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Subwoofer woes

post #1 of 17
2/20/12 at 6:14pm
Thread Starter 
I hope that I am posting this in the right area (and thank you in advance for stopping in. I try to pay it forward in other areas where I am much more of an expert). I bought a beautiful set of 5.1 PSB speakers from the previous owner of my house. Everything was great up until 2 years ago when my sub started to hum whenever it was turned on. I read a lot on this issue and I purchased a whole bunch of stuff from the shack hoping to cure the problem. I do remember specifically buying ground loop adapters and various electrical boxes. Nothing seemed to help.

Fast forward two years later and I am digging out my sub after finishing of my new home theater. I turn on the sub - same problem. Is it possible that the sub is defective?

Here is a list of what I have tried:

- various adapters (as mentioned above)
- unplugging from the HT receiver
- moving it to different rooms
- turning off EVERY circuit in the house except for one and turning on ONLY the sub

I thought I remembered touching a screwdriver to one of the screws on the back and having the hum lessen but I can't reproduce that now.

Any thoughts on what I can do now?

Here is what I own.

Some audio and video of the problem. Thank you very much in advance!

http://youtu.be/F3b1RubruiI
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post #2 of 17
2/20/12 at 6:35pm
Sounds like the amp may need service.
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post #3 of 17
2/20/12 at 6:43pm
It shouldn't hum. Might try a ferrite core on the power cord but it could be the amp or a connection inside (try taking it apart and see if there's anything obvious is what I'd do to start). Maybe a local electrician can check it out for you.
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post #4 of 17
2/20/12 at 6:56pm
Have fun. I sent my sub in to the local shop and they had to send the amp into B&W for service. Its already been back and forth twice and I still haven't got it back. Its been three months now. The good news is I got impatient and bought a Submersive HP. Now I don't really care when they send it back. My advice is start shopping for a new one and sell the old one if they can fix it. Life's too short to be without a good sub.
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post #5 of 17
2/20/12 at 7:27pm
Thread Starter 
Thanks for the replies - I really appreciate them. I guess it couldn't hurt to call the local repair shop to see if they'll even look at it. I could take it apart but I really don't have much of an idea as to what I should look for.

I just dumped a few grand into a projector and surrounds in the new room and I'd hate to have to buy a new one. Then again, I'd hate to not have this setup without the sub.
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post #6 of 17
2/20/12 at 7:35pm
Quote:
Originally Posted by Slump Buster View Post

Thanks for the replies - I really appreciate them. I guess it couldn't hurt to call the local repair shop to see if they'll even look at it. I could take it apart but I really don't have much of an idea as to what I should look for.

I just dumped a few grand into a projector and surrounds in the new room and I'd hate to have to buy a new one. Then again, I'd hate to not have this setup without the sub.

You can also contact PSB and see what they suggest/offer even if you're not under warranty it never hurts to ask. OTOH a new and better sub isn't a bad thing...lots of great choices out there.
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post #7 of 17
2/20/12 at 8:11pm
Quote:
Originally Posted by lovinthehd View Post

You can also contact PSB and see what they suggest/offer even if you're not under warranty it never hurts to ask. OTOH a new and better sub isn't a bad thing...lots of great choices out there.

+1

The manufacturer is perhaps the best place to call, but more than likely it will be the most expensive option too. If you don't like what they have to say, or the solution turns out not to be cost effective, there are indeed a number of very good subs available for reasonable prices.
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post #8 of 17
2/21/12 at 5:08am
I had something like your situation a few years ago when a sub very slowly started humming more and more. As the sub was not worth fixing (relatively inexpensive, and also discontinued), I gave it to a high school kid and told him what the problem was.

I had prior gone through all the standard things for eliminating ground loops like you did.

It can cost $200-300+ to get a sub repaired and the repair is guaranteed for 30-90 days. Sometimes you can get lucky and replace a few capacitors and the amp is repaired.

Or try the PE 300w BASH amp
http://www.parts-express.com/pe/show...number=300-750

I used the PE 500w BASH amp as a replacement on one of my subwoofers.
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post #9 of 17
2/21/12 at 10:54am
You may be able to replace the plate amp with similar power like this. $120

http://www.parts-express.com/pe/show...number=300-804
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post #10 of 17
2/21/12 at 5:35pm
Thread Starter 
Quote:
Originally Posted by wwinkler View Post


Or try the PE 300w BASH amp
http://www.parts-express.com/pe/show...number=300-750

I used the PE 500w BASH amp as a replacement on one of my subwoofers.

