Not sure what you mean. A "very large" room is a different acoustic environment to a "domestic scale" one; the subwoofers are clustered together to increase SPL through mutual coupling (rather than putting them in separate locations around the room for a smoother bass response.) The design, positioning and angling of the other screen speakers is intended to provide good room coverage, i.e., trying to optimise for even levels and frequency response from front to rear whilst avoiding "throwing" the sound to places from which higher frequency sound reflections would be detrimental, such as the ceiling or back walls. (Not sure this video shows them after alignment has been done with a laser, they're just left suspended in somewhat random directions.) There is an upper centre speaker which is found in full 6/12 channel IMAX installs. It's a legacy from earlier days of IMAX, and I'm not sure if it's even used on any modern releases. It is (or certainly has been) omitted in smaller scale multiplex-type IMAX screens.

New technology can't even come close to the approximately 12K-16K resolution of IMAX film.

I think I remember 3 screen changes, first was for the digital installation. That screen was found defective… the part of the screen that was defective was sent to the manufacture for analysis. Then the screen was changed again when the laser was installed.

Hi, The brain lights or take off unit lights are indicators to the operator that the sensors mounted in the film gap of the take off unit are working. As you say red is indicating the drivers are slowing the patter and the green indicates a speed up, all very sensitive and quickly controlling the demand of film feed to the projector.

Thank you Sarah for your message and all the best to you.

These are the only PTRs used, the colour changes over time from a light green when new to a dark burgundy from absorbing the photo guard on the film.

If you look at 07:00 to 07:20 you will see I’m winding the film on the take up platter. Once the film is finished, it is ready to play again as the leader is in the centre of the platter where the film plays out.

Hi, that is called a dubber, it was originally designed as a 6 channel audio recorder. The head was changed for play back as a sound source for trailers. It runs magnetic coated 35mm film stock containing 6 channel sound.

@@HughDenbigh Wow, That's good to know. Great work

I believe I taped this in the early 90s

Hi, yes the entire sound system relies on frame count of the film. If the frames are not replaced after a crash the sound sync will be out. When ever a crash occurs resulting with damaged film, that damage must be accounted for and replaced with generally black frames by counting frame lines or sprockets holes. If the repair is large in terms of frames, this will become noticeable on screen. Depending on the severity, the film may need a replacement real. Replacing with black slugs can be very difficult to get right, a reference frame line near the damage in the film has to be found. As the film runs through the projector, a small electro/mechanical spinning wheel with optical sensors mechanically attached inside the projector sends pulses to the sound system. These pulses represent the frames of the film. So physically the film frame count from start frame to last must be maintained.

@@HughDenbigh OMG ! Thank you for explaining it ! An optical soundtrack on the film is so much simpler !! Ha !

Hi, 1570 film doesn’t contain any sound information. The 35 mm film is soundtrack played on what is called a dubber that has been largely phased out. In this video it is primarily being used as soundtrack for previews. All sound for IMAX 1570 is synced through frame count passed to and synced to sound equipment.