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Thread: Help please. JBL madison lx3 crossover help!

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    Lightbulb Help please. JBL madison lx3 crossover help!

    Okay, this is frustrating lol. I have a pair of jbl lx3 crossovers for a pair of madisons. The use the same crossover the jbl minigon and dale use. Its the lx3 not the lx3-1. I cant find a reliable schematic or forum. The schematic here shows a 1uf cap and a choke on the tweeter. My crossover's choke is inline with the woofer. I read a forum that mentioned a 3uf cap in his. My capacitance meter shows roughly a 7.5uf on the originals. I dont have a scope. I want to get these recapped. Anyone help?

    Ive learned that the lx3 came with the earlier 16ohm models and the lx3-1 was in the later 8ohm models and they are different from each other. Plenty on the lx3-1 but nothing on the lx3.

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    Quote Originally Posted by SirKapusta View Post
    Okay, this is frustrating lol. I have a pair of jbl lx3 crossovers for a pair of madisons. The use the same crossover the jbl minigon and dale use. Its the lx3 not the lx3-1. I cant find a reliable schematic or forum. The schematic here shows a 1uf cap and a choke on the tweeter. My crossover's choke is inline with the woofer. I read a forum that mentioned a 3uf cap in his. My capacitance meter shows roughly a 7.5uf on the originals. I dont have a scope. I want to get these recapped. Anyone help?

    Ive learned that the lx3 came with the earlier 16ohm models and the lx3-1 was in the later 8ohm models and they are different from each other. Plenty on the lx3-1 but nothing on the lx3.
    The old mylars will drift high after enough time
    What are you building or do you just want some help with a re-cap?
    I'll be happy to do the networks for you if all you need is a straight across re-cap

    Joe

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    Quote Originally Posted by Joseph Smith Jr View Post
    The old mylars will drift high after enough time
    What are you building or do you just want some help with a re-cap?
    I'll be happy to do the networks for you if all you need is a straight across re-cap

    Joe
    Im just wanting to recap the networks. Theres only the one cap per xover. I can handle the labor if i could find the stock cap value or xover frequency. The only label on the cap is lx3 101.

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    Quote Originally Posted by SirKapusta View Post
    Im just wanting to recap the networks. Theres only the one cap per xover. I can handle the labor if i could find the stock cap value or xover frequency. The only label on the cap is lx3 101.
    So you just want a stock rebuild? Tell me again what you pulled them from and what you want to put them back into, Madisons? A lot of the C48 Madisons just ran the LE8 full range, sometimes the S5? Which ones do you have? I assume from your schematics you have the S5 with a LE30, yes?
    With some of the ancient marking systems the third digit is a multiplier-using the most comon practice of the day then your cap should be marked "105" though? Weird, because we know it's not a 10pF

    If this is the thread you are referring to, the network in the photo appears to have been worked on previously, that sure looks like an electrolytic in there to me and the OP said it was assembled with screws
    A 3uF paper or film type from the early 1960s would be huge compared to what I can see in that photo
    http://www.audioheritage.org/vbullet...X3-1-crossover
    The value is certainly OK and safe enough for a tweeter, I just don't think it's what was originally in there
    The almost default value I see most often in vintage first order networks is 2uF, so I would tend to believe that that's what someone was thinking when they made a repair some point in time ages ago

    I would trust the Techbot's schematic as it agrees with the catalogs and your Minigon tech sheet

    Joe

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    Quote Originally Posted by Joseph Smith Jr View Post
    So you just want a stock rebuild? Tell me again what you pulled them from and what you want to put them back into, Madisons? A lot of the C48 Madisons just ran the LE8 full range, sometimes the S5? Which ones do you have? I assume from your schematics you have the S5 with a LE30, yes?
    With some of the ancient marking systems the third digit is a multiplier.

    Joe
    Yeah. Just a stock rebuild. Theyre in the older madisons with the s5 package. Everything is16ohm. Im giving them a good cleaning, new caps, new foam, new binding posts on inputs. They have the le30. Which was starting to sound dull. Im sure the caps are out of spec. They both are reading close to 7.5uf.

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    Quote Originally Posted by SirKapusta View Post
    Yeah. Just a stock rebuild. Theyre in the older madisons with the s5 package. Everything is16ohm. Im giving them a good cleaning, new caps, new foam, new binding posts on inputs. They have the le30. Which was starting to sound dull. Im sure the caps are out of spec. They both are reading close to 7.5uf.
    Would certainly make sense
    I think the 1uF cap value is the correct one
    The only problem I am having is the "100" marking on your old cap, are you certain that's not "105"?
    The 8 versus 16 topic has been much discussed, it doesn't make any difference what the labels say, treat things as if they were 8
    With your LX3 versus LX3-1 I can't find anything to indicate any issues there either-I am sure I am combing through the same material as you already have
    There is that sort of consistent inconsistency in those really old catalogs
    The 1962 catalog does make it clear that that is indeed the correct network, sans the 1 but again, it is in complete agreement with both of the verified schematics
    I'd go with that

    Joe

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