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Thread: Yet another 4425 DIY

  1. #31
    Senior Member jerv's Avatar
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    8th order filter

    Yes, the RLC 1031 is a form of notch filter. This filter topology is called an elliptic or Cauer filter. The added capacitor (C1031) in addition to the standard 4th order topology creates a notch with increases the filter rolloff substantially. It is possible to get up to 60dB/oct rolloff with as little as 5 components. This filter is optimised for 48dB/oct rolloff slopes. For more on Cauer filters, see http://ldsg.snippets.org/FILTERS/Cuadra/elliptic.php3 or varoius forum postings (do a search) on www.htguide.com.

    These two drivers are not really well behaved in the crossover range. The 2214 has a pronounced peak at 1.9kHz, the 2416 has its resonance frequency near (with two ugly impedance peaks, one at 1350 Hz).

    With 4th order filters I could not get rid of the 1.9kHz 2214 peak with a conventional LRC series notch filter in parallell with the driver without messing up filter slopes - probably because the notch is so close to the crossover frequency. Only an 8th order filter makes it (though you can still see it down at -27 db).

    The broad 2 dB peak at 2 kHz in the summed frequency response is because of the tweeter. (See simulations below with individual curves. The simulation looks a little bit better that the measurement). The impedance peak at 1350 Hz at a point where the response is at its strongest makes a good design using passive components difficult. (An electronic filter might be easier, and is a future design option). Anyway, I fully agree that the 8th order maybe needs some more work.
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  2. #32
    Senior Member northwood's Avatar
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    parts

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  3. #33
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  4. #34
    Senior Member northwood's Avatar
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    hope it is useful
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  5. #35
    Senior Member John W's Avatar
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    They have some 4425 networks in the tent sale (3rd page in).

    http://www.jblpro.com/commerce/tent_...x.php?cPath=23

    I just picked up a pair for my DIY project.
    Last edited by John W; 01-10-2007 at 03:11 PM. Reason: more info

  6. #36
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    Northwood

    Nice shots.

  7. #37
    Senior Member jerv's Avatar
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    8th order filter, version 2

    I have done some additional work on the 8th order filter. Frequency response is now within plus/minus 2 dB from 200-20000 Hz, and phase tracking is very good. See attached graph - version 1 is black, version 2 is the red curve.

    Unfortunately, the number of components has gone up somewhat. To get rid of the 1.3 kHz peak in the 2416, I used a parallell notch filter in series.

    To my ears, the new crossover sounds very good - as dynamic and engaging as the original L200t, but with less perceived high-frequency harshness.
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  8. #38
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    Quote Originally Posted by jerv View Post
    Unfortunately, the number of components has gone up somewhat.
    Yeah, that happens.

    Nice job!

  9. #39
    Senior Member jerv's Avatar
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    This is my last endeavour with my (strongly) modified 4425 crossover. The topology is now 6th order. The component count is way down compared to the 8th order version, at the expense of some slight frequency response unlinearity at 2 kHz. But it's all still more or less within +/- 2dB 200Hz-15kHz, - and the phase tracking is better then the 8th-order version.

    When I built the network, I charge-coupled (thanks, forum!) all capacitors in the HF section and used foil inductors in the LF section. I think this version is a keeper.
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  10. #40
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    Very nice!

  11. #41
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    Thought I'd bump this up from the depths of the LHF glacier ( for Heather's interest ).

    Jerv, this was some mighty fine network design ( plus, all accomplished over a decade ago ! )

    Do you still have and listen to your special 4425 efforts ?

    Any chance ( if you still have them ) of posting frd & zma files for the drivers used ?

    thanks

  12. #42
    Senior Member jerv's Avatar
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    Quote Originally Posted by Earl K View Post
    Thought I'd bump this up from the depths of the LHF glacier ( for Heather's interest ).

    Jerv, this was some mighty fine network design ( plus, all accomplished over a decade ago ! )
    Do you still have and listen to your special 4425 efforts ?
    Any chance ( if you still have them ) of posting frd & zma files for the drivers used ?
    thanks
    Wow! This was a really unexpected and nice surprise: seeing my old 4425-thread resurrected like that!

    Thanks for your questions - which I, unfortunately, cannot answer.
    The 4425-DIY's are long gone.
    They have, in turn, been superseded by a long string of JBL-DIY's (all with special crossovers, of course): 4430, 4333, 250ti, 4313, 4345 variants, and so on. Even DIY M2 monitors.
    Had to try them all.
    And a pair of very special "250XPL" (as I call them): with LE14H-3, 2108A, 093ti and 046ti (they became keepers, and are still in my house).

    Now I'm mostly into large horn systems, with JBL and TAD drivers.
    And, alas, the 4425 frd & zma files disappeared long ago in a computer crash.

  13. #43
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    Ahhh then, thanks for the update Jerv.

    It's most appreciated .


  14. #44
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    I just pulled four L200T3's out of the graveyard, and would be of limited use as a source of information presently. Maybe you wanted a photo of some internals or something before they go under the knife?

  15. #45
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    Quote Originally Posted by 314carpenter View Post
    I just pulled four L200T3's out of the graveyard, and would be of limited use as a source of information presently. Maybe you wanted a photo of some internals or something before they go under the knife?

    I appreciate the offer, but, I don't think there's anything ( visually oriented ) that I need .

    I was simply trying to match-up my network reworks to Jervs results ( of his crossover designs ).

    My problem is I don't actually own any of these drivers/horns which makes it tough to get reliable results ( when using extrapolated frd & zma files ).

    Thanks for the offer!


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