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Thread: JBL / Altec diaphragm compatibility?

  1. #1
    Senior Member Doc Mark's Avatar
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    JBL / Altec diaphragm compatibility?

    Morning, Friends,

    I have a pair of JBL 2420 drivers, and also a pair of Altec 902-16HF drivers. I wonder if the diaphragms for these drivers are interchangable? I am seeming to remember that the hole patterns in them are different, but can't recall, for sure. Also, I dug out a pair of NIB Altec #3467 diaphragms, and am considering changing out the 16 ohm diaphragms that currently reside in the 902's, with the 8 ohm version. But, I also considered trying them in my 2420's, just for grins. However, none of this will actually happen until later this Summer. Just wanted to run it past you all before thinking further on the matter. Take care, and God Bless!

    Every Good Wish,
    Doc

    P.S. Somewhere on this forum, I found a discussion of the EV T35A, with lots of interesting opinions on both sides of it, both good and bad. This morning, when I was down digging out my goodies, I ran across a box in which I'd once mounted my 2420's, and I had forgotten that I actually used an EV T35A inside that box with the JBL! I recall being very satisfied with the musical sound of it, and it definitely added some sparkle to the 2420's on the high end of it! For what it's worth, thought I'd mention that here, just for grins.
    The only thing that can never be taken away from you, is your honor. Cherish it, in yourself, and in others.

  2. #2
    Senior Member Steve Schell's Avatar
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    Hi Doc Mark,

    Though your JBL and Altec drivers share a common ancestry they do not have interchangeable diaphragms. The voice coil dimensions are compatible, but the locating pins and ring mounting screws are on slightly different diameters.

    When Jim Lansing left Altec in 1946 to begin JBL, most dimensions from the Lansing 801 of 1937, later employed in the Altec 802, were carried over to his new 175. He enlarged the diameters for the locating pins and screws by 1/16" though, perhaps to eliminate the possibility of Altec diaphragms being used as replacements in his drivers. These dimensions have remained different all through the years in the Altec and JBL product lines. Another change was that the tangential compliance on the JBL diaphragm "spins" in the opposite direction from the Altec compliance.

    Most of this info comes from my friend Robert Grunberg who happens to be here at the moment and knows these drivers inside out.

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