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Thread: 4430 enclosure plans etc.

  1. #1
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    4430 enclosure plans etc.

    Hello,

    so I've decided to build a pair of 4430's. I've found a set of drawings in an old (1984) German DIY electronics magazine, but I've also found out that they cannot be right. The main difference appears to be the phase correction baffle, which in my drawings is flush with the main baffle's upper edge, whereas it can clearly be seen in videos etc. that the original horn baffle is flush with the enclosure's upper panel. Do there exist detailled drawings anywhere?

    And I've also found out that JBL used three different HF drivers during the 4430's production run, starting with 2421's, then swapping for 2425's, and finally for 2426's. Did they also modify the xover networks? I have the circuitry for the 2421's only. And are there major sonic differences between the three drivers?

    Best regards!

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    Administrator Mr. Widget's Avatar
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    I can’t help you with your other questions but the 2421B driver is the smoothest sounding due to its aluminum diaphragm. Titanium was used because it is more durable and will take more abuse than the earlier aluminum diaphragms so JBL moved away from aluminum in their pro applications.

    JBL continues to use aluminum in their higher end home designs... magnesium and beryllium being even better but more costly. JBL uses these diaphragms in their current top of the line offerings.


    Widget

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    Thank you, Widget! That's very helpful!

    In the meantime I did a thorough search here and found this old thread by Hofmannhp. Problem successfully solved, I'd say .

    Pardon me, please, for my annoying question!

    Best regards!

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    Hello,

    the plans say that 19 mm or 3/4" chipboard was used in the originals. The main advantage of this material is it's cheapness. But it requires elaborate and expensive surface treatment, e.g. by applying veneers.

    Decades ago I've done many enclosures from chipboard, mainly for musical instruments. I covered them with Tolex, something that definitely won't comply with a living room environment.

    May I replace the chipboard panels by multiple layer fagus plywood? thicknesses of 18 mm or 21 mm are available here in Germany. I could stain the readily assembled enclosures to my needs then and varnish them with clear laquer, which I can all do by myself. What are the plywood's acoustical properties? I hope they aren't worse than the chipboard's .

    Or should I prefer MDF, or even OSB? Yes, I know, both would also require veneering...

    Best regards!

  5. #5
    Administrator Mr. Widget's Avatar
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    I wouldn’t use OSB. Plywood may be fine, but MDF is particularly good because it is dense and to some extent it is self damping.

    We typically refer to fagus as beech. Can you get beech veneered MDF? Here at better lumber yards (the places where professional cabinet makers buy their materials as opposed to the larger home improvement stores) you can get MDF cores with a wide variety of surface veneers. There are also hybrids with a plywood core and layers of MDF under the veneer surface.


    Widget

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    Thanks, Widget!

    Unfortunately I've not yet seen veneered MDF here, but still need to research thoroughly. Yes, it would be a good idea to use it (if available, of course), and do mitre joints at the edges - same as I would do with plywood.

    Best regards!

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    Senior Member quindecima's Avatar
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    Quote Originally Posted by Kay Pirinha View Post
    Thanks, Widget!

    Unfortunately I've not yet seen veneered MDF here, but still need to research thoroughly. Yes, it would be a good idea to use it (if available, of course), and do mitre joints at the edges - same as I would do with plywood.

    Best regards!
    If you are going to use miter joints make sure they are interlocking, that's a weak joint by itself

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    Thanks, this is true! To cope with I'd apply 1 x 1" cleats at each inner edge, fastened with screws or dovels.

    Next questions (pardon me ): The drawings in that old thread show two separate baffles for the horn and the control unit. I guess these weren't glued to the main baffle, but screwed to it instead (to ease access e.g.). Were there some kind of gaskets between main and auxillary baffles? The screws for the control baffle came from behind the main baffle, and the ones for the phase correction baffle came from behind the horn's flanges?

    Best regards!

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    Quote Originally Posted by quindecima View Post
    If you are going to use miter joints make sure they are interlocking, that's a weak joint by itself
    May I inquire why? After all the interface area of a 45° mitre is 1,41 (square root of 2) times larger that that of a butt joint?!?

    Best regards!

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    Hi,

    as far as can I see it in the drawings of the front baffle and the horn/Lpad baffles, the horn/phase correction baffle is secured by four scews beneath the horn flange and next to the square cutout's edges. It isn't clear, though, how the control baffle is fixed to the front baffle, as there is an 'undefined cutout'. Does anyone know? I think there must be some recess, as the control knobs are flush with the front decal?

    Best regards!

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