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Thread: L 65a woofer?

  1. #1
    Member toddrr's Avatar
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    L 65a woofer?

    Ok, I figured out that i have a jbl L 65 (A) model Jubal (see attachment)

    I have researched this site and found out lots of information
    before i started another thread. Here is what i know.

    Three models of Jubals.
    Jubals (126a woofer),
    L65a (122a woofer),
    L65b (128h woofer)

    Question A: Can i use a different woofer than the 122a?
    Question B: Is one of the 3 woofers above considered the better woofer?
    Question C: If i use a 126a woofer, does it have a diff. polarity or
    anything else i should know?

    other photo's of my speakers...
    http://www.audioheritage.org/vbullet...ad.php?t=10150

    Thanks guys I am learning so much from all of you!
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  2. #2
    RIP 2011 Zilch's Avatar
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    128H(-1)'s not in any of them, but it's the recommended replacement woofer.

    The networks are each different:

    http://manuals.harman.com/JBL/HOM/Te...Jubal%20ts.pdf

    http://manuals.harman.com/JBL/HOM/Te...Jubal%20ts.pdf

    http://manuals.harman.com/JBL/HOM/Te.../L65B%20ts.pdf

  3. #3
    Senior Member edgewound's Avatar
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    The woofer in the L65B is a 129H. The 122A gets reconed with C8R129H which is a current product. Recone price is $172.00 ea. That would be the thing to do.

    126A has a small spider and lacks the bass extension of the other drivers.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  4. #4
    Administrator Robh3606's Avatar
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    "Can i use a different woofer than the 122a?"


    The 122A and 129H are the same woofer with the exception of Alnico vs. Ferrite. The 129H's are few and far between, 122's are on Ebay all the time. You may want to keep an eye open for a pair they are your best bet.

    Rob

  5. #5
    Senior Member markd51's Avatar
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    Howdy Edgewound/All, Just joined the forum.

    I am not quite sure about the fact that the 126A driver used a smaller spider, nor had a poorer bass extension?

    Not that I'm saying you are incorrect, but my standard L-65 doesn't seem to lack any bass extension at all.

    No doubt there are differences in the Driver, and X-Over Specs between the three models, the L-65 L-65A, L-65B, otherwise JBL would've never changed the model.

    One should no doubt believe, and correctly assume that JBL back then wouldn't certainly go backwards in technology, later resorting to poorer performance within this speaker model, or any other of the speaker models of the day, and that the A, and B versions should indeed be an improvement versus the standard, first L-65 Version, correct?

    I wonder exactly how much difference in frequency specifications there was between these models, and if the X-Overs made up for any lack in the original 126A Bass Driver? I gather there were some similarities between the three drivers, such as magnet size, basket size, and shape, voice coil diameter, but as you say, the spider may have been different, materials slightly different, etc.

    No doubt the very reason why the recone kits are not interchangeable between the 126A, and 122A. Mark

  6. #6
    Administrator Robh3606's Avatar
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    The 126A has a different frame than the 122A. There is also a larger magnetic pot structure on the 122A. Different frame different spider diameters

    Here is a 126A, 122A and a 129H cone

    Rob
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  7. #7
    Senior Member edgewound's Avatar
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    Quote Originally Posted by markd51
    Howdy Edgewound/All, Just joined the forum.

    I am not quite sure about the fact that the 126A driver used a smaller spider, nor had a poorer bass extension?

    Not that I'm saying you are incorrect, but my standard L-65 doesn't seem to lack any bass extension at all.

    No doubt there are differences in the Driver, and X-Over Specs between the three models, the L-65 L-65A, L-65B, otherwise JBL would've never changed the model.

    One should no doubt believe, and correctly assume that JBL back then wouldn't certainly go backwards in technology, later resorting to poorer performance within this speaker model, or any other of the speaker models of the day, and that the A, and B versions should indeed be an improvement versus the standard, first L-65 Version, correct?

    I wonder exactly how much difference in frequency specifications there was between these models, and if the X-Overs made up for any lack in the original 126A Bass Driver? I gather there were some similarities between the three drivers, such as magnet size, basket size, and shape, voice coil diameter, but as you say, the spider may have been different, materials slightly different, etc.

    No doubt the very reason why the recone kits are not interchangeable between the 126A, and 122A. Mark
    Howdy Mark...

    As Rob so kindly pointed out, there are clearly differences in the 126A driver as compared to the 122A/129H. The frame/magnet is more like a D123.

