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Thread: JBL 2425J replacement diaphragm question/opinions

  1. #1
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    JBL 2425J replacement diaphragm question/opinions

    Hi All.

    I have a question for you all as a horn newbie that I hope you can help me out with. I recently acquired a pair of JBL 2425J drivers on the cheap and found, when I took them apart to check the diaphragms and to get rid of the decaying foam inside, that they contain an original titanium JBL diaphragm in one, and a knockoff titanium diaphragm in the other. By all reports, and some quick listening, the JBL sounds noticeably better. I am at the point where I would like to either buy another 16 Ohm JBL diaphragm (the one I have measures very close to the top end of the 6.5 Ohm +/- 10% spec at 7.1 Ohms, so this may be a problem), or purchase a new pair of Radian 1225-8 diaphragms instead. I will be using these drivers with either 511Bs or a pair of CD horns that I have on hand, with a Peavey FH1 as a bass bin. This two way will be used for home hifi use with low wattage tube amps (my primary hobby is building tube amps, mostly SETs). I am hoping that you have some advice on what would be the best way to go, and any tips that you have on properly installing the diaphragm or diaphragms that are recommended would be much appreciated.

    Cheers,
    Tiz

  2. #2
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    I'd vote for the radians for home use, if you can tweak the XO etc. to suit.

    Quote Originally Posted by tizman View Post
    Hi All.

    I have a question for you all as a horn newbie that I hope you can help me out with. I recently acquired a pair of JBL 2425J drivers on the cheap and found, when I took them apart to check the diaphragms and to get rid of the decaying foam inside, that they contain an original titanium JBL diaphragm in one, and a knockoff titanium diaphragm in the other. By all reports, and some quick listening, the JBL sounds noticeably better. I am at the point where I would like to either buy another 16 Ohm JBL diaphragm (the one I have measures very close to the top end of the 6.5 Ohm +/- 10% spec at 7.1 Ohms, so this may be a problem), or purchase a new pair of Radian 1225-8 diaphragms instead. I will be using these drivers with either 511Bs or a pair of CD horns that I have on hand, with a Peavey FH1 as a bass bin. This two way will be used for home hifi use with low wattage tube amps (my primary hobby is building tube amps, mostly SETs). I am hoping that you have some advice on what would be the best way to go, and any tips that you have on properly installing the diaphragm or diaphragms that are recommended would be much appreciated.

    Cheers,
    Tiz

  3. #3
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    Quote Originally Posted by tizman View Post
    Hi All.

    I have a question for you all as a horn newbie that I hope you can help me out with. I recently acquired a pair of JBL 2425J drivers on the cheap and found, when I took them apart to check the diaphragms and to get rid of the decaying foam inside, that they contain an original titanium JBL diaphragm in one, and a knockoff titanium diaphragm in the other. By all reports, and some quick listening, the JBL sounds noticeably better. I am at the point where I would like to either buy another 16 Ohm JBL diaphragm (the one I have measures very close to the top end of the 6.5 Ohm +/- 10% spec at 7.1 Ohms, so this may be a problem), or purchase a new pair of Radian 1225-8 diaphragms instead. I will be using these drivers with either 511Bs or a pair of CD horns that I have on hand, with a Peavey FH1 as a bass bin. This two way will be used for home hifi use with low wattage tube amps (my primary hobby is building tube amps, mostly SETs). I am hoping that you have some advice on what would be the best way to go, and any tips that you have on properly installing the diaphragm or diaphragms that are recommended would be much appreciated.

    Cheers,
    tizman
    Tiz,

    I think you'll find that the lower limit of the 2425/6/7 series of legacy drivers is around 600hz ( no matter what size horn is attached to the driver ).

    Currently I don't think the lower limit of the Radian diaphragm has been established ( it might well be higher than 600hz ).

    You can easily check this question out for yourself ( the LF limit ) by attaching the one 2425J ( with original JBL diaphragm ) onto a Altec 511b horn and then taking a response measurement .

    The Peavey FH1 ( like the original La Scala ) might have an upper limit that isn't high enough to mate with the low end limit of these metal diaphragmed drivers.
    - Have you measured the response limits of your FH1's ?

    As Klipsch did, I believe you might need to use a phenolic diaphragmed driver that can reach down to at least 400hz ( there may well be a Selenium or PRV driver that can do that > but I don't really know ).

    Should you end up going with a phenolic diaphragmed driver you'll need to add a super tweeter.

    I think Bob Crites has most ( if not all of ) the answers to the challenges you'll be facing to make your concepts work.


  4. #4
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    Quote Originally Posted by Earl K View Post
    Tiz,
    ......Should you end up going with a phenolic diaphragmed driver you'll need to add a super tweeter.

    I think Bob Crites has most ( if not all of ) the answers to the challenges you'll be facing to make your concepts work.

    Earl, thanks for this link. Have you (or anyone else) had ears on these mid frequency drivers? Any opinions?

  5. #5
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    Rusty,

    I haven't heard that mid/driver but there's an LHF member ( from Australia ) who bought a pair for use within his custom 3-way build.

    I'll look for his thread and then post the link.

    OK, that was easy!

    Here ya go ( click the first pic );





    Yes! Very Cool Build!


  6. #6
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    Thanks Earl, I remember that build, but didn't catch the mid driver. Lovely speakers.

  7. #7
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    If you want phenolic, these phragms are supposed to fit, though they take more care in setup (missing alignment pin slots as I understand). Definitely will need a supertweeter with phenolic. I'm thinking about picking up a pair of 2470 cores and slapping these in there, but don't really need a new project.

    https://www.amazon.com/Replacement-D.../dp/B07KX4D4WZ

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