Electronic Media 

Published: 05-22-95 



SURROUND SOUND WORKS-WITH THE RIGHT SPEAKERS 



Byline: Joe Fedele 



 I recently overheard two people comparing notes on TV set

features. When one brought up stereo Surround sound, the other

replied, ``Don't waste your money! I have it, and I can't hear

any difference in the sound.''

 Well, I had to butt in and ask if he had extra speakers hooked

up to the Surround sound output. I got a blank stare in return.

 He'd made a common mistake: Sets with Surround sound require 

additional speakers in order to work.

 Surround sound is a patented audio processing system, developed

by Dolby Laboratories to give TV viewers a movie theater feel.

 Here's how the system works:

 Programing produced in the Surround process encodes the left,

right, center and surround channels into two audio tracks.

 On the receiver or decoder end, the two channels are put

through a relatively simple passive matrix that splits the audio

back to its original form. The left and right channels carry the

conventional full bandwidth audio found in stereo broadcasts.

The center channel carries special effects, dialogue and other

on-screen audio.

 The Surround channel generally contains subtle audio effects,

such as wind, and background noise that gives the illusion of

``being there.''

 Programs that are not produced in Surround are routed to the

set's left and right or mono speakers. Likewise, sets that don't

have Surround simply pass the left and right or mono channels

without any added distortion or audio imbalance. 

 The speakers you choose for the different channels should be

selected carefully to get the maximum effect. The stereo

speakers should be capable of reproducing the full audio range, 

should match well and should provide good spectral balance.

 Simply put, don't cheap out when you buy them. 

 Ideally the center speaker should be the same type of speaker

as the stereo pair, although cost considerations may make this

impractical. A smaller speaker can be substituted, so long as

its mid- and high-frequency response is comparable to the stereo

pair.

 The Surround channel requires a good mid-range speaker capable

of handling from 100 Hz (cycles per second) to 7 KHz. This is

the frequency range used to produce the channel, and anything

above or below is really unnecessary.

 In some systems, the center and Surround channel may use the

same speaker. TV systems that use quality amplifiers and

speakers can deliver an impressive sound when the speakers are

placed at the proper distance and angle from the viewer.

 And, yes, there is a whole science devoted to where and how you

position the speakers.

 If you're serious about TV audio, and want more information

about setting up a Surround system, Dolby offers a helpful

``Listener's Guide to Dolby Surround'' pamphlet. The literature

hot line number is 415-558-0344.