JBL PB12 - Major Problems - NEED HELP (1 Viewer)

[RickM]

I need some serious help. About 5 years ago I used the expertise in this forum to help me setup a sweet home theater (at least within my budget ). Well since then I have mainly been a lurker just popping in from time to time to read about current issues and try to lend a hand when I had some interesting info. This time I need to try to figure out what the heck is going on with my subwoofers.
Description of problem:
At about 6am Sunday morning, my wife and I jump out of bed when we start hearing a loud rumbling in the house. After about 40 seconds of running around trying to find out where the noise is coming from we realize it’s the subwoofer in the basement. Nothing else is on, not even a light. The subwoofer is just hammering/firing away at full volume (louder than I have ever heard it during any movie). We turn it off and deal with the now awake baby – so much for sleeping past 7am. Why on earth would a subwoofer start going off like that? It was in standby mode, and had been for months, since we use it almost every night. Well tonight I tried turning it on again and it just starting hammering away the instant it came on. Then I unplugged it from the Receiver and turned it on – same thing, it just hammered away. Then I moved it over to another outlet, still unplugged from the receiver – it still hammered. What should I do with this thing trash it?
Strange, but true, information:
:frowning: Back in 1998, I purchased a JBL PSW-D112 powered sub from my local Best Buy. In November of 2001, the subwoofer started doing this hammering thing (firing with no other equipment on). Since it was still covered by the extended warranty, I took it back for repairs. After 8 weeks I began calling them every week for an update. Each time they said that it just JBL was waiting for the parts to fix it and it should be back in a week or two. Well after 5 more weeks (total time over 3 Months), I spoke with the manager and he said that he would call the next Monday and tell me where we stand. Wednesday of that week, I called him again, and they said it had been fixed and would be ready for pickup next week. The next week (almost 4 Months with out a sub now), I called and he said that JBL had lost it. WTF!?!?! They couldn’t find the thing and that weekend I had them replace it with a new JBL PB12 ----only 9 Months have passed and that is subwoofer I am writing about. Both subwoofers were using the same APC SurgeArrest (and my Receiver, DVD and TV use it also with no problems).
Equipment Details:
Pioneer VSX-D608 (Receiver)
Pioneer DV-C503 (5-Disc DVD Changer)
Toshiba VCR (its HI-FI stereo though)
Zenith Cable box (courtesy of COX cable – ok, I still got cable, don’t laugh)
Toshiba Cinema Series TP61G90 (61 inch progressive scan RPTV)
JBL PB12 (powered sub) – THE PROBLEM.
JBL speakers for all other channels (they are all matched and have had for years).
Using a standard APC SurgeArrest power strip for all of these (except cable box)
Sub Connection Details:
I was using a standard “Monster Cable Subwoofer cable” (RCA Connections) straight from the Receiver “subwoofer output” to the “line level in L” on the subwoofer. The LFE was set to “ON” and the Receiver was configured correctly (Sub ON, and Front speakers to SMALL). I checked this but have since changed them back to Sub Off and Large for the front speakers (as my sub is now dead to me).
If you need any additional information, please ask me. Otherwise I plan to pay a special visit to Best Buy and speak with the stores manager this weekend.
Thanks in advance.
Rick.

 

[David_Stein]

would you say that its a 60Hz signal? im not an expert by any means, but it seems to me the only way it could do that is if somehow the ac power signal is getting "leaked" into the input...

? i dont know, hope someone here has seen this...

 

[Chris Tsutsui]

The problem simply appears to be a technical one with the subwoofer. The only place it can get a signal from explained above would be the electric outlet and it is highly unlikely for that to cause a sub to hammer away.
I've heard of Reliability issues with the PB12, this may just be another on of those cases. You did get it from JBL so it could have been a "fixed" model and not an updated bug free model. (Just guessing)
Even if it was getting a 60hz signal it's a technical fault with the amp. I wonder if this what it sounds like when a subwoofer oscillates?

 

[Brian Fellmeth]

You have 2 options. The obvious one is to replace it with a Sony wm-40, SVS, adire or Hsu etc. If budget is tight, you can salvage it by using some funky old receiver from the 70's that may be in the attic or from a garage sale to power it. you would have to bypass the JBL amp which is probably hopelessly fried. Email if you want instructions on how to do this.

 

[CollinMorphew]

What a coincidence! Last night, my PB12 did something similar. It is doing a machine gun like sound. I think I messed something up when I added some polyfill. Anyway, it does this popping when there is no signal from a receiver. I can hold the woofer down and it stops but if i move it a little it starts again. If I try to put a signal to it from the receiver--it just pops. I would be interested in knowing how to by pass the JBL amp. I have a couple of amps with open channels but they are NOT high powered and not bridgeable. I have an extra Sony from a prior set up but I would like to still use the JBL--any thoughts. (sorry to jump on your thread Rick with the same issue and no resolution)

 

[Jason Hammerly]

One thing that concerns me.

