Question about JBL PB12 Subwoofer

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"Dhoom" sound from subwoofer

My subwoofer used to work perfectly, but after I unplugged the power once without turning the unit off, it stopped working. Even after giving the LFE input from my Harmon Kardon receiver, the light remains red. Plus, it makes loud "Dhoom" sounds intermittently when power is on.

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  • 2 Answers

SOURCE: Infinity PS-12 Subwoofer clicking in and out of standby

I've got the same problem with my PS-10 from Infinity. It works great for about 30-45 minutes, then click in and out of standby mode. It sounds to me like a overheating safety fault. When I take off the amp panel (unplugged), it feels quite warm, and you can see that there is really no way for heat the escape. I tried running it briefly with the amp panel outside and it seemed to work fine! Since I'm out of warranty, I think I'll try cutting some ventilation holes. I noted there are 2 oval shaped holes near the bottom (just above amp), but covered with the panel sticker. I'll try cutting those open first.

Posted on Dec 19, 2009

  • 308 Answers

SOURCE: JBL Subwoofer - Intermittent operation

Sometimes bad caps show a lifting or rounding of the top of the cap, sometimes this top will split from heat and pressure and sometimes it will not show any sign of damage but will be dry inside and its capacitance value will drop to a very low value. Replace the big power supply caps and test again. Get the same size, value and voltage rating. You can go higher on voltage rating and a bit on value. Getting a similar size or something that will fit in the same space is important also.

Posted on Mar 24, 2010

  • 14 Answers

SOURCE: The subwoofer stops working and makes a loud flat

One year waranty period from JBL on the electronics.

To find the authorized JBL service center in your area:

  • Go to:
  • Click on United States
  • Click on Support at the top
  • Click on Find My Product
  • Enter your Model Number or Select your Product from the drop down list; then SUBMIT or SEARCH
  • On the list on the left side, click on Service Center
  • Supply your zip code at the next screen, then FIND
  • A list of service centers in your area will come up.

Posted on Nov 23, 2010

SOURCE: I have a JBL venue sub10 subwoofer. I noticed a

Hi well i would think that perhaps a capacitor in a cross-over network may have failed? What top do is open up the speakers and locate the capacitor, and inductor, cross-over network, that's the part that splits the frequencies to each speaker, hi, mid, bass, and simply replace the capacitor "On Spec" as it were, this or simply replace the entire cross-over network? this may help. It's worth a shot anyway? It also may simply be a bad speaker? again replace "on spec".I don't think from what you describe that you have "Overlooked" anything at all, it's just bad luck.
"on spec' simply means to replace without thinking about it....

Posted on Sep 26, 2011

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No sound plugged in with low green light on and connected properly. This unit worked perfectly for 3 years never an issue, now there is only a low hum, with no response to the input.

If the fuse has gone you would get no power at all. Subwoofers are basiacally mono amps that only put out bass tones. So when you get no sound the likely cause is the semiconductor that does most of the work that amplifies the signal. It could be an IC amp or FET or a Transistor, it could have an heatsink on it. But I would look to that for the cause of your problem.

Dec 16, 2012 | Sunfire Super Junior Subwoofer

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Humming sound in subwoofer after it's been playing for a while

It sounds like you are describing an earth loop problem. I won't go into detail in this post, but try an isolation test first. disconnect everything from the reciever except the sub and try connecting say a BATTERY powered mp3 player or cd player to minimise connections to the electrical mains earth. you could also isolate things by taking your sub to a friend's house and trying it on their system.
If it is an earth loop use a process of elimination to find out which two pieces of equipment causes the earth loop. then apply filtering.
you can buy earth loop isolation transformers for about AU$26 and I've used one on my sub myself. Theyhave RCA (phono)plugs on each end and they connect inline with the signal cable to the sub amp.

as for the thumping sound it might be the speaker protection circuitry cutting off the amp to protect the subwoofer speaker from damaged. This might be triggered if the earth loop sound is causing the sub amp to overload and clip.

Failing this there might be a dried out overheated electro capacitor in the amp circuit causing the hum. Hav a chat to your local electronics person, who should be able to spot it!
Hope this puts you on the right track
Happy Hunting!

Jan 07, 2010 | Sunfire Speakers & Subwoofers

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yes. A good idea. Kill power to the sub, then unplug and remove everything from the sub. go ahead and plug it in again and check for buzzzz.
That is test one. if you have buzz still, its the sub assembly. bad luck, but not impossible. If the buzz is gone its one of the signals to the sub. They can produce a buzzz without any signal coming from your stereo equipment. Replace the feed line, enjoy! BTW...Kef sure does sound clean. good choice.

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No sound

1. Verify unit is plugged in and power outlet used is active.
2. Is power switch on?
3. Is auto turn on/off set properly?
4. Is unit receiving an input signal from your source?
5. Have all controls on subwoofer (volume, crossover, phase, etc.) been
properly set?
6. If unit has been running at high levels, one of the protection circuits may be engaged.
7. Has the built-in amplifier overheated?

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I will try as best I can... There is no light on the unit. There is a two position switch, that's your on/off switch located on the botttom of the unit next to the pwr cord input... When the straight lined side is pushed down the unit is energized. When you pwr up the unit you should hear a light bump, not a cracking noise. There is a fuse on the main input/output board that is pretty easy to pop and swap.

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Sounds like an inadequate ground wire in the signal cable. You may have to replace the cable between the reciever and bass module. It also, however, may be IN the bass or reciever module.

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