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Thread: Problem with JBL subwoofer

  1. #1
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    Problem with JBL subwoofer

    I have a strange problem with one of my JBL subwoofers. Its the L8400P, part of the current Studio L Series.

    Its always in "Standby" mode. When it gets a signal from the receiver (HK AVR630) and switches on, it makes a loud noise, a "whistle". After that, it operates normally.

    I have another L8400P, and it switches on silently. As do two other JBL subs (E150P, Sub 12). Currently, only the "noisy" sub is hooked up to the system, which is a 7.1, consisting of all Studio L Series speakers.

    Any suggestions as to the cause of this "whistle"?

    I seem to recall reading a service bulletin on this very subject from JBL, but darned if I can find it after searching the net...

    Any advice would be appreciated.

  2. #2
    Senior Member rdgrimes's Avatar
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    That's the L8400 "chirp". Get used to it.

    Not sure why you have one that does and one that doesn't, but it's pretty much standard equipment on the L8400s. I think of it as a nice feature, cause it lets me know the sub has turned on.

  3. #3
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    I find it highly irritating!

    And its not consistent, sometimes it does it, sometimes not.

    If anyone can find that service bulletin, and post it, I'd appreciate it.

    If another JBL sub has this problem, and JBL advises how to fix it, maybe this noisy L8400P can be fixed too.

  4. #4
    Senior Member rdgrimes's Avatar
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    I suppose your best option will be to call JBL support and ask.

  5. #5
    JBL 4645
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    The auto-sense circuit
    http://manuals.harman.com/JBL/HOM/Owner's%20Manual/L8400P%20OM%20ADDENDUM.pdf

    http://manuals.harman.com/JBL/HOM/Ow...rev12-1-05.pdf

    Quote Originally Posted by rdgrimes View Post
    That's the L8400 "chirp". Get used to it.

    Not sure why you have one that does and one that doesn't, but it's pretty much standard equipment on the L8400s. I think of it as a nice feature, cause it lets me know the sub has turned on.
    I’d switch it off and leave it in normal operation mode so it can react fast! You won't see cinemas using this LOL there is thing called power ON/OFF when not in use switch it OFF like you would with the rest of the equipment.

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