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Thread: Woofer surrounds question

  1. #1
    Member Steelyfan's Avatar
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    Woofer surrounds question

    I have a pair of L36 with 125A woofers which have been refoamed
    with a surround that is too generous ; as a result the roll is protruding more
    than the standard one. 9mm or 1/3" "above" the cone edge
    My question is : Can the speaker get damaged ?
    Does this affect sound ? Compared to other speakers (more expensive and much younger I must admit) the reproduction of mids is very weak. Maybe the surrounds are the cause ?

    All suggestions are welcome

  2. #2
    RIP 2009
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    My personal feeling is that a larger surround wouldn't allow for any more damage than normal because the spider also limits travel, and the speaker isn't going to go farther than the current in the voice coil allows for anyway. When it reaches the limit of its magnetic travel, it's not going any farther... It could conceivably affect the sound a little, because the compliance, (support stiffness), is likely different.

    John

  3. #3
    Member Steelyfan's Avatar
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    Quote Originally Posted by Steelyfan
    I have a pair of L36 with 125A woofers which have been refoamed
    with a surround that is too generous ; as a result the roll is protruding more
    than the standard one. 9mm or 1/3" "above" the cone edge
    My question is : Can the speaker get damaged ?
    Does this affect sound ? Compared to other speakers (more expensive and much younger I must admit) the reproduction of mids is very weak. Maybe the surrounds are the cause ?

    All suggestions are welcome
    I have never paid attention to it but in fact my speakers smell very "chemical"
    do other owners of L36 have the same , or is this condenser leaking ?
    I would open them up , but I am not shure if visual inspection can show the failure.
    (fortunately the pots work without cracks)

  4. #4
    RIP 2013 Rolf's Avatar
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    JBL Smell

    Quote Originally Posted by Steelyfan
    I have never paid attention to it but in fact my speakers smell very "chemical"
    You have probably (for the first time?) got the JBL smell in your nose. Aaaaaa... sniff sniff.... I love it!

    Rolf
    It's really all about music.
    Rolf

  5. #5
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Steelyfan
    I have a pair of L36 with 125A woofers which have been refoamed with a surround that is too generous
    Who did the repair?
    bo

    "Indeed, not!!"

  6. #6
    Member Steelyfan's Avatar
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    whodunit

    Quote Originally Posted by boputnam
    Who did the repair?
    It was done by a technician
    here in Belgium, I im not sure that it is really out of spec. The quality of the reconing job itself is magnificent. In the picture it seems irregular in thickness, but that is the poor quality of the picture.

  7. #7
    Senior Member morbo!'s Avatar
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    maybe a seperate amp jbl`s dont like the the b channel

  8. #8
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by morbo!
    maybe a seperate amp jbl`s dont like the the b channel
    Dammit, morebo! !
    bo

    "Indeed, not!!"

  9. #9
    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    Quote Originally Posted by Steelyfan
    ...the roll is protruding more than the standard one. 9mm or 1/3" "above" the cone edge
    Picture looks pretty good to me.

    Granted, the cone seems slightly visually off-center - or maybe the surround is misformed...? But, can you hear any rubbing at low-frequency, maybe 30Hz? You might sweep the cone with a frequency generator and listen for any voicecoil rubbing. Use only about a 2 or 3 voltage drive. Should be plenty...
    bo

    "Indeed, not!!"

  10. #10
    Member Steelyfan's Avatar
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    Quote Originally Posted by boputnam
    Picture looks pretty good to me.

    Granted, the cone seems slightly visually off-center - or maybe the surround is misformed...? But, can you hear any rubbing at low-frequency, maybe 30Hz? You might sweep the cone with a frequency generator and listen for any voicecoil rubbing. Use only about a 2 or 3 voltage drive. Should be plenty...
    It is only the picture. The woofer is fine it does not give any problem itself ; it works 100% fine. It's the mids that do not come through in an A/B comparison. (I found another thread that talks about LE5 voicecoil former glue deterioration.)

  11. #11
    Senior Member GordonW's Avatar
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    Could be the LE5 voice coil former, or could be the L-pad (volume control) for the mid that's at fault. I've seen both, in several instances.

    I'd check the crossover L-pads, and look at the caps while you're there. It's not unheard-of for a cap to be bad, but usually, frankly, the LE5-6 will usually go out like a lightswitch, before the caps get taxed in the least... it's definitely usually the driver that gets toasted first.

    BTW: Woofer looks fine, on perfunctory inspection of the picture. I'd doubt that a surround could cause midrange weakness, anyhow... if there were bass issues, then I'd be concerned about the woofer, but the LE5 is going to be the target, if there's lack of midrange (I usually found the opposite, on a properly working L36, I wound up turning DOWN the midrange quite a bit, to like -3 or so, by my personal taste)...

    Regards,
    Gordon.
    This Is Gordon's Page: www.geocities.com/gordonwaters

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