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Thread: 4345 monitor plans

  1. #61
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    The Spice curves.

    One of the things I am looking at is S/K filter options for unity gain like the JBL cards or equal component values that offer easy adjustability of crossover point, slope and Q but the higher order filters and high Q options have gain in the passband.

    See also Giskards graphs here
    http://www.audioheritage.org/vbullet...+voltage+drive



    Ian
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    Last edited by Ian Mackenzie; 04-09-2004 at 05:44 AM.

  2. #62
    Administrator Mr. Widget's Avatar
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    I guess I got my wires crossed. Too much cross talk in my brain. Perhaps it was a different JBL monitor that used the 18dB card for a "special" curve.... hmmmm.

  3. #63
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    I can see me casting my L100 off after laying eyes on those darlings.........



    Ian

  4. #64
    Administrator Mr. Widget's Avatar
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    You guys are sick, they're only speakers.

    OMG, what have I said....

  5. #65
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    No No,

    Today is officially JBL Blue day...even down here.

    Ian

  6. #66
    Alex Lancaster
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    Wink

    Giskard:

    I thought You could not use profane words, like You just did, in these forums.

  7. #67
    Senior Seņor boputnam's Avatar
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    Originally posted by Ian Mackenzie
    More enlightening however is comment from Greg Timbers:

    ...You will note that the specifications call for 290 Hz for the electronic crossover and the passive one is 320 Hz. This was done to get the best response possible from off the shelf electronic curve shapes.
    That is most odd, because the graphics I posted show that the passive internal crossover was 290Hz. Odd...

    You boys been BUSY this morning...!!

    Oh, and subwoof - you are correct (good eyes... ). That is the 2405H. The only AlNiCo motor in these is the 2421B - which Widget thinks I've otherwise luckily "tamed" quite pleasingly in my setup/EQ. There is no indication anything in these had been tampered with, except one of the 2245H's which look like someone dropped a screw driver through it, and after repairing the pierce (oh no - more white glue noise...!! :shock: ) re-installed it in a non-factory orientation. But I have two new 2245H's that are going in those gaping baffle cuts...
    Last edited by boputnam; 04-09-2004 at 11:50 AM.
    bo

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  8. #68
    Senior Seņor boputnam's Avatar
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    Originally posted by Giskard
    ...electrical ... which means active.
    Yea, exactly right. Odd this was on the 4345 brochure, while the 5234A is a separate, and obviously, quite tedious, part to work with... :rotf:

    Then again, I can see where tri-amped is somuch simpler...

    Thanks, dood...
    bo

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  9. #69
    Senior Seņor boputnam's Avatar
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    Yes, indeedy...

    From this:
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    bo

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  10. #70
    Administrator Robh3606's Avatar
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    Hey I want a copy

    Rob

  11. #71
    Senior Seņor boputnam's Avatar
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    Dood...

    No sweat - pm me your email, and you'll get filled!
    bo

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  12. #72
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    Done it already


    Ian

  13. #73
    Senior Seņor boputnam's Avatar
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    I know. Buy YOURS is printed upside down...
    bo

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  14. #74
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    Oh,

    Okay..

    Better post the original.........with the instructions.......from our Legend Greg Timbers.

    I should point out that without his kind assistance we certainly would not be where we are today with these Forums. Take it away Greg Timbers....

    "I have attached some internal Engineering Specification sheets for the 4345 system. I hope they prove useful.


    I do believe the gross (excluding the MF sub enclosure) volume on that system was 9 cu.ft. The fiberglass lining adds volume in about the same amount as the stiffeners and back side of the woofer subtract it - giving a net internal volume of 9.The enclosures were lined with 3/4" fiberglass on all surfaces but the baffle. I don't have accurate records of the tuning frequency, however, the impedance curve indicates around 26 Hz. That method usually reads a little lower than the effective tuning when real motion is occurring. I would guess that 27 - 28 Hz is what the system really was. The tuning was somewhat empirically done, based on the results of listening tests. One can change the tuning frequency of that system by +/- 2 Hz and still get a very presentable low frequency curve. It really came down to the preferred sound character. The DCR of the LF inductor will have an audible effect on the sound in the tuning range. The inductor in the 4345 had a DRC of around 0.5 ohms. Your 0.2 is a better number (unaffordable for us in production). It might result in the need to raise the tuning frequency by 1-2 Hz. Your choice of tuning will not hurt the woofer any and should be done to satisfy your taste.

    Good luck with your project. "

    Greg
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    Last edited by Ian Mackenzie; 04-09-2004 at 04:57 PM.

  15. #75
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    The graphs
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