1. Technology
You can opt-out at any time. Please refer to our privacy policy for contact information.

Discuss in my forum

Surround Sound - The Audio Side of Home Theater

Part One - Beginnings: From Mono to Stereo to Fantasound and Quad

By

Introduction

Ever since Stereophonic sound became popular in the 50's the race has been on to create the ultimate home listening experience. Even as far back as the 1930's, experiments with surround sound were conducted. In 1940, Walt Disney incorporated his innovative Fantasound surround sound technology in order to totally immerse the audience in both the visual and audio sensations of his animation achievement, Fantasia.

Although "Fantasound", and other early experiments in surround sound technology could not really be duplicated in the home environment, that didn't limit the quest by recording engineers for both music and film to develop processes that would eventually result in the surround sound formats that are enjoyed in home theaters all around the world today.

Monophonic Sound

Monophonic sound is a single-channel, unidirectional type of sound reproduction. All elements of the sound recording are directed using one amplifier and speaker combination. No matter where you stand in a room you hear all the elements of the sound equally (except for room acoustic variations). To the ear, all the elements of the sound, voice, instruments, effects, etc... appear to originate from the same point in space. It is as if everything is "funneled" to a single point. If you connect two speakers to a Monophonic amplifier, the sound will appear to originate at a point equidistant between the two speakers, creating a "phantom" channel.

Stereophonic Sound

Stereophonic Sound is a more open type of sound reproduction. Although not totally realistic, stereophonic sound lets the listener experience the correct sound staging of the performance.

The Stereophonic Process

The main aspect of Stereophonic sound is the division of sounds across two channels. The recorded sounds are mixed in such a way that some elements are channeled to the left part of the soundstage; others to the right.

One positive result of stereo sound is that listeners experience the correct soundstaging of symphony orchestra recordings, where sounds from the various instruments more naturally emanate from different parts of the stage. However, monophonic elements are also included. By mixing the sound from a lead vocalist in a band, into both channels, the vocalist appears to be singing from the "phantom" center channel, between the left and right channels.

Limitations Of Stereo Sound

Stereophonic Sound was a breakthrough for consumers of the 50's and 60's, but does have limitations. Some recordings resulted in a "ping-pong" effect in which the mixing emphasized the difference in the left and right channels too much with not enough mixing of elements in the "phantom" center channel. Also, even though the sound was more realistic, the lack of ambience information, such as acoustics or other elements, left Stereophonic sound with a "wall effect" in which everything hit you from front and lacked the natural sound of back wall reflections or other acoustic elements.

Quadraphonic Sound

Two developments occurred in the late 60's and early 70's that attempted to address limitatons of stereo. Four Channel Discrete and Quadraphonic Sound.

Problems With Four-Channel Discrete

The problem with Four Channel Discrete, in which four identical amplifiers (or two stereo ones) were needed to reproduce sound, was that it was extremely expensive (these were the days of Tubes and Transistors, not IC's and Chips).

Also, such sound reproduction was really only available on Broadcast (two FM stations each broadcasting two channels of the program simultaneously; obviously you needed two tuners to receive it all), and four channel Reel-to-Reel audio decks, which were also expensive.

In addition, Vinyl LP's and Turntables could not handle playback of four channel discrete recordings. Although several interesting musical performances were simulcast using this technology (with a co-operating TV Station broadcasting the Video Portion), the whole set-up was too cumbersome for the average consumer.

Quad - A More Realistic Surround Approach

Taking a more realistic and affordable approach to surround sound reproduction, than that of Four Channel Discrete, the Quadraphonic format consisted of matrix encoding of four channels of information within a two channel recording. The practical result is that ambient or effects sounds could be imbedded in a two channel recording that could be retrieved by a normal phono stylus and passed through to a receiver or amplifier with a Quadraphonic decoder.

In essence, Quad was the forerunner of today's Dolby Surround (in fact, if you own any old Quad equipment--they have the ability to decode most analog Dolby Surround signals). Although Quad had the promise to bring affordable surround sound to the home environment, the requirement to buy new amplifiers and receivers, additional speakers, and ultimately lack of consensus amongst hardware and software makers on standards and programming, Quad merely ran out of gas before it could truly arrive.

Continue on to Page 2: The Emergence Of Dolby Surround

  1. About.com
  2. Technology
  3. Home Theater
  4. Home Theater and AV Basics/Set-up Tips/Installation/Product Reviews
  5. Home Theater Audio Basics
  6. Surround Sound - The Audio Side of Home Theater

©2014 About.com. All rights reserved.