    I only posted the differences because, as a JBL Authorized Service Agency, I've reconed lots of these over the last 18 years...but thanks for keeping me honest.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  8. #8
    Member toddrr's Avatar
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    OK

    Ok, this is great

    Thanks for clarifying.
    It is interesting that the replacement woofer for both the jubal, and
    the L65a is the 128h according to the network information that
    Robh provided. I now know the 122a and 126a woofers are bit
    different in design, however its seems like they might still be
    interchangeable.

    thanks for your help

  9. #9
    Senior Member markd51's Avatar
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    Hi Todd, I think you mean129H, and not the 128, which others have mentioned was never in any of the L-65's.

    Oh sure, the 126A would surely work, and probably blow your socks off too in the meantime!

    Just like those cruddy MCS woofers worked, so would the 126A. Any 12' woofer would work provided it's an 8ohm speaker, and is a drop in replacement without having to take a tomahawk to the cabinet to get it to fit.

    I've never had any need of "bass", or lack of "Bass Excursion with my stock L65's. The four of them can easily, and effortlessly shake the room, and offer plenty of clean, tight, deep bass, and I usually keep everything set flat.

    I believe my standard L-65 version originally used a 1Mh Iron Core inductor for the Bass Driver, and there may be just a slight difference in value within your L-65A Unit. Maybe something like a 1.5Mh Inductor? Maybe someone else can quote the exact value.

    Using the wrong driver would be akin to you owning a 55 Chevy Bel Air that calls for a 265 CI V-8, and you drop in a 283 CU V-8 instead. Very close, and it will probably work just fine, but no cigar. No doubt your best performance will be with the 122A, and your speakers will retain theri highest value will all the correct drivers inside.

    I've never doubted JBL's expertise. IMO, they were some of the best speakers in the world then, and even still to this day theri vintage models can hold their own quite well in the audiophile world.
    Mark
    Last edited by markd51; 04-12-2006 at 04:39 PM. Reason: typo

  10. #10
    Senior Member edgewound's Avatar
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    Quote Originally Posted by markd51
    Hi Todd, I think you mean129H, and not the 128, which others have mentioned was never in any of the L-65's.


    Mark
    Mark,

    The current replacement driver for all L65/A/B is the 128H-1...if the original is not usable. It is the only exact acoustic replacement for the 129H in the L65B.

    L65 Jubal had 126A with 1mH inductor, L65A had 122A with 2mH inductor, L65B had 129H with 3.3mH inductor. I just looked at my JBL Service Manual to confirm this.

    There was also a revision to the crossover networks mid band and hi pass in all three versions.

    But it is nice to know that you care about the correctness, as this is the Technical Help forum and all info should be correct
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  11. #11
    Senior Member markd51's Avatar
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    Interesting info Edgewound, and I appreciate the time you've taken to share this info (and I'm sure Todd, and others do also)

    I notice that the 122A did not have a vent at the rear like the 126A, and can you elaborate some on this?
    Did the 122A use a ferro-fluid or something on that order for voice coil cooling?

    Although the Woofers, and X-Over changes where made with the three versions, I assume that the O77 high freq. driver was used in all. The O77 Driver in my original L-65 was 16ohm, and wonder if they were 16ohm in the A, and B versions?

    And for the mid driver, on mine is the LE5-5. I assume this didn't change.

    Other notables, was a change in the driver layout, and port position on the front baffles from the L-65 to L-65A. Mine (L-65) is clearly different from Todd's L-65A

    About 5 years ago, I literally toasted 2 X-Overs within two of the four L-65's I own. Just like you took a propane torch to them! Ruined. I figured I had two choices, try to piece the destroyed X-Overs back together from parts from JBL (or Wherever) or, build all new.

    I chose the latter option to have four very high quality
    X-Overs built, and adhering to JBL L-65 Specs made by Madisound. I went from Iron Core Inductors, to I believe it was Goertz 300w (and I think the other was 100w) Air Core Inductors, and Solen Poly Caps throughout.

    Madisound quickly, and beautifully (and also very reasonably) built me four "works of art" X-Overs for my L-65's! They were so pretty (And heavy), I wanted to place them on my fireplace mantle for display.
    Also gone from the mix, was of those sand cast resistors from the X-Over, with more modern resistors.

    As far as the sound, the custom Units didn't deviate at all from the original sound as I remembered it. I had roughly 25 years of auditioning these speakers to determine this, the mids, and highs appeared to be smoother, less grainy, better integrated, and the bass response improved, being cleaner, tighter, better defined, less flop, better control.

    I should also mention all internal wiring went to the garbage, Edison Price Solid Copper 5-Way Binding Posts installed and all speakers were internally rewired with high grade copper 12ga from Binding Posts to X-Overs, from X-Overs to Woofers, and 16ga from X-Over to mid, and tweeter, 16ga also to the L-Pads. All soldered up with WBT Silver solder.

