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  • Crossover help

    Hopefully someone can confirm/educate me on my thoughts regarding resistors in a tweeter network. If I put a large value resistor, say 20 ohm after a capacitor in the + line of a 4ohm tweeter does the amplifier see a 24ohm load? If so, I would need to greatly reduce the capacitance before the resistor correct? Would this change the tweeters response?


  • #2
    Originally posted by Jake View Post

    > If I put a large value resistor, say 20 ohm after a capacitor in the + line of a 4ohm tweeter does the amplifier see a 24ohm load?

    Yes .

    > If so, I would need to greatly reduce the capacitance before the resistor correct?

    Yes .

    > Would this change the tweeters response?

    Resistors in series with drivers do change the response due to the reactance
    of the driver itself . Best to carefully listen .
    .

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    • #3
      hitsware2: thanks for the response. Normally I use an l-pad, but I haven't found the right resistor combination. That's why I'm considering one large value, hopefully without Ill effects.

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      • #4
        https://www.amazon.com/Elenco-Resist.../dp/B0002KX76M

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        • #5
          The amp would see the resistor plus the R of the tweeter at some point but the tweeters impedance varies with frequency which means it could be much higher as the capacitor rolls off the lower frequencies. The resistor can tilt the top frequency down but it would not replace a capacitor in the circuit which changes the roll off/ blocks bass frequencies from the tweeter.
          John H

          Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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          • #7
            Thanks for the sim kornbread. jhollander, I know the resistor would not replace the capacitor. My question was how much the resistor could alter the value of the capacitor. Correct me if I'm wrong, with this resistor I would need about 1/6 th of capacitance value for a 4ohm speaker. Sound about right?

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            • #8
              If I take a flat 4n(ohm) load (like a planar/ribbon), and add a series 20n resistor, I can cross the tweeter w/a 3uF cap.
              That gives me an Fc (crossover freq., which is -3dB for a 1st order) at 2kHz. It also gives me about -14dB of attenuation and a Z-min of 24ohms.
              If I use an L-pad (SR=4n and PR=1n) and a 15uF cap, I can get the same attenuation and Fc, but w/a Zmin of about 5ohms.
              The advantage of the L-pad is that you've got a pair of resistors throwing off heat, AND the parallel resistor helps flatten out the tweeter's Zmax at Fs (if it's NOT a planar or ribbon).
              Also, while the higher Z (24n) lets you use a smaller cap, it does require a larger (shunt) coil, if going 2nd order.
              The lower Z (w/the "L") needs a larger cap, but the coil can be smaller.

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              • #9
                There's lots of guessing going on here. Why not take a risk and tell us what your want to do?
                John H

                Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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                • #10
                  Originally posted by jhollander View Post
                  There's lots of guessing going on here. Why not take a risk and tell us what your want to do?
                  Thanks Jon, Chris pretty much covered it for me. It was just me understanding the basic concept. I was just tinkering and trying to learn.

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