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Thread: stock 4345 crossover 3145 schematic

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  1. #1
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    Red face stock 4345 crossover 3145 schematic

    Hi everone, i am gathering information in order to build a pair of 4345's in the next year (or so) and I have realized that most of my hobby of restoring pieces, is my work to reach their factory setting - not better, not worse.
    Before people post answers like "The charged coupled networks are better" I would like to say that the idea for me is (generally with my hobby of vintage Hifi) that if i want to have something "better" i could just buy something else - and leave the old pieces as they are, representations of a time and a way of production that i admire - this is a big part of my hobby, and i hope you acknowledge this.
    I am aspiring to build the pair as exact replicas of the originals. that means that everything will be done in the same scale and materials, with the same treatment to parts and enclosures as the original JBL.
    That being said I would also like to build two crossover networks and these should as the rest be new productions of the original crossovers - with new quality components of course.
    The problem that i seek to answer, exist that in spite of 5 days of searching (on google and this page) i haven't been able to find a readable schematic.
    I have seen the schematic on the JBLpro site, but i can't seem to read the values of components, due to low resolution.
    I have found several charged coupled schematics, but since i would like to remake the stock network i was wondering if someone could point me to a better-resolution schematic or scan of this?

    best regards
    Soren from denmark.

  2. #2
    Senior Member BMWCCA's Avatar
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    Do you intend to re-create the enclosure for the crossover, too, including the clunky multi-pole switch for bi-amp function? As a car restorer, while I admire your purist philosophy, I'd think you'd be better off trying to find a used original pair and restoring those. Unless you're able to actually re-create the plastic housing, decals, labeling, metal mountings, and connectors exactly, I don't see the point. I'm not discouraging you from trying and I'm not even going to discuss the resulting improvement in audio quality available in a modern equivalent since that doesn't seem to be your goal. More power to you if you can actually pull-off what you're suggesting! Have you seen photos of what the original looks like? The schematic would seem to be only one of your worries if the goal is really to re-create the original in appearance as well as function.

    My first Google search on the topic netted this: http://www.jblproservice.com/pdf/Net...45 Network.pdf
    It seems fairly clear to me. Maybe what you found was different?

    You might also check out this thread, if you haven't already: http://www.audioheritage.org/vbullet...r.-A-pictorial

    Best of luck and be sure to post your progress with plenty of photos.
    ". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers

  3. #3
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    Thank you for you're concern, I have seen the pictorial thread and found it very informative - And yes I intend to build everything as the original, about the plastic housing, it might be the only thing i still need to find a way to deice upon - The decals will be custom-made to my project with another subtext to the foil cal: instead of "James b. Lansing Sound INC..." it will read, with the same font; "Copy by Søren Iversen, Denmark"
    the same will happen to tags and decals- everything will be made to replicate the original in its manufacture and it will resemble the 4345 perfectly, but I will not make the speakers being mistaken as an original pair since they are copies made by me.
    The problem about buying and why i have chosen not to.
    I live in denmark, firstly they are hard to come by over here in their original condition, and they are extremely expensive to have shipped. (maybe not more expensive than the project, but I need a project and it is to prove that if you want to, and do the research probably, you can build an exact replica in any way when cost is no object.
    It also allows me to make one investment at a time (buy the midrange first, then the woofers... so on)
    It is a project i really look forward to start and I do have a little team of project members, which include a professional furniture restoration guy, who is assisting me in applying the veneer, alongside a couple of JBL 43XX, Marantz and JBL amp collectors with a huge resource of documents and speakers I can compare to when trying to match colors and finishes.

    best Regards
    Soren from Denmark
    Last edited by santashooter; 11-29-2011 at 03:36 AM. Reason: bad internet connection stole my original post!

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    about the clunky switch and the enclosure - I haven't yet decided the degree of exactness, in this function - could think of making the enclosure, but designing the cosmetic appearance and arranging of the crossover differently, also adding switch that would be less prone to filth and bad connection than the original switch.
    My goal is, that the electrical (meaning the crossover being a passive design) and the cosmetic appearance outward are exact matching the original speaker.
    About caps - I intend to buy "quality" caps - meaning factory standards in this field, not High-end caps, since i am quite sure that JBL used good quality Industrial standards in their crossover - not fancy gold oil caps.
    I am yet to decide brand and make, but these are my thoughts.

