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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Amp situation critical
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Heath Dutton
Film Handler
Posts: 37
From: Montgomery, Alabama / United States of America
Registered: Jul 2005
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posted 08-10-2005 03:45 PM
First off I'd like to send a huge "thank you" to everyone here, this forum has been the single best thing that has happened to my booth. I had less than two weeks of "training" with other projectionists before running a set of 16 projectors alone on weekends. Two years or so later I'd like to think I've surpassed those who taught me in a big way, and I have you guys and gals to thank!
I am working in the first-ever-built of the "Rave Motion Pictures" theater chain. It is an all-stadium seating all-digital multiplex monster (I mean that it the nicest way ). We now have 19 theaters and counting. Our biggest selling point has always been that their presentation (on screen) is our foremost concern.
Now on to the problem: The theater I work in is now 5 years old (the oldest of our chain), and our amps are dropping like flies. We have BGW Millenium series 2 and 3 on all houses, and about 11 of these amps have one channel (usually high) that is only functional most of time. Some of these amps have to be "tapped" every morning for them to work during the first show. On some of them I can never get both channels to work at the same time. Usually by the end of the day they have warmed up to the point that all but 3 or 4 are working completely (this tempts me to keep them on 24/7).
In the past the company's answer to this has been to simply send off the amps to get repaired. This has turned out to be a very costly venture, as I have personally shipped off 12 amps in the past two years for repair. The turn around was usually 2 months and the last two amps sent out NEVER CAME BACK! Luckely one was our only spare. Unfortunately that means that one of our small auditoriums has a single amp delivering right and left sound (combined). We havn't had a single complaint, but I wouldn't dare watch a movie in there. I have also noticed that the amps that come back are usually the ones that die again in 6 months. One came back once that was completely non-functional after an hour of use (it could have been damaged in shipping, but it didn't appear to be).
I've suggested that they stop this madness and start replacing the BGW amps, but I heard back that the complication would be that our amps have built in crossovers, and amps like that are rare and expensive. I find this rather confusing since the crossovers are only used for L/C/R and our speakers are all JBLs which came with built in crossovers. While changing speakers I noticed that the crossovers have been unscrewed and left laying by the speaker boxes in one of our large auditoriums so that the speakers could be wired directly to the amps. Why was this done? Are JBL crossovers unreliable or something? Why do we need amps with crossovers when we could put the JBL ones back in?
I have heard QSC talked about alot in here, and I would like to have a game plan to suggest to management about overhauling our audio in the next budget. Note that I havn't checked all our L/C/R speakers to see if their crossovers are sitting by them like this, but I probably will soon.
Since only L/C/R amps seem to have problems I would like to suggest replacing half of the theaters L/C/R BGW amps with QSC, and keep the ones we replace as tenative replacements for the other half over the next couple years. We have yet to have a surround amp go out, and only one sub amp has needed repair in the past two years, so I'm not too concerned with those.
I need to convince corporate that we will be saving money in the long run by replacing these crappy amps. Do you agree? How long does an average QSC amp last before it starts having problems?
Any thoughts? Suggestions? I'm eager to stop hitting amps in the morning...
I have been told in the past that I should never use my real name or tell anything about my theater online (and in fact that conversation led me to this site), but honestly I think we have nothing to loose and all to gain by asking for help from the pros
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John Walsh
Film God
![](http://www.film-tech.com/ubbmembers/168.jpg)
Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999
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posted 08-11-2005 08:19 AM
Hi, Heath, and welcome to Film-Tech. I will give you my opinions, but remember these are just my own and there are several people here who do know more than I.
I agree with most people (above) that BGW's are not that great, although I've never heard of that many problems. I don't know if your upper management allows it, but I would call BGW and describe what is happening (be prepared to give the serial numbers of the amps returned.) They may do something. You should ask your theater's service tech if he knows the history of this install to see if there are any weird, 'gotchas' like if the amps were purchased used, etc. You should ask him if it's OK for you to follow up on these issues because some techs get upset when someone else gets involved the equipment.
It might also be a good time to see if you can get the design blueprints for the theater and verify the amps and speakers are large enough for each auditoriums. They may be too small for the size, and the amps are being overdriven. Also, it would be a good learning experience to go through the place and see if your calculations agree with what's there. If you read the "Blown Subwoofer" topic from about a month ago, Steve G wrote an excellent example of how to calculate the sub amp power needed vs. the auditoriums size and provided a Dolby guide in the manuals download.
Your idea of swapping out amps is a good one. I have found QSC's to be very reliable; of the 300-350 I saw installed, there were (I think) two failures (not including the now-discontinued USA-series.) If rack space is a concern, the QSC DCA-series amps are only 2U, but are more expensive. A popular model is the DCA2422, which will cost you about $800 each. If rack space is not a concern, the ISA-series costs less, but uses a regular (non-switching) power supply, so is heavy. A cheaper alterative might be to purchase 'B' stock (used, scratched, demo product) from QSC; it has the same warranty as new, but avaiablity is very limited. Once you figure out how many amps you'd like to replace, contact a dealer. Your company probably has a dealer they like to work with, and you should go to that person first.
Lastly, I applaud your honesty in using your real name and company, however your upper management may not be too happy to have someone listing problems at a location. For example, instead of stating that 11 auditoriums at the "XXX Theater" have sound problems, you might just say you are having a problem with a few BGW's and leave out any location details.
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