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Topic: 70mm Magnetic Sound Formats

Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 09-09-2000 10:04 AM

What are the names for the different 70mm Mag sound formats?

Academy is 6-track with 5 screen channels and a surround channel, right? Todd-AO is 6-track with 3 screen channels, split surrounds and a sub track, right? Dolby A-type or SR was only used with the Todd-AO format, right? Was there ever 4-track on 70mm? Am I right, or am I way off? Are there any other formats that I haven't heard of?

I haven't had the pleasure of running 5 perf 70mm (so I don't know a lot about it yet) and I am trying to write a proposal to convince my company to install a 70mm mag soundsytem so we can run older 70mm films on our large format (15/70) screen. I just want to make sure I have the different formats correct.

Thanx for your help.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-09-2000 01:07 PM

ToddAo is five screen channels and mono surround
If it has no noise reduction it is format 40 on a CP200
If it has noise reduction it is format 41 (A or SR is dependent on which cards are plugged in)
Dolby 70 with baby boom is 3 Screen channels (LCR) Lc/Rc is summed into the sub and mono surround
Noise reduction is dependent on which cards are plugged in

Dolby 70 splitsurround is format43 and is 3 screen channels
The lowfrequencies on Lc/Rc are summed into the subs
above the crossover point the high frequency of Lc and the lowfrequency on track 6 feed Left Surround(P)
The high frequency above the crossover point on Rc adn the lowfrequency on track 6 go to the right surround (Q)
The noise reduction is dependent on which cards are plugged in
The crossover point has change several times since it's introduction with Superman and the first SA5's for the CP100's
Hope that helps

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 09-09-2000 04:42 PM

So Dolby 70 with Baby boom is that format 42?

The rest was clear, thanx Gordon. I guess I was a little off, huh?

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-09-2000 04:47 PM

Dolby70 with baby boom is 42

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 09-09-2000 04:59 PM

Ok, thought of another question.

Are format 42 and 43 the only 70mm mag format avaliable on the CP-500? Is there any way to add more formats other than getting the Panastereo sub-rack?

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-09-2000 06:00 PM

42 and 43 are the only supported formats unless you want to go into the software and pin patch a sum of Lc into L and Rc into R
but some older todd ao prints might act a bit weird
As far as cost is concerned the sub rack which will provide you preamps and noise reduction would be the best
I am a little leary of useing the dubbers MPU as most dubber heads have a different impedance than a projectors head and maynot eq properly
What make of dubber and what make of preamps is it some have presets that would help because otherwise you would have to re eq the preamps when changeing back and forth between the simplex and the dubber.

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 09-09-2000 06:21 PM

I hadn't actually thought about using the dubber preamps for the Simplex. I agree that it isn't really an option. I was thinking about trying to find a Dolby MPU-1, but then I would lose the Lc and Rc.

Or would that be a viable option to have 70mm Mag for not a lot of cost? From what I understand there weren't many real prints with 70mm Mag SR noise reduction, so that's not really necessary. Todd A-O isn't that common, and those that are I have heard that you are required to run changeovers with, and I have to run off a platter. So that really eliminates everything except for 42 and 43. Are most films on 70mm in 42 or 43?

Any input is apreciated.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-09-2000 06:41 PM

Basically correct but some were SR

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Ari Nordström
Master Film Handler

Posts: 283
From: Göteborg, Sweden
Registered: Jan 2000

posted 09-10-2000 12:44 PM

Why can't you run Todd-AO prints on a platter? Are you not allowed to splice the reels together?

An MPU in itself won't lose the Lc and Rc channels; that happens because the CP500 can't handle those channels. The only means for you to get Todd-AO is either a Panastereo unit or an older Dolby processor (in effect the CP200 since the CP100 is way too old, and would give you other problems...)

Dolby, bring back the CP200 or make an AUX rack for the CP500! Please!

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 09-10-2000 12:50 PM

I don't know if it's true or not, that's just what I have heard.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-10-2000 01:52 PM

Certain film archives will not permit any of their prints on a platter or mounted up on large reels in some cases.

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Ben Wales
Jedi Master Film Handler

Posts: 602
From: Southampton. England
Registered: Jul 99

posted 09-10-2000 02:13 PM

The Art House cinema I worked at did run old 70mm mag prints on a platter without any problems as far I can remember, but carefull inspection for sprocket damage etc is the upmost importance when running old 70mm prints, they can certainly split into two prints on any platter system!.

The Pictureville Cinema at Bradford, Yorkshire in England run all their 70mm prints of a Platter and these include some very rare achive prints.

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Dick Vaughan
Phenomenal Film Handler

Posts: 1032
From: Bradford, West Yorkshire, UK
Registered: Jul 2000

posted 09-13-2000 01:57 AM

Ben ,What you say is partly correct. We do run our 70mm prints off a platter but we are not allowed to run certain prints because of this. The National Film Archive requires their 70 prints to be run on change overs as they don't want the heads and tails removing.However as most of their prints were standard theatre release prints before passing to the archive they have usually been topped and tailed on many occasions .

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Martin Frandsen
Master Film Handler

Posts: 270
From: Denmark, Europe
Registered: Jun 99

posted 09-13-2000 02:31 AM

Someone ran a 70mm mag print overhere on a platter. The projectionist did not have any Bevan Poo's, so he used magnet's on the platter. Result, a tumbing noise every sec during the end credits!

BTW the print was 'Out of Africa'

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 09-13-2000 03:22 AM

Probably ran it on a SPECO or other magnetic deck platter...a VERY bad idea for any magnetic 70mm prints.

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