There are two basic types of audio people: two-channel purists and the rest of the world. To write about the two-channel people of the world would require opening a full-time threaded internet discussion board to handle all the grousing about how others just don't get it; something I just don't have the wherewithal to do. So, if you are an immovable two-channel aficionado sitting in your favorite listening chair, perfectly aligned between your two speakers, I'll leave you alone now with your $120K per pair Wilson Audio robot-style transducers to enjoy Vivaldi.
Ok, now that those folks have left the room, let's get down to some real audio fun; surround sound. Surround sound is that explosion enveloping you in the theater. It's also the scary glass breaking from behind you that makes you tingle. Or perhaps it's applause, or the violin section, or a dog barking. The cool thing about surround sound is that if it's properly created and reproduced, our senses are compelled to appreciate the total experience more fully, whether it is a movie, music video or live concert.
Surround sound may seem to be a recent phenomenon, especially since DVDs and home theaters have become popular, but in reality, movie surround sound goes all the way back to the 1940s when Walt Disney had his visual epiphany and created the stunning cartoon classic Fantasia.
Walt's audio vision for Fantasia included not just live orchestras, but also dedicated sound systems that toured with the film. These sound systems consisted of three mono optical film sound tracks (and a control track) that played to not only left, center and right channel speakers, but also house left and house right speakers derived from the screen left and right channels. In other words, a surround system.
Surround sound in music playback goes pretty far back as well. In the late '60s and early '70s-which by the way was also the heyday of another psychedelic profit, Timothy Leary-perceived limitations with two-channel stereo systems were attacked with four channel discrete and Quadraphonic sound systems. Four channel discrete systems flopped like 8-track tapes, but Quadraphonic sound actually had the ability to matrix encode four channels of information within a two-channel recording. This process eventually became the original analog Dolby surround. But, like many solid and emerging technologies, Quadraphonic sound succumbed to an early death due to costs, lack of technical standards and programming content.
Original Dolby surround sound, called AC3, offers a minimum of four channels of information; front left, front right, front center and rear surround, all encoded into a two-channel signal. This allows for a more realistic listening environment in which main sounds emanate from the left and right speakers, dialog from the center channel and effects from the rear speakers. Music performances are enhanced as well, though post-production mixing with spatial cues and source placement being offered to help put the listener into the concert space more fully than a pure stereo mix. Some purists reject this, as the true effectiveness of spatial cues in a surround system designed for movies, doesn't quite make it with music, but nevertheless, music surround formats like SACD (Super Audio CD) and DVD-Audio are popular anyway. Take a close listen to the Eagles' 1994 Hell Freezes Over live concert DVD, especially cuts like "Hotel California" or "New York Minute" and you might just become a true believer in surround sound concert DVDs. For a more recent impression, view the 3 Doors Down live concert promo video put out by cable icon Noel Lee of Monster Cable, which touts being the first ever "on stage" surround mix.
Advances in Dolby technologies produced Dolby Pro Logic which improves the listening experience by adding decoding of directional cues in the surrounds and extracting dialog to a dedicated center channel. Dolby Digital 5.1 adds stereo to the surround channels (left, right, center, surround right, surround left) and a dedicated subwoofer (the .1 in any surround system format is the mono subwoofer. A .2 system would have stereo subs). Dolby Digital EX adds a surround back channel (6.1) that helps make spatial movement more precise as sounds move from back to front in the sound field. Dolby Digital EX is compatible with 5.1, so if you do not have a 6.1 decoder and that extra amplifier/speaker in the rear, things will just matrix out fine in a 5.1 channel system.
The latest cinema surround buzz is focused on the Sony Dynamic Digital Sound (SDDS) often referred to as 7.1, which places five speakers in the front and middle of the listening space, along with stereo surrounds and a subwoofer channel. Although there is little or no pure content in this format outside of film theaters, manufactures of decoding and other home theater gear have the format available to either synthesize existing formats for reproduction into the added speakers or to just prepare for the future.
And there are other surround sound formats; Digital Theater System's format, DTS, is a 5.1 or 6.1 format that some experts say sounds better, due to less compression in the encoding process; others say the bass is too boosted in DTS. DTS has found a niche in mixing and reproducing music DVDs and videos. Lucasfilm developed the THX format-named for Lucasfilm's technical director Tomlinson Holman and his sound eXperiment-in 1982 for Return of the Jedi, as an attempt to playback sound in the theater exactly as recorded during filming. SRS Labs has its Tru-Sound and Circle Sound, which is more about total immersion in the sound field than precise spatial placement. Virtual speaker encoding from a number of developers allows for spatial placement of sound through the use of precise timing of signals to "fool" our ears into perceiving specific 3-dimension directional positions from only two or even one speaker. Headphone surround sound is pervasive using similar technologies. There are even MP3 surround formats being developed, by the Fraunhofer Institute and perhaps others.
So what does all this mean for listeners and the business that supplies them with equipment and systems? It means that surround sound is big and getting bigger. The need to try and grow the complete human entertainment or presentation experience is just too alluring to ignore-think plasma screens and projectors-and systems contractors will benefit from the need.