Film-Tech Forum ARCHIVE: Sound dropping to SR, is it supposed to be so QUIET

This is topic Sound dropping to SR, is it supposed to be so QUIET in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Dubrois (Member # 3042) on 08-13-2005, 10:12 PM:

We have had a few digital readers in the past with problems. When they dropped out of digital into SR, there was a large difference in sound volume. Is this the way its supposed to be? I could have sworn I was at a theater where the sound dropped to SR, all you heard was a pop... but now, the sound really drops. We have Dolby CP650's and DTS 6AD for our digital readers. Is there a way to boost the SR sound so its at least LESS noticable if it ever drops again? I'd like to prevent us from handing out passes in future.

Posted by David Stambaugh (Member # 1102) on 08-13-2005, 10:29 PM:

In the limited selection of theatres around here, when SR-D drops to SR, the digital and analog levels seem to match very well. Sometimes (depending on what's going on in the sound mix) a slight "tick" in the sound is the only real clue to the dropout.

Posted by Mark Gulbrandsen (Member # 72) on 08-13-2005, 10:30 PM:

Your Dolby Calibrate levels probably need to be set up, should be checked twice yearly. When they are set correctly there is no real noticable difference between digital and analog. Somnetimes the analog track can actually sound better than the digital track!!

MArk

Posted by Richard Hamilton (Member # 321) on 08-13-2005, 10:41 PM:

Frank,
Are these the same projectors that are less than 1 year old?

Posted by Frank Dubrois (Member # 3042) on 08-14-2005, 12:30 AM:

No, these are about 5 years old. We dont have any currently that are dropping out, but it was just a question I thought I'd ask. A few weeks ago we had a drop out problem and the sound got so low it was hard to even hear voices and the surround speakers dont seem to work...OR their SO low we cant hear them. This is a dramatic difference in sound.

Posted by Dustin Mitchell (Member # 372) on 08-14-2005, 01:14 AM:

Is your analog sound provided by excitor lamps or LED's? If excitors when was the last time the bulbs were changed? If LED's perhaps the voltage needs adjusting.

Posted by Frank Dubrois (Member # 3042) on 08-14-2005, 01:23 AM:

I didnt think brightness would have anything to do with volume.

Posted by Richard Hamilton (Member # 321) on 08-14-2005, 02:28 AM:

Frank,
As Mark said earlier, your Dolby levels should be checked. Also, make sure all of the optics are clean. Too many times I have walked into a theater and just cleaned a cell or lens and the sound is "magically" better!
Rick

Posted by Monte L Fullmer (Member # 2797) on 08-14-2005, 02:33 AM:

Yep, time for the one month "oil change" - as I call it when I do Dolby Tones to set levels. Levels actually have to be checked quite frequently since they love to drift.

-Monte

Posted by Richard Hamilton (Member # 321) on 08-14-2005, 02:41 AM:

Monte,
I wonder if this step is being overlooked or done less frequently, since most new plexes have SRD and DTS?

Rick

Posted by Mark Gulbrandsen (Member # 72) on 08-14-2005, 08:39 AM:

In many places calibration only happens once a year or thereabouts. With the average reverse scam system you start to see a pretty big difference after about 6 months, the one exception is BACP readers in which the LED does not fade as fast. The other thing to check is to see if the installing tech set the gains in the processor all the way up and then adjusted the power supply down to make dolby level... this greeatly peolongs LED life span. And are the LED's switched on and off or are they on all the time? On & Off = alot longer life while always on = short life.

Mark

Posted by Frank Dubrois (Member # 3042) on 08-14-2005, 07:32 PM:

I'm afraid thay adjust levels is a bit beyond me right now. I want to learn, but am finding no time. The LEDS are on when the projectors are on all day. At the end of the night, of course everything gets shut down.

So, not totally understand levels etc, is the problem with the SRD levels being to high, or the SR levels being to low. Assuming they are somewhat easy to adjust, can it be done in the menu display, or is test film and other components necessary. Eiter way it sounds like I'll have to call a tech, but I'm curious how difficult or how screwed up I could make this if I attempted it on my own with nothing more than the manual and some test film [thumbsup]

Posted by Mark Gulbrandsen (Member # 72) on 08-14-2005, 07:41 PM:

It sounds like as long as the booth is powered they are on. This is not a good way to have them hooked up. A simple relay across the motor to switch them on and off or interface with the exciter circuit is allthats needed. LED's hooked up this way will last towards 10 years, about half that when running continously. I find myself replacing alot of LEDs lately because most of the scanners that went in (before I was working in this area) as retrofits are always powered up. I always change that over so its switched as I make the rounds and I believe that I have most of them chenged over now. The only exception to that rule is BACP. But they too can also be switched if desired.... there's no arguement for extending LED life! Who ever installed your stuff ought to come back at N/C and make those LED hookups right!

You will need a loop of Dolby Tone in order to calibrate your 650's... I guarantee you its not the SRD level thats off because its fixed, its the SR level that has dropped due to LED fading. I reccomend that you read carefully through the manual and get a feel for whats involved before you attempt it...although thats the easiest adjustment in a booth I don't know how far you've carried your technical abilities!

Hope this helps,

Mark

[ 08-14-2005, 11:45 PM: Message edited by: Mark Gulbrandsen ]

Posted by Frank Dubrois (Member # 3042) on 08-14-2005, 10:05 PM:

Yes it helps...I really appreciate your time (and everyones) time in assisting me.

By the way thats an interesting quote...not sure what thread you got it from: quote:

The audience doesn't know what his diet was during the previous 30 days nor what his normal exercise was.

[Confused]

Posted by Mark Gulbrandsen (Member # 72) on 08-14-2005, 11:46 PM:

That was just Redifer messing around......

Mark

Posted by Michael Schaffer (Member # 1204) on 08-15-2005, 07:51 AM:

quote: Mark Gulbrandsen
That was just Redifer messing around......

Mark

Posted by Mark Gulbrandsen (Member # 72) on 08-15-2005, 08:41 AM:

Posted by Dominic Espinosa (Member # 2122) on 08-15-2005, 03:39 PM:

When an LED begins failing doesn't the sound get a bit distorted first?
I've always noticed that the sound is more and more distorted as it gets quieter.

Posted by Gordon McLeod (Member # 33) on 08-15-2005, 03:56 PM:

If you have failed segments in the LED then it will get distorted but overall level drop you will just have noise reduction mistracking issues

Posted by Frank Dubrois (Member # 3042) on 08-15-2005, 04:27 PM:

Oh ok...I guess he has some growing up to do.

Posted by Andy Summers (Member # 3207) on 08-15-2005, 05:41 PM:

Frank,

Browse on though the operations manual for the Dolby CP-650, as for levels dropping from digital to SR analogue even if it is mixed spot on from discrete Dolby digital, effects like rain always stick out like a sore thumb, or sounding like pink noise and the general crosstalk nature with analogue?