  5. #5
    Administrator Robh3606's Avatar
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    You cannot build "stock" networks. You cannot get the tapped Inductors in the schematic. Use a Charge Coupled equivalent for best results

    Rob
    "I could be arguing in my spare time"

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    I am not going to build stock networks, I am going to build a passive clone of the network using the design - this means i will have to source either tapped inductors or find some way to get the same electrical parameters with a substitution inductor.
    How i will find them I still don't know, since i can't read the schematics i have found, and thus i haven't got a parts list with the components.
    I will not Build CC networks as they are too far from the original design for me.

    If it shows that i can get the exact same electrical properties from a CC network compared to the stock crossover i will build a pair - but otherwise i am aiming for a clone using available parts.

    best regards
    Soren

  7. #7
    Administrator Robh3606's Avatar
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    The Inductors are custom wound for JBL using their drawings. They are NLA. The CC networks are correct equivalents without the Inductors. If you have the CC network schematics that's all you need.

    Rob
    "I could be arguing in my spare time"

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    Quote Originally Posted by Robh3606 View Post
    The Inductors are custom wound for JBL using their drawings. They are NLA. The CC networks are correct equivalents without the Inductors. If you have the CC network schematics that's all you need.

    Rob
    Thank you - i didn't realize the CC schematics were close equivalents to the stock network.

    can anyone really say how long the 9v battery lasts in the networks?

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    Decapitate!

    Quote Originally Posted by santashooter View Post
    I am not going to build stock networks, I am going to build a passive clone of the network using the design - this means i will have to source either tapped inductors or find some way to get the same electrical parameters with a substitution inductor.
    How i will find them I still don't know, since i can't read the schematics i have found, and thus i haven't got a parts list with the components.
    I will not Build CC networks as they are too far from the original design for me.

    If it shows that i can get the exact same electrical properties from a CC network compared to the stock crossover i will build a pair - but otherwise i am aiming for a clone using available parts.

    best regards
    Soren
    I would simply remove the double caps and battery wiring from one of the DC biased schematics. i.e. 20+20=10. About as close as you're going to get, I'd guess. I did this with a 3155 crossover and it worked just fine; the total capacitance values are unchanged. Mike

  10. #10
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    It sounds to me like you have to wait for a pair of the networks to show up on eBay or Audiogon. You might want to spend most of your time searching in Japan since that is where most of them ended up. The 3144 and 3145 are the same except for wire lengths to components and L-Pad foilcals.

    Here's the stock network parts list. The tapped autotransformers are set to approximately -4 dB for the 3155 and approximately -8 dB for the 3144/3145 (they all use the same tapped cores).

    The shunt resistors in front of the tapped autotransformers attempt to mitigate their rising impedance thereby presenting a flatter load to the preceeding series capacitors.

    5.4 mH
    20 uF
    20 uF
    20 uF
    20 uF
    20 uF
    7.5 ohm
    10 uF

    20 uF
    20 uF
    20 uF
    4.8 mH
    1.8 mH
    14 uF
    5.1 ohm
    5.1 ohm
    39 ohm
    39 ohm
    8 ohm L-Pad

    8 uF
    62 ohm
    62 ohm
    62 ohm
    tapped autotransformer 1.0 mH primary winding 0.143 mH secondary winding
    12 uF
    0.24 mH
    3 uF
    8 ohm L-pad
    20 ohm

    1 uF
    39 ohm
    39 ohm
    tapped autotransformer 0.16 mH primary winding 0.026 mH secondary winding
    1.5 uF
    8 ohm L-Pad

  11. #11
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    Quote Originally Posted by Mannermusic View Post
    I would simply remove the double caps and battery wiring from one of the DC biased schematics. i.e. 20+20=10. About as close as you're going to get, I'd guess. I did this with a 3155 crossover and it worked just fine; the total capacitance values are unchanged. Mike
    So you would be able to take the CC networks (as posted numerous places on this forum) and remove the double caps with a single of half value and then you wouldn't need the battery?
    how are peoples thoughts about the sound of these.
    I would like to go all passive, but if i could achieve the same SPL with a passive network instead of a CC i might consider that.

    best regards
    Soren

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