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Thread: Underhung voice coil specs

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  1. #1
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    Underhung voice coil specs

    I've recently come into possession of a number of alnico 15 inch drivers. 2220A, 2220B, 2205B, 2231A, 2 x K145, 2 x LE15.
    All have been reconed incorrectly. One K145 looks to be a 2220 kit perhaps, curvilinear cone. The other is an empty basket. The LE15s look correct but the back of the cones have 2235 written so I assume someone has reconed incorrectly. The others have E140 kits in, which I will extract to be used in some E140 baskets. I now plan on getting these all back to proper stock kits.

    I've found someone in the UK who has a regaussing machine so thankfully they can all get recharged back to the proper magnetic strength. However, there is now the problem of the correct recone kits. All these kits are NLA, so I have to resort to aftermarket. I have had good experience with aftermarket kits currently on the market. I know Edgewound (Upland Loudspeaker) has used aftermarket voice coils with good results, however thats only with ones that are produced correctly, E series, 2202 2225 etc.

    As far as I know, the underhung series, K145, LE15, 2220 were originally with small copper voice coils. The only aftermarket coils on the market available for them are aluminium. I have reconed another pair of LE15 I have with some of these aluminium voice coils and they sound good, but I know they aren't as good as the originals were.

    Now comes the good news, the person I have found to do the regaussing also has an edge wound coil winding machine! He used to do a lot of work for Martin audio, Turbosound back in the day so he is very qualified to produce some new in spec JBL voice coils for me. However, what we do not have is that spec!

    We need the number of turns, voice coil depth, etc etc, all the specifications required to reproduce these voice coils. This is where I need some help. Is there anyone on this forum that has this info, and would be happy to assist me in bringing these drivers back to life? I do have a dead LE15B cone kit I removed, so we could measure the voice coil from that. My regausser guy also has a 2215, he could extract the kit to measure the coil, but we would like to be as informed as we can be with this project. If anyone has any info to share I would really appreciate it.

    My plan is to recone the 2220, K145 and LE15 back to stock. Then I was thinking if the 2235 kits that are currently in the LE15 are still good, I could remove them and transplant into the 2205 and 2231, then I would have a pair of nice alnico 2235.

    If I come up short I could always use the aluminium coils on the market, however I would like to avoid that if possible!

  2. #2
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    I cant help with specs for your coils.
    But i would love to get in touch with this guy since i need som coils
    not aviable anywhere myself.

  3. #3
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    Sorry, I also can't help with VC specs, but am interested to get in touch with anyone who's able to regauss those AlNiCo-V magnets to their original strength.

    I have a question, too: How does one extract a complete cone assembly without damaging it?

    Best regards!

  4. #4
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    Quote Originally Posted by Kay Pirinha View Post
    Sorry, I also can't help with VC specs, but am interested to get in touch with anyone who's able to regauss those AlNiCo-V magnets to their original strength.

    I have a question, too: How does one extract a complete cone assembly without damaging it?

    Best regards!
    There are a couple of people in the UK who can do it, but the person I've found is by far the most likeable and friendly I'm not sure of anyone in Germany who does it. Alternatively you could send them to him, won't be cheap though.

    In terms of extracting a cone, since they are recones, I don't think the glue will be as 'cured' as they were be if they were from the factory. So I'm hoping a generous amount of MEK will help. If that doesn't work then I'm sure he has a few industry secrets up his sleeve to be able to do it. Perhaps we would have to remove the surround and spider, then install some new suspensions. With the 2235 the foam has gone so that will be relatively easy to remove from the frame in one piece. Some MEK and a very sharp scalpel under the spider.

    Quote Originally Posted by FE3T View Post
    I cant help with specs for your coils.
    But i would love to get in touch with this guy since i need som coils
    not aviable anywhere myself.
    If we succeed I would be more than happy to share but we need to get the spec first!

  5. #5
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    Thanks budney!

    I hadn't realized that the glue that fixes the surround and the spider to the basket is soluble.

    Anyway, if we'd try to extract an intact 2235H cone or any other one with foam surrounds I guess that the surrounds gets damaged by the solvent?

    Best regards!

  6. #6
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    Quote Originally Posted by budney View Post
    If we succeed I would be more than happy to share but we need to get the spec first!
    What i need are coils for the 2108H and 2122H.
    Those specs are already aviable on this site.

    The specs you need are sadly enough, not.

    What i dont have are someone to wind them, without forcing me too pay for hundreds of them.

  7. #7
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    Hello,

    I would also be interested in some Edgewound VC by original specs for 2122, four at least.

    thanks
    looking for a JBL 2346 horn

  8. #8
    Senior Member Flodstroem's Avatar
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    Quote Originally Posted by budney View Post
    If we succeed I would be more than happy to share but we need to get the spec first!
    Have count the turns for 2215H, 2220A and the LE8T voice coils:

    2215H = 63T, 7.8 mm in length (Cu wire 8 ohms, DCR 5,8 ohms)
    2220A = 100T 7.8 mm in length (Cu wire 16 ohms, DCR 14.2 ohms)
    LE8T = 38T, 3.8 mm in length (8 ohms, Al wire)

    I think JBL also used the 2220A voice coils for the LE15A, or vice verse because they measure the same physical dimension and DCR.
    Flodstroem

  9. #9
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    Thanks Flodstroem for taking the time to do that.

    That's good info!


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