This is topic Raising One projector's analog surround levels in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Demetris Thoupis (Member # 833) on 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
Posted by Pete Naples (Member # 761) on 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?
Posted by Steve Kraus (Member # 476) on 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.
Posted by Michael Schaffer (Member # 1204) on 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.
Posted by Brad Miller (Member # 2) on 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?
Posted by Demetris Thoupis (Member # 833) on 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?
Posted by Steve Guttag (Member # 268) on 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
Posted by Peter Hall (Member # 695) on 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 ?
Posted by Brad Miller (Member # 2) on 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.