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Thread: One L300 louder than the other. New crossovers needed question for the experts?

  1. #16
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Giskard
    Why? Did someone tell you all the work I did on the LX300/N333/3133 network was wrong? Or did you determine that with your own pair of L300's or 4333's?
    Nope. All's I'm saying is that the 7 kHz or 8 kHz UHF crossover frequencies thus far detailed for the DIY crossover Todd is recommending here are not optimum for use with the slot drivers, which I HAVE tested with it, and that I am working on moving that up to ~10 kHz for them, as others have recommended here.

    I am also statiing that they have NOT been tested in L300's, and that such application of them would be experimental, at best. Further, this part of the discussion clearly belongs in DIY, not here. I didn't post it, and I can't control what others post, or where they post. But, if it contains some implicit endorsement attributed to me, it's only appropriate I qualify that.

    I'm agreeing with you Giskard, is all. And others here, as well. While John apparently wants to ultimately do it anyway, a wholesale crossover swap is not how I'd approach solving his immediate problem, regarding which I'm certain you may have recommendations to offer, once the actual source is determined....

    Note of potential interest: Giskard's L300 equivalent crossover design is here:

    http://audioheritage.csdco.com/vbull...=&threadid=166

  2. #17
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    Quote Originally Posted by Zilch
    Nope. All's I'm saying is that the 7 kHz or 8 kHz UHF crossover frequencies thus far detailed for the DIY crossover Todd is recommending here are not optimum for use with the slot drivers, which I HAVE tested with it, and that I am working on moving that up to ~10 kHz for them, as others have recommended here.

    I am also statiing that they have NOT been tested in L300's, and that such application of them would be experimental, at best. Further, this part of the discussion clearly belongs in DIY, not here. I didn't post it, and I can't control what others post, or where they post. But, if it contains some implicit endorsement attributed to me, it's only appropriate I qualify that.

    I'm agreeing with you Giskard, is all. And others here, as well. While John apparently wants to ultimately do it anyway, a wholesale crossover swap is not how I'd approach solving his immediate problem, regarding which I'm certain you may have recommendations to offer, once the actual source is determined....

    Note of potential interest: Giskard's L300 equivalent crossover design is here:

    http://audioheritage.csdco.com/vbull...=&threadid=166

    I'm assuming that you've tried changing the caps from 1.5 to 1.0 mfd and/or reduced the coils to ~0.2 mH instead of 0.3?

    The L300 circuit uses a few more parts and would be more costly to build..., with potentially no sonic benefits other than it crosses the HF over a little higher. It will put that ~9KHz peak in the HF (for whatever reason) as was demonstated in DIY some time back.

  3. #18
    Administrator Mr. Widget's Avatar
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    Hi Todd,

    It seems you are suggesting "improvements" to the original design? I think the object here is to figure out what is wrong with this pair of L300s and make this pair of speakers operate as originally intended.

    Maybe I misunderstood your post?


    Widget

  4. #19
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    Quote Originally Posted by Mr. Widget
    Hi Todd,

    It seems you are suggesting "improvements" to the original design? I think the object here is to figure out what is wrong with this pair of L300s and make this pair of speakers operate as originally intended.

    Maybe I misunderstood your post?


    Widget
    Agreed with all that it is imperative to first find the problem..., no arguement here.

    But that was not the original request of the poster who specifically asked for a crossover circuit. When no one initially stepped up to answer his call, I was just obliging.

    I recognize that this should be in DIY, but like some others, should I be arrogant and state that because the poster put this in the wrong forum he should be chastized and/or ignored? That doesn't build commradrie..., just contempt.

    The recommended diagram is JBL-based. It is simply the L200A crossover with the N7000/N8000 installed on the same board. The woofer and MF compression driver are similar to those in the L200 and there is no reason they shouldn't work in his application too.

    As for the ~9K response peak, in the past I believe you said this was of propriatary knowledge on a need to know basis. Can you elaborate on its need?

    As for improvements to the original design, that is not my intent, though I'm sure that by using modern, higher-quality components (and for what it's worth, Theta by-pass caps), we've achieved that too.

  5. #20
    jbl
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    Try connecting one driver at a time directly to the crossover, out of the cabinet and with the L-Pad disconnected. If the output is the same, reconnect the L-Pad and test again. This will rule in or out each CO or L-Pad. You'll need the SPL meter as stated above.
    If the driver is at fault, try it with the other CO.

    Ron

  6. #21
    Senior Member CONVERGENCE's Avatar
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    Quote Originally Posted by CONVERGENCE
    Hi,

    If your drivers are Alnico they might require remagnitizing.
    Or the woofers could need a complete retrofit. Voice Coil, Cone,New spiders etc.
    Both drivers have to be done simultaniuosly by a professional speaker
    repair tech. He does not need your XO to do a perfect match. The Xo is not important for him.

