Film-Tech Forum ARCHIVE: Dolby Stereo s/n ratio and frequency range ?

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Posted by Lionel Fouillen (Member # 1475) on 10-14-2006, 02:01 PM:

Hello,

I'm writing a paper about Dolby Stereo and miss some information about signal to noise ratio. I searched Google but found nothing about it. So I would be grateful if somebody could tell me what the signal to noise ratio (dB) of the following media is:

- 35mm SVA Dolby A
- 35mm SVA Dolby SR
- 70mm mag Dolby A
- 70mm mag Dolby SR
- Dolby Digital
- DTS
- SDDS
- CDS

Also, what is the usable frequency range (Hz) of 35mm SVA, magnetic 70mm and digital sound for the movies ?

Thank you !

Posted by Jeffry L. Johnson (Member # 453) on 10-15-2006, 12:05 PM:

Dolby Technical Library
Are Movies Too Loud?

Digital Film Sound Formats

Posted by Lionel Fouillen (Member # 1475) on 10-16-2006, 12:03 PM:

Thanks for the links, Jeffry.

Posted by Manny Knowles (Member # 1171) on 10-17-2006, 06:36 PM:

Be sure to check out the book "The Dolby Era" by Gianluca Sergi.

Posted by Michael Coate (Member # 757) on 10-18-2006, 01:05 AM:

I've had that book on order for a while. I'm beginning to wonder if they printed only enough copies for the author and his mom!

Manny, I'm assuming you think the book is worthwhile since you're recommending it to Lionel. Is it?

I did some Web searching and found a review where the reviewer mentions the book author failing to account for the many different versions of Dolby Stereo and the ambiguity of presentation notations found in newspaper ads and on theatre marquees. So in light of this, I'll take a moment to copy-and-paste some information I posted in the "quick guide to 35mm optical (mono vs. Dolby stereo) & Dolby Analog NR formats by year" thread.

Without knowing the scope of Lionel's project, this info may not be of any interest (or he may already have it or something similar). But here goes.

Year of Introduction: film gauge and sound format, noise reduction type
First and/or early significant titles released in format

Introduced 1974: 35mm optical, mono, A-type Noise Reduction
"Callan"

1974: 35mm magnetic, 3-track, A-type NR
"The Little Prince"

1975: 35mm optical, 3-channel, A-type NR
"Lisztomania"

1975: 35mm magnetic, mono, A-type NR
"The Rocky Horror Picture Show"

1975: 35mm magnetic, 4-track, A-type NR
"Nashville," "A Star Is Born"

1976: 70mm magnetic, 6-track (5-screen, 1-surround), A-type NR
"Logan's Run," "A Star Is Born"

1976: 35mm optical, 4-channel, A-type NR
"A Star Is Born," "Star Wars," "Close Encounters Of The Third Kind," "Saturday Night Fever"

1977: 70mm magnetic, 6-track "baby boom" version #1, A-type NR
"Star Wars"

1977: 70mm magnetic, 6-track "baby boom" version #2, A-type NR
"Close Encounters Of The Third Kind," "Days Of Heaven"

1978: 70mm magnetic, 6-track "split surround," A-type NR
"Superman," "Apocalypse Now," "Pink Floyd: The Wall"

1986: 70mm magnetic, 6-track "baby boom," SR-type NR
"Star Trek IV: The Voyage Home"

1987: 35mm optical, 4-channel, SR-type NR
"Innerspace," "RoboCop"

1991: 35mm digital, 6-track (5.1), SR-type NR
"Star Trek VI: The Undiscovered Country," "Newsies," "Batman Returns," "Honey, I Blew Up The Kid"

Posted by Michael Schaffer (Member # 1204) on 10-18-2006, 08:56 PM:

That indeed sounds (pun intended) like an interesting book:
http://www.amazon.com/Dolby-Era-Contemporary-Hollywood-Popular/dp/071907066X/sr=8-1/qid=1161222559/ ref=sr_1_1/104-6864809-9683167?ie=UTF8&s=books
But pricey. Apparently, they have affordable paperback editions, though.