    Also upgraded, were the 10w L-Pads to 100w versions, and mounted to the rear of cabinet, leaving the original 10w L-pads intact, and undisturbed.

    Although I'm no longer bone stock, it was a worthy upgrade breathing new life into my now 32 year old Jubals.

    If I would've had worries, or concerns about these mods ruining resale value in the future, I probably would've never done these mods, but when I leave this earth, there's going to be two coffins at my burial, one for me, and the other for my JBL's, and Mac Amps! They'll be with me till the end of time. Mark

  12. #12
    Senior Member edgewound's Avatar
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    Quote Originally Posted by markd51
    Interesting info Edgewound, and I appreciate the time you've taken to share this info (and I'm sure Todd, and others do also)

    I notice that the 122A did not have a vent at the rear like the 126A, and can you elaborate some on this?
    Did the 122A use a ferro-fluid or something on that order for voice coil cooling?

    Mark
    Mark,
    Sounds like you're very fond of your Jubals...as you should be.

    Your mids and HF are LE5-5 and 077, respectively.

    If you look more closely at the pics Rob posted you'll notice the vent hole in the 122A motor assembly. Ferrofluid wasn't invented yet when these speakers were built. I think the only low freq drivers larger than 12" from JBL without a vent hole was the LE15's and 2215/2216, 150-4 and possibly the K145(?). I'm not positive but it seems these all shared the same motor.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  13. #13
    Senior Seņor boputnam's Avatar
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    L65 Series Tech Sheets

    Seems you guys need this...
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    bo

    "Indeed, not!!"

  14. #14
    Senior Member GordonW's Avatar
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    If you're reconing a 128H and want it to act more like a 129H or 122A (for which, if my info is current, no 122A/129H kits are available), you can use a 128H-1 kit, and have the reconer add 10 grams of mass (mass ring) to the assembly, before installing the dustcap. The primary difference between a 128H and 129H is cone mass (approx. 90 grams for the 128H, 100 grams for the 129H). This should put the upper-end response in check closely enough, for the factory crossover to work within spec...

    I've done this before, and verified it works on LEAP/LMS... the T/S (box-tuning) parameters work, and the measured FR is proper, too.

    JBL used to have 10g mass rings... but, apparently, no more. In that situation, I've made my own, using sliced-apart lead tire weights. Get a strip of tire weights, and slice it lengthwise (persistance with a very sharp utility knife will work). May take some experimentation to get the exact right thickness to get the right weight (one tip- weigh and measure the entire lead weight strip before cutting it... you can use PROPORTIONALLY smaller strip widths to get the right resultant fraction of the total strip)... but it can be done. Once the right weight is achieved, glue the resultant ring into the very top of the inside of the voice coil (as far as possible away from the pole piece down below), then install the dustcap. You should wind up with something like 1/8" thick, so it should be fine as far as cone excursion is concerned (it won't hit the polepiece)...

    Regards,
    Gordon.

  15. #15
    Senior Member edgewound's Avatar
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    Quote Originally Posted by GordonW
    If you're reconing a 128H and want it to act more like a 129H or 122A (for which, if my info is current, no 122A/129H kits are available), you can use a 128H-1 kit, and have the reconer add 10 grams of mass (mass ring) to the assembly, before installing the dustcap. The primary difference between a 128H and 129H is cone mass (approx. 90 grams for the 128H, 100 grams for the 129H). This should put the upper-end response in check closely enough, for the factory crossover to work within spec...

    I've done this before, and verified it works on LEAP/LMS... the T/S (box-tuning) parameters work, and the measured FR is proper, too.

    JBL used to have 10g mass rings... but, apparently, no more. In that situation, I've made my own, using sliced-apart lead tire weights. Get a strip of tire weights, and slice it lengthwise (persistance with a very sharp utility knife will work). May take some experimentation to get the exact right thickness to get the right weight (one tip- weigh and measure the entire lead weight strip before cutting it... you can use PROPORTIONALLY smaller strip widths to get the right resultant fraction of the total strip)... but it can be done. Once the right weight is achieved, glue the resultant ring into the very top of the inside of the voice coil (as far as possible away from the pole piece down below), then install the dustcap. You should wind up with something like 1/8" thick, so it should be fine as far as cone excursion is concerned (it won't hit the polepiece)...

    Regards,
    Gordon.

    I will re-iterate. This the the Technical Help Forum...NOT DIY.

    The C8R129H is on the latest revision of the JBL Professional Transducer Parts List

    The Tech Manual also states that the cone kit might have Aquaplas instead of mass ring.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

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