Published on Nov 12, 2015
The IMAX (Image Maximum) system has its roots in Canada where multi-screen films were the hit of the fair. A small group of Canadian filmmakers Graeme Ferguson, Roman Kroitor and Robert Kerr decided to design a new system using a single, powerful projector, rather than the cumbersome multiple projectors used at that time.
The result is the IMAX motion picture projection system, which would revolutionize the giantscreen cinema. IMAX delivers just that on a screen four times the size of conventional movie screens. Multi channel digital sound with excellent picture quality gives the viewers the feeling of being present.
IMAX was premiered at the Fuji Pavilion, EXPO '70 in Osaka, Japan. The first permanent IMAX projection system was installed at Ontario Place's Cinesphere in Toronto in 1971. IMAX Dome (OMNIMAX) debuted at the Reuben H. Fleet Space Theatre in San Diego, CA in 1973. Sonics Associates of Birmingham, Alabama developed the IMAX
digital sound system. In 1993, Sonic introduced the IMAX 3D sound system with 10 channels.
IMAX -3D is a new motion picture process that creates the illusion of depth (or 3D) by projecting on the screen an image for the right eye, then an image for the left eye (30 times per second). Special goggles allow only one eye at a time to see the screen. The liquid crystal goggles are in sync with the projector via infrared signals beamed at the goggles on your head.
Theater speakers produce 8 channels from 4 CD disks synchronized with the15-perforation 70mm filmstrip running through the projector horizontally past a 15,000-watt lamp at 48 frames per second. The 3D headset has 2 additional channels for the binaural Personal Sound Environment (PSE). Binaural sound emanates from the headsets' two small speakers, just above and slightly in front of your ears; they cover all but the frequencies below 100 Hz.
Low bass is handled by a pair of subwoofers behind the giant screen. Four full-range speakers, also behind the screen, keeps sound tied solidly to the films image even if you turn your head; if you have trouble imaging binaurally (as some people do), these speakers will prevent front sounds from seeming to come from the sides or rear. Two more speakers, in the rear of the theater, carry only surround ambience; the headset's binaural speakers carry sounds that are supposed to originate behind you.
Eight channels of an 18,000-watt, 10-channel amplification system feed the speakers; the other two channels feed the binaural signals to the headsets. These amps are fed from four audio CDs, computersynchronized with one another and with the projectors. The headsets can receive four separate soundtracks, so a movie could be presented in
different languages simultaneously if the theater provides enough channels.
The difference between the IMAX sound system and the surround systems in conventional theaters is that the typical IMAX screen is close to a conventional 4:3 aspect ratio, but much, much bigger. So you have a great deal of vertical, which gives you the opportunity to do a 'voice-of-God' loudspeaker. IMAX system power varies depending on the size of the room, but it is typically in the range of 12,500 watts.
The power is not there for the loudness; it's there for clarity and freedom from distortion. The enclosures are three-way systems using components custom-designed and manufactured to specifications and combines four low-frequency loudspeakers in each cabinet with nested high- and mid-frequency horns.
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