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Thread: L 65a - new Crossover. where to start?

  1. #1
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    L 65a - new Crossover. where to start?

    Hello everybody.

    I am looking for plans/ideas for a new x-over in my L65as. I want to build it myself, but I need to start somewhere so I wondered if anyone ever did that. Ive read good things about how a "good or better" x-over does really improve the L65a

    Thank you!

  2. #2
    Administrator Mr. Widget's Avatar
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    I assume from your post that you want to replace the stock passive crossover with a newer design. I moved your post from the electronic crossover section to the general Lansing DIY area which may get better visibility.

    Hopefully someone with direct experience with L65s or similar JBLs will be able to share their experiences.


    Widget

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    Senior Member markd51's Avatar
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    Hello,
    As for sticking with Passive Crossovers that will properly duplicate the factory values, I see little harm-foul with that, and should be a safe bet and perform just fine.

    But I have heard it said many years ago that Air Core Inductors were not preferred versus Iron Core types.

    I came to this crossroads many years ago with my L-65 Jubals. 4 of them. Age, and a bit of excessive volume one day damaged 2 of the Crossovers, and also took out 2 drivers, LE5-5 Mid, and 077 Tweet. Had them fixed-replaced of course.

    I suppose much could be said pro-con for the original Crossovers, and staying bone stock. Or at least go through Caps-whatnot with decent matching parts.

    I chose to go another route, I faxxed the original specs to a company who then made me 4 passive custom 3-way Crossovers that were beautifullly made, but with Air Core Inductors, all Solen Caps. L-Pads were getting sort of bad, and I went through them also.

    The power handling of both Crossover's Inductors, and L-Pads were higher than stock values, (figuring they'd be better able to handle higher wattage without strain or self destruct again. Of course the Drivers are what they are, and are all stock 126A, LE5-5, 077.

    While I did the swap, much more began to be eyeballed and suspect, and I wasn't so much caring about resale value-worth, as I had no plans to ever sell them.

    So, all Binding Posts were replaced with the now gone Solid Copper Edison Price, very beefy 5-ways, all new high quality copper Internal Wiring, I did a little bit of internal Cab improvements like fileting all seams with carpenter's glue, Further glued and strenghtened areas such as the Port Tube Attachment, and the small internal Midrange enclosure. All drivers were as well gasketed to the front baffle.

    12ga wiring from binding posts to crossover now mounted to the Bottom of the Cab, and also 12ga to Bass Driver. 16ga used everywhere else, and soldering where required was done with WBT.

    When all was done, I was more than pleased, in fact wowed. I am the original owner of these speakers, bought brand new back in the day.

    This all wasn't cheap because of quality of parts used, but also wasn't prohibitive in expense.

    Madisound was the folks who made me the crossovers, but not sure if they do such work anymore?

    I'm an electronic hack, but the swap and going over all was relatively easy with no foul ups.

    Most here might frown at what I had done, but this was the personal route I wanted to go, and had hoped such would address some weak areas of manufacture, parts consist and of course being built to a price point.

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    Senior Member markd51's Avatar
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    I'm not sure that I've ever read about such here, going the Charge Coupled route with L-65's?

    I suppose other mods could be bypassing L-Pads with Resistors-etc, but to me, that sort of kills the versatility of these speakers, unless playing-swapping such is easy peasy for you. In general, these speakers sounded about as good as they could with both L-Pads set to flat give or take a smidgen.

    I sort of felt right off the bat, that I wasn't going outguess and build a better mousetrap with crossover mods and veer from bone stock factory values.

    There's some facts of course, all 3 versions of the L-65 possessed some x-over changes, and different Bass Drivers, Port-Baffle Layouts, voicing-etc.

    They're sort on an odd speaker, not a Bookshelf, but a bit too small for a floor stander. They should have some nice custom stands.

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    Quote Originally Posted by marmelbirne123 View Post
    Hello everybody.

    I am looking for plans/ideas for a new x-over in my L65as. I want to build it myself, but I need to start somewhere so I wondered if anyone ever did that. Ive read good things about how a "good or better" x-over does really improve the L65a

    Thank you!
    https://www.audioheritage.org/vbulle...6&d=1144944024

    I would simply replace the capacitors with more modern parts.

    These jbl networks have inductors with specific dcr. The dcr is an important criteria for the crossover filters to work correctly. It’s best left alone unless you have the original factory parts lists.

    They generally used Mylar capacitors in that era. Any metalized polypropylene capacitor is going to offer more transparency. The Mylar capacitors sound like a pillow over the loudspeaker.

    If your interested in the charge coupled Solen Fast Cap crossover upgrade l suggest to keep the original crossover and mounting the Solen capacitors on a separate piece of plywood.

    The values will be 27uF x 2, 8uF x 2, 3uF x2. The 1/4 watt 2.2 meg ohm resistor should be also hot melt glued to the board. The battery can be mounted with a 9 volt battery holder on the plywood board. Simply remove the existing capacitors from the stock crossover and run flying leads to the charge coupled capacitors. Depending on the rest of your system there should a noticeable improvement in transient detail and transparency overall.

  6. #6
    Administrator Robh3606's Avatar
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    There are 3 schematics for the L65 use your driver load to choose the closest one. They are significantly different. This is a link to L65A and B

    https://manuals.harman.com/JBL/HOM/T...Jubal%20ts.pdf


    https://manuals.harman.com/JBL/HOM/T.../L65B%20ts.pdf

    Rob
    "I could be arguing in my spare time"

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    Hi Rob,

    The link to the Harman tech sheets was previously broken. Is it now working?

