Alesis M1Active MKII User Manual - Page 29

Surround Sound CHAPTER 3 SURROUND SOUND ABOUT SURROUND SOUND Surround sound is the term used for several different systems which use multiple channels of playback in the listening room to recreate a truly threedimensional sound experience. The practice of recording music-only in surround sound is a fairly recent innovation. Surround sound for video, however, has been around for over ten years. With modern encoding methods, multichannel audio may be delivered to consumers on standard video tape, video discs, and even through broadcast, with the proper encoders (devices which take multiple channels of audio and combine them into two channels) and decoders (used at the receiving end to split the signal back into multiple channels). Systems are in use which use three (left, right, and surround), five (left, center, right, left surround, right surround, often supplemented by a sixth subwoofer channel), and more speakers. The original Dolby Surround of the mid-eighties was a matrixed three-channel-only system. It had left, right and a mono surround (rear) track, which was usually played through two surround speakers. In 1987, Dolby Pro Logic, a four-channel matrix system, was introduced. Pro Logic added a dedicated center channel to which most dialog was assigned. The rear surround channel was still in mono. In 1996, Dolby Digital (AC-3) and DTS, fully discrete six-channel audio delivery platforms with separate left-rear and right-rear channels first became available to consumers on laserdisc and, more recently, on DVD (Digital Versatile Disc). With so many listeners hearing music through their multimedia systems, it is important for engineers to produce music on surround systems, even if they're not working for film or video applications. Powered monitors like the Alesis M1 Active Mk2 Biamplified Reference Monitor have proven to be a simple, cost-effective way to add five-channel surround to control rooms. M1 Active Mk2 Reference Manual 31