Film-Tech Forum ARCHIVE: Specifications of the Magnetic Sound?

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Posted by Christian Mueller (Member # 1036) on 09-29-2003, 03:47 AM:

Hi!

First of all:
This is my first Posting here. Big Compliment to the Producer(s) of this GREAT Site. Is one of my Favorite in the Net! [thumbsup]

My Question:
Everyone knows everything about the conventional optical Dolby Formats and the three digital Sound Systems.

But I'm not able to find any Specifications about the Magnetic Sound. Just:

http://members.aol.com/cds3570/specs1.jpg

and

http://members.aol.com/cds3570/specs2.jpg

But I really can't imagine that these Specs are correct.

Can you tell me the true Specs and for example the Frequency Ranges of the 35mm-4-Track, 70mm-Conventional, 70mm-Dolby-A and 70mm-Dolby-SR Formats? Or the Dynamic Range, Distortion, Noise Level and Channel Separation of these Magnetic Sound Systems?

Thanks a lot.

Chris from Vienna

Posted by Gordon McLeod (Member # 33) on 09-29-2003, 10:19 AM:

There is a lot of variable involved and in many cases varried from sounding facility to another
Also the oxide used made a big difference
The Standard Formats for Comag prints were
35mm

Format 20 35mm mag no nr no surround
Format 21 35mm mag no nr with surround
Format 22 35mm mag NR (dolbya) no surround
Format 23 35mm mag NR (dolbyA) with surround

70mm
Format 40 6 track toddao configuration no nr
Format 41 6 track toddao configuration with nr (dolby a typical)
Format 42 6 track with baby boom (LC RC bass info only) with nr (dolby a typical but could be SR no code number different though)
Format 43 6 track with baby boom and split surrounds with NR (typically Dolby a but could be sr)
The level of reference could be all over the place as well as the recording eq even though dolby applied acadmeny filters to all non nr formats some of the 4 track stuff in particular was wide range. The level is officially 50% modulation is 185nwb currently
On a dubber full coat 35mm mag is up to 8 channels and the audio cyclopedia is the best source of response covverage with the SMPTE and CCIR curves discussed

Posted by Stephen Furley (Member # 1277) on 09-29-2003, 10:58 AM:

Gordon, is there a format number for mono mag on 35mm?

Posted by Christian Mueller (Member # 1036) on 09-29-2003, 11:25 AM:

Thanks for your Answer! [beer]

And what do you think was/is the best possible Sound Performance of all Mag Formats? I guess 70mm-Dolby-SR?

What Frequency Range, Distortion, Dynamic Range, Noise Level and Channel Separation was/is possible at the Best 70mm-Dolby-SR Presentation?

quote:
Gordon, is there a format number for mono mag on 35mm?

Was there any Filmprint with mono Mag? I only know Magopticals incl. 4-Mag-Tracks and a very small optical Monotrack on the same 35mm-Print...

Chris

Posted by Stephen Furley (Member # 1277) on 09-29-2003, 11:47 AM:

There was a mono mag combined format, but it was almost never used. I've seen it once. More common was a separate track.

Posted by Christian Mueller (Member # 1036) on 09-29-2003, 11:54 AM:

Which Filmtitles? And which of the 4 Mag-Tracks was it (maybe Track 2)?

Chris

Posted by Stephen Furley (Member # 1277) on 09-29-2003, 12:04 PM:

I can't remember, it was many years ago, I remember that it was sent to a cinema which couldn't run it, and couldn't get another print in time, so they had to cancel a show, which suggests that it may have been mag only, but I'm not sure. the projectionist did show me a roll of film, but I can't even remember what perfs it had. This was when I was still at school, so it would be over thirty years ago.

Posted by Hugh McCullough (Member # 1542) on 10-01-2003, 04:11 PM:

Stephen. I believe the film that you are thinking of is 'Summer Holiday'.
I remember showing this in mono mag with standard sprocket holes. There was a mono optical track under the mag stripe.
The idea was that when cinemas equipped with mag had finished with the print the stripe was washed away leaving an optical track for use in non mag houses.
This was the first film we showed at the ABC Croydon on the, then, new Philips FP20s that we had on evaluation test for philips.
They also had the pulse discharge lamps. Hopeless for a 135ft throw.
In theory if say a fuse blew we were supposed not to replace it, but to inform Philips and they would send an engineer down to find out why it blew.
Oh yeah, we followed this instruction to the letter.

Posted by Peter Hall (Member # 695) on 10-01-2003, 11:40 PM:

Hugh -

I note you have worked in the ABC Croydon - I guess you know but it closed a few weeks ago. Twas in a pretty sad state when it closed, with a very poor fourth screen (in the bar adjoining screen 2) never having seen much business. Curious to know when you were there - the site had obviously really been something in it's day (did it have 70mm in screen 2 and not screen 1?).

Seats remained for the bulldozers, all projection gear stripped although the Westrex and Vitavox speakers, some stuffed with JBL drivers, remain

Regards

Posted by Hugh McCullough (Member # 1542) on 10-02-2003, 06:47 AM:

Hello Peter.

I was the Chief of the ABC Regal Purley, but used to run both the
Purley, and Croydon cinemas when the Croydon Chief was away being
stage manager on the live shows that some ABCs had at the time.
Blackpool being one of these venues.
The 70MM was, for some unknown reason, put into the smaller screen 2,
and not, as one would expect, the large theatre No1.
The only 70MM film I can remember being shown was 'Dr Zhivago',
but there might have been others.
The last time I was in the cinema was as a patron sometime in the
middle 1970s.
Can not remember what the film was.
In the 60s it used to be used for stage shows, Bert Weeden,
the Walker Brothers, and other pop stars of the day.
At this time it was the ABC circuit southern England flagship.
I never knew that a fourth screen had been added.

By the way, I have not yet received my 16mm spacing.