    Ian

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    Senior Member jbl4ever's Avatar
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    I rebuilt a pair last year. I did not even have to remove the foilcal or Lpad assembly. It was rebuilt on the front of the baffle board. The wire leads are long enough. I would not change the inductors as said because the new coils will not be in value as the old. The tweeter has a stepped inductor and the mid has a very high dcr value. I did change all the caps with better modern versions using Mundorf AL/ Oil caps with AudioCap bypass. What I have seen on these crossovers are the 10watt resistors burnt to a crisp. 1 problem is these are laying flat on the board with no room for air circulation under it. Put some Mills 12 watt in and keep them off the board for air circulation

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    Burnt resisters is a tell tale sign of power amplifiers clipping. The square produced at high frequencies exhibits far greater power dissipation than a sine wave.

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    Administrator Robh3606's Avatar
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    Hello Ian

    Was last night I would grab what you want before it goes down again

    Rob

    Quote Originally Posted by Ian Mackenzie View Post
    Hi Rob,

    The link to the Harman tech sheets was previously broken. Is it now working?

    Ian
    "I could be arguing in my spare time"

  11. #11
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    Talking

    Quote Originally Posted by Ian Mackenzie View Post
    https://www.audioheritage.org/vbulle...6&d=1144944024

    I would simply replace the capacitors with more modern parts.

    These jbl networks have inductors with specific dcr. The dcr is an important criteria for the crossover filters to work correctly. Its best left alone unless you have the original factory parts lists.

    They generally used Mylar capacitors in that era. Any metalized polypropylene capacitor is going to offer more transparency. The Mylar capacitors sound like a pillow over the loudspeaker.

    If your interested in the charge coupled Solen Fast Cap crossover upgrade l suggest to keep the original crossover and mounting the Solen capacitors on a separate piece of plywood.

    The values will be 27uF x 2, 8uF x 2, 3uF x2. The 1/4 watt 2.2 meg ohm resistor should be also hot melt glued to the board. The battery can be mounted with a 9 volt battery holder on the plywood board. Simply remove the existing capacitors from the stock crossover and run flying leads to the charge coupled capacitors. Depending on the rest of your system there should a noticeable improvement in transient detail and transparency overall.

    Hey, sounds interesting but i am not sure what that charge coupled Solen Fast cap upgrade is! Are there more informations to be found?
    The link you posted is linked to a shematic which i already have

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    Quote Originally Posted by markd51 View Post
    I'm not sure that I've ever read about such here, going the Charge Coupled route with L-65's?

    I suppose other mods could be bypassing L-Pads with Resistors-etc, but to me, that sort of kills the versatility of these speakers, unless playing-swapping such is easy peasy for you. In general, these speakers sounded about as good as they could with both L-Pads set to flat give or take a smidgen.

    I sort of felt right off the bat, that I wasn't going outguess and build a better mousetrap with crossover mods and veer from bone stock factory values.

    There's some facts of course, all 3 versions of the L-65 possessed some x-over changes, and different Bass Drivers, Port-Baffle Layouts, voicing-etc.

    They're sort on an odd speaker, not a Bookshelf, but a bit too small for a floor stander. They should have some nice custom stands.
    odd indeed and so, so beautiful! I cant imagine a better looking (vintage) speaker tbh! No, not even the blue baffle ones

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    Quote Originally Posted by jbl4ever View Post
    I rebuilt a pair last year. I did not even have to remove the foilcal or Lpad assembly. It was rebuilt on the front of the baffle board. The wire leads are long enough. I would not change the inductors as said because the new coils will not be in value as the old. The tweeter has a stepped inductor and the mid has a very high dcr value. I did change all the caps with better modern versions using Mundorf AL/ Oil caps with AudioCap bypass. What I have seen on these crossovers are the 10watt resistors burnt to a crisp. 1 problem is these are laying flat on the board with no room for air circulation under it. Put some Mills 12 watt in and keep them off the board for air circulation
    you mean parts of the L65a were burnt???
    Is that a common problem?

  14. #14
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    Quote Originally Posted by peter123 View Post
    Hey, sounds interesting but i am not sure what that charge coupled Solen Fast cap upgrade is! Are there more informations to be found?
    The link you posted is linked to a shematic which i already have
    It’s arrangement where two capacitors are connected in series and a positive Db voltage with a high impedance source is applied to the centre connection of the two capacitors. There are numerous threads in this approach. There is also some material in the forum technical references and the Library. If you use the Solen Fast Caps - 250 volt l can say without qualification you will hear a difference when the +9 volts is applied. It’s neither a cheap or easy implementation to organise.

    Like a lot of things in Audio and Hifi such novel ideas are not always easily accepted by the majority in the world of public online opinion. As long as no one gets hurt in the exchange of opinions. That is important.

    If you try it and like it that is what matters. Let your ears be the judge. What l am saying is if this hobby was shrouded in rules and etiquette it would be a rather dull and bland past time. I am a firm believer in the technical science of sound reproduction. Precision when applied to loudspeakers and driver levels does improve subjective outcomes.

    But how the human ear and mind interprets musical sounds is very much an individual thing. The study of psycho acoustic explains some of our listening behaviours. Acousticians can measure and explain why some individuals are more sensitive to certain types of sounds than others.

    As long as your happy. That’s what matters.
    Last edited by Ian Mackenzie; 09-29-2022 at 08:48 PM. Reason: Tyo - updated CC Description

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    Huh?

    Quote Originally Posted by Ian Mackenzie View Post
    Its arrangement where two capacitors are connected in series and a positive Db voltage with a high impedance source is applied. ....

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