Film-Tech Forum ARCHIVE: Digital cinema sound problem

This is topic Digital cinema sound problem in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Thomas Pitt (Member # 4322) on 11-19-2007, 05:58 PM:

I've just come back from seeing half of Beowulf in 3D. Yes, half of the movie - the other half was ruined by a malfunctioning sound system!

Everything started up properly; a 30-minute advert and trailer reel (35mm) which then changed over to the Real D system for the movie. During the first half of the movie, there were a couple of noticeable 'bloops' on the audio, but that was nothing compared to what happened later!

Approximately halfway through the movie, around the point where the golden horn returns to Beowulf, all the sound channels went to white noise at maximum volume! The white noise cut off after about 30 seconds and the movie sound returned, but only in the centre front channel. From that point onwards, the white noise kept blasting out at random - sometimes returning to the movie sound, other times to silence.

Many people in the auditorium, myself included, covered their ears when the white noise struck - some kept their ears covered afterwards in case it happened again!
During the silence I could just hear a beeping noise coming from the booth - perhaps some alarm?

Sometimes the noise was more like air blowing across the top of a microphone, but most times it was like when you play a data CD on an audio CD player.

After 10 minutes of sitting there with my fingers in my ears, I'd had enough - we called the manager, who gave us all a refund and a free ticket to any other showing in the cinema. I could still hear the white noise blasting out of the auditorium occasionally, even when standing in the lobby - that gives you some idea how loud it was!

Anyway, the reason I'm posting this here is to ask if any of you have had similar problems with digital cinema audio. Based on the symptoms I describe, what would you say happened to the sound system?

Posted by Mark Gulbrandsen (Member # 72) on 11-19-2007, 07:18 PM:

Well, that certainly is the pitts when something like that happens!

I've had the same thing happen with the USL VX crossovers. They have on occasion put out full level noise of some sort into the B chain blowing all the HF diaphrams in the process.

I'd be curious to know what Digital Server they were using for that show. Servers will still do occasional wierd things but generally nothing that a system re-boot won't solve. Donno about other servers but the Dolby Server after re-booting will just start up where it left off.....

Posted by Dustin Mitchell (Member # 372) on 11-20-2007, 05:07 AM:

The doremi, at least with AccesIT's software, has a 'recovery point' for restarting a show after reboot as well.

Posted by Mark J. Marshall (Member # 1409) on 11-20-2007, 07:17 AM:

That does suck! For what it's worth, I've seen an SDDS DFP-D2000 do that. Not digital cinema, I know, but the sound is digital so I thought I'd throw it out there.

Posted by David Graham Rose (Member # 1450) on 11-20-2007, 01:33 PM:

Greetings

Another example of the half-baked cauldron of bodgery that is D-Cinema at the moment!

David

Posted by Dustin Mitchell (Member # 372) on 11-20-2007, 03:09 PM:

Because 35mm sound systems NEVER have any problems [Roll Eyes]

.

Digital projection still uses a cinema sound processor btw so it is perfectly possible that is what was at fault in this case.

Posted by Bobby Henderson (Member # 840) on 11-20-2007, 04:11 PM:

The first time I saw Interview with the Vampire, at the AMC Memorial Square 8 in Oklahoma City (a theater which no longer exists), its Dolby Digital system crapped out big time in the middle of the movie -with very loud white noise being the result. The staff had to stop the show for around 10 minutes. When the show resumed it played only in analog.

Posted by Mark Gulbrandsen (Member # 72) on 11-20-2007, 04:25 PM:

quote:
Another example of the half-baked cauldron of bodgery which is called Film at the moment!

David, I think I'll have that put on a t-shirt and wear it during my upcomming D-Cinema installs [Cool]

Posted by Peter David Bruce (Member # 4447) on 11-21-2007, 09:16 AM:

ok im having this problem (to a lesser degree) alot of beeping on the soundtrack itself (most noticably in the quiet bits). ive cleaned and cleaned it and simply cannot remove the problem.

im running CP650 Dolby Processors, with Ashly FTX Series III amps. Dolby EX.

i need to sort this if i can. id hate to think im stuck with it, or it may get worse...

also the print is constantly running at error rate 7!

Posted by Patrick de Groot (Member # 858) on 11-21-2007, 10:17 AM:

I suppose you're using a 35mm print.
Option 1: bad/damaged film print (if other prints play ok)
Option 2: bad alignment of sound head
option 3: one or more defect LEDs (look at the leds through a cd)

Posted by Peter David Bruce (Member # 4447) on 11-21-2007, 10:30 AM:

thanks patrick. i will investigate

Posted by David Graham Rose (Member # 1450) on 11-21-2007, 01:54 PM:

Greetings Mark!

"David, I think I'll have that put on a t-shirt and wear it during my upcomming D-Cinema installs"

When you do, please send me one. I have yet to see a system that works correctly, despite being a convert to D-Cinema!

Goodnight

David

Posted by Louis Bornwasser (Member # 3063) on 11-21-2007, 03:35 PM:

Me, too!! Sounds like a profitable venture for someone. Louis