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Imax Sound System
IMAX Dome Luxury,
Copenhagen, Denmark
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This article first appeared in
..in 70mm
The 70mm Newsletter |
Written By: Chief projectionist Rene Sørensen, Tycho Brahe Planetarium & Omnimax Theatre.
Pictures by Thomas Hauerslev |
Issue 50 - September 1997 |
Believable
Effects
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The
writer is seen here standing on top of the IMAX dome beside one cluster of
speakers. Each channel consist of JBL speakers model 2404 H tweeter, 2445 J
driver, 2123 H midrange and 2245 H woofer.
Imax theatres
require a sound system able to produce believable effects and operate
reliably at unusually high power levels. The Imax sound system by Sonics
provides extremely high sound quality that does full justice to the unique
film presentation. A Sonics sound system operates in an environment which is
quite different acoustically from most other theatres. The Imax film program
depends on the optimum performance of the combined projector and sound
system to achieve maximum audience impact.
In 1988, Imax acquired Sonics Associates Inc. as an affiliate. Alabama based
Sonics is a world leader in sound system design and offers customers the
benefits of more than 26 years of research and hands-on experience in the
IMAX theatre network.
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Further in 70mm reading:
IMAX Projector
The First 70MM IMAX
Cinema in England
The Passing of Bill
Shaw - IMAX Pioneer
IMAX, IMAX Dome,
IMAX Solidi, IMAX 3D, IMAX Magic Carpet, IMAX HD
Internet link:
Tycho Brahe Planetarium
& Omimax Theatre
Gammel Kongevej 10
1782 Copenhagen V
Denmark
Phone: +45 3312 1224
Web site
www.tycho.dk
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IMAX Sound in the Theatre
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The 35mm sound dubber with 6 channel magnetic IMAX sound. To
the left all the amps are located.
I will try to
describe how the audio system works, from projector to the audience. Sound
for an IMAX or IMAX Dome film program historically has been supplied on 35mm
sprocketed magnetic film which runs at 90 feet per minute (45.7 cm/sec.).
The sound reproducer, often called a dubber, is located in the
projection room.
This multi channel playback unit was originally developed for film studios
where banks of them are used when mixing sound tracks. It provides
exceptionally high quality sound reproduction and feeds the six channel
system plus sub-bass through IMAX TAC-86 multi channel audio control
computer. Maximum playing time is one hour with a reel capacity of 5000 feet
(1500 m).
An interlock circuit between the projector and the reproducer maintains
frame-to-frame synchronization of projected picture and sound. A rotary shaft
encoder required for synchronizing audio reproduction is installed in
the IMAX projector.
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IMAX Digital
Sound
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Most newer
IMAX films are now using the IMAX digital sound DDP designed by Sonics. DDP
is short for Digital Disc Playback. The system is a digital sound
source specifically made for IMAX. Sonics uses compact disc technology to
create the highest quality sound delivery possible today. Wide frequency
response, dynamic range and the accurate perception of time are the
attributes of DDP. A frequency response of 20 – 20.000 Hz is maintained
over the entire audio spectrum of ten octaves. Six octaves is found in
conventional cinemas. Three CD’s are used for each soundtrack, one CD for
every 2 channels. The audio is sent to the Sonics TAC-86. From the TAC-86
the signal is sent to the computer-controlled 1/3 octave equalization unit,
developed for IMAX. This unit matches the sound system performance to suit
the acoustics of the particular theater in which it is installed. The
equalization can also be used to compensate the response of particular films
for optimized playback in a particular theater.
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Power Amplifiers
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The complete
23 meter dome seen from above.
After the
equalization, the signal is sent to the power amplifiers. The amps deliver
more than 2000 watts per channel. The entire system is more than 15000
watts. The six audio channels are fed to a 4-way JBL speaker array. Every
section is equipped with JBL models no: 2404 H (Ultra-High Frequency), 2445
J (Wide Range), 2123 H (High Power Low Frequency), and 2245 H (Medium
Efficiency Extended Bass). They are located to give strong directional
effects and placed as follows: Channel 1 Left rear (theater), Channel 2 Left
screen, Channel 3 Center screen, Channel 4 Right screen, Channel 5 Right
rear (theater), Channel 6 Top of screen.
A special subwoofer with 8 JBL model 2245 H (Medium Efficiency Extended
Bass) in one enclosure (a cabinet huge like a caravan) is provided to extend
the range of the main channels and reproduce such sounds as rocket launches,
thunder, close-flying aircrafts, etc. at loudness which approaches that of
the original sound source. Because the lowest pitched sounds that human can
hear are also felt, this enhances the realism, making the audience feel they
are actually experiencing the event.
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The writer
is seen here standing inside the subwoofer. The subwoofer is equipped with 8
JBL 2245 H woofers.
The group of sub-bass speakers, located at the front of the theater behind
the screen, is fed a mix of low frequency sound derived by the TAC-86 from
all six channels. The power amplifier for sub-bass is more than 3000 watts.
The price for the Sonics sound system is more than 300,000 $.
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Hear All
Details
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The
IMAX Dome cinema in Copenhagen.
After 7 years
of work with Sonics sound system, there has never been one complaint about
the sound system, except maybe that it is too loud. I have listened to the
system many times with hi-fi enthusiasts, and they always say it is the best
cinema system they have heard. Because of the enormous power you can always
hear all details.
Thanks to Sonics for the good experience.
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Updated
28-07-24 |
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