This is topic 70mm Magnetic Sound Formats in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Dave Cutler (Member # 515) on 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.
Posted by Gordon McLeod (Member # 33) on 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 inDolby 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
Posted by Dave Cutler (Member # 515) on 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?
Posted by Gordon McLeod (Member # 33) on 09-09-2000, 04:47 PM:
Dolby70 with baby boom is 42
Posted by Dave Cutler (Member # 515) on 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?
Posted by Gordon McLeod (Member # 33) on 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.
Posted by Dave Cutler (Member # 515) on 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.
Posted by Gordon McLeod (Member # 33) on 09-09-2000, 06:41 PM:
Basically correct but some were SR
Posted by Ari Nordström (Member # 288) on 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! 
Posted by Dave Cutler (Member # 515) on 09-10-2000, 12:50 PM:
I don't know if it's true or not, that's just what I have heard.
Posted by Gordon McLeod (Member # 33) on 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.
Posted by Ben Wales (Member # 92) on 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.
Posted by Dick Vaughan (Member # 540) on 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 .
Posted by Martin Frandsen (Member # 74) on 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'
Posted by Brad Miller (Member # 2) on 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.
Posted by Gordon McLeod (Member # 33) on 09-13-2000, 05:32 AM:
What was almost as bad was ORC used to put the screws into the platter decks with a magnetised screw gun
That was the source of many a ticking soundtrack
Posted by John Walsh (Member # 168) on 09-13-2000, 10:33 AM:
I used to use one of those magnometer(sp?) to see if the sprockets, etc. were magnetized- but then I'd also check all the simple tools left out (screwdrivers, pliers, etc.)I woked in a place where the installer put one of the rectifers right next to the rewind table (a reel placed on the left spindle was less than 6 inches away.) Duh!
Posted by Gordon McLeod (Member # 33) on 09-13-2000, 06:59 PM:
I use a magnetometer too and always found it amazing how cinecanica Vic8 always put a 50 gauss magnetic in the oil pump windo 1/2" away from the inboard edge of the magfilm passing through the penthouse 
Posted by John Walsh (Member # 168) on 09-13-2000, 08:51 PM:
Now, now Gordon.. you know they come out.. Although, after removing that magnet, that screw-in sight glass would leak oil. I had to tighten...loosen..tighten...etc. until it stopped leaking...
Posted by Thomas Hauerslev (Member # 566) on 09-14-2000, 01:41 AM:
Regarding Martin´s note about "Out of Africa" and the hump on the soundtrack. I have to admit that I was that person. I have sort of left my signature on that print. It happend in 1986 at ABCinem+D where I splized it together after getting it from the 9 month run at Imperial Bio.Regards, Thomas
Posted by John Pytlak (Member # 331) on 09-14-2000, 06:37 AM:
Thomas, how could you, of all people, do such a thing to a precious 70 mm print? 
The important thing is to learn from our mistakes, so they won't happen again. Sharing these "oops" experiences here will help others avoid the same mistake.
For example, a good friend who is a projectionist at a small 3-plex near Rochester just called, and told me that he accidently "dumped" a print on the floor while trying to move it by himself (no platter reel or clamps on the print). Took him from 8:00pm until 1:00am to put it back together. He had read my comment here about "moving an unclamped print unassisted is like Russian Roulette -- 5 times out of 6 you get away with it, the 6th time, you have a real mess on the floor", but he was rushed, and did it the wrong way anyway.
Good news was that it was on Kodak VISION print film with the anti-static backing, so little dirt was picked up from the floor. But the print is now full of the splices he needed to untangle it.
------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Posted by Dick Vaughan (Member # 540) on 09-14-2000, 07:10 AM:
Well Thomas you just reinforced the argument for DTS 70.Don't think you can magnetise that!!Anyway what you did is nothing compared to someone I heard of who stored 70mm prints behind the scren next to a sub bass speaker. 
Posted by Gordon McLeod (Member # 33) on 09-14-2000, 10:06 AM:
John they all got removed real fast and some silicone stopped any leaks but what a dumb pace to put it in the first place
Posted by Brad Miller (Member # 2) on 09-14-2000, 02:00 PM:
Actually, there is a right way and a wrong way to pick up a dumped print off of the floor. I'll have to get some junker print and intentionally push it off to make a "how to" page. Done properly, no one should even know it was dumped.
Posted by Ben Wales (Member # 92) on 09-14-2000, 02:53 PM:
There is a Art House cinema in Ireland that just have installed two Philips DP70's and a Potts 35/70 Platter.Are these suitable to run old 70mm prints?.
Posted by Aaron Sisemore (Member # 145) on 09-14-2000, 03:19 PM:
>>two Philips DP70's and a Potts 35/70 Platter. Are these suitable to run old 70mm prints?<<Absolutely. Though i would lean toward a Christie AW370 for the platter, the Potts should do fine. and you can't get much better than the DP70...
Aaron