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This topic comprises 2 pages: 1 2
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Author
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Topic: Help - can anybody here record on 35mm mag (cs format)?
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 06-15-2004 07:04 AM
Frank,
You are only partially correct...
Depending on the analog optical processor, EQ is applied to all formats or only the optical soundtrack.
For instance, the CP-50 only applied processing to the optical soundtrack and allow magnetic to pass-through. The CP-50 was always considered an add-on processor to an existing system. Note, if you didn't order the CP-50R, you didn't even get the ability to control volume either since many theatres had existing volume controls.
However with full-fledged processors like the CP-100, CP-200, CP-55 and later...EQ is applied to all formats.
In the days of magnetic sound prior to Dolby, things were much more wild. The system depended on the room response to set the tonal qualities. Back then, most any quality theatre was using an Altec A-4 (or A-5 if smaller) and most of them were barns. As such, speaker wise there was more uniformity then than THX has ever had now. When the films were mixed, they were mixed to such rooms. Any emphasis that was needed was done at the recording stage since they were mixing to the old rooms, sans EQ.
This subject has caused great problems with people that see the lack of a specified response curve to mean everyone should not apply any pre-emphasis and thereby not de-emphasize the track on playback. The truth is when you are mixing a film to a non-EQed system, you are going to sweeten the sound until it sounds natural to you. As such, if the playback speakers are rolled off by the screen and their natural response, the recording engineer is going to compensate by ear to make it sound natural.
If you play back that track in a like environment...it too will sound natural.
If you take that same track, play it back on a system tuned to today's specs (ISO 2969/X-curve) it will sound quite harsh and hissy. BTW...the same sort of effect will occur in the bass region too.
In Dolby's CP-200, when you select format 40 (or 20/22), it will apply a bit of an HF roll off to mimick the response of an old theatre sans-EQ. Even on the CP-55, on the Mag inputs, there was a 4.5K LPF to tone down the HF response. Even though the Cat. 242 never received a suffix of A or B...etc...when the CP-65 came out, the roll off was removed since 4-track mag was more rare than needing the extra input for something else.
Now this would lead some to believe that all they need to do is nix the EQ for playing back old films...nope...two of the missing parts of the equation are the Altec speakers and the old room response.
I recently was afforded the opportunity to work with an old 1950s/1960s system (70mm) that was essentially unmolested except for the Solid State amps had replaced the Altec Tube amps. Listening to a 1957 film through the system did NOT have much if any apparent hiss or spittiness. The vocals sounded clean and natural. The music had that 1950s sound.
What was nifty was that this is a back-to-back theatre with identical theatres running the same film on both sides.
I upgraded one theatre to a modern 70mm processor and playback. All was tuned to THX perfection. The same 70mm film was nearly unlistenable with the new equipment. The moment the sound was unmuted on the film...HISS assaulted the ears and the dialogue was anything but natural and it was quite spitty.
Here we had a missmatch...old recording, new system. So I applied a roll-off that approximated the X-curve to the Magnetic A-chain...result...no-hiss, natural sound and more detail than ever before. All this with a non-Dolby encoded print. At this point one could compare the two theatres and the new system was considered to be an improvement now for ALL formats. The other theatre was similarly converted.
So there is your long winded answer...EQ is done to equalize a room, not a track...however both the recording and playback end of things MUST have a similar response (identical if possible) if the intended sound is to be reproduced properly.
Steve
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 06-15-2004 10:15 AM
Steve, as always, very enlightening. I guess the idea of referencing each system to a standard curve -- applying it in the recording system in the mixing studio and the same reference in the theatre playback system, regardless of the room acoustics in either place, was a very smart industry move. I suppose Dolby can take credit for it, but I do recall it was in an Altec brochure that I first saw their promotion for what they dubbed their "Theatre Voicing" that concept which was just an ungainly looking 1/3rd octave stand-alone equalizer. Of course not everything can be fixed with room eq, but they were on the right track and I imagine this was around the early 70s, before Dolby's entry into cinema sound.
We have one of those barns -- 2500 seats and, yes, the entire system back then was Altec. An Altec audio mixer (12 channel with those big round knobs on pots for faders instead of sliding faders), double Voice of the Theatres for each channel with additional multisectional HF horns in the center aimed at the far mezzanine and the balcony, all driven by those beautiful Altec tube amps, what were they 1580s? -- four 6L6s in parallel push-pull output and something like 100 watts each, if that. But by George, we got plenty of sound out of that super efficient system and best of all, the sound was meeelllllooooow. And everything was Altec green.
And what you are saying about mixing engineers mixing for the known, general acoustics of the existing rooms does hold true because I distinctly remember a 900 seat Century theatre in Fresh Meadows, NY where I frequented as a kid, and I recall that occasionally I would hear this fairly loud THUD, which I came to know later was the sound of a splice. But strangly, although today we do backflips to eliminate that occurrance, back then, even THAT sound had a warm, "friendly" character to it. I actually used to like to hear when it happened. So you are right, the combination worked well in those days. But the problem is, as you say, that uniformity of theatre and system design has gone the way of the movie palaces themselves.
We do play quite a number of mag prints and luckily our booth channel outputs run to a mixing console, so I have the luxury of parametrics on each channel and it is not an arbitrary reference but basically my ears that are the final determination of how to eq the tracks on a mag print. We can get almost any track, even the ones that sound like fingernails on a blackboard to sound, if not great, then at least listenable in that space.
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