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About AudioEnz |
Doing the DSP Dance
The Numbers Game - a new spin on an old routine.
By Max Christoffersen
November 2000
I was rummaging through old audio magazines getting a bunch ready for
paper recycling when an unusual back page ad stuck out big time.
Nothing really unusual about it, here was another black box featuring
ambient rear speakers and a few concert hall ambient effects to create
the 'missing link' in stereo. Read it all before, been there done it -
so what.
What
was unusual was this was a 1980 copy of Stereo Review. A full 20
years ago Koss was advertising a new Digital Delay system with a built-in
amplifier and matching ambient speakers.
Many new home theatre enthusiasts believe DSP hall-type sound effects
and delay are developments of the 90s, designed for the Playstation generation.
But audio R&D has been around a long time and while the Koss system
may have been a crude first attempt at domestic '4.1 multi-channel' audio
it is a symbol of the failure of two channel audio to be able to truly
recreate a live musical event.
So the question posed by this 1980 'DSP' advertisement is what have we
learned in the past 20 years and what has improved in between?
You have to say that the obvious changes are the development of faster,
more powerful digital processing chips and more channels with which to
hear them.
One thing hasn't changed though and that is that DSP (as applied to room ambience devices) is still an enhancement-added process not an ambience-extraction process. The reverb and delay is placed 'over and above' an existing recording and the effects are largely random. And sometimes so random as to be obviously artificial.
[There are several ambience-extraction technologies that can work very
well - Meridian's Trifield and Lexicon's Logic-7 approaches come to mind.
But you can just about guarantee that any functions built into a home
theatre receiver are as Max describes above - Editor]
Some may claim (for marketing purposes) that their multi-channel system
is more capable through improved steering logic to "recreate the
artists' intent" from the out-of-phase information recorded on the
soundtrack, but the fact remains in 20 years we haven't really improved
the multi channel audio playback system.
In 1980 Koss was taking much the same approach as we are hearing now
- their own ambience 'settings' tell the story: you can choose between
Auditorium, Concert Hall, Theatre and Hall. Sound familiar?
The point behind all this is we now find that genuine multi-channel audio
is on the horizon. True discrete multi-channel encode-decode audio designed
to widen the palate on which musicians can create their music and engage
the listeners in a new ground breaking manner. The real deal.
But as always just when it's possible to start something new, the marketers
themselves can't work out what to call it. The real concern is the increasing
numbers game going on with some multi-channel systems.
On-line you can read of any number of multi-channel systems right up
to and including 10.1 systems. It may be pedantic, but if we're going
to set a standard let's get the standard right.
Right now there is huge confusion about what is what - a V8 in audio
terms can be a straight 6, or flathead 4. And is a 6.1 system the same
as a 7.1 or 8.1 system - does anything over and above 5.1 actually deserve
the nomenclature 'x.1' anyway?
For the sake of clarity and knowing what people are buying it would be
great to think we could all agree on what system is what.
To me, the description of '5.1' implies discrete multi-channel encode-decode
audio with a dedicated bass effects channel. And that base standard of
description suggests 5 speakers and a sub.
To me 6.1 suggests six discrete channels and sub and to me 7.1 suggests seven discrete channels with a seven channel speaker set-up.
Only in the real world I'd be wrong. Any number of users and manufacturers
are muddying the waters by describing their systems as 7.1 or 8.1 when
in fact they are a basic 5.1 discrete channel system with two or more
added synthesized channels. The confusion is hurting the buy-in of enthusiasts
to the new Dolby/THX EX and DTS ES systems. Is it discrete/matrix or not?
Looking at the nomenclature it's very hard to tell.
And that's because in the ever changing numbers game we really haven't
arrived at a standard consistent description of multi-channel audio and
as manufacturers seek that extra market share they will play an artificial
numbers game to stand out from the crowd. And everybody is doing it.
To me it's wrong. And I will insist on describing audio and home theatre
systems as 5.1 discrete channels with derived additional ambience channels,
when that's exactly what is being done.
Twenty years ago Koss probably didn't know the size of the can of audio worms it was getting into, but you can bet that the phrase 4.1 never entered the advertising copy.
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