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This topic comprises 3 pages: 1 2 3
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Author
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Topic: 16mm Sound problem
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 12-16-2017 09:37 AM
Some misconceptions here. There is no Academy curve, per-say. The filter was derived based on measurements of the end result of the normal record/playback process pre-EQ era. That is, speakers played back flat (Altec A4s, typically) in a pre-1970 theatre (large barn, typically). The Academy filter was added by Dolby to mimick the "typical" response of an old theatre since once a CP100/CP50 were installed, one EQed the room to a more flat response. Mono movies, with pre-emphasis would sound bright/sibilant. Furthermore, the noise of the track would seem increased since the high-end was no longer being "naturally" attenuated by the playback equipment/room.
16mm never had the same presumption of playback. Most 16mm projectors made had their own preamp/amplifier built in and by and large were played back on smallish speakers but in also relatively small rooms. The theatrical aspect of the format was not predominate at all. Furthermore, the speed of film and comparatively smaller area for the soundtrack also limits its potential frequency response, noise and dynamic range. If that wasn't enough, 16mm was often duped, further degrading the picture and sound.
There really isn't a "right" response for it. It is something that often has to be adjusted on a film-by-film basis for what sounds best, which is subjective.
Now there are SMPTE documents (now mostly marked "stable" regarding 16mm record/playback response but those relate to making the equipment as "flat" as possible and what the frequency range should be without regard to the room it is played in.
To tune it, I would forget about ⅓ octave graphic EQ (it would add more problems than it would fix...ever look at the actual response when one tries to use multiple frequenciy to shape a response? It isn't pretty). Start with just simple tone controls. I would put the bass frequency at 100Hz and the Treble at 2KHz. You might add a low-pass at 8KHz (there nothing above that but noise).
Another thing that can improve 16mm is a dynamic range expander with 10-20% expansion. It can clean up a track and undo what had to be done to get the audio to "fit" on the 16mm optical track. Having a full blown drag and drop DSP would be quite beneficial here. Another thing that I've had decent results with is actually a Kintek processor (separates or a KT-700, nothing later). Kintek's optical preamp was decent enough for 16mm and the system has the dynamic range expander built in.
As for 16mm optical preamps, I found that Elmo really had the best. The later Kinoton preamps (circa 1993 and later) also seemed to be decent. Most 35mm preamps don't mate up well. Yes, they work but the slit loss is all wrong and it never seems to sound good to me. Most any microphone preamp will work but remember that you have a DC offset introduced by the cell so the preamp has to be able to deal with that. Cells like to be loaded down (act like current sources) so don't be afraid to put a ressistor across the cell if the preamp doesn't load it enough for a flat response. You'll lose output level but gain a better response.
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