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Thread: How smooth is smooth...

  1. #1
    Trying to be nice Infredible's Avatar
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    How smooth is smooth...

    Few weeks ago I decided to order some new JBL factory diaphragms for my 4343 2420. I got the 2421 aluminium one. Yesterday with Mr Widget's help we did the replacement. Simple job you might thing. It was not that simple.
    My drivers are in mint condition and were never open. I think I read here that the 2420 came from factory without any red seal. Mine do have seals but not the wax type but a nasty red glue that hardly dissolve with solvent. It took well experienced Mr Widget and I over an hour to open both drivers. One had a particularly resistant screw that didn't want to come out. So after an hour of battling Mr Widget won over the screw but lost a screw driver.After that it was easy to replace the diaphragms to center them and sweep tone test them. Will back home late I decided to reassemble everything and to give those new guys a spin. Wow! what a difference! it is really obvious that the old one sounded much more harsh. They were in really good condition, they looked like brand new but the 2421 are so sweet. I can't compare them to Mr Widget TADs which are amazing but I can say that now my mids do sound a little like the TADs. It's got the same openness and effortless sound. So my take here is that anyone with old compression driver should go the extra mile and spend some money on really good diaphragms, it's really worth it.
    Thanks again Mr Widget, without you I would have never been able to open those guys by myself without destroying something.

    Fred.

  2. #2
    Senior Member
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    Thanks for that testamonial !

    It really does help the cause.

    <> EarlK

  3. #3
    Administrator Mr. Widget's Avatar
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    Glad I could help!

    It was a surprise at just how difficult it was to open those 2420s. Luckily we didn't have to chuck the beast into a vise on the mill and mill the screw out.

    I am glad to hear it was worth it. Let me know when you have some more Guinness and I'll be by for a listen.

    Widget

  4. #4
    Senior Seņor boputnam's Avatar
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    Re: How smooth is smooth...

    Originally posted by Infredible
    So my take here is that anyone with old compression driver should go the extra mile and spend some money on really good diaphragms, it's really worth it.


    Add this Thread to, well, this Thread! Refresh your vintage compression drivers

    And, yea, shucks - "Widgie" is a nice guy...
    bo

    "Indeed, not!!"

  5. #5
    Senior Member Ian Mackenzie's Avatar
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    Fred,

    Nice to see your JBL's now in A1 Condition.

    Ian


  6. #6
    Figge
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    Re: How smooth is smooth...

    Originally posted by Infredible
    So my take here is that anyone with old compression driver should go the extra mile and spend some money on really good diaphragms, it's really worth it.

    i´ll second that!

  7. #7
    Senior Member lpd's Avatar
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    Funny thing you mention the red glue!!! I too found a red gluelike substance, and used a white gas to loosen it up. It made for a nightmare replacing the diaphrams. If memory serves me right I had one screw that wouldn't budge and took the better part of a day to remove. Was the red glue applied at the factory or after the fact?

  8. #8
    Administrator Mr. Widget's Avatar
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    I am pretty sure that it was used at the factory after they stopped using red wax seals with the JBL stamp. These 2420s came out of a seemingly never before opened pair of 4343s and had the stuff on all of the screws.

    We used acetone to help dissolve the stuff. At first glance I thought it was just red lacquer, but it proved to be much thicker and on some screws it had run all the way down the threads. I don't think it was red Loctite, it seemed like a type of hard wax.

    I guess they stopped using it after they discovered how difficult it was to remove during their early warranty repairs.

    Widget

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