Home Theater

What equipment do I use for configuring a Surround Sound system?

A very good option: 5.1-channel surround

5.1-channel surround sound is the most common home theater configuration today, and no wonder — it provides an amazing level of realism. Let's take a look at some of the 5.1 options.

Dolby Digital

Dolby® Digital quickly established itself as a reigning surround format, largely thanks to DVDs. Although Dolby Digital, strictly speaking, is simply a method of encoding audio information digitally, the term is often used to refer to 5.1-channel audio — its most popular form.

Unlike earlier forms of surround sound, Dolby Digital 5.1-channel audio is a "discrete" multichannel surround sound system. Discrete means that the sound information contained in each of the six available channels is distinct and independent from the others. These six channels are described as a "5.1-channel" system, because there are five full-bandwidth channels with 3-20,000 Hz frequency range for front left and right, center, and surround, plus one "low frequency effects" (LFE) subwoofer channel devoted to frequencies from 3-120 Hz. (To see how the speakers are arranged in a multichannel surround system, check out the diagram above)

Advantages to Dolby Digital include the following:

• Dolby Digital is the chosen multichannel digital audio format for DVDs and HDTV
• Any receiver with Dolby Digital decoding can also decode Pro Logic
• With six discrete channels, sounds can be placed very precisely, for improved dialogue clarity, soundstage size, spaciousness, and realism
• You get stereo surround channels; you can hear separate off-screen sounds to the left rear and right rear simultaneously
• You get a dedicated subwoofer channel, for plenty of deep bass

DTS: Another 5.1 surround option

Like Dolby Digital, DTS® provides 5.1 channels of digital audio. However, DTS uses less compression than Dolby Digital. As a result, some say that the sound produced by DTS is slightly more accurate than the sound produced by Dolby Digital. However, fewer DVDs are encoded for DTS, compared to the number of Dolby Digital DVDs. Fortunately, you don't have to choose between the two. Today, just about any receiver that has Dolby Digital will also have DTS.

Even better: 6.1-channel surround

Although 5.1-channel is still the most popular surround format, and many of the home theater systems being sold today are 5.1-channel systems, 6.1-channel audio is becoming increasingly common. A 6.1 system delivers an even more enveloping surround effect than a 5.1-channel system.

Dolby Digital EX and THX Surround EX

These playback formats are a collaboration between THX and Dolby Labs designed to give surround sound improved directionality. They do essentially the same exact thing, both adding another one or two "back surround" channels for use in a 6.1-channel or 7.1-channel speaker system, in order to provide a more fully 360° wraparound experience.

Currently, many newer DVDs are encoded for Dolby Digital EX, and have that extra channel of surround information ready to go. Also, if you're playing a regular Dolby Digital 5.1-channel DVD, a Dolby Digital EX or THX Surround EX™ decoder will simulate 6.1- or 7.1-channel surround by processing the audio information in the regular surround channels and sending it to your back surround speaker(s) as well.

DTS-ES: 6.1 surround from DTS

DTS-ES™ uses existing digital multichannel technology to deliver the "5.1" channels of regular DTS, plus it adds a discrete, full-bandwidth back surround channel. That additional channel may be played through one or two speakers. Although there are not as many movies encoded for DTS-ES as for Dolby Digital EX< there are still plenty. And as before, there's no need to worry about a format war. Today's 6.1-channel receivers are likely to have both formats.

What about 7.1-channel sound?

There isn't really a surround sound format for 7.1 sound, but many receivers can process audio and send it through a 7.1-channel speaker system. As a result, it's hard to really compare 6.1-channel and 7.1-channel sound. Some soundtracks may end up sounding even more spacious after 7.1 processing has been applied, but others may not sound any different with 7.1-channel processing than they did after 6.1-channel decoding.

More 5.1 and 6.1 options: Dolby Pro Logic II and IIx and DTS Neo:6

Dolby Pro Logic II works on the same Dolby Surround-encoded and stereo sources as Dolby Pro Logic, but improves the surround experience with special circuitry that creates convincing 5.1-channel audio. This includes two independent full-bandwidth surround channels and a dedicated low-frequency channel for your subwoofer. Many recent home theater receivers also offer Pro Logic IIx processing, which can turn the same sources into even more enveloping 7.1-channel sound (complete with four separate surround sound channels). Also, video game manufacturers have started to actually encode game sound for Dolby Pro Logic II and IIx (instead of just permitting it to be a stereo signal which is processed to produce surround sound).

Receivers with Dolby Pro Logic II and IIx give extra intensity to the thousands of VHS movies and TV broadcasts recorded in either stereo or Dolby Surround. They also include special modes tailored to turning stereo music into realistic surround sound. And they are certainly must-haves for today's gamers.

DTS Neo:6 is essentially identical to Pro Logic II — it's simply the processing DTS came up with to deliver five or six channels of sound from a two-channel stereo source. And just like Pro Logic II, it's amazingly effective.

"My brand-new receiver has other surround formats, too"

Sometimes, manufacturers will put their own special processing on a receiver, either in addition to or in place of the formats described above. Often, it's because the manufacturers prefer their own proprietary format. Occasionally, it's because they have opted not to license the decoding from Dolby Digital or DTS. Generally, these components provide convincing multichannel sound. Some of them offer sound that is identical to Dolby Digital or DTS decoding, because they're actually using Dolby Digital or DTS decoders — even if they're not identified as such. But basically, you don't need to worry. You're likely to be getting excellent surround sound anyway.Properly creating 7.1 channel surround sound requires seven channels for high frequencies and at least one channel for low frequencies.

The High frequency channels consist of Left main, Center, Right main, Left surround, Right surround, Left back, and Right back. Each speaker system needs to be driven by an amplifier channel.

For low frequencies, a Subwoofer that has a built-in power amplifier will work perfect. Some preamplifiers/receivers utilize a Mono subwoofer output, others incorporate stereo subwoofer outputs. Regardless of how many subwoofers you use, the addition of low frequencies completes the ".1" in a surround sound system.