This also looks quite interesting:
http://www.amazon.com/Hollywood-Theory-Non-Hollywood-Practice-Soundtracks/dp/0754605825/ sr=8-9/qid=1161222559/ref=sr_1_9/104-6864809-9683167?ie=UTF8&s=books
Although it is more about film sound esthetics than technology - but those two areas can not be really separated anyway.

Which is why I always doubt that "film makers" who do not understand at least the basic technical parameters of film technology can not really create good content - how can they make best use of a tool they don't understand? Yet most film school people have *no clue* about all that.

Posted by Michael Coate (Member # 757) on 10-18-2006, 09:59 PM:

quote: Michael Schaffer
Which is why I always doubt that "film makers" who do not understand at least the basic technical parameters of film technology can not really create good content - how can they make best use of a tool they don't understand?

This reminds me of a screening I attended a few years ago that was followed with a filmmaker Q&Q. I asked the director a technology-oriented question regarding the soundtrack of one of his films, and he gave me one of those "Why on earth would anyone want to know that?" looks! Needless to say, he did not have the answer.

I won't say the name of the filmmaker in question; it would be impolite to do so. But to give a hint, he directed "The Cowboys," "The Rose," "On Golden Pond," "The River," "For The Boys," etc. [Big Grin]

And to add a bit of irony to the incident, I should mention that three of those films I cited were nominated for Best Sound Oscars.

I'm also reminded of a remark former Monty Python member and now filmmaker Terry Gilliam once gave during an interview. If I'm remembering the question and subsequent answer correctly, it went something like:

Q: How do you account for your success as a filmmaker?

A: Hire great people to work for me and then make sure to stay out of their way!

The point (I think): it is not entirely necessary for a filmmaker to know the specifics of any particular technology. It can't hurt, of course, but hiring talented and skilled people and then directing like a conductor seems to be a technique that can produce excellent results.

Posted by Mark Gulbrandsen (Member # 72) on 10-19-2006, 10:32 AM:

Re: Signal to noise of Dolby formats... Too many variables there to really tell but the quietest playback system I have ever heard for magnetic is the Stagg Theater. All that stuff is long gone now...CP-200 and DP-70's They had some sort of star grounding system at that place in which everything from each sudio was seperately terminated to a burried copper drum of some sort... at least thats what I was told years back at THX class....

Mark

Posted by Lionel Fouillen (Member # 1475) on 10-19-2006, 02:12 PM:

Thank you to all for your replies. Actually, regarding the scope of my paper, what I want to do is explain in a few pages what are the media used in today's projection booths and how their pictures and soundtracks are tailored. So I want to tell a few words about 35mm, 70mm and D-Cinema image, and analog and digital stereo sound. I know that 70mm Dolby Stereo is obsolete but however I want to talk about it because some booths are still equipped to playback Dolby formats 42/43/45/46 on occasional reruns.

Thanks to Jeffry's links, I could find a document with a graphic comparing the s/n ratio of different sound processes.

As for the frequency range, what I'm looking for is not an explanation on the ISO2969 curve and stuff, but rather accurate information on the theoretically possible frequency range of 35mm SVA and 70mm mag considering the reader slit thinness, film length at 24fps (and recording limitations of the optical printer in 35mm and magnetic head in 70mm).

Thanks... [Wink]

Posted by Louis Bornwasser (Member # 3063) on 10-19-2006, 02:39 PM:

35mm optical: most of us are able to get 16Khz down 1 db; flat down to bass. 70mm and optical: 20KHz flat is not problem. This is with test films.

For recording: I understand that there is a low pass filter at 15K; but magnetic & digital should be flat to 20 K. Louis

Posted by Lionel Fouillen (Member # 1475) on 10-20-2006, 03:01 AM:

Thanks Louis!