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Thread: Field Guide to the JBL 10 inch Midbass driver 2121 2122 2123

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    Heather [Senorita member] hjames's Avatar
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    Field Guide to the JBL 10 inch Midbass driver 2121 2122 2123

    One of the magical things about the 4340/41, 4343 and 4345 Monitors is the 10 inch Midbass driver. This driver helps the big woofer (15 or 18") handle just the really low notes, and keeps the horn/compression driver from having to go below its optimal range.

    Here's a thread showing how Infredible redid the surrounds on a pair of those ultra-rare 2121s - http://audioheritage.org/vbulletin/showthread.php?t=3527

    In an older thread, Giskard said

    The 4343 uses the alnico 2121 and the 4343B uses the SFG ferrite 2121H. Both have the 4" inverted paper dust cover.

    The 4344 and 4345 use the newer 2122H which has a harder 3" dust cap. It is less susceptible to break-up.

    All of them use a 3-inch edgewound copper ribbon voice coil.
    *****
    "Isn't this inconsistent with what we would normally use above 300Hz? I would assume aluminum would be desired due to the lightness and quick response at the higher frequencies."

    Sure, it just wasn't in the cards way back then. The newer 2123H uses an aluminum voice coil.

    Thanks for that info, G!

    One thing thats a problem for modern fans is that the original model 2121 driver is unavailable. It was replaced by the model 2122 - which is rapidly getting near impossible to find as well. You can occasionally find a replacement cone (as of May 2007) for a rebuild, but even they are in quite short supply.
    Some folks have substituted the model 2123 driver - but its not equivalent, its more efficient (higher output levels), and has a different response curve that the earlier 2 drivers. You'd need to re-design the crossover and, frankly, its just not the same driver.
    But some folks do like it.



    Thanks to Subwoof for these amazing pictures!

    The Lineup up basic JBL 10 Inchs

    At the bottom -
    For those who can read the design specs - here's a chart Giskard has posted numerous time showing the different parameters.
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    2ch: Oppo981, DDE3DAC, JoLida 502CRC, JBL L212, VonSchweikert VR4V
    7.1: Oppo BDP-103D, B&K, 2pr UREI 809A, TF600, JBL 4641

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    Heather [Senorita member] hjames's Avatar
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    Thanks again to Subwoof for these amazing pictures!

    The Voicecoil comparison
    2121 on the Top
    2122 in the Middle
    2123 below
    Attached Images Attached Images    
    2ch: Oppo981, DDE3DAC, JoLida 502CRC, JBL L212, VonSchweikert VR4V
    7.1: Oppo BDP-103D, B&K, 2pr UREI 809A, TF600, JBL 4641

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    Heather [Senorita member] hjames's Avatar
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    Yet again, thanks to Subwoof for these pictures!

    Comparison of the magnet structure

    2121 beside the 2121H

    2122H beside a picture of my 2123H driver (now in Maui)

    (Sorry for the dissimilar style of the 2123 picture, but I know there is enough interest that it was worth including)
    Attached Images Attached Images   
    2ch: Oppo981, DDE3DAC, JoLida 502CRC, JBL L212, VonSchweikert VR4V
    7.1: Oppo BDP-103D, B&K, 2pr UREI 809A, TF600, JBL 4641

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    Obsolete
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    Just a quick note that the LE10A in the photo is sporting the wrong dust cap (might even be an LE10H-1 recone kit in it).
    It used the same dust cap as the 2121 next to it.

  5. #5
    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by X_X View Post
    Did JBL ever publish a response curve for the 2122H? I can't find it...
    Quote Originally Posted by Giskard View Post
    I posted it somewhere.
    Right here, G -
    and X_X - the forum search tool is your friend!
    2122H - http://audioheritage.org/vbulletin/s...ad.php?t=10637
    2ch: Oppo981, DDE3DAC, JoLida 502CRC, JBL L212, VonSchweikert VR4V
    7.1: Oppo BDP-103D, B&K, 2pr UREI 809A, TF600, JBL 4641

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    Senior Member Fangio's Avatar
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    Not to forget –

    early 2121 with lansaloy surround.
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    Senior Member ivica's Avatar
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    [QUOTE=hjames;171653]Thanks again to Subwoof for these amazing pictures!

