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Thread: OEM 2421 Diaphragms just won't fit

  1. #1
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    OEM 2421 Diaphragms just won't fit

    Hi all I am at the very end of a 4345 build and am eager to hear these beasts for the first time. Long story short I have 4x OEM 2421 Diaphragms made in mexico. I have 3x 2425 compression driver to play with but only one will accept the OEM phragms. You can instantly feel the former or voice coil is rubbing on something. I initially thought the phase plug must have shifted at some point so I bought another 2425 to try, it's even worse. Aftermarket diaphragms will fit comfortably in these drivers. Any tips on how to get this to work? I am quite pissed off none of my NOS diaphragms seem to work.

  2. #2
    Senior Member RMC's Avatar
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    Hi kelossus,

    Looking at a JBL dia. interchange table. I see for the 2425 that D8R2421 and D16R2421 are listed, among others, as possible alternatives. So, doesn't seem like operator bad choice of dia. The problem is elsewhere. Sorry can't help you further.

    Richard
    POWERED BY: QSC, Ashly, Tascam, Rolls Mosfet, NAD, and Crest Audio

  3. #3
    Administrator Robh3606's Avatar
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    Can you post a picture or 2??? Could be they are out of round or the voice coil returns don't line up with the keys in the cores. Could also be the returns are not flush against the coil. Can you see a difference between what fit's and what doesn't?? The gap is .031 if you want to check the cores.

    Just throwing things out there. Hope you can figure it out.

    Rob
    "I could be arguing in my spare time"

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    That tangential diaphragm is the aftermarket one that fits
    Attached Images Attached Images      

  5. #5
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    The OD and ID seems very similar on all the diaphragms, aftermarket included. I think the problem might be with the lead wire coming off the voice coil. It feels a tad raised.
    Attached Images Attached Images    

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    Wow, that's truly a bummer ( though not such a surprise given the known teething problems with moving US production to Mexico > more than a decade ago ).



    I imagine this magnet ( shown above ) is the single JBL core that you mention accepts a new diaphragm ( because of the opposing >> slightly "hogged-out" areas seen within the VC gap ).

    That's what needs to be done >> slightly enlarge the gap ( but only in the immediate VC leads area ).

    Barry runs a Hi-End custom machine shop so maybe he'll chime in.


  7. #7
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    Your one driver with the + sticker on it does not appear to have much if any opening in the gap for the voice coil leads. Machining out the gap on a magnetized driver does not sound like a good idea, I don't think there's enough sticky tape available to clean out the gap!

  8. #8
    Senior Member 1audiohack's Avatar
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    Sorry to be so slow. Iíve been meaning to bounce in here for a week.

    If I had to save this thing I would pour it full of RigidAx to keep the debris out and sinker EDM the relief profiles in it. If not EDM, micro mill machine the reliefs, clean the debris out of the pockets and melt the RigidAx out of it. But thatís nuts.

    Letís just find another 2426 core with reliefs.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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