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PCD to Xsim offset calculations

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  • PCD to Xsim offset calculations

    I tend to use PCD to draft up the crossover, then X-sim to simplify the schematic. In order to validate the response simulations, you need to calculate the X-sim delay in inches using your PCD XYZ settings using good old geometry.

    I just made this super simple Excel sheet to do that for me. Use if you like. In order to get around the file type limitations for attachments I renamed the extension of the file. Change this back to a .xlsx file to get it to open.

    Enter your PCD XYZ settings in meters, change the listening distance in meters if you like, and the required offset for the woofer will be calculated for you. If you notice something, let me know if I'm missing anything in the calculation.
    Attached Files
    Electronics engineer, woofer enthusiast, and musician.
    Wogg Music

  • #2
    A^2 + B^2 = C^2

    I don't have much experience with xsim, but from what I've seen all measurements should be made from the same mic position for the greatest accuracy in xsim, since it doesn't make any assumptions of driver location on a baffle, just a simple distance delay value between drivers.

    In PCD, since it can account for driver location on the baffle, measurements can be taken on the driver axis, and then entered in to PCD for simulation from any mic location, keeping in mind that only the phase relations are taken into account in the simulations, and not any diffraction effects.
    "The large print giveth and the small print taketh away." -Tom Waits

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    • #3
      I use the same files in XSim as in PCD to set the offset (delay) on the woofer. The only watch out is to remove the smoothing on the files in XSim.

      Process is:
      Tw plus Woofer raw FRD load in the frequency response window under Curves, Get File, (change the smoothing)
      Draw the 2-way circuit representing the Tw plus Woofer in parallel.
      Load the tweeter FRD, minimum phase file
      Load the woofer FRD, minimum phase file

      Adjust the woofer delay to get the curves to match in the frequency response window.

      I use minimum phase files in XSim as that's what I'm using in PCD. Without getting into the whole minimum or measured phase debate, I like using minimum phase as I'm manipulating the driver tails.

      Also while it's not required, I'll load the zma files just to make the "!" go away.

      John H

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

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      • #4
        Originally posted by jhollander View Post
        I use the same files in XSim as in PCD to set the offset (delay) on the woofer. The only watch out is to remove the smoothing on the files in XSim.

        Process is:
        Tw plus Woofer raw FRD load in the frequency response window under Curves, Get File, (change the smoothing)
        Draw the 2-way circuit representing the Tw plus Woofer in parallel.
        Load the tweeter FRD, minimum phase file
        Load the woofer FRD, minimum phase file

        Adjust the woofer delay to get the curves to match in the frequency response window.

        I use minimum phase files in XSim as that's what I'm using in PCD. Without getting into the whole minimum or measured phase debate, I like using minimum phase as I'm manipulating the driver tails.

        Also while it's not required, I'll load the zma files just to make the "!" go away.
        That smoothing tip is an excellent thing to watch out for. That eliminates the difference I'm seeing between PCD and Xsim entirely. The spreadsheet I've posted to calculate the Xsim delay eliminates the need to just adjust the delay until the charts match.
        Electronics engineer, woofer enthusiast, and musician.
        Wogg Music

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