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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Best sound test film for clipping
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Pete Naples
Phenomenal Film Handler
Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001
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posted 05-19-2005 04:15 PM
Sam, that's pretty much what I do, although I don't splice together a loop of buzz and Cat97, I run buzz, then left-right, then buzz, then left right, then buzz....., until no further improvements can be made.
If you want to see a slit lens that adjusts width un evenly, try a Projecson laser unit! It adjusts from one side only, which actually isn't that much of a problem. One adjusts lateral scan to get quiet one one side, then adjust the width until the other side shuts up.
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John Hawkinson
Film God
Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 12-21-2005 02:57 PM
RTFM is a crude way of telling you to "read the instructions."
It would help if you could tell us more about the processor. What model and brand?
The discussion in the other thread about setting levels with Cat69T is about setting the preamplifier levels for proper Dolby A and Dolby SR decoding (300mV). But you seem to be talking about the main output level when you discuss a VU meter from -25dB to 6dB.
This makes it quite confusing. We do not understand your question.
The preamplifier gain needs to be set properly so that Dolby decoding can take place, and that voltage is internal to the processor. If you do not have Dolby decoding, then the preamplifier gain is less critical. Others may have better advice, but I think you probably want to set it to the middle of the range between the minimum sufficient to hear the track and the point at which clipping is noticable.
As for the master output gain of the processor:
When you calibrate the processor, you should set it to a nominal level (probably does not matter much what exactly it is) and inject pink noise into the processor, and adjust for 85dBC from the speakers. Do this once for each channel.
When you play a film, start at the nominal volume level to which the process has been calibrated, and adjust "by ear."
If your question is what nominal level to choose, in your case I would use 0dB, but it is arbitrary (as long as you have sufficient headroom to make soft movies louder and loud movies softer).
--jhawk
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Brad Miller
Administrator
Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99
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posted 12-21-2005 03:45 PM
John, you have never installed a Dolby processor, have you?
First, he has a CP50.
On the CP50 is a card (cat109) with analog meters on them that are used to quickly calibrate dolby level with a dolby tone loop running (make sure you are in MONO when you do that Matthew.) That is what he is referring to.
Remember also he has cat64 cards, not cat64B cards. The levels must be set properly on those or even if everything else in the processor is spot on, he can have distortion.
Also it is important to calibrate the processor with the fader at 7, as it is "stepped" and calibrating at say "4" would end up with slightly skewed balancing between channels (levelwise) and also because 7 is the point in the fader where the lowest noise floor resides. This is why I always laugh when I walk into a theater and find the faders between 4-5. Properly calibrated, the fader should sit at 7 for most features and never go lower than 6, and yes this is without customer complaints. Any machine that has to run lower than 6 either has crappy speakers, poor aiming or was over-EQ'd by a tech looking for that perfect X curve (which causes the end result to sound like ass).
Marin - upload a picture of what the image looks like on your oscilloscope and we can tell you what's wrong. Just seeing a bench perfect alignment image won't help you figure out WHY yours doesn't look like the manual.
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Marin Zorica
Jedi Master Film Handler
Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003
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posted 06-08-2009 05:38 AM
To don't open new thread......can anyone tell me how much cinemeccanica front scan with original slit lens can go flat when calibrated with pink noise?
I do have some Polish prexer machines here, they do have slit lenses and slit is maded by adding silver surface to on of lens, but problem is to get it adjusted, they don't have any focus ring, so you need to move whole optics in holder, and when is best to get it tighten, but always sometimes get bit moved, or focus, or phase.....but, with cinemec is better because they have ring, only don't know are they better than this, because with prexer one's I can reach 16KHz flat with adding some HF eq!
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