Film-Tech Forum ARCHIVE: Random POPPING noise in speakers

This is topic Random POPPING noise in speakers in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008234

Posted by Frank Dubrois (Member # 3042) on 08-30-2006, 11:48 PM:

We have a few auditoriums where we hear popping noises coming form the speakers. It happens every 30 seconds to a minute or so. Its usually just a quick pop. We use film guard, but I thought maybe static could still be an issue? We are using a variety of processors everything from Dolby to Ultrastereo to Smart, so I'd rule out any processor malfunction since this happens in all auditoriums. If it is static, what else could be done to get rid of it? Other than the occasional POP, the sound is fine. These are all analog auditoriums.

Posted by Monte L Fullmer (Member # 2797) on 08-31-2006, 12:01 AM:

in your processors, have you pulled the cards and reseated them? You could have some cards that are breaking contact with the sockets causing the popping (in all channels, or just a certain channel-this would help also if you can be more specific in the speaker area..) in the sound.

As you mentioned analog, wonder if there is hairline cracks in the optical tracks since sound optics are very sensitive in this area to pick up. Cracks from film operations, buildup procedures, et.al.

-Monte

Posted by Mike Babb (Member # 1379) on 08-31-2006, 12:02 AM:

Potts/Strong microswitch platters? Could be the payout triggering...

Posted by Frank Dubrois (Member # 3042) on 08-31-2006, 12:18 AM:

Strong platters...I thought of the microswitch problem, but in all auditoriums? All cards were reseated, same problem. Popping is coming from all speakers.

Posted by Ron Curran (Member # 3631) on 08-31-2006, 12:31 AM:

See if there is a fluctuating fluoro tube in the building. Then check your earth lines.

Posted by Jack Ondracek (Member # 1466) on 08-31-2006, 12:40 AM:

I'd look at the incoming power, since it's happening in several unrelated rooms. Something big enough to put a serious impulse on the lines... elevator... hvac motor... something like that.

Several years ago, I had an elevator in the building next door throwing so much SCR hash in the lines, it would get into my audio gear, and that of the theatre. Some caps at the elevator's power supply's power input terminals fixed the problem.

If you put your sound processors on-line, does this happen before your customers arrive? When things are quieter (before/after the day) it might be easier to eliminate the possibilities.

Posted by Monte L Fullmer (Member # 2797) on 08-31-2006, 02:20 AM:

(uh-oh, wonder if his amps are getting dry caps inside and they are having a hard time holding charge .. and discharging when they want to...)

Posted by Stephen Furley (Member # 1277) on 08-31-2006, 02:44 AM:

Do you only get it on optical film sound, or on our sources, e.g. non-sync, video etc., as well?

Posted by Mark Gulbrandsen (Member # 72) on 08-31-2006, 07:04 AM:

Check and see if your platters are on the same phase as the sound system processors. I've had many instances of microswitch noise comming back on the power line and interfering. This has mostly been in older theaters. I've even had popcprn poppers with internally arcing patrts cause sound interference. Power amps with failing output transistors and several other types of failing parts can also exhibit this symptom. Failing output devices can also be very hard on the speaker's drivers since the pops amount to DC hitting the voice coils randomly.

Mark

Posted by Louis Bornwasser (Member # 3063) on 08-31-2006, 09:24 AM:

The most sensitive part of the sound system is the pickup system (red LED reader, Jaxlite, etc.) and its wiring. Probably all of these are the same and I would look there first.

What do you have in use? Louis

Posted by Frank Dubrois (Member # 3042) on 08-31-2006, 11:54 AM:

If it is a general interference issue (like an elevator, which we dont have) would the popping happen at exactly the same time in all auditoriums? Meaning, if I was in one room and someone else was in another, would we hear the noise at the same time? As opposed to microswitches on the platters where the popping would occur as the platter pays out? Im not near this theater, so its nothing I can immediately test. The only general interference we might have is business equipment, wireless radios (not in use when the noise was occuring), and of course hvac equipment. The noises were heard only when the film was running, not during the non-sync pre-ads

Posted by Jack Ondracek (Member # 1466) on 08-31-2006, 12:33 PM:

Yes, if it's electrical interference from outside, it would probably occur in all affected rooms at once. Is that not the case?

As Louis said, the pickup is the most sensitive part of the whole system, so it would be far more likely to pick up problems than line level sources, like a CD player or other non-sync source.

Is this something that's just recently started? New theatre or not? It could be challenge to find this, because shielding, the type of wire used to the pickups, conduits & routing can all be involved. If somebody's just recently added some equipment around there, you might have had this problem for some time and never known about it.

Good point though... can you say if the popping is randomly travelling around the booth, and not happening in every affected room at the same time? That would make a difference.

Posted by Eric Robinson (Member # 2966) on 09-07-2006, 01:23 AM:

I had a popping problem once. The popping was very random. After wasting many hours I finally rigged up an outlet strip and extension cords to power up the audio rack from other outlets down the hall--VIOLA--no more popping.
I then used an oscope to monitor the 120VAC incoming to the audio rack and after many a bored hours confirmed that there were spikes coming in.
I then found every device which shared this circuit. One of them happened to be one of the "WRONG" water circulators. When the circulator was removed from the circuit - no pops. When plugged in - pops. After further investigation, I found the water circulator submersible pump was intermittently shorting to ground. This cooler has been trashed and the sound is great.
Hope this helps... [beer]

Posted by Gordon McLeod (Member # 33) on 09-07-2006, 10:51 AM:

All sensitive electronic systems like sound systems should have noise/tvss on them