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Thread: "Worst refoam job EVER" -rescue project

  1. #16
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    Hi Flodstroem

    Earl K, the specs 1.2 Tesla and 0.9 Tesla you mention is from (I guess) the JBLīs T/S parameter list. This spec is given to the "flux density"(eg. Tesla or Gauss), not the "total magnetic flux" (eg. Maxwells or Weber) which was what I meant but couldnīt explain so clear.
    - Yes, you're right. I'm aware that "flux density" is only part of the electromotive equation. I haven't seen comparitive figures ( for a 2225 vs a le15 ) of "total magnetic Flux" . ( Maybe I haven't looked hard enough ). I usually consider the overall "BL" figure as a good generalized term that has accounted for the "total Magnetic flux". But I realize that it (BL ) is also not the full story. Two speakers with identical BL figures but vastly different gap topologies will usually have different "sonic characters" .

    Its means it is not for sure that the total magnetic flux in a 2225 is higher than in a LE15/2215 (H). The magnetic assembly differs (only?) in the top plate thickness. (if compare 2225H with a 2215H) what I can see. Thats also why the higher "flux density" in the 2225īs magnetic gap.
    I do find the top plate thickness a significant contributing factor to "resolution" / everything else being equal . The ME150h woofer is a good example of that.

    I think the total magnetic flux is the main factor which controls the Fs in a speaker. Maybe Giskard is the person who knows anything about the magnets in these speakers ?
    I agree, in the last 15 years, JBL has increased the thickness of their top-plates for their newer generation speakers ( while maintaining similar BL figures ) . There has also been a small rise in Fs and an increase in midband output . I happen to really like these developments - others may view them as a waste of extra magnet weight & polished steel . These speakers do come with extra resolution - whether the market responds positively to JBLs' gamble / still remains to be seen.



  2. #17
    Senior Member Flodstroem's Avatar
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    "new JBL" ??!!

    Yeah Earl K The "new" generation of JBL bassdriver with a thicker top plate is exiting, but new ehhh? (only the mechanical assambly is different not the idea is it?)

    My 2215H pair is not any newer but merely a vintage speaker. But what a speaker. It think it is a better model then the older LE15/2215. Its sound is a litle bit more distinct than their predecessors, you could say "faster" to responding to transients in the bass music drums etc.

    Hope I soon could start to build my TL speakers with these speakers as subs
    eg. the speakermodel will be a ML TQWT, Mass Loaded Transmission line Quarter Waveleght Tube based on an idea of Mr Martin King (I think). But now we are at a new thread isnīt we (ok, I mean -me).

    BTW, It is to bad that the new generation subs not is on the market and available to home speaker builder (like you and me?)

    Wander how big the differance would be between the 1500AL and the 2215H

    Flodstroem

  3. #18
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    Hi Flodstroem

    My 2215H pair is not any newer but merely a vintage speaker. But what a speaker. It think it is a better model then the older LE15/2215. Its sound is a litle bit more distinct than their predecessors, you could say "faster" to responding to transients in the bass music drums etc.
    - I'm not surprised at all that you like the "H" model ( Ferrite) more than the Alnico. I find any "H" version of the alnico "A" equivalent, always has more immediate "torque" to it's response.

    - I don't think the 1500AL should be thought of as a "subwoofer".
    - "Woofer" with great bass & midbass response, yes.
    - "SubWoofer" with authority in the VLF , no. JBL has other models that do better.
    - The 1500AL is available for purchase in Europe .



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