You didn't have this thing plugged into the outlet on your receiver did you? When you said you unplugged it from the receiver you meant the LFE feed right? Just making sure. I'd say this looks like a good excuse to get a new subwoofer if you ask me. CAn you do a DIY subwoofer? I built a Nice sealed Tempest with a 250 watt amp for around $250 with little more than a circular saw, some glue, drill and screws, and a few 24" clamps. Looks very nice to. Just a thought.

 

[Fred K]

A couple of weeks ago my PSWD112 started thumping at 3:30 in the morning; freaked my wife out- she thought there was somebody trapped in our garage banging to be let out (heh-heh-heh). Made it downstairs just in time to here the SW make a sort of squelch sound and give up the ghost. A friend of mine and I bought two of these JBLs on-line for $167 (shipping included) two years ago. His blew after about eight months and then again about three months following its JBL-authorized repair.

Mine lasted a full two years, so I consider myself one of the luckier PSWD112 owners; at $83.50 per year, not too bad. I junked it and yesterday ordered a HSU. There was a rumor that the PSWD112 suffered from a particular kind of amplifier flaw that was subsequently corrected, but I’m really skeptical of that now. You can read on the forums of PB12s and even Infinitiys suffering the same fates- so I kind of wonder if it isn’t something inherent in the less expensive Harmon Kardon SWs.

Anyway- from everything I’ve heard and read, I wouldn’t worry too much about when your PB12 is repaired- probably won’t last long, anyway.

 

[RickM]

This is why I like this forum, lots of nice people trying to help! Thanks everybody!
So far the suggestion of the AC power leak into the woofer and the 60Hz power oscillation seems to be a logical possibility. If some internal components are just passing the power straight through to the woofer it might just make a 'hammering' noise. Of course it still means that JBL subs have some serious design flaws (I have had 2 in a row do this).
David_Stein: I really don’t know what range it was, not sure I could guess – still kind of a newbie. The sound seems to be more like 60Hz - 100Hz spread. You can really really hear and feel it. I bet the sub would do a little floor dance if it wasn’t so heavy (about 25-30 pounds).
Chris Tsutsui: Yea, I’m not really sure if JBL makes a quality product anymore. When I went to Best Buy and spoke with the manager about my lost JBL sub, he told me to just go and pick up another one right off the floor. So this unit came straight off the Best Buy floor, and was being sold as a new unit. It wasn’t a factory-refurbished unit.
Brian Fellmeth: This is what I’m afraid of, and I really don’t have the money to replace it right now. Maybe if I get a Christmas bonus (I work in the telecom sector) I can replace it with something. I don’t really have any extra equipment to try to bypass the Amp – we donate working stuff or trash broken things. Since I still have my Best Buy paperwork, and this new unit should still be covered by the extended warranty I had – It may be best to try and get them to replace it with another brand (of my choice from their limited selection).
CollinMorphew: First I’m sorry that your sub is starting to act up. Secondly, you are more than welcome to ‘jump on’ this thread! I haven’t made any modifications to my PB12, and it never gave any clue it was about to die (no power hums, pops, etc.). Good luck with yours.
Jason Hammerly: The plug (power) came from a powerstrip, not the Receiver. I did mean that even with the LFE not connected to the receiver, it just hammered away, even when plugged (AC) into different outlets in the house (made sure they were on different circuit breakers). A DIY setup wouldn’t be too bad, except for the fact that I just don’t have the time. Its good idea, but with a 21 month old and the holidays, it would be really hard to find the time to put it together.
Fred K: Sorry to hear about your sub, but that is almost exactly what happened to us. Only mine is still hammering if it’s plugged into the wall and turned on (standby mode). Regardless of how this turns out, if the unit needs to be replaced, a JBL product will not replace it. Seems like JBL has dropped the ball with these models…
Thanks again everybody, I have lots to think about! I will keep this thread updated with any additional information I find.
Take care,
Rick

 

[TheLongshot]

As I've posted before, my PSW-D112 also bit the dust the same way a couple of weeks ago. I'm probably going to have a friend of mine, who is a musician and master salvager, take a look at it to see if we can fix the amp. Otherwise, I'll wait until I get my year-end bonus to pick up a new sub, most likely an SVS...

Jason

 

[Jo_M]

I've had my PB-12 for almost a year now and so far no issues. It does hum when it's on and the room is very quiet but I just figured that it was the amp that hums.