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Thread: 4343 crossover modifications

  1. #46
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Earl K
    Hi There (again) ,
    - Back to this 52uf cap question. ( After a couple of years )
    I study all information about Caps and I just realize the Value of the Schematic of 3143 is 52 MF and all caps mesure is in MF Values



    It is a schematic error or what???
    I check in situ if write on parts and no precision appear...


    Anybody Please confirme if is UF OR MF caps

    Jean.

  2. #47
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    MF = uF on JBL schematics...

  3. #48
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Giskard
    MF = uF on JBL schematics...
    Big thanks Mr Giskard



    Jean.

  4. #49
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by jeph
    [color=black]Originally I replaced most of the caps in the crossover used on the HF and UHF drivers with vintage Jensen paper in oil caps (1 uF, 1.5 uF, 1.5 uF and 4 uF).
    I again Jeph,

    I read and re-read with big interest your quote but I realize a surprise...

    You change the old caps by .... vintage caps jensen paper in oils caps???

    this type of caps is not change in time ???

    thanks for hint...

    Jean

  5. #50
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    B&KMan

    About those voltage drives for your network, which you posted on the first page ;

    - They do look sort of wacky to me .

    - Can you post one for the 2121 midrange ?

    - Are you sure that your B&K test equipment leads aren't "loading" that network and therefore "skewing" the results ?

    - What impedance leads are you using ?

    - The voltage drive for the woofer doesn't make much sense to me / it looks like it has a builtin Very Low Frequency ( VLF ) HiPass filter built into it . Maybe it's your test leads .

    - By The Way ( BTW ) . JBL is noted for employing all sorts of various shapes in the stop-band slopes of a crossover . So when you see a bunch of different "turn-over" points show up don't panic / they were designed to be there .

    - Nothing in the JBL world of crossover design is simple / if you want simple / try old Altec stuff ( excluding the Model 19 ) .


  6. #51
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Earl K
    B&KMan

    About those voltage drives for your network, which you posted on the first page ;
    The generator is real generator type 0 and produce extreme wide frequency,

    In this regards 3hz to 25K at white random noise...


    Quote Originally Posted by Earl K

    - They do look sort of wacky to me .
    EUH... Sorry I'm not understand ...

    Quote Originally Posted by Earl K
    - Can you post one for the 2121 midrange ?
    OKAY I have a test but, maybe I'm repeat, but I'm feeling to overload the tread... but no problem, I have perfom test impedence of driver too Do you have pict of this ???

    Quote Originally Posted by Earl K
    - Are you sure that your B&K test equipment leads aren't "loading" that network and therefore "skewing" the results ?

    - What impedance leads are you using ?
    Well I run with same cable standart for evaluation as lab test loudspeaker...
    In this case I prefer to pass directly by a mono 5hz -25KHZ (flat phase response) B&K amplifier special design for shaker and speaker load in nominal 8 Ohms.

    but sound is appear same of my stereo

    The cable speaker link is Monster cable 1 feet.. so it is realy short.
    the cable, for keep mesure, is probe same as portable electric meter with-out MOhms resistance inside...


    Quote Originally Posted by Earl K
    - The voltage drive for the woofer doesn't make much sense to me / it looks like it has a builtin Very Low Frequency ( VLF ) HiPass filter built into it . Maybe it's your test leads .
    Well acoustical test is appear relatively normal test... but You touch my curiousity. I check . But remember I keep mesure in load all driver in contact at network and work... so my my probe is parallele in standart of load driver. In other side the amp is standart nominal load 8 ohms so do you ahe othre idea where the load is possible not good ???

    For my commitment I test, before all start new bunch of test, the integrity of connection

    In this case I put my probe direct of post speaker of network for check if amp or speaker is flat response... I send this pict if you want but it is realy flat over a 1000 average works for the test.


    Of course JBL Is serious approch and I respect for but in begin in this electronic aspect it is difficult to acquire fast the competence so thanks for this reply and any other...

    Jean

  7. #52
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Earl K
    B&KMan

    - Can you post one for the 2121 midrange ?

    There is as your wish


    Attached Images Attached Images  

  8. #53
    Senior Member Guido's Avatar
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    Looks not too bad.

    Pic shows theoretical voltage drive.
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  9. #54
    Senior Member Guido's Avatar
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    Quote Originally Posted by Giskard
    The 52 uF capacitor needs to stay.
    This I don't understand.
    The 52 (+4) uF Cap is part of the high pass section of the bandpass for the 2121. Why the HF and UHF can't bypass it?

  10. #55
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    "Wacky" ,,,,,, EUH... Sorry I'm not understand ...
    "Wacky" = Wierd = or maybe Wrong = or perhaps Messed Up .

    B&KMan ;

    You had asked quite early on, whether the results you were getting made sense .

    - I can't answer that since I don't have a 4343 to measure .

    - Maybe someone else can help out here about how the acoustic tests "look".
    EDIT : Thanks Guido for your voltage driver pic .
    Others have mentioned the wisdom in biamping ( without a projected $40,000 investment ) ;

    - I agree with them . Biamping is a great way to go . I think you can make it happen quite nicely for under $2000.00 Cdn ( all included ) .

    You have mentioned rebuilding some of the network.

    - I think you should start with the Horn Circuit and the Tweeter Circuit ( as well as biamping ).
    - "Charge - Couple ™" those parts with Solen caps to start with.
    - Its a cheap start.
    - If you don't like the sound I have some others to suggest .
    - The thing is you have to start somewhere to get a reference point on the sound of caps to be able to create an opinion ( like the one you have about silver cables ).



  11. #56
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    Quote Originally Posted by Guido
    This I don't understand.
    The 52 (+4) uF Cap is part of the high pass section of the bandpass for the 2121. Why the HF and UHF can't bypass it?
    Ok. Let me examine it again.

    ***

    The 3143 schematic posted on the JBL website appears to be wrong. Compare with 3141. Thanks for catching that Guido!

  12. #57
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Earl K
    B&KMan

    - Can you post one for the 2121 midrange ?

    Earl K

    Here impedance test in dual channel according to Thiel and Small including a 1000 Ohms precision resistance.

    the drive is direct and out of box.

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  13. #58
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Earl K
    [i]

    You have mentioned rebuilding some of the network.
    I not shure if I'M write or read correct but I'm never re-build network, this is my project now and it is my first time...
    (Maybe I'm not understand all double sense : my english is too poor)

    and realy happy and thanks for Guildo for pict of voltage curve.

    I'm print on the spot and analyse response theorical in regards of my response driver...

    At this regards my UF is definitively not cut correctly at end... and the double curve down of my 2231 is expression of caps is dry and not maintain charge ...

  14. #59
    Senior Member Guido's Avatar
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    Quote Originally Posted by Giskard
    Ok. Let me examine it again.

    ***

    The schematic posted on the JBL website appears to be wrong.
    The schematic on JBLPROSERVICE says HF and UHF BEHIND 52 uF in passive mode.

    I modified my 3143 networks last year, checked this and it is cabled according to schematic.

    Damned, now you confused me

  15. #60
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    I confused you?

    They confused us!

    I really should have paid more attention.

    Just use the 3141 passive schematic. Hang on, let me go look at them both again real close.

    BTW, run your voltage drive with both 8 ohm and 16 ohm loads and compare the results.

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