Through the Surround Sound Barrier
By Jim Bray
Confused about Dolby Surround, simulated surround, Pro Logic, Dolby Digital,
DTS, and all that?
You arent alone.
Surround sound isnt the be-all and end-all of good sound, but if
you want to recreate a movie theater or concert hall at home, a good surround
sound system is the best way with which to do it.
In this column, Ill outline what you really need to know about
surround sound, without all the nuts and bolts. This entails glossing
over a lot of technical stuff, but so what?
Back in the 1970s quadraphonic sound began making audio waves.
True quad offered four identical channels of sound, though most quad programming
was available only in a couple of less satisfying matrix surround
(read fudged) methods. The hardware was expensive, competing
quadraphonic formats created confusion, and a lack of software titles
I loved quad, but it died out about the same time that Dolby Surround
was wending its wonderful way into movie theaters around the world.
Dolby Surround eventually found its way to home theaters, too, but it
was really just via a set of rear channel amplifiers and speakers that
would carry monaural (single channel) surround information. The biggest
problem with Dolby Surround was that the dialogue would come from the main
front speakers, as a ghost image that could appear almost
anywhere between the two speakers depending on where they were placed
and where the viewer sat.
Dolby Pro Logic, which was more like the cinematic Dolby, changed that
by adding a center front channel to the mix, ensuring that dialogue and
other sounds that were supposed to originate at the TV screen actually
came from there. There were also some other tweaks that, combined, made
it a big step forward in terms of home theater enjoyment.
The downside was that even Pro Logic only gave you a monaural surround
track that didnt offer the full audio range. It was okay for effects
like gunshots and wind noises, but it was still lacking in ultimate value.
Then came the computer and digital technology, and home theater audio
took another giant step forward.
Dolby Digital (also called AC-3) and later, DTS (Digital
Theater Systems), upped the ante considerably. Both formats offer
five discrete, full range audio channels (three front and two surround),
plus a low frequency effects (LFE) channel that cries out for a subwoofer.
These five main channels and the extra channel of oomph, which
only requires about one tenth of the bandwidth of the main channels, is
referred to as a 5.1 configuration.
The five discrete channels allow for movie makers and recording technicians
to put excellent sound just about anywhere in the room they want. So not
only can you have high quality music coming from any direction, you can
now listen to a helicopter circle the room around you as, for example,
at the beginning of Apocalypse Now. Another excellent example
of surround sound is in Dragon Heart, when Dennis Quaid is
conversing with the dragon as flies in circles around him.
Okay, these are still just effects, but theyre definitely effective!
Dolby Digital and DTS are the two main forces in movie and home theater
audio. Sony also has a system for theaters, but it hasnt made much
of a splash in homes.
Naturally, you need a decoder in your audio system to hear the surround
information, but these are extremely common now.
If youre interested in being state-of-the-art (and relative high
end), you may also want to keep track of some new enhancements that supposedly
promise even more home theater fun.
Dolby Digital EX and DTS ES add at least one center rear channel to make
the placement of sounds even more accurate. Of course you need a new amplifier
and decoder to take advantage of these discs but fortunately the software
titles are backward compatible and will play just fine on
5.1 systems by directing the center rear signals to the other surround
I havent heard a 6.1 or 7.1 system yet, so Im skeptical.
Then again, I was skeptical of 5.1 until I began living with it, and now
And Dolby Pro Logic II is an enhancement to the older Dolby standard,
and I wouldn't worry about it too much.
When will it all end? Probably never, which is frustrating for consumers,
but job security for me!
Jim Bray's technology columns are distributed by the TechnoFILE Syndicate. Copyright Jim Bray.
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