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Thread: JBL LX 16 Crossover conversion

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    JBL LX 16 Crossover conversion

    On the schematic for the LX16 it suggests converting it to a LX16A.
    This is to protect the high frequency driver it says but l was wondering if it changes the crossover frequency as well?
    The cap and inductor are changed from a 1.2mH to 0.7mH and the cap is changed from a 12uF to 6uF only on the LE85 high frequency driver the bass components stay the same.

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    Senior Member audiomagnate's Avatar
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    Quote Originally Posted by JBeL View Post
    On the schematic for the LX16 it suggests converting it to a LX16A.
    This is to protect the high frequency driver it says but l was wondering if it changes the crossover frequency as well?
    The cap and inductor are changed from a 1.2mH to 0.7mH and the cap is changed from a 12uF to 6uF only on the LE85 high frequency driver the bass components stay the same.
    That's exactly what it does (raise the crossover frequency) and rather significantly at that.

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    Senior Member Eric M.'s Avatar
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    Brining this thread back to life.

    So, if the LX16A was modified for a higher crossover point at the high end (to protect the LE85) and nothing was done to the low end circuitry, wouldn't you end up with a gap in the response?
    The original LX16 crossed at 1200 Hz, I have no idea what the new HIGH end crossover point is after the mods to LX16A, I don't think JBL ever published that .... and how would that look - 1200 Hz at the low end and 2500 Hz at the high end?? That wouldn't help sales!
    But as stated above, t's a big jump based on the changes to the high end cap and coil.

    Has anyone ever noticed a dip at that frequency point on the L200 with the LX16A mod or any speaker configuration using the LX16A?
    Maybe the LX16 offers a smoother response if you can keep your listening level low enough not to damage the LE85 (something I could never do when running an LE85 with an LX5 back in high school!)

    Thanks,
    Eric M.

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    Quote Originally Posted by Eric M. View Post
    Brining this thread back to life.So, if the LX16A was modified for a higher crossover point at the high end (to protect the LE85) and nothing was done to the low end circuitry, wouldn't you end up with a gap in the response?The original LX16 crossed at 1200 Hz, I have no idea what the new HIGH end crossover point is after the mods to LX16A, I don't think JBL ever published that .... and how would that look - 1200 Hz at the low end and 2500 Hz at the high end?? That wouldn't help sales!But as stated above, t's a big jump based on the changes to the high end cap and coil.Has anyone ever noticed a dip at that frequency point on the L200 with the LX16A mod or any speaker configuration using the LX16A?Maybe the LX16 offers a smoother response if you can keep your listening level low enough not to damage the LE85 (something I could never do when running an LE85 with an LX5 back in high school!)Thanks,Eric M.
    Resonant circuitry calculations show crossover frequencies of around 1.3khz and 2.4khz for the LE85. This would imply a slope of 12db/octave, subject to any other crossover components other than the capacitors and inductors mentioned.

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    Senior Member Eric M.'s Avatar
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    That would indicate 6 dB down at the actual crossover, intersection point of about 1850 Hz, 3 dB more that what is desired at that point.
    So it seems there would be about a 3 dB dip in the response of the LX16A at around 1850 Hz as apposed to the LX16.

    Has anyone ever listened side by side (or tested) the LX16 vs 16A? I'd be curious to know how noticeable that dip is.

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    Senior Member Eric M.'s Avatar
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    I have a client who has a pair of LX16 and LX16A crossovers. He wanted to rebuild a pair for his L200s. His mother was the original owner, they are original with the LE15B, 8 ohms and the LE85, 16 ohms, there have been no changes or mods done since new. He sent me one LX16 and one LX16A and kept one of each for himself - a LX16 in one speaker and a LX16A in another. The plan was to rebuild the pair he sent me as LX16A. I rebuilt one and did some listening with some basic speakers I had in the shop. I really felt there was a gap in the crossover as mentioned above. I asked him to do a comparison with the LX16 and 16A he had in his speakers. He reported the same. Now, this could be due to his LX16 being 50 years old or it could support my claim above. He has opted to rebuild the crossovers as LX16 not 16A.

    I have one crossover presently rebuilt as a LX16A and will do the second as a LX16. I want to run some comparison tests on both before changing the first LX16A rebuild over to the LX16 design. I'll post up the results once done.

    Eric M.
    MCIaudio

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    Administrator Mr. Widget's Avatar
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    I was not aware of the LX16A, but I always thought the crossover was the weakest link in the original L200. If you could build your own networks and insert some of the additional filtering to "extend" the highs as was done in the L200B I think you would be ahead.

    I have never worked on the LE15B/LE85 HL91 crossover point so this would require some experimentation to dial in, but based on past experience I bet you can do better than JBL did in the early 70s.


    Widget

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    Senior Member Eric M.'s Avatar
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    Quote Originally Posted by Mr. Widget View Post
    I bet you can do better than JBL did in the early 70s. Widget
    LOL, Probably!

    I think the best upgrade for the L200 is the L300. Addition of the 077 for that extended highs your looking for and a completely new crossover design, the N333. With those you can upgrade to the Nelson Pass design or the Nelson Pass Charge Coupled design. The funny thing about the L300 is the crossover point is even lower than the L200, it's at 800 Hz and for some reason that is acceptable for the LE85, JBL never issued a fix for the N333 or L300 that involved shifting the crossover point for the LE85 and we know the design of the LE85 didn't change.

    Most of the work I do is rebuilding JBL products as original, using modern (Translation: better) parts for those old, worn out 50 year old speakers. I'll do upgrades if someone wants them (Pass Designed crossover, Charge Coupled or others) or can design a crossover for someone building from scratch using crossover software. Most I deal with are looking for rebuilds as original, they are "collectors" of JBL.

    I think in another post I compared it to rebuilding a 64, 427, tri-powered Corvette. Would it be faster, more reliable and get better mileage with a modern fuel injected crate motor? Sure, but take it to a car show and Corvette collectors would scorn you. And then someone here posted pictures of their beautifully restored 64 Corvette and the post went off in an entirely different direction! It was a beautiful car.... with the original motor.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Eric M. View Post
    I think in another post I compared it to rebuilding a 64, 427, tri-powered Corvette. Would it be faster, more reliable and get better mileage with a modern fuel injected crate motor? Sure, but take it to a car show and Corvette collectors would scorn you. And then someone here posted pictures of their beautifully restored 64 Corvette and the post went off in an entirely different direction! It was a beautiful car.... with the original motor.
    I get that, but JBL made some of the finest drivers... too bad that other than in a few exceptions it took them a few more decades to make some of the finest speakers with their own drivers.

    I love vintage JBL, Altec, and Klipsch... I would just rather appreciate them than listen to most of them.


    Widget

  10. #10
    Senior Member Eric M.'s Avatar
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    Quote Originally Posted by Mr. Widget View Post
    I would just rather appreciate them than listen to most of them. Widget
    I think a lot of people feel that way. If I get a pair of drivers with the white (or yellow by now) Lansaloy surround intact (hard as a rock, but no crack), I will list it for sale as is for the collectors who want an all original JBL driver. I list it as parts, not working, warn that this 15" woofer sounds like a tweeter due to the surround being so hard and that if used regularly, the surround will crack. I will post that if it has not sold in 3 months, I'll replace the surround and relist. I have never go that far, some collector will usually purchase it. Most of the time I'm shipping those sort of drivers to Asia.

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