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Thread: "Charged Coupled" crossovers?

  1. #76
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    Quote Originally Posted by Russellc View Post
    I agree with charge coupling, but have a implimentation question: Does one need to CC the cap in the woofer zobel? I didnt do that on the one I built and was wondering. CC the zobel cap or not?

    russellc
    I just bias the whole mess as a matter of course. I hardly ever use N.P.E.'s in conjugates either.

  2. #77
    Senior Member Russellc's Avatar
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    Quote Originally Posted by 4313B View Post
    I just bias the whole mess as a matter of course. I hardly ever use N.P.E.'s in conjugates either.
    Agreed. Thanks for the response.

    Russellc

  3. #78
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    Beside the Point / but this cant stand

    A current flowing through a capacitor or inductor will always produce phase shift. Charge coupling will actually double the phase shift up to somewhere near 180 degrees.
    - I really don't know what you're thinking here, but because of that second sentence, your understanding of basic electrical theory appears to be in doubt .

    - 2 caps in series ( with that high an "R" value given to the feed resistor ), will ultimately produce essentially the same amount of phase shift ( as a single cap of equivalent value ) / down into the "stop-band" .

    - ie; 90 degrees .

    - Above F3, phase shift diminishes to near zero ( about a couple of octaves up ) .

    - F3 is indentified as a 45 degree phase shift ( for a single passive component ) .

    >< cheers

  4. #79
    Senior Member pierce's Avatar
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    the phase shift as measured in degrees depends on the frequency, capacitance, and impedance of the circuit. a circuit that causes a 90 degree phase shift in a 8khz signal will only shift a 60 hz signal a degree or less. two 20uF caps in series is electrically equivalent as 1 10uF cap (neglecting the details of dielectric absorption and other such minutia).

  5. #80
    Administrator Robh3606's Avatar
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    Here's what Leap says about a pair of series caps and a single both the equivalent value. No difference the curves overlap

    Rob
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  6. #81
    Senior Member pierce's Avatar
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    of course, LEAP probably models a theoretical perfect capacitor and doesn't cope with things like dielectric absorption, internal resistive leakage, parasitic inductance, or any of the rest of the little nasties of the real world, eh?

    [note I said probably, I've never used LEAP, I'm just guessing]

  7. #82
    Senior Member Hoerninger's Avatar
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    Quote Originally Posted by pierce View Post
    ... or any of the rest of the little nasties of the real world ...
    I was curious, I did not expect this
    ■ Capacitor
    This component also includes parasitic models for series resistance and inductance. It also includes a exponential frequency dependent model to simulate various types of dielectric behavior.
    which would be an overshot for calculating series capacitors.

    Download EnclosureShop Brochure
    ____________
    Peter

  8. #83
    Senior Member Steve Schell's Avatar
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    Rob, I am fascinated by your argumentative stance in this thread. I would really like to understand your thoughts on the subject. Do you think that biasing capacitors is without merit? If so are your objections based on theoretical grounds, or have you experimented and failed to hear an improvement?

    There is of course plenty of silliness in audio, but IMO based on direct experience, charge coupling does work and produce positive sonic results. In two elaborate, all horn systems with which I am very familiar, the sound improved rather dramatically within a few seconds of connecting the 9V batteries. Part of what motivated me to build up some CC crossovers was Greg Timbers' enthusiasm for the technique, and I know him to be about as far from a wild eyed tweaky audionut as one can get, though blessed with razor sharp perception. I'm just curious why you are "fighting the good fight" on this one.

    Aren't your eyelids becoming heavy? All we want you to do is to go to sleep... go to sleep and become one of us...

  9. #84
    Senior Member pierce's Avatar
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    Quote Originally Posted by Hoerninger View Post
    I was curious, I had not expected this
    ...
    which would be an overshot for calculating series capacitors.
    indeed. and the other link...

    http://www.linearx.com/cgi-bin/fileb...p_Brochure.pdf
    [the crossover shop brochure...]


    I'm impressed. I'd seen various LEAP graphs here, but not being an audio designer, hadn't looked deeper, and was (stupidly) assuming it had Spice style simplified models of the components. Sadly, at $1500, its not likely I'll be playing with it any time soon...

  10. #85
    Senior Member 1audiohack's Avatar
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    LinearX is currently having a 20% off sale, usually a Febuary thing. Their support as well as their product is outstanding, a bargain even at regular prices I think.

    Through 06-15-2009.

  11. #86
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    In simple terms what does charge coupling do? And it effects the listening experience how? Are there draw backs?

  12. #87
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    Quote Originally Posted by midlife View Post
    In simple terms what does charge coupling do? And it effects the listening experience how? Are there draw backs?
    It's exactly like adding kiwi to a strawberry drink. The drawback is, if you don't like kiwi or strawberry you're screwed.

  13. #88
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    Quote Originally Posted by 4313B View Post
    It's exactly like adding kiwi to a strawberry drink. The drawback is, if you don't like kiwi or strawberry you're screwed.
    Perfect, thats all I'll ever need to know about CC, very insightful.

  14. #89
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    Quote Originally Posted by midlife View Post
    Perfect, thats all I'll ever need to know about CC, very insightful.


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  15. #90
    Senior Member pierce's Avatar
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    Quote Originally Posted by midlife View Post
    In simple terms what does charge coupling do? And it effects the listening experience how? Are there draw backs?
    while I think 4313b may have nailed the ghist of it, I'll try to answer literally in the most non technical terms I can come up....

    • Capacitors are a key component used in crossover networks to filter out the frequencies so the highs go to the tweeters and the lows go to the woofers (and the mids to the mid).
    • Audio signals are 'AC' in that they alternate between + and - voltages many times a second.
    • When a capacitor changes from + to - or back, there's a little tiny glitch in the signal, on the order of a few millivolts, caused by an effect known as "Dielectric Hysteresis".
    • "Biasing" is a techie term for adding a DC voltage to a AC signal.
    • By biasing these capacitors, the capacitor stays entirely on the "+" side, avoiding this glitch entirely.

    the net effect is, the speakers 'sound smoother'.

    To do this, you replace a single capacitor of X microfarads (uF) with two capacitors in series of 2*X uF (which has the same net capacitance), then connecting the midpoint of these two caps with a several megohm resistor to the + side of a 9V transistor radio battery.. The battery - side goes to ground.

    the simplest crossover is a cap in series with a tweeter, this blocks low frequencies that would damage the tweeter. here's two versions of this, the lower one modified with this 'charged coupled' design.



    (pardon my crappy drawing skills, I don't have any decent schematic editing software and was forced to use "Dia").

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