    Good luck.
    I forgot to add that all your drivers LF, HF, TWEETERS need to be checked.
    If HF driver is defective then new diafragm is needed.
    It usually takes them 1/2 hour to give you a diagnostic.

    .................................................. ......................................

  7. #22
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by toddalin
    I recognize that this should be in DIY, but like some others, should I be arrogant and state that because the poster put this in the wrong forum he should be chastized and/or ignored? That doesn't build commradrie..., just contempt.
    I am not sure where this thread should be... and I agree that worrying too much about that is silly at the least and has bread contempt and a heck of a lot of disharmony at the worst.

    In any event I was under the impression that the thrust of this thread was... "help me get my speakers working properly."

    Quote Originally Posted by toddalin
    The recommended diagram is JBL-based. It is simply the L200A crossover with the N7000/N8000 installed on the same board. The woofer and MF compression driver are similar to those in the L200 and there is no reason they shouldn't work in his application too.
    This confuses me... why would someone with L300s want a modified L200 network instead of the real deal? I could see someone who is a fan of hot rodding gear getting into the N333 networks and messing around with updated parts and wires, but I sure wouldn't think going the L200 route makes any sense. But what the hell, people do all kinds of things to get results they are happy with.


    Widget

  8. #23
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    This little battery powered chip amp is supposed to be outstanding... and they only cost $30 for the little stereo bugger from Parts Express.

    It should really bring out the best of the 2405.

    I actually bought one, but trying it out is on that long to do list.



    Widget
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  9. #24
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Mr. Widget
    This little battery powered chip amp is supposed to be outstanding... and they only cost $30 for the little stereo bugger from Parts Express.
    Still needs a filter ahead or after it, no?

  10. #25
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    Quote Originally Posted by Giskard
    The "10 kHz" 24 dB/octave filters in the 4315, L300/4333, 4343 and 4350 all had that little 8-9 kHz bump to varying degrees - no comment. If I recall correctly the 4350 had the smoothest voltage drive amongst those models.
    As I recall, that "little" bump wasn't so little. However, like usual, you pulled your pic so I can't display it and no one can see it.

    And why doesn't anyone want to "comment" on the bump that is the result of the cap/coil/cap as opposed to just a properly sized cap/coil which would not produce this bump?

  11. #26
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by toddalin
    And why doesn't anyone want to "comment" on the bump that is the result of the cap/coil/cap as opposed to just a properly sized cap/coil which would not produce this bump?
    It's three-pole (18 dB/octave) versus two-pole (12 dB/octave), if I understand what you're asking.

    The bump's an independent issue.

    I can't find this specific subject "bump" discussion. Link us to it, please, so that we may refresh our respective recollections....

    Quote Originally Posted by Giskard
    I suggest a very careful analysis of all these filters before trying anything new.
    I HATE 2405....

    [2407 is more fun.... ]

  12. #27
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    Quote Originally Posted by Zilch
    It's three-pole (18 dB/octave) versus two-pole (12 dB/octave), if I understand what you're asking.

    The bump's an independent issue.

    I can't find this specific subject "bump" discussion. Link us to it, please, so that we may refresh our respective recollections....
    Can't..., Giskard pulled it.

  13. #28
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Giskard
    It's 24 dB/octave.
    That fact is reinforced on the Engineering Design Specification document.
    I see that. But how, electrically?

    Where's the fourth pole?

    Quote Originally Posted by Zilch
    [Workin' on that part....]
    O.K., thanks, Giskard. I'll look to the other options you cite....

  14. #29
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    Hi,

    I have measured and noticed that when I mocked up a 4343 crossover model the bump has more to do with the time constants and the effective Q of the filter and its reactance with the actual driver.

    However, when combined with the 2420 driver who's response is actually falling in consideration of the horn high pass filter in the 3143 and its own mass rollover the resulting overall acoustic amplitude response is reasonable. If you understand what I mean.

    Getting back to the problem. My instinct is its a mechanical contact problem that needs repair. The inspection of both internal crossovers would remedy other causes either value/ invalid.

    If the cable looms from the crossover or the Lpads and to the drivers are not secure they will fatigue and work loose with vibration or movement. Stress on the driver terminals will lead to poor connection.

    I hope this assists in resolving the issue.

    Ian

  15. #30
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    John,

    Your in Framingham, MA!

    I stayed in Milton and Boston when I was there. Nice place to visit.

    Assuming you want to nail the problem without a lot of upheaval it may pay to take them to an authorised JBL service centre in your region and get the boxes checked out by a tech rather than endure pain of pulling them apart unless you really want to do that.

    This thing is just going to nag you otherwise.

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