PRE-DOLBY FILM SOUND AND THE ACADEMY CURVE (2 Viewers)

[Ross Campbell]

Mr Harris,
It is a great thrill to be able to correspond with you, being such a great admirer of your work over many years.
Your 70mm restorations have played very successfully here in Melbourne, Australia, many of them at the Astor Theatre in St Kilda, wherein I have had a long association.
The advent of Blu-ray has improved my home video projection system enormously: the clarity of detail in the longest of long shots is truly superb. And sound quality, the Achilles Heel of standard definition DVDs, is greatly improved.
However, there is a problem with both DVD formats: it appears that many audio technicians preparing DVDs have no knowledge or appreciation of the sound quality of pre-Dolby tracks and how they once sounded in cinemas.
A simple Google search for Academy Curve will reveal how frequencies above 8,000 Hertz on a mono optical sound track were "rolled off", dating from a time when optical sound tracks had a substantial level of ground noise and valve amplifiers had an audible hiss in the upper frequencies. Lower frequencies were also rolled off, to a lesser degree, to overcome "boominess" in large theatres.
All this is well known.
What is less understood is that in order to compensate for this substantial roll-off, a HIGH FREQUENCY PRE-EMPHASIS was added to the track in the final mixing stage.
This gave an extra "kick" to the sound when reproduced in theatres. This was demonstrated most recently here at the Melbourne International Film Festival when a restored print of Jean Cocteau's masterpiece, BEAUTY AND THE BEAST (1945) was screened (under my supervision).
The Mono setting on the cinema's Dolby processor had been set to match the Academy Curve, and the sound in the auditorium was quite perfect; within the recording limitations of the period, dialog sound was clear and the music rich, warm and nicely articulated.
NOT SO WITH THE BLU-RAY DVD !!
As with most DVD transfers, audio engineers seem ignorant of the high frequency pre-emphasis and allow it to pass through where it is reproduced in full on any modern audio system which plays back to 20,000 Hertz. "This is how old movies sounded," the young technicians probably say to themselves.
The results are incredibly shrill and introduce a screeching quality which can only be overcome by introducing a graphic equaliser into the system (as I have done for years) and mimic the Academy Curve roll-off. Normal bass and treble controls on an amplifier are incapable of doing this task. A concomitant boosting of lower frequencies completes the "restoration" and one begins to hear how these tracks once sounded in cinemas (sometimes better!).
The superb work achieved in the visual restoration of classical films from the past is truly wonderful; how disappointing this is rarely carried through in the matter of mono optical sound.
Best wishes!

 

[zoetmb]

I know this is an old post, but I thought I'd respond anyway.
I agree with you when a DVD/BD is made from a print with optical sound. The roll-off should be taken into account. But for post-WWII films in which mag tracks still exist, your comments don't apply. The full frequency range of the mag track should be mastered for the DVD/BD, even in the cases where no mag prints were ever made for exhibition.
While it's true that "optical sound" is the way most of us heard those films originally, the limited frequency response of those tracks was not a desired characteristic and if modern audio processing can get more out of them that increases dialog intelligibility or makes the soundtrack more pleasant to listen to, I think it should.
The Academy Curve actually started rolling off at 2K, not 8K. It was down 10db at 5KHz and 18db at 8KHz. The fact is that most old theatres had very long reverb times partially because many started out as music halls and partially because amplifiers of the day were very low powered and the long reverb times were the only way to get the audio into all the seats. But that also highly reduced dialog intelligibility. The reality is that pre-mag theatrical sound really sucked.
Unfortunately, most modern AVRs no longer have tone controls. If they did, you could simply turn down the treble, even though most tone controls operated at 10KHz. They had a wide-enough Q that it would still work.
Having said all that, I have found the sound on most pre-1948 BD releases to be amazingly good, considering the technology in use at the time and the fact that most of the releases are made from prints as the negatives are long gone.

 

[Lord Dalek]

Sounds just like the RIAA curve... a load of hot air.

 

[zoetmb]

Huh? Play your LPs without the RIAA curve and see how bad they sound.

 

[FHM]

Mr. Brooks is correct.


F. Hudson Miller
Sound Editor
www.rhapsodypost.com