Surround Sound at Home
In the home, multiple-channel sound had its origins with the reproduction of music in stereo. Multiple-channel technology only recently expanded to accommodate surround sound movie soundtracks.
Early Multiple-Channel Experiments
For decades, music recording and reproduction was monophonic. However, there was a real desire for a multiple-channel system to more accurately represent the live musical experience. Initial industry experiments with stereo recording took place in the early 1930s. These early experiments employed an "infinite" number of microphones deployed in a type of curtain in front of the recording musicians, and an equal number of speakers used to reproduce the sound. Later, engineers discovered that they could use phantom imaging to reproduce the stereo soundstage with just two speakers.
The 1950s and 1960s: Stereophonic Sound
Practical multiple-channel recording came into being in the 1950s with the introduction of the two-channel stereophonic system. The first commercial two-channel stereo LP was released in 1958, and by the early 1960s stereo recordings became the norm. Stereo reproduction over the airwaves began in 1961, when the first stereo FM radio broadcast took place.
Early 1970s: Quadraphonic Sound
The desire to reproduce a 360-degree sound field led to the development of four-channel, or quadraphonic, recording. Quadraphonic sound officially debuted in 1969 with the release of the first consumer-level four-channel reel-to-reel tape deck. Soon the quadraphonic process was being applied to both eight-track tapes and vinyl records.
By the early 1970s multiple quadraphonic technologies were competing in the marketplace. JVC's CD-4 system, introduced in 1971 for vinyl records, employed four discrete channels of audio informationfront left, front right, rear left, and rear right. The SQ and QS systems, introduced in 1972 by CBS and Sansui, respectively, were both matrix technologies for vinyl records, in which the rear channel information was matrixed into the two front channels and then separated out by a surround decoder. And RCA's Quad-8 format, introduced in 1970, was a discrete format designed specifically for eight-track tape players.
Unfortunately, the confusion generated by these competing technologies, along with the high cost of four-channel amplifiers and additional rear speakers, led to the abandonment of quadraphonic sound by the end of the decade.
Late 1970s: Stereo Video
Even though stereo audio recordings and broadcasts had been around since the late 1950s, it took until the late 1970s for stereo sound to be applied to video recordings and broadcasts. The first two-channel stereo videocassette was released in 1978, and the first stereo television broadcasts occurred in 1986.
The 1980s: Dolby Surround and Dolby Pro Logic
True surround sound came to the home in 1982, with the introduction of Dolby Surround technology. Dolby Surround was designed to reproduce the cinema's Dolby Stereo surround soundtracks in a home environment. The Dolby Surround technology consisted of three channelsleft, right, and a single surround channel, which was matrixed in with the front two channels. (This single surround channel was frequently sent to two rear speakers, resulting in a four-speaker system.)
Dolby Surround got an upgrade in 1987, when the Dolby Pro Logic system was introduced. Dolby Pro Logic is a four-channel version of the early three-channel Dolby Surround technology, with a separate center channel, primarily used for dialogue. To this day, Dolby Pro Logic is the surround sound standard for prerecorded VHS videotapes.
The 1990s: Dolby Digital and DTS
Home surround sound went digital in 1995 with the introduction of the first Dolby Digital laserdisc. Like the cinema version, home Dolby Digital is a 5.1-channel system, with left front, center front, right front, left surround, and right surround, along with a separate LFE or subwoofer channel. The first Dolby Digital DVD was released in 1997; Dolby Digital is also the official sound format for high-definition television broadcasts.
The competing DTS system was released in a home version in 1996. DTS works similarly to Dolby Digital, but with higher data rates, which often results in slightly better sound quality. However, DTS is an optional format for the home theater environment, and is not included on many DVDs; there are many more DVDs with Dolby Digital soundtracks than with DTS soundtracks.
2000 and Beyond: More Channels, More Options
The new millennium brought significant enhancements to all the major home surround-sound technologies. Dolby Laboratories introduced the concept of rear channels to the mix, placed behind the listener to supplement the normal side-firing surround speakers. The new system, Dolby Digital EX, is available with either single (6.1) or right and left (7.1) rear channels. The new rear channels are matrixed into the original channels, and then subtracted out via a surround decoder.
DTS also embraced the separate surround and rear channel concept with DTS-ES. This is a 6.1/7.1-channel system with matrixed rear channels. However, DTS upped the ante with DTS-ES Discrete, which uses a discrete rear surround channel for better channel separation.
Finally, the aging matrix-surround approach got a boost with Dolby Pro Logic II. This new technology is designed to simulate a surround sound field from two-channel sources; you use it to listen to stereo soundtracks in a surround sound system. (Dolby Pro Logic IIx is an enhanced version designed for 7.1-channel systems.)
Going forward, it's likely that new developments will focus on adding even more channels to the surround mix (possibly wide left and wide right front channels, as well as additional side channels) to more accurately reproduce a true 360-degree sound field.