I sure hope someone can help me with this, cause it's a mystery so far. I'm a contractor who has replaced and installed two new subwoofers for a retail client of mine. I have audio production background, so I figured I was qualified to plug in an rca cable. Uh oh...little did I know.
Here's the scoop:
Okay, of the two old subs, one was rattling, and the other was dead. So the client just said replace them both with the same model. They are Paradigm PDR-12 v.3.
I installed the two new PDR-12's. The both worked fine. I returned to the store one week later to wire in a couple more satelite speakers. When I turned the system back on, both subwoofers blew fuses.
I replaced the fuses. One sub worked fine again. The other would immediately blow a fuse. Two weeks later, the one working sub blew a fuse again. I replaced it and it's now working again. I took the board off the other one and sent it to Paradigm to see if there is an internal short. Waiting for their reply.
The subs are controlled by an X-20 low pass controller wired into the pre of the Kenwood receiver. The satelites are controlled by a Niles SSVC-4.
Yesterday I opened up the old sub that was dead and it had a blown fuse too, so this has been a problem for a while I guess.
I find it hard to believe that 2 brand new subwoofers would both have faulty amps. Paradigm makes good stuff don't they?
So, any thoughts as to why the fuses keep blowing? An electrican checked the receptacles and they were fine. He checked the draw on the one working sub and it was under 1 amp.
What type of store is this and does the staff have access to the system before or after shop hours? Rattling subs are almost always a sign of the driver being overdriven at some point. Possibly an overly generous nineteen year old in for an early/late clean up who was stocked with his personal favorite CD's. Constantly blowing fuses would make me suspect the same cause. Unauthorized access to the remote control.
Unless Bonzo the Chimp did your AC wiring, there shouldn't be much to suspect in the incoming voltage. I don't know the crossover you're using but the only culprit I can guess at quickly is the possibility of a surge reaching the subs, possibly at system power up or down. If, that is, you don't suspect a chimp at the volume/bass control. It's possible there are electrical problems that a mere check with a multimeter won't detect as they would be transient in nature. A good surge protector would likely solve that issue.
I would wait for Paradigm's reply and suspect the finding will be burned resistors/transistors. If that's the case, locking up the system from prying hands would be the solution.
Thank you for the excellent response. It's better than anything I've received so far from Paradigm or Kromer, (the supplier).
That rattling subwoofer actually had more to do with how it was mounted more than anything. I neglected to mention that these subs are 20 feet above the floor, firing down, and the bracket that holds them was rattle culprit. I wouldn't reccomend mounting them like this, but it's a big chain of retail stores with a big head office that wanted it that way. And if you understand corporate culture, than you can understand that it's not advisable for suppliers to try to stear the ship. In any event Paradigm okayed them to be installed like this, and it really doesn't have any bearing on the fuse issue. That said, it does require me to rent a scissor lift to replace them. Or at the very least to get an extension ladder in there to replace the fuses every time they blow. I relly want to choke the tech rep at Paradigm evertime he says "bring 'em on in". Ya, at $600 for the scissor lift to bring them down and then put them back up.
It's a girls clothing store staffed by young girls. They do have access to the system, but from what I can tell, they haven't been driving it hard they all want it off as soon as possible when I'm there so they can relax.
All the fuse failures have been right at start up. This is an auto on speaker by the way. I did not know that voltage problems could be transient like that. I think a surge protector is going to be the answer. I really want this nightmare to be over so I can invoice for the job.
When the fuses blow, they blacken the glass on the fuse. The electrician, who perhaps has a flair for the dramatic, says that is the sign of a catastrophic short in the amp.
I will forego comment on the girls clothing store thing for fear of seeming creepy. The pre amp is at fault here, and the Paradigm high mount are stupid.
Replace the Paradigms with Peavey PV7's or CV 12 inch, ditch the pre and your problems are gone. As far as speakers, anyhow. The business end is your problem. Good luck with that.
Assuming I don't replace the Paradigm's, (I really can't get more $ out of the client for that), you think a new amp will solve it? Aren't the fuses in the subs there for AC protection. Can a pre amp cause a power surge?
It's in a mall if that has any bearing on power surges btw.
I'm not at all sure what Nuck is thinking by laying blame on the "pre amp". So, I eagerly await his explanation. "Ditching" the pre amp section of a Kenwood receiver would seem a difficult, and costly, task to perform. Have you used this set up in any other installations? Not to question your skills, but are you certain you have the subs wired properly as far as output/input is concerned? How hard are the subs operated to your knowledge?
The plate amps of most decent quality subwoofers are built by a handful of companies and, personally, I don't see swapping amplifiers as a solution. If the Paradigm amps are at fault, Paradigm should accept responsibility for a defective product and make a properly functioning replacement available.
At this point the response from Paradigm will say more than I can guess. I suppose you will use this as a lesson and insist all future installations have a clause which protects you from mid level managerial oversight should "catastrophic" failures occur.
If possible and depending on the answer you get from Paradigm, I would delay re-installing the subs for a few days after they come back from Paradigm in order to run them on another AC circuit. See if you can duplicate the failure in any way. If they don't blow while you have them, you have a bit of a leg to stand on when dealing with billing. If they do blow, you will have saved the rental of a lift. Talk to your electrician about installing an AC line fuse at a different, more accessible, location in the shop. Most well built surge protectors have some fuse or circuit breaker protection. Possibly the surge protector can be located at a more convenient spot such as close to the main system install. Power surges that affect only the subs are unusual if they share a power source with the main system. At that point, if the sub amp blows a fuse, the main system should be affected also. I'm inclined to want the subs to share a common AC source with the main system, if at all possible.
My suspicions still run to a power surge at power up or down. If the subs or any part of the system presently resides on a switched AC circuit, this could be the problem. How to prove that idea? I'm not certain. Running the subs off a different, always on circuit would be where I would begin. If possible, leave the receiver and X20 powered up at all times, even after the store closes. A good surge protector should keep the system in good shape no matter what the weather.
You are absolutely within your right to question my skills. I am not an audio installer by trade. I do general repairs for the store, (carpentry, drywall). I used to produce audio for Television. I had an experienced recording studio engineer do all the wiring. He has rewired studios before, and I can only trust that he knows what he is doing. Perhaps this is a different beast for him, but it is my strong belief that he did everything properly. He came recommended and his work is very clean, wires are properly labelled and tied. Also, the blown fuses predate his work. He is also at a loss as to why this is happening. As is Paradigm and Kromer.
RG6 cables with rca jacks run from the X-20 to the subs.
I also strongly believe the subs are not being driven too hard. The blown fuses happen at start up. If I had to guess, I would say that Paradigm will say the amp is fine. I'm saying that because both subs blew a fuse at the exact same time upon start up, and it would seem inconceivable that two brand new subs would have coincidal internal failures. If Paradigm made speakers that were that fragile they would not be in business.
I will let you know what they say. It could take a week though.
The Kenwood is switching on with a 'bang', as it is supposed to. The amps are picking up the 'bang' with a good response. Using a time delay fuse would likely solve the problem(like a motor starter fuse), but might not be legal for the application. With investment, an input cap(or bank) would solve it, but I presume that further investment is not in order. TD fuses would be my next step. And ditch the Kenwood, will ya?
I'm using slow blow fuses. Is that the same as TD? I will confess that I bought the fuses from Radio Shack. Perhaps a better fuse would be a good idea as well as a good surge protector. I agree with your comments on the Kenwood. However creating a "functioning" system is my first priority.