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Thread: Upgrading a 4343 to 4344 components

  1. #1
    Senior Member porschedpm's Avatar
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    Upgrading a 4343 to 4344 components

    I have a pair of 4343 monitors whose 15" and 10" drivers need refoaming. I figured that I would use this opportunity to upgrade the components to 4344 specs. I've located the a pair of the 2235H drivers and a pair of the 2122H drivers. I've run into a snag though on the 2425J compression driver: First of all I'm not finding any on eBay or when I checked a couple of the local JBL service centers. Secondly, when I called JBL Pro they said the 2425J is NLA and has been replaced by the 2426J. My question is: Is the 2426J sonically comparable to the 2425J? Or should I be patient and keep looking for a pair of the 2425J.

    My next dilemna involves the crossover. The 3144 crossover specified for the 4344 monitor also appears to be unobtainable or at least very rare. How much different is the 3144 crossover vs the 3143? Can I get by without changing it? I will be bi-amping the speakers and using an electronic crossover so I really only need to address the difference as pertains to the crossover section for three upper drivers. Or is there a different crossover solution that I haven't but should be considering. And are there other upgrades that I'm overlooking.

    Any recommendations you all can provide will be greatly appreciated. Thanks.

  2. #2
    Administrator Mr. Widget's Avatar
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    I would keep your 2420s and replace the diaphragms with 2421Bs (D16R2421). Alternatively you could replace them with the 2425J (D16R2425) diaphragms. I think the 2421s sound better. They do cost considerably more, but it is your choice. In either case there is no reason not to use your 2420 motors.

    As for the crossover, it is the most important part of the upgrade. Here is Ian's thread that will tell you how to build the crossovers. (The 4344 and 4345 use the same crossover.) http://audioheritage.org/vbulletin/s...&threadid=1812

    You may need to retune the cabinets for the 2235H. I don't know what the difference in tuning is between the 4343 and the 4344. It will certainly work well without retuning, but to get the full benefit I assume there is a slight change in the tuning.

    Widget

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    Senior Member Guido's Avatar
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    I personally never heard a 4344 but own a 4343.
    I see not so much sense to change the components.

    Refoam your 2121 and recone your 2231 to 2235. Buy new dias D16R2421 as Widget posted.

    Change the capacitors in the 3143 networks to high end types and bypass them.

    I think that's it!

    That is the way I went (still waiting for the D16R2421) and I'm very satisfied with the results.

  4. #4
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    "I would keep your 2420s and replace the diaphragms"

    Definitely! D16R2421 or D16R2425, whichever you prefer.

    "As for the crossover, it is the most important part of the upgrade."

    Assuredly!

    "Or is there a different crossover solution that I haven't but should be considering."

    Build a charge-coupled 3-way for the 2122H, 2420, and 2405 based on the 3145 passive filter in bi-amp mode and box up your 3143's.

    "Refoam your 2121 and recone your 2231 to 2235. Buy new dias D16R2421 as Widget posted.

    Change the capacitors in the 3143 networks to high end types and bypass them."


    Well, there's that too!

  5. #5
    Senior Member porschedpm's Avatar
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    2425 vs 2421

    Thank you for the recommendations. I did not realize I could could upgrade the 2420 motor by changing out diapragms. By the way what is the difference(s) between the 2421 and the 2425? I'm inclined to go with the 2425 for the sake of sticking to the 4344 design formula. But Widget, why do you prefer the 2421 vs the 2425?

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    Administrator Robh3606's Avatar
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    The 2421 is the last generation Aluminum diaphram that uses the diamond surround. The 2425 diaphram is Titanium, uses the same surround type and is more rugged and fatigue resistant. That said some prefer the "sound" of the aluminum diaphrams to the titanium. I for one cannot comment having never compared the two diaphram metal types.

    Rob

  7. #7
    Administrator Mr. Widget's Avatar
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    In addition to what Rob said the aluminum diaphragms are measurably lower in distortion. I would speculate the lower distortion is why they sound less hard to me. Some people do prefer the titanium sound. In an A/B comparison I would bet most would not. As mentioned above the titanium have two advantages. They will last longer. (not really an issue for home use) Secondly they are about 60% less costly.

    Widget

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    "As mentioned above the titanium have two advantages."

    They also don't shatter when they contact the phase plug and leave their guts all over the inside when they explode.

    Oh! Plus I think I read somewhere that they "tell the truth".

    Some can't handle the truth!


  9. #9
    Senior Member porschedpm's Avatar
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    To Tell the Truth

    So is the aluminum considered more "truthful" or the Titanium? I could not tell which one Giskard was referring to.

  10. #10
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    Sorry! I read WAY too much JBL literature while I was being potty trained!

    http://lansingheritage.org/images/jb...-ti/page03.jpg

    It's all propaganda. Choose whichever you prefer. I run aluminum in my 4430's. The titaniums are put away, not thrown away.

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