Question about JBL PB10 Subwoofer

1 Answer

Thump at the time of shutoff

Recently I had a current spike in my house while using my stereo system that shut off all my components (turntable, preamplifier, amplifier and the two JBL PB10). The spike was about one second long, or so. I turned everything back
on and each component worked fine again. When I turned
all system off, using my surge protector, I heard a quite
loud thump in the left JBL PB10 subwoofer (that also was
turned off from the same surge protector). This thump was
heard for the first time in 2-3 years sicne I'be been using
the pair of the JBL PB10. Now is does the same every time
when I turned the system off. What might be wrong with
that JBL BP10 powered subwoofer? Or, how to eliminate
the thump (turning off manually the JBL before turning off
the other components?). Thank you in advance for any
possible assistance and support in this matter,
Emil - Harford, CT

Posted by on

  • Emil_anghel Mar 08, 2008

    To Renosean:

    Thank you very much for your response and clarifications. The problem here is there was never

    a thump in my left JBL SB10 subwoofer at the shutooff using the same powerstrip command to turn of all components off. I personally don't see

    why shutting off the subwoofer from a power strip

    and not from its own power switch would induce that bothersome thump. I believe that something happened to the output capacitor you're referring to and therefore it needs to be replaced, but I am

    not tottally sure that this will solve the problem. In

    any case, thank you very much again.

    Emil - Hartford, CT


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The amplifier in the sub as with any other amplifier has a capacitor in it. Essentially a battery that holds a charge. When you trun things off such as subs or amps with a powerstrip instead of the intended on off button, the power supply has been cut, but the capacitor is still energizing the unit. So it catches the noise in the line.

Posted on Mar 08, 2008

  • Sean Johnson
    Sean Johnson Mar 08, 2008

    It is very possible that it was damaged, but many factors play into a pop, before you may have been using a different brand or protection level of strip. Also nearby wires could be affecting it. Depending on the value of the sub you may find it cheaper to replace the entire sub. Capacitor jobs can run cheap or expensive depending on if the part or board needs to be replaced.


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