Dolby Surround

In the early 1980s, consumers we were making their first foray into digital storage media, and the Compact Disc was replacing analogue storage methods like records and tapes. People started watching movies at home on VCRs, and home theater began to take form. But two-channel audio for music and now film was firmly entrenched. When Dolby introduced Surround in 1982, they had clearly learned from Quadraphonic's errors.

(what's this?)

Dolby Surround at a glance:

Dolby's first consumer multi-channel surround format.
Three-channel surround matrix: Left and right front, one rear surround channel.
Not a true multi-channel format, as third channel is a matrix of the stereo source.
Compatible with stereo source material, only requires a decoder or receiver.
Lack of center channel can cause uneven soundtrack distribution and muffled dialogue.
Made obsolete by newer surround matrix system Dolby Pro Logic that adds a needed center channel.

Dolby Surround was a three-channel matrix surround method. Matrix means it isn't really a three-channel system, just two. The third channel is "matrixed" from the two-channel stereo signal. Certain sounds that were common in both left and right channels within a limited frequency would get sent to the rear channel to be played from two usually smallish speakers in the back of the room. Since the range to the rear was limited, this meant the rear sound effects only added some ambient qualities and didn't project a lot of sound. Small surround speakers became the norm.

The significance of this method's compliance with two-channel stereo cannot be understated. It was the reason Dolby Surround and especially the later improvement to Surround in Pro Logic really took off. This meant your CDs and VHS tapes (popular two-channel source material of the era) could be read by a receiver with Dolby Surround, without having to buy a new CD player, VCR, tapes, CDs, etc. Yes, it was technically inferior to Quadraphonic, but it was cost effective because it fit snugly into the two-channel audio system of the day.