5.1 and DTS 5.1-have the goal of immersing you in movie sound in your home, each tackles the problem a little differently. The main difference is the number of separate channels of sound delivered by your speakers.
Dolby Surround creates four channels of information: front left, “phantom” center (created by left and right), front right, and rear surround. There is a greater separation in channels if you move up to Dolby Pro-Logic, which also incorporates a dedicated center channel, but still has the same signal in both rear speakers. Dolby Digital (also called Dolby 5.1 or AC-3) adds stereo rear surrounds as well as a dedicated subwoofer channel (the .1 in 5.1). You must have a Dolby Digital receiver (or amplifier) to accurately decode the signal, because Dolby Digital uses its own encoding process.
Digital Theater Systems (DTS) has its own home theater surround process. Like Dolby Digital, this system also incorporates five separate channels plus a subwoofer. While DTS uses less compression, and some audiophiles suggest that DTS is best for listening to music-as opposed to Dolby Digital’s emphasis on movie soundtracks-there is little difference between the two. A rear center channel has now been added by the latest formats-Dolby Digital-EX and DTS-ES-creating new 6.1-channel sound.
You may have seen the label “THX” on certain home theater equipment, as well as on one of those nifty trailers at the beginning of movies. Home THX Audio Systems, developed by George Lucas’s (yep, that George Lucas) THX Division, have become industry standard for home theater. THX licenses its technology to various manufacturers, and a component with the THX logo on it meets Lucasfilms’ standards for home theater (movies, not music). THX certifies everything from preamps/processors, receivers and power amps to laserdisc players, speakers, and even speaker wire and interconnects.
The Speakers
There’s no difference between speakers used for surround sound and the “regular” speakers you might already have hooked up to your stereo. They’re all constructed of woofers and tweeters, and their job is to produce accurate sound from the highest note (20khz) to the lowest (20hz). In a Dolby Digital surround-sound system, you have two front speakers (left and right), a center channel, and two rear surround speakers (left and right).
Ideally, all five speakers should be from the same manufacturer so that they can be “timbre-matched.” Timbre matching is having the speakers sound tonally the same, so that the sound from your movie blends together seamlessly.
The center channel produces approximately 80 percent of all the sound heard in an average movie, carrying much of the dialog as well as music and some effects. Place this speaker either directly on top of, or directly below, your television. The left and right front speakers should match the center channel and be mounted an equal distance from the center channel, pointed toward the listening area.
If you need to save money on speakers, the best place to cut costs is on the rear surrounds. Because they produce mostly ambient sounds and special effects and aren’t required to deliver low bass tones, rear speakers can be small and inconspicuous. The low end of the price range for quality speakers is about $150 to $350 per pair. Whether mounted on a wall, in the wall, attached to stands, or on a bookshelf, surround speakers ideally should be placed above and only slightly behind the listening position. Ideally, the speakers should be tilted toward the listening area. Installation at a height about 2-3 feet above viewers’ heads helps to minimize localization effects, making it more difficult to pinpoint exactly where the sound is coming from and adding to the reality of the experience.
A subwoofer is optional but highly recommended for a true movie experience. Almost all Dolby Digital and DTS soundtracks now have a “.1 LFE” (low- frequency effects) track designed specially for a subwoofer. Subwoofers are typically cube-shaped, with a large single woofer pointing either directly at the ground or directly at the listener.
Standard subwoofers are usually placed in a corner of the room, but a subwoofer can be placed so that it is impossible to determine the direction the sound is coming from. “Powered” subwoofers are subwoofers with their own onboard power amps. Movies have more low-bass information than music, so subs are particularly effective in a home theater. Soundtracks recorded as Dolby Digital 5.0 do not include an LFE track. Subwoofer prices range from about $300 to $2,000.
The Wire
“Interconnects,” another term for audio and video cables, physically connect all of the equipment together. As with most audio-video components, you can spend as much or as little as you want on wire. Generally speaking, you don’t want to use the audio-video cables that come with your components, as they tend to be of the lowest quality.
Each speaker has to be physically wired back to the receiver. “Gauge” is a unit used to measure wire thickness. The smaller the number, the thicker the wire, so 10-gauge wire is much thicker than 16-gauge wire. Around 12 gauge is ideal; above 18 gauge is not recommended for the highest-quality home theaters. A good 14-gauge speaker wire is perfectly good for most applications. Anything much more expensive than that, and you’re getting into differences that only dogs (and audio elitists) can hear.
If you are planning to do the job yourself, strip the ends of the speaker wire, then twist the bared strands tightly together to prevent shorts across terminals. You can use “banana” plugs to ensure solid connections, if your speakers and receiver allow for these connections. Connect the positive and negative (usually red and black) terminals on each amplifier channel to the corresponding terminals on each speaker. To make this easier, speaker cable is coded with a bead or stripe down one lead’s insulation, and/or different-colored wires.
Final Touches
Next you have to tell your receiver about your system, programming in the kind of speakers and subwoofers that are connected. Let your receiver know if your speakers are either “large” or “small.” If your system has a subwoofer, select Subwoofer “Yes.” The test signal generator on your receiver will help you balance the channels.
The quality of your audio can be affected by everything from the size of your room to the kinds of drapes you hang on your windows. Dolby’s Web site (www.dolby.com) provides many tips for speaker installation and placement. The more expensive and sophisticated the equipment you own, the more important it will be to have a professional audio/video installer calibrate your home theater audio system for you.
