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Thread: Everest Listening Impressions

  1. #61
    Webmaster Don McRitchie's Avatar
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    It's the same basic design as the 2450 as far as the motor and phase plug goes. The major differences are that the 476Be has no throat and uses a beryllium diaphragm with an Aquaplas coating. It shares the same "Coherent Wave" phase plug. It should be noted that the 475Nd from the M9500 uses an internal magnet structure and is thus shielded while the 2450/476Be both use an external structure. The lack of a throat means that an optimized flare rate can be chosen depending on the application. The throats on all of JBL's previous large format compression drivers used the 300hz flare rate from the original W.E. design. Since there is no need for that low a cross-over frequency for this compression driver, an optimized horn can be designed for any specific use.
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    Don McRitchie

  2. #62
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Don McRitchie
    It's the same basic design as the 2450 as far as the motor and phase plug goes. The major differences are that the 476Be has no throat and uses a beryllium diaphragm with an Aquaplas coating. It shares the same "Coherent Wave" phase plug. .
    Which would sound as if it's a 2451 with the Be/Aquaplas diaphragm.

    2451 is a 2450 with no throat....both have Neo motor.

    2447 is a ferrite motor with "Coherent Wave" phase plug and no throat, 1.5" exit...2446 is same with 2" throat/exit. Drop in "SL" aquaplas coated Ti diaphragm and you're getting a value in a big driver.

    Think $400.00 vs $3500.00. Is the trade off worth it?
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  3. #63
    Webmaster Don McRitchie's Avatar
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    Thanks. You're right in that I forgot about the 476Be being a 1.5" exit.

    Don

  4. #64
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by edgewound
    Think $400.00 vs $3500.00. Is the trade off worth it?
    I recall concluding from the text description of 476Be that its design was distinguished in other ways, as well.

    I can tell you that "Next Generation" 2452H-SL measures and sounds VERY different from 2450 with SL diaphragm:

    http://audioheritage.org/vbulletin/s...766#post123766

  5. #65
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Zilch
    I recall concluding from the text description of 475Be that its design was distinguished in other ways, as well.

    I can tell you that "Next Generation" 2452H-SL measures and sounds VERY different from 2450 with SL diaphragm:

    http://audioheritage.org/vbulletin/s...766#post123766
    Most likely due to the "throatless" design...better HF extension, less "honkey"? Reduced HF phase cancellations without the thoat.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  6. #66
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    Quote Originally Posted by Maron Horonzakz
    In the Everest DD66000 Technical White Paper is a small line illustration of the 476 Be mid/high frequency driver (fig 6) A very small cutaway drawing showing internal workings....I need a larger more detailed drawing. Does anyone know if a LARGER illistration is available???? Maybe JBL can furnish one for our library. Can Don McRitchie inquirer???? I need to compair with drawing of driver in K2 M 95000.....
    In addition to Jan's post, which shows the internal structure more clearly imho, here with english description.
    ____________
    Peter
    Attached Images Attached Images  

  7. #67
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Maron Horonzakz
    In the Everest DD66000 Technical White Paper...
    Could someone post a link to the White Paper? I seem to have missed it.
    Thanks,

    Widget

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  9. #69
    Administrator Robh3606's Avatar
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    I don't ever remember seeing an acoustic seal on the gap and the tuned resonance ring on other drivers. Also the machined chambers in the top plate and the under the surround. Solid copper sleve as well not plated. Don't think the standard drivers are so equiped.

    Rob

  10. #70
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Robh3606
    I don't ever remember seeing an acoustic seal on the gap and the tuned resonance ring on other drivers.

    Rob
    Me neither. That's one of the "distinguished in other ways" I referred to above. There's more in the text. It's not just a matter of slapping an Aquaplas'd Be diaphragm in a stock driver, I don't believe....

  11. #71
    Webmaster Don McRitchie's Avatar
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    No, it is considerably more than that. This is what I get for not looking up the white paper. I remember Greg initially describing the driver to me as based on the 2450, but this was obviously in reference to a general concept, and not the specifics of the design. Obviously Jerry Moro did considerable investigation and experimentation, particularly with the magnet circuit stability so that this represents a significant improvement on past designs. Therefore, it is definitely not fair to describe the 476Be as a beryllium diaphragmed 2450.

    Don

  12. #72
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Zilch
    Me neither. That's one of the "distinguished in other ways" I referred to above. There's more in the text. It's not just a matter of slapping an Aquaplas'd Be diaphragm in a stock driver, I don't believe....
    I never said it was a "matter of slapping in...".

    But there are some striking features that the ferrite 2447 motor shares with the 476Be: throatless 1.5" Optimized Aperature exit, Coherent Wave phase plug.

    Two very desireable traits that DIYers can have for very little cost in relation to the high dollar one. Put the Aqua'd diaphagm in and the razzies are minimized...not bad for a $6000.00+ savings on pairs, eh?

    Roll in a 2407 for UHF @15Khz+ and it's probably pretty usable, don'tcha think Zilch?
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  13. #73
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by edgewound
    Roll in a 2407 for UHF @15Khz+ and it's probably pretty usable, don'tcha think Zilch?
    2407 on the $10 JBL horn?

    You betchum!

    With 7 kHz crossover, this sucker is ruler flat "outta the box." Knocked me OUT first time I saw it on RTA!

    I chose 2" 2450 with SL diaphragm because it's got the flattest response curve.

    With 1.5", 2352 Optimized Aperture is about the only "available" JBL horn option that'll play low (800 Hz) presently.

    I've never run 2447 on it. Hafta measure one with SL diaphragm to know.

    2452H-SL works 2-way on that one, with simple compensation....
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  14. #74
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    Thank you....I knew I could count on you Wizz Kids to come up with the information I needed. (I mean wiz kids...Kids in relation to my age)
    Vlad

  15. #75
    Senior Member edgewound's Avatar
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    Quote Originally Posted by Zilch
    2407 on the $10 JBL horn?

    You betchum!

    With 7 kHz crossover, this sucker is ruler flat "outta the box."

    I chose 2" 2450 with SL diaphragm because it's got the flattest response curve.

    With 1.5", 2352 Optimized Aperture is about the only "available" JBL horn option that'll play low (800 Hz) presently.

    I've never run 2447 on it. Hafta measure one with SL diaphragm.

    2452H-SL works 2-way on that one, with simple compensation....
    The reason I said crossed over at ~15kHz for the 2407...your 2452 curve looks impressive until that spike at about 18kHz....the 2407 would be walking in the park on that octave to about 30kHz...(quasi) DD66000 territory.

    My point being that the crossover would be out of the way for high piano note fundamentals
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

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