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Life With THX In
Hollywood Part 1
of living with the technology...
This article first appeared in
The 70mm Newsletter
Written By: Paul Rayton, senior projectionist at the
Hollywood Galaxy 6, Hollywood Boulevard, Hollywood, USA.
Issue 47 - December 1996
is senior projectionist at the
Hollywood Galaxy 6, Hollywood Boulevard, Hollywood, USA. Picture by Thomas
The THX Concept
The THX concept was born in 1980 out of George Lucas┤ desire to create the
ultimate theatre experience. His goal was -- and remains -- to assure that
the quality of the original picture and sound of a film is delivered into
each and every venue so that audiences can enjoy films as the filmmaker
intended. Following three years of research and development, the first THX
Sound System was installed in two commercial movie theatres in 1983 for the
release of "Return of the Jedi" amongst 17 x 70mm and 6-track Dolby Stereo prints
in the Los Angeles area.
For much of the moviegoing public, there is a considerable mystery about
what REALLY is in a "THX". And, actually, THX is more a set of
guidelines and specifications than proprietary equipment. Following the
specifications will enable a given cinema to reproduce sound through
components that have met certain levels for performance (based on tests
performed by the THX division of Lucasfilm), which will theoretically make
for high quality performance in "your local THX cinema".
The letters comprising the "THX" name and logo are now almost
commonplace. They are seen in theatres, of course, but now can be seen at
the end of some films. They are also increasingly seen on high-end video
systems and even videotapes. The THX concept was originally developed as an
integrated approach toward improving the overall sound experience in movie
theatres. These recent diversifications into "Home THX" and the
application of THX to videotapes are demonstrations of commercialism which
(in my opinion) can have possibly less-than-beneficial results. More about
that later on.
As time has gone by, over the last several years, Hollywood has obsessed
more and more on sound, and left the picture situation almost forgotten. Not
completely forgotten, but almost! But truly, I have had shows (special
screenings) where I could see an obvious problem on the screen...but the
post-production personnel were so worried about a perceived 1/2 decibel
level adjustment in a stage channel that they never even saw the visual
problem. This "blindness" is quite hilarious, really, when a
significant number of audio professionals feel that, in the main, most
people will only perceive level differences of about 2 dB! A few years ago,
THX put out some publicity buttons, saying "Digital Sound in a THX
Theatre -- The Ultimate Film Experience". What they forgot, at that
time, was that the TRUE ULTIMATE cinema experience would be to use 70mm as
the picture source!
I'll give you a quick summary of my theatre, its location and equipment, and
then tell a bit more about Life With THX.
My cinema, the Hollywood Galaxy 6, is a fairly new (opened Nov., 1991)
multi-screen operation. We are located in the heart of Hollywood, just one
block west of Grauman's Chinese theatre [now called "Mann's"
Chinese, reflecting the name of the man and the company presently operating
the place]. The Chinese is one of the most famous cinemas in the world. Also
nearby, on the other side of Hollywood Blvd., is the El Capitan, which the
Disney studios use as their west coast showcase location. The El Capitan
often presents films with an accompanying live stage show. And, several
blocks away, on Sunset Blvd., you will also find the Cinerama Dome theatre.
As you can see, we are in prestigious company. And our customers tend to be
from "show biz" fields, too. Directors, Producers, actors and
actresses, and people from all the other crafts involved in making films
join the public walking in our doors. I've even seen Tom Holman, who created
the "THX" concepts and whose name is the "TH" in THX,
watching films at our cinema. (I worry when I see him here: will we be
somehow criticized at his next seminar? He usually doesn't mention specific
names, but he does talk about bad experiences he observes, so it keeps us on
the alert. I belive he's been reasonably pleased by conditions at the
Michrophones amid the seats for audio measurements in Galaxy screen # 2.
Picture by Paul Rayton.
With all the historic and famous cinemas nearby, we must offer something
special, too, which we try to do with top notch images and sound. We -- all
of these Hollywood cinemas -- also operate a little bit differently than
many cinemas in other parts of the country (and the world) because: we are
so near to the studios, we are visited by projection engineers and sound
engineers VERY often, and our systems are probably adjusted
("tweaked", they sometime say) much more frequently than anywhere
else in the world!
Further in 70mm reading:
Life With THX In Hollywood Part
Revolution: The Phantom Improvement
"To DLP or Not to DLP. That
is the Question !" "Reporter's Notebook"
View of a Dolby MPX-4, a michrophone multiplexer. This allows one RTA (Real
Time Analizer) to hear sound in the auditorium as if it were in 4 different
locations. Picture by Paul Rayton.
The 6 screens of my cinemas are all operated with Cinemeccanica projectors.
