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Thread: Jubal woofer fubar?

  1. #1
    Senior Member DanMan's Avatar
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    Jubal woofer fubar?

    Question about my L65's, and before you give me grief, lansing heritage automated email sent me my birthday greeting today.... so thanks and be kind ;-)

    I bought these Jubal L65's on ebay long ago, so I'm way over the 30 day return policy... ;-)

    It appears to me that the woofers were refoamed incorrectly - I added my comments in red in the pics below > I'm used to seeing my JBL woofer surrounds glued to the other side of the spacer onto the basket. (pardon if my terminology is incorrect).

    Are these surrounds indeed on incorrectly?

    The ohm meter shows 7.7 ohms across the woofer - what does that mean?

    The speakers 'sound' 'ok' up to about 85db, but I wont turn it up louder than that in fear of harming either the speakers or the amp.

    I bought these for the sound quality not quantity.

    Am I in fact getting distortion throughout the volume range or only at the new peak excursion limits?

    Is there a different mix of frequency response if they're on incorrectly?

    Should they be refoamed?

    Thanks.
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  2. #2
    RIP 2011 Zilch's Avatar
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    Yes, they should be refoamed.

    That's REALLY stupid what they did there. It's supposed to be UNDER the gasket at the edge, on the metal frame.

    At the cone, it should be on the rear, but that takes effort by someone who knows what they are doing.

    If the cone kit is available, have a full recone done by a pro.

    You were screwed by an idiot....

  3. #3
    Senior Member SEAWOLF97's Avatar
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    they are wrong. I wud have them refoamed.

    Z gave a better answer, while I was looking/typing.
    “If you think that’s the dumbest thing you’ve ever heard,
    just wait a couple minutes!”

  4. #4
    Senior Member grumpy's Avatar
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    ouch. clench your buttocks before pricing a recone... it would appear that an OK set
    of L65's might go for about the price of a pair of recones for this driver. Think I'd be looking for either
    a re-refoam (bastard side or not) or a functioning set of bass drivers that someone else
    has pulled. Someone else check me on this. -grumpy

  5. #5
    Senior Member DanMan's Avatar
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    thanks guys. recone it is.

    i guess that just leaves two questions that at this point are really more theoretical than functional -

    1- Am I getting distortion throughout the volume range or only at the new peak excursion limits?

    2 - Is there a different frequency response curve if they're on incorrectly (I'm assuming weaker in the bass region)?

  6. #6
    Senior Member grumpy's Avatar
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    Quote Originally Posted by DanMan View Post
    thanks guys. recone it is.

    i guess that just leaves two questions that at this point are really more theoretical than functional -

    1- Am I getting distortion throughout the volume range or only at the new peak excursion limits?
    almost certainly throughout... it appears you're already about 1/2 way out of the gap one way
    (harmonic distortion, which you may or may not pick up as sounding "bad")

    Quote Originally Posted by DanMan View Post
    2 - Is there a different frequency response curve if they're on incorrectly (I'm assuming weaker in the bass region)?
    I would -expect- so, and level dependent. One could look up studies on dynamic offset
    for characteristics that would be mild in comparison.

    Way to buck up for the recone... best way to go if these are keepers. -grumpy

  7. #7
    Administrator Robh3606's Avatar
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    almost certainly... it appears you're already about 1/2 way out of the gap one way
    (harmonic distortion, which you may or may not pick up as sounding "bad")
    Hello Grumpy

    You really don't know that as these are probably the wrong surrounds as well. The foams relative position has changed you need to look at the driver as a whole to determine what's actually going on. What you need to do is see where the spider is at rest. If it's flat he may not have as much of an offset issue as you would think.

    Rob

  8. #8
    Senior Member grumpy's Avatar
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    Quote Originally Posted by Robh3606 View Post
    Hello Grumpy

    You really don't know that as these are probably the wrong surronds as well. The foams relative position has changed you need to look at the driver as a whole to determine what's actually going on. What you need to do is see where the spiders is at rest. If it's flat he may not have as much as an offset issue as you would think.

    Rob
    Good points, and true... I don't know about the surround history and going
    from pictures is a bit of guesswork at best... a good spider is very likely to determine
    cone position at rest with a soft surround.

    Also true that it's way too easy for me to talk when it's someone else's $$$$.

    -grumpy

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    Wow, that's the screwiest resurround job, looks like one where the owner didn't even let the driver out of the cabinet or be unscrewed (although theoretically you could do a resurround in the cab).

    Another option is to just purchase a new (to you) used pair of woofers that have th correct surrounds or can be resurrounded, might be a cheaper alternative. There has been some discussion of potential interchanges of woofers for the Jubal cabinet, do a search and see what your options might be.

    Since a lot of L65/Jubals are being parted for the 077 tweeter, the correct woofers come up actually fairly often.

    As for the current woofers, if the cosmetics aren't a huge issue, you could consider stripping off the incorrect surrounds off the cone and trim pieces and start over, could be a fun learning experience to correctly resurround these. If you need trim pieces, they are easily obtained as are the correct surrounds. The only problem will be a somewhat unsightly edge where the old glue was located, but that can be hidden from view with the grilles on.

    Regards,

    Bart

  10. #10
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by mech986 View Post
    As for the current woofers, if the cosmetics aren't a huge issue, you could consider stripping off the incorrect surrounds off the cone and trim pieces and start over, could be a fun learning experience to correctly resurround these.
    Good perspective Bart!

  11. #11
    Senior Member edgewound's Avatar
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    Refoaming might be an option....if it's a JBL voice coil.

    That's a definite hack job. Not only is the surround on top of the non-JBL gasket, it makes the voice coil forward-biased to jump out of the gap due to the fact that there can't possibly be equal travel in both directions of the cone/coil assembly.

    The DC resistance is wrong too. What woofer is it? 126A, 122A or 129H

    The DC resistance range of the 126A and 122A is 4.5-5.5 ohms dc. The 129H DC res is 5.3-6.1 ohms, so your voice coil is suspect.

    C8R126A is no longer available, 122A and 129H both get reconed with C8R129H for $190.00ea.

    Your woofers could be rebuilt with clean take-out JBL cone coil assemblies.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  12. #12
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    Quote Originally Posted by edgewound View Post
    Your woofers could be rebuilt with clean take-out JBL cone coil assemblies.
    MMMMmm, JBL takeout, that's my kind of menu. Makes me hungry just thinking about it.

    Good point about the voice coils, didn't even think about the fact these could be incorrect woofers or even really bad recone jobs with the wrong parts. As evidenced by the workmanship, anything could be possible here.

    Regards,

    Bart

  13. #13
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    Look at the depth of the cone--or should I say lack of it? Doesn't it seem somewhat flat compared to normal?

    I'd pull them out and get a good look at the spider before doing anything else. If it is pulled forward, then it's probably distorted for good, and recone is the only solution that still uses those frames.

  14. #14
    Administrator Robh3606's Avatar
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    Here's a 122A

    Rob
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  15. #15
    Senior Member edgewound's Avatar
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    That fubar'd woofer is, in fact, a JBL factory cone.

    The DC res is suspect in that maybe someone did some "fancy stealth surgery" by replacing the voice coil and reusing the intact cone/dustcap...

    Hell...I dunno exactly what was done without seeing the guts of it....but it sure ain't right and it's not even pretty.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

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