Thanks for the links to the amps - it hadn't occured to me that I could switch them out. If I may ask a completely novice question - do I need to do anything else? I saw one of the comments in the link above say that a psb owner had a similar problem and was able to switch out the amps. Is this fairly easy to do? I've modded other electronic devices but I've never opened up a sub or speaker.

Once again, thank you to all of your help. This forum has always been a fantastic resource.
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post #11 of 17
2/22/12 at 4:38am
Most of the time the replacement amp is slightly different in size than the original amp. In my situation, I had my son glue 2"x4"s in a rectangular shape in the rear of the subwoofer to which he attached the replacement amp. He needed to lengthen the two power cords that attach to the speaker. The old amp was 7"x13" and the replacement 8"x12".

Sometimes, it is somewhat difficult to take off the old amp because it has been glued down. In that situation, you need to slowly pry the amp loose. The remaining situations are when you merely unscrew the screws and remove the plate amp.

You can also contact PSB to determine whether it is possible to purchase a replacement amp (which would be the exact size that you need).
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post #12 of 17
2/22/12 at 4:52am
Thread Starter 
Ah, thanks much for that info. So if the sizes are different is it a matter of drilling new holes into the case in an atempt to get at least some of the plate attached to the cabinet? I'll probably need to visit the DIY section at some point. I saw a guy post that PSB asks almost $400 for a replacement amp. I do have a ticket open with them but their site says they are backed up.

While searching for replacement amp info I came across a post from a guy that had a similar situation with his psb amp and he was able to correct it by plugging the amp into a 3-prong plug and running a grounding wire inside the amp. I've asked him for more details. It couldn't hurt to give the $5 solution a try.
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post #13 of 17
2/22/12 at 5:00am
I'm pretty sure there is some proprietary circuit for that ported design, if you decide to pick up a plate amp, stuff the port and go sealed. Start with PSB for advice....
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post #14 of 17
2/22/12 at 5:07am
Quote:
Originally Posted by Slump Buster View Post

Ah, thanks much for that info. So if the sizes are different is it a matter of drilling new holes into the case in an atempt to get at least some of the plate attached to the cabinet? I'll probably need to visit the DIY section at some point. I saw a guy post that PSB asks almost $400 for a replacement amp. I do have a ticket open with them but their site says they are backed up.

While searching for replacement amp info I came across a post from a guy that had a similar situation with his psb amp and he was able to correct it by plugging the amp into a 3-prong plug and running a grounding wire inside the amp. I've asked him for more details. It couldn't hurt to give the $5 solution a try.

If you remove the old amp then the new must completely fill the opening and be sealed (by whatever means it takes).
You do not have to mount the new amp to the sub, simply drill a small hole and run new or extended wires to the subs speaker (disconnect from old amp), make sure you caulk/silicone the hole to seal it.
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post #15 of 17
2/24/12 at 7:21am
Thread Starter 
Quote:
Originally Posted by jackbuzz View Post

If you remove the old amp then the new must completely fill the opening and be sealed (by whatever means it takes).
You do not have to mount the new amp to the sub, simply drill a small hole and run new or extended wires to the subs speaker (disconnect from old amp), make sure you caulk/silicone the hole to seal it.

So what are the external mounting options? Some kind of external bracket? This approach sounds better as I would, in theory, have to account for a smaller hole. Would I have to also purchase some wire extension kit as well?
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post #16 of 17
2/24/12 at 7:22am
Thread Starter 
PSB did finally get back to me. I am guessing that this is probably outside of my skill level and not worth paying for because (as others have said) you don't know if that will fix the problem.

You have a SubSonic II or SubSonic III subwoofer due to the style of Amplifier shown. These are the first two models of Powered Subwoofers PSB offered.

From the video, I would say that you need to have the amplifier serviced.

Due to the age of this model, it could be the Capacitors in the power supply are starting to dry out. If those are replaced, we would also recommend replacing the 15V regulators at the same time.
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post #17 of 17
2/24/12 at 9:45am
Quote:
Originally Posted by Slump Buster View Post

So what are the external mounting options? Some kind of external bracket? This approach sounds better as I would, in theory, have to account for a smaller hole. Would I have to also purchase some wire extension kit as well?

If looks aren't a concern than any kind of wood box (or whatever) to hold the new amp would work (then just set on top of sub or in rack, wherever). Just leave plenty of room for heat build up, especially around the heat sinks, maybe a somewhat open design or drill some holes for ventilation.
Disconnect old wire and add to them for the appropriate length.
Yes you could attach to back of sub with some sort of brackets or scrap lumber build up and screw/bolt on. Might create a hazard for electrocution if left completely open.
For looks:
Best option would be to find an amp with a little bit bigger cut-out and enlarge the hole.
Or make a plug for hole and cut new opening (into plug) for new amp.
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