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No RMA or FRD file - Use Zobel?

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  • No RMA or FRD file - Use Zobel?

    I have 12 of the almost free PE buy out 6.5" poly midbass woofers in a line source. Actually I have three line sources of 12 woofers and 12 ribbon tweeters, so there is a big investment here. No FRD or ZMA files seem to be available for this driver. I would simply buy the test equipment, but it will not be available until November at least.Can I just use a Zobel network to make the resistance curve flat and calculate based on nominal resistance?

    I have the Re (3.37 ohms) and Le (0.48 mH)

    The drivers are four in series creating three parallel circuits. Resistance and inductance are additive when in series so it seems pretty simple using these equations. http://audiojudgement.com/impedance-...zobel-network/

    I'm considering putting a Zobel on each parallel leg.


  • #2
    PE part# ?

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    • #3
      If its the 299-609, then use R=16ohms and C=4uF for each 4-driver series string.
      That makes each string a 14.5ohm "nominal" load from 100Hz to 20khz, +/- 0.5 ohms.
      I plugged the T/S model into WinISD and displayed its "estimated" impedance plot.
      Then I FPTraced that plot, THEN multiplied the data by 4x (for the 4-driver string).
      Finally I used an XO sim to trial-and-error the Zobel components for the flattest Z-plot I could get.

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      • #4
        Chris - Thank You Big Time!

        Yes it is. If you saved that work could you check the values for a single zobel across all three strings of four drivers?

        I'm putting the cross over outside the box in order to easily change components. The strings are tired together inside the box.

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        • #5
          The equivalent would be 5.3ohms (5 close enough) and 12uF.
          You MIGHT need more than the usual amount of power handling on the resistor though?

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