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Thread: Am I building these correctly - JBL 4355 Crossovers

  1. #31
    Senior Member martin2395's Avatar
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    I will never forgive JBL the polairty madness!

    By the way, can I simply replace the EQ section (= everything after after S6 and S8) with 8 and 16 ohm L-pads or am I missing something?

  2. #32
    Senior Member Odd's Avatar
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    Quote Originally Posted by martin2395 View Post
    I will never forgive JBL the polairty madness!

    By the way, can I simply replace the EQ section (= everything after after S6 and S8) with 8 and 16 ohm L-pads or am I missing something?
    These are the two L-pads.
    Replace this with two L-pads shown on the drawing.

    Name:  3155 Equivalent Network.jpg
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  3. #33
    Senior Member martin2395's Avatar
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    Are you sure? This looks more like a 2-way switch for 2 different, fixed EQ options to me.

  4. #34
    Senior Member Odd's Avatar
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    Quote Originally Posted by martin2395 View Post
    Are you sure? This looks more like a 2-way switch for 2 different, fixed EQ options to me.
    Yes, use the drawing I posted earlier.
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  5. #35
    Senior Member martin2395's Avatar
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    Quote Originally Posted by Odd View Post
    Yes, use the drawing I posted earlier.
    Now it's clear, it confirms that it's just an L-Pad, no hidden catch, no strings attached

    Odd, do you have any address in Europe for 16 ohm l-pads? I can find 8 Ohm ones without any trouble but no 16's.

    By the way, are there any requirements where a passive network has to be placed inside a speaker cabinet?
    I was even thinking about simply screwing each section of the network to the back of the front panel of the cabinet.

  6. #36
    Senior Member Odd's Avatar
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    Quote Originally Posted by martin2395 View Post
    Now it's clear, it confirms that it's just an L-Pad, no hidden catch, no strings attached

    Odd, do you have any address in Europe for 16 ohm l-pads? I can find 8 Ohm ones without any trouble but no 16's.

    By the way, are there any requirements where a passive network has to be placed inside a speaker cabinet?
    I was even thinking about simply screwing each section of the network to the back of the front panel of the cabinet.
    16 ohms is a bit difficult.
    I buy mostly from US.
    I have only found 16 ohms with short Shafts 8/3 "
    Parts Express
    You can build crossover in a separate box.
    Look back to post 12
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  7. #37
    Senior Member martin2395's Avatar
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    I like the external one, like it a lot but I'm concerned if I don't get itchy fingers to tweak it since it's so easily accesible

    When I look at the schematics I might aswell replace it with resistors but risk a level mismatch due to room acoustics.
    Does the 50% on the schematic say that the l-pad is set at 50% or is it just for reference?

  8. #38
    Senior Member martin2395's Avatar
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    Guys, I wonder if this is an error or not but I see that on the original 4343 the L-pad for the midwoofer is rated for 16 ohm and the unit itself is 8 ohm, why?

  9. #39
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    Power handling.

  10. #40
    Senior Member Odd's Avatar
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    The 50% on the schematic has no meaning.
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  11. #41
    Senior Member martin2395's Avatar
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    Slow but steady, getting there.
    I'm still waiting for 2 coils - .16 and 2.4mH.


  12. #42
    Senior Member martin2395's Avatar
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    Major design failure While measuring the height and width of the crossover I totally forgot the depth and that the bass reflex pipes are so long on the 4343. It turns out that there is only 5.2cm (2.05 inch) clearance between the upper board and the b-r pipe.

    The upper board will house the mid and high section and the bottom one the mid and the 9V CC module so I had to make the total area is a lot bigger than on the 3143 hence the Jantzen Cross Coils are simply massive and the amount of caps is sometimes double (4x1uF in place of 2x2uF for example).

    Is it "doable" or maybe should I drill some holes around that place to let air pass through?


  13. #43
    Senior Member martin2395's Avatar
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    I have finished 1 crossover but it doesn't sound good at all and I can hear hum when the amp is turned on.
    Back to the design phase...

  14. #44
    Senior Member martin2395's Avatar
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    They are done, fixed some errors and they work.

    I built my 3155's with Jantzen Cross Coils, Superes resistors, CrossCap caps and silver plated copper wire with teflon insulation. The L-pads are standard 3143 ones but cleaned.

    First I wasn't so happy with them but then I found out that the l-pads were wired backwards

  15. #45
    Senior Member Odd's Avatar
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    Quote Originally Posted by martin2395 View Post
    They are done, fixed some errors and they work.

    I built my 3155's with Jantzen Cross Coils, Superes resistors, CrossCap caps and silver plated copper wire with teflon insulation. The L-pads are standard 3143 ones but cleaned.

    First I wasn't so happy with them but then I found out that the l-pads were wired backwards
    Do not drink and solder.
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

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