From: j_adams@fc.hp.com (John Adams)
Newsgroups: rec.video.releases
Subject: Re: Very Basic Questions
Date: 22 Jan 1993 20:32:05 GMT
Organization: HP SESD, Fort Collins, CO
Distribution: usa
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Charles E Rick Taylor IV (charlet@hubcap.clemson.edu) wrote:
: byd999@unagi.measurex.com (Ben Dai) writes:
: 
: >1) THX
: 
: There's lots of debate on this one. :)  What *I* heard was that THX was a 
: type of sound system/speaker setup, *then* I heard that THX was a method
: of recording somewhat akin to Dolby Surround.  You be the judge ;-)
: 

Alright enough already.  Here's a copy of a posting made sometime ago by
a THX designer.  I believe that this should clear up any misconceptions.
This is posted without permission so I hope I do not offend anyone.

John Adams


----------------
Newsgroup: Rec.arts.movies
Subject: The DEFINITIVE word on THX
Date: 26 Jun 91 15:14:13 GMT

I work at Skywalker Sound North, and the debate here about THX has made
it clear that few people (even the self-styled experts) understand what it
is. In the interest of education, i spoke with my friend Laura who
works at THX, and asked her to help out. The following is her response,
intended for the net:

WHAT IS THX?

Hi, I'm Laura Ackley, the THX System Designer.  I'm responsible for the
design of all professional and commercial THX Sound Systems, so I thought
I'd try to clear up some of the confusion regarding THX.

THX is a set of implemented design and quality control standards for theatre
sound presentation.  First, the actual physical theatre must meet certain 
acoustic criteria:  

It must have low background noise, (no loud air conditioners or projectors),
good isolation (so the lucky patron doesn't get to hear the gunfight in the
theatre next door), and specific reverberant characteristics based on the
volume of each individual theatre.  Also, the theatre can't have any nasty
slap echoes or reflections.

When an individual theatre meets these standards, it means that the dialogue
will be more intelligible, the high frequencies will reproduce clearly,
the bass will not build up excessively within the room, etc.

Most of the sound one hears in the movies comes from behind the screen,
from 3 channels usually.  (Occasionally 5, but THAT'S a different lecture!)

Because of this, the theatre must also have a good length/width ratio.
(i.e., No bowling alleys.)  From the visual standpoint, this
is of course desirable, and from the audio standpoint, it means having 
a good "stereo image" between the left and right channels, so that the patron
is actually hearing in stereo -- in every seat in the house!

Once a theatre is accepted for the aforementioned preliminary THX
criteria, the owner must choose the equipment to be used from a list provided
by us.  This list includes amplifiers, processors, screen and surround
speakers.  They can choose from a number of different products by various
manufacturers, but they all the products have been
objectively tested here to conform to very high standards.

These high-quality components assure a wider dynamic range and more
faithfully reproduced sound, plus adequate power for the room size.

Incidentally, the ONLY Cinema Processors which were accepted until quite
recently were made by Dolby, so any THX theatre was by default a "Dolby"
theatre... and ever-so-much more! 

Thus, we're not in competition with Dolby, we're a COMPLEMENTARY TECHNOLOGY 
to Dolby Processing.  Recently, Ultra-Stereo also had a processor approved for
use in THX Theatres.

Also, we're not in the business of selling any equipment, just assuring high
quality hardware in THX theatres.  The ONLY piece of hardware that is
specifically "THX" is an electronic crossover network, which is LEASED,
not purchased by the theatre.

Our design office takes the architectural plans for every theatre, and designs
the placement of the screen speakers and surrounds.  The screen speakers are
set in a special baffle structure behind the screen.  This structure has
certain acoustic properties, and the speaker placement within the structure
is coordinated to best match the projected film image.   

The surround speaker array is designed to provide optimum sound pressure
and audience coverage.  (and to integrate with the interior design whenever
possible).

We coordinate all this with the architects, owners, and equipment 
installers.  Once the theatre has been completed or successfully retrofitted,
our field technicians visit the theatre to align and "tune" the sound system,
then they measure the acoustical characteristics to make sure that they meet
our requirements.  This test data is then evaluated, and if the theatre
passes on all counts, it becomes a "certified" THX site.  

This, of course, entitles the theatre to use the THX name and show the
THX trailer.  (You know, "The Audience is Listening.")
The theatre is re-tested every 6 months to ensure that the quality of
sound remains high.

Our "philosophy" is to recreate the film soundtrack mixing environment as
closely as possible so that the audience hears the soundtrack as the film-maker
intended.  (This is all tied up in a DIFFERENT lecture on the history of
film sound....)

In conclusion, we're NOT a method of recording, encoding, OR processing
movie soundtracks!  We're a design and quality control system for the
PLAYBACK ENVIRONMENT.

This means that EVERY FILM will sound better in
a THX theatre, not just a select few.  The premium quality of a THX theatre
is often well-demonstrated by "special-effects-extravaganza" films, because
they are mixed with a very wide dynamic range and a lot of "loud" or "low"
sounds that might distort when played back through a lesser system.

THX theatres are especially well-equipped to handle the demands of the
new digital theatre soundtracks (like "Cinema Digital" and "SR-D") because
of their high performance and headroom.

SO, that's the scoop on the THX COMMERCIAL THEATRE and PROFESSIONAL MIXING
ROOM system.  The new Home THX system consists of a family of licensed 
products that various licensees have developed to meet specs. designated by
our engineers.  The pricing of the home system is dependent on the licensee.
These are sold through dealers like regular home A/V equipment, and we do
not design these systems.

Any questions about THX (serious only, please)  should be directed to:

Julie Petersen
Director of Marketing
THX Division
P.O. Box 2009
San Rafael, CA 94912

Thanks for reading, and I hope this helps clarify things!

Xref: sparky rec.video.releases:4398 rec.arts.sf.starwars:10515