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Topic: Raising One projector's analog surround levels

Demetris Thoupis
Phenomenal Film Handler

Posts: 1167
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001

posted 11-17-2002 04:27 AM

I have this for you,
In a changeover theater (v 5's with kelmar stereo solar cells) the first projector gives perfect distribution to all channels in analog and the surrounds rock the theater. On the second projector though, although the sound is clear, the surrounds are not lound enough. Forgot to mention that we are talking about a CP 65 processor. Is there something that can be done to raise the surround levels of the second projector only but not affect the surrounds of the first projector?
Demetris

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Pete Naples
Phenomenal Film Handler

Posts: 1080
From: Dunfermline, Scotland
Registered: Feb 2001

posted 11-17-2002 05:26 AM

In a word, no. BUT from what you've said I'd wager that the 'A' chains on both your machines need some attention. You really shouldn't be able to audibly detect any difference between them.

You have checked Dolby level on both machines with the SAME loop of test film?

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Steve Kraus
Butt God

Posts: 3666
From: Chicago, IL, USA
Registered: May 2000

posted 11-17-2002 11:11 AM

It may simply need the levels set with Dolby Tone but if that does not correct the problem then you or your technician will need to get in there to see what is going on using a number of test loops, an audio analyzer (RTA) and oscilloscope. If you don't have these tools you won't be able to do it yourself. But please do check the levels first because it may be as simple as that. Make sure you clean the solar cell and the slit lens optics first. Perhaps consider putting in a new exciter bulb if the existing one is old and could be suffering from a sagging filament--if you do then do it before setting the level since it will change complete with the new bulb.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4141
From: Boston, MA
Registered: Apr 2002

posted 11-17-2002 03:49 PM

If the Dolby level procedure does not cure the problem it is likely that the two solar cells are out of phase. In that case, the center channel should also be affected.

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Brad Miller
Administrator

Posts: 14737
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 11-17-2002 04:02 PM

Could be the "working" projector's azimuth is just a slight bit off, resulting in a little more bleed to the surrounds. If this is the case and that is coupled with the surround outputs being just a bit too low, that could give the results you are hearing.

Have you shut off all speakers except for the surrounds and listened for dialogue leakage?

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1167
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001

posted 11-18-2002 06:24 AM

Well,
On the first projector we have almost zero (seriously) dialogue leakage, you have to stick your ear to the speaker in order to hear the dialogue in analogue sound. On the second projector we have a bit more leakage. So Brat. You are suggesting that is the azimuth?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 6882
From: Annapolis, MD
Registered: Dec 1999

posted 11-18-2002 07:13 AM

I have come across a couple of solar cells in my life where the two cells were partially shorted together such that you had a little of each signal in the other channel! This would cause the problem you describe. This shouldn't be confused with the normal crosstalk associated with forward-scan systems...this was an actual electrical short.

Steve

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Peter Hall
Master Film Handler

Posts: 275
From: London, UK
Registered: Dec 2000

posted 11-18-2002 01:32 PM

Sounds like the azimuth is out - if reference levels were off the dialogue would be over to one side. Is P2 less responsive at the top end ?

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Brad Miller
Administrator

Posts: 14737
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 11-18-2002 01:58 PM

Adjust your system so that the projector without dialogue leakage into the surrounds is balanced and sounds good. Then do a full A-chain on the other one and see if the problem does not disappear. If it doesn't, then it's time to start looking into other possibilities. Odds are it's just the azimuth on the A-chain.

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