We have 3 "THX"-equipped screens, and each of them use the
"V-8" projector, which is dual 35-70mm capable. Each of these have
about 520 seats. The other, smaller, cinemas use "V-5" machines,
and are not THX. All 6 screens have curtains, all 6 can play DTS digital,
plus we have 2 with Dolby SR.D and one SDDS. The SR.D and SDDS are placed in
the THX houses, cohabiting with DTS.
I presume that most readers of this article understand reasonably well what
is THX, but for anyone not acquainted, here is a brief summary: the THX
system is primarily three things:
1.) A large, solid wall, built immediately behind the screen surface, with
loudspeakers mounted into it;
2.) A sound system "crossover network" at the amplifier rack that
takes the various audio elements, separates out the lower and higher
frequency components, and directs those to the appropriate amplifiers and
3.) A set of architectural, electronic, and acoustic specifications which
are incorporated into the auditorium, either during original construction,
or later on, in a "retrofit".
That's basically IT. That's the THX system. There are two other things to
keep in mind, though:
4.) All amplifiers and speakers must be "approved" by the THX
5.) The various cinemas must be periodically re-certified by THX if they
wish to continue to be able to advertise the film as playing "in
This is because, even though proper equipment may have been originally
installed, it may have changed and/or degraded its performance as time
passes. Re-certification allows for corrections to be made if something goes
out of compliance.
As you can see, the THX system is thus, largely, maintenance free once it is
installed and certified. There's not much adjustment to do to it, assuming
it is receiving good information from the projector sound pickup system(s)
and that all speakers are working correctly.
If you turn off the "THX Monitor", the device which also contains
the THX crossover device, you lose ALL sound, and you will quickly be
notified of BIG problems with your show! With the advent of the new digital
processes -- all of which can deliver a "knockout punch" to your
speakers if you let them! -- we have had much more trouble with speakers
than we did a few years ago.
The most common problem is a damaged high-frequency driver. If this happens
to the center channel, you can lose all intelligibility of dialogue and may
have to shut down to replace it. (Virtually all dialogue comes through the
center channel.) The most notorious recent event like this happened next
door at the Chinese Theatre (thank God!), during the invitational premiere
of Schwartzenegger's "Eraser". A loud sound of some sort, in the
middle of the film, burned out the high frequency driver of the center
channel. Dialogue was totally muffled, being heard only through the low
frequency (below 500 Hz) components of the center channel.
Needless to say, within seconds, dozens (or so it seemed) of Warner Brothers
executives were in the projection room, and...well, it's not a situation
you'd ever want to be in! Usually, failure isn't so catastrophic that we
must shut down, and we can replace the problem driver during an intermission
(if time permits), or the following morning.
A 4-michrophone multiplexer. Picture by Paul Rayton.
The second most-common problems would probably be found in the
sub-woofer(s). With the many explosions and blasts, and loud music, found in
commercial films these days, the subwoofers get a good workout. Sometimes,
their internal protective devices (if any) just don't do the job. Again,
it's the dynamic range of the digital tracks (along with the apparent desire
of producers and directors to deafen the audience) that makes this happen.
Subwoofer power amplifiers can give up, and/or their speaker cones can rip.
The THX crossover system is happy as can be to pass all these loud,
wide-ranging signals along to the speakers, because it (the THX crossover)
isn't designed as a "limiter". It is intended to pass on the best
information possible to the amps and speakers on down the line. And so it
does, with these sometimes troublesome results!
In our Galaxy THX installations, all the speakers are easy to reach -- if
you are a monkey! We humans, on the other hand, need to get up on rather
long ladders for access. This design may assist in better THX sound, but it
doesn't make the repair process simple. However, it also serves as theft
protection for equipment backstage. Fortunately, counting all our 6 screens,
we only have to climb up anywhere about once a month.
I myself keep a Component Engineering Co. pink noise generator card at the
cinema. It includes an audio spectrum tone generator so that I can check
each channel's operation. If I suspect a damaged driver somewhere, I can
usually locate the problem rapidly, and replace it with one of the 3 spare
high-frequency drivers we keep on hand for such cases.
Another aspect to the operation of THX is how it is adjusted. The THX
crossover has basically no adjustments; as noted before, it is a
pass-along-the-information device. And of course, the THX wall behind the
has no "adjustments".
Where things get really interesting, however, is the adjustments and
settings for what goes into the THX crossover, and who makes those
As mentioned earlier, with the proximity of the major studios, we get
visited quite often by representatives of the studios and/or the various
sound companies. The problem is, there is no real, true, exactly
standardized way to measure and set up something "alive" like
sound waves bouncing around in a room.
To be continued in The 70mm Newsletter issue 52.
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