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Thread: 4365 has quality problems

  1. #16
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    It appears to these eyes that the metal in the dome of 476Mg is interacting with that of the phase plug ( just a guess ).

    Were there loose oxides present in the shape of those 4 concentric rings ( matching the slits in the phase plug )?


  2. #17
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    Quote Originally Posted by martin_wu99 View Post
    Today two local audiophile complained that their 4365s have quality problems after two years using,they said thses problems are very common in 4365.
    1.476Mg cladding material is easy to exfoliate,this will block the gap.
    2.the magnetic steel is easy to rust.
    These problems caused the compression drivers don't have same SPL.
    Why?
    What was JBL response? Did they get new drivers?

    I am waiting on answer.

    Seems to me like incompatible metals are used togheter, causing galvanic corrosion.

  3. #18
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    Here's a relevant thread (hosted over at DIYaudio ) about Corroding Magnesium cones on SEAS drivers!






    Some ideas within that thread on cone protection.


  4. #19
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    Replacing with TrueExtent Be diapraghms would solve the problem, you think? Or are other parts likely damaged/corroded as well?
    My service guy told me only diaphragm was affected.

  5. #20
    Administrator Robh3606's Avatar
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    Replacing with TrueExtent Be diapraghms would solve the problem, you think?
    Probably not the response curves are not identical so trading one problem for another so to speak.

    Rob
    "I could be arguing in my spare time"

  6. #21
    Administrator Robh3606's Avatar
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    Hmm wonder what's going on? How is so much moisture getting inside the drivers?? Could condensation do that?? Cold driver vs damp humid air??

    Rob
    "I could be arguing in my spare time"

  7. #22
    Dang. Amateur speakerdave's Avatar
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    Two suggestions for JBL (and Seas): 1) hire a metallurgist; 2) create an upgrade path by re-engineering the crossover with a true extent/JBL Be diaphragm. They have a crack engineering staff that could put that together in good time. Oh, wait . . . .never mind.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

  8. #23
    Senior Member 4345's Avatar
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    Rust

    Could JBL have made the phase plug using a different method or material? Could it be plated metal rather than solid metal? Could it be from a new factory using inferior metals. Maybe they are importing this part and not making it as they did for the last 70 years? I think it said" Designed and Engineered in the USA". Not "MADE IN THE USA".

  9. #24
    Senior Member baldrick's Avatar
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    Have never opened mine 4365... how do one remove the driver?

    476mg is used also in S9900 and DD65000, so this could probably be a quite huge problem for JBL!?

  10. #25
    Senior Member HCSGuy's Avatar
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    On a whim, I cracked one of mine open - looks pretty clean, though there is a faint shadow on the diaphragm. This is good as I got mine "Sideways" as bare drivers and don't have any warranty recourse against JBL. I also live in the high desert, so very low humidity, which can be a blessing, as nothing rusts, and also a curse, as your sandwich gets stale if you don't eat it in a hurry Lastly, I wonder if there is any production change - my drivers are very early production. Here are a few pics:Name:  Diaphragm4mp.jpg
Views: 259
Size:  56.5 KBName:  Driver4mp.jpg
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Size:  56.0 KB
    That the internet contains a blog documenting your life does not constitute proof that your existence is valid. Sorry.

  11. #26
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    HCSGuy , So coincidentally (??) your non-rusted phase-plugs are mated to a diaphragm with a cleaner glue line ( than the others have displayed above ).



    The rust around the edge of the phase-plug perimeter is in quite close proximity to the glue line seen on the inside of the diaphragm.



    Reactive\\\Corrosive glue maybe ( that's out-gassing ) ?




  12. #27
    Senior Member Mctwins's Avatar
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    Quote Originally Posted by martin_wu99 View Post
    Today two local audiophile complained that their 4365s have quality problems after two years using,they said thses problems are very common in 4365.
    1.476Mg cladding material is easy to exfoliate,this will block the gap.
    2.the magnetic steel is easy to rust.
    These problems caused the compression drivers don't have same SPL.
    Why?
    In the first picture where one can see the cable(negative wire) there is a faston connection. Can this be right, I thought it schould be soldered. The tiny cables looks strange as well, compare to some pictures I have seen, more of a flat cable and solder too.

    When you are saying "they said thses problems are very common in 4365." who is they?

    The trancducers must have been in some moisture enviroment for some time. Just my guess.

  13. #28
    Senior Member Mctwins's Avatar
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    Quote Originally Posted by Earl K View Post





    Thanks, great pictures, excactly what I mean about the cables.

  14. #29
    Senior Member HCSGuy's Avatar
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    Quote Originally Posted by martin_wu99 View Post
    Today two local audiophile complained that their 4365s have quality problems after two years using,they said thses problems are very common in 4365.
    1.476Mg cladding material is easy to exfoliate,this will block the gap.
    2.the magnetic steel is easy to rust.
    These problems caused the compression drivers don't have same SPL.
    Why?
    There seems to be a miscommunication in this thread - the aquaplas "cladding" is on the side of the diaphragm that is away from the magnetic gap - if it all flakes off, it will fall into the insulated back cover of the driver, but will not go into the magnetic gap, as the diaphragm separates the aquaplas from the gap. However, if there is a problem with flaking rust on the phase plug, this will easily fall into the gap, causing the problems mentioned.
    That the internet contains a blog documenting your life does not constitute proof that your existence is valid. Sorry.

  15. #30
    Senior Member martin_wu99's Avatar
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    Quote Originally Posted by 4345 View Post
    Could JBL have made the phase plug using a different method or material? Could it be plated metal rather than solid metal? Could it be from a new factory using inferior metals. Maybe they are importing this part and not making it as they did for the last 70 years? I think it said" Designed and Engineered in the USA". Not "MADE IN THE USA".
    Yes,it is Mexico made.
    46 lover

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