Film-Tech Forum ARCHIVE: Crackling

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Crackling

Author

Topic: Crackling

Jeremy M Smith
Film Handler

Posts: 48
From: Taupo New Zealand
Registered: Aug 2008

posted 07-16-2012 08:48 PM

Just wandering if anyone has had this problem.

In one of my cinemas a have a Crackling noise coming from the center and more so from the right channel. It will only do if with some prints ie Spider Man is fine TED is not but TED is fine in another cinema that has the same sound head. We have had a tech look at it twice also.

Thanks
Jeremy

| IP: Logged

Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 07-16-2012 09:36 PM

It could come from a scratched soundtrack.
It could be because of a misaligned A-chain or something wrong in the processor.
It could be a bad amp or a bad speaker.

The difference between movies could be because of a problem with the print. (e.g. The above-mentioned soundtrack.) It could also be because of the way the movie is mixed but it could also be a coincidence.

What projector/sound head are you using?
What sound processor are you using?

Are you playing any or all of the prints in digital? (Dolby Digital or DTS?)

The difference between the sound quality of different prints could be because one is playing in digital but the other isn't. In that case, you would need to perform a complete tune-up on both the analog/optical A-Chain and the digital reader alignments.

While you've got the equipment out (or while you have a technician on-site) you could do a complete A-chain alignment, a digital alignment and a B-chain EQ.

Since we are now in an era dominated by digital projection, it would serve you well to have your film projector working as well as you possibly can. The smart move would be to call a technician and have him tune the whole system.

| IP: Logged

Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 07-18-2012 12:53 PM

I called it a cracked diaphram in the horn driver.

They're made of very thin aluminum if any low frequencies went to the horn, it will take out a diaphram in a quick. But age itself can cause diaphram cracking.

The cracks are created at the base of the dome of the diaphram-very hairline cracks to noticable ones. One can check this out by taking off the rear cover of the driver to inspect the diaphram itself.

They're easy to change out-just follow polarity, but a tech is your best bet to find out the problem.

Common issue is older cinemas having speakers set for low wattage amplifiers (the Altec/Lansing "Voice of the Theatre" - A4, A7 - speakers are a good example: a transistor radio can drive these speakers and make that radio sound great) and when that cinema do a digital sound conversion with higher wattage amplifiers, this setup will easily create horn problems.

| IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.