    The Voicecoil comparison

    2121 on the Top
    2122 in the Middle
    2123 below[/QUOTE]

    Very instructive photos, difficult to find .
    Do you have the same photos of the voice coil for E110 and K110.
    It would be interesting to see the difference of the coils

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    Senior Member 1audiohack's Avatar
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    The voice coil and spider on the E110 looks just like the 2121 pictured, VC is 0.300" tall, the cone is only 0.014" thick. By comparison the 2123's VC is 0.440" tall and the cone is about 0.024" thick. I don't have a 2122 kit to look at.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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    Heather [Senorita member] hjames's Avatar
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    Quote Originally Posted by ivica
    Quote Originally Posted by hjames View Post
    Thanks again to Subwoof for these amazing pictures!

    The Voicecoil comparison
    2121 on the Top
    2122 in the Middle
    2123 below
    Very instructive photos, difficult to find .
    Do you have the same photos of the voice coil for E110 and K110.
    It would be interesting to see the difference of the coils
    The Pix on the 10 inch series were primarily from Subwoof -

    >> Thanks to Subwoof for these amazing pictures!
    2ch: Oppo981, DDE3DAC, JoLida 502CRC, JBL L212, VonSchweikert VR4V
    7.1: Oppo BDP-103D, B&K, 2pr UREI 809A, TF600, JBL 4641

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    RE: Member when? subwoof's Avatar
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    coiled, ready to strike

    If I remember, the K110 and E110 had the same coils but the former changed a few times on the "E" which made for a slightly different spec.

    I don't have any of those open or kits to compare at the moment BUT I think I have some pretty rare K110-4 kits in storage. When it thaws I will look.

    sub
    << too many to list anymore >>

  11. #11
    Senior Member ivica's Avatar
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    Quote Originally Posted by 1audiohack View Post
    The voice coil and spider on the E110 looks just like the 2121 pictured, VC is 0.300" tall, the cone is only 0.014" thick. By comparison the 2123's VC is 0.440" tall and the cone is about 0.024" thick. I don't have a 2122 kit to look at.
    Thanks for info,

    1.
    so concerning the VC differences - thickness and length, are they all 8-ohms VC for three ( E110, 2121 2123), or 16 ohms
    2.
    do you have any experience about re-coning E110 basket with 2123 re-cone kit

  12. #12
    Senior Member 1audiohack's Avatar
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    Yes, the last six I assembled were E110 baskets with C8R2123H kits.

    To clarify, thickness I made reference to is the cone material of the radiating element, not the voice coil or former.

    The dimensions of a 2123H coil and former are approximately 2.995" I.D., former and wire combined thickness 0.028" and wound coil height 0.440".

    E110H about 2.995" I.D., former and coil combined thickness 0.022" and wound wire height 0.285"

    Hope this helps.
    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  13. #13
    Senior Member ivica's Avatar
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    Quote Originally Posted by 1audiohack View Post
    Yes, the last six I assembled were E110 baskets with C8R2123H kits.

    To clarify, thickness I made reference to is the cone material of the radiating element, not the voice coil or former.

    The dimensions of a 2123H coil and former are approximately 2.995" I.D., former and wire combined thickness 0.028" and wound coil height 0.440".

    E110H about 2.995" I.D., former and coil combined thickness 0.022" and wound wire height 0.285"

    Hope this helps.
    Barry.
    Many, many thanks,

    So I understand that I can put re-cone kit for 2123 without any modification into E110 basket.
    Is there any large differences in the sound between E110 and 2123 (after re-conning)??

  14. #14
    Senior Member 1audiohack's Avatar
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    The E110 / 2123 basket / motor assemblies are identical. A 2123 kit in a E110 basket will be a proper 2123, except for the foil cal.

    All the best,
    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  15. #15
    Senior Member grumpy's Avatar
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    Quote Originally Posted by ivica View Post
    ...
    Is there any large differences in the sound between E110 and 2123 (after re-conning)??
    I would expect so, partly depending on how they are used; in a system or standalone:

    http://www.audioheritage.org/vbullet...php?29742-2123
    http://www.audioheritage.org/vbullet...p?10635-E110-8

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