Question for 2nd order Butterworth XO

I’m trying to calculate the crossover frequency for an existing crossover, which I know how to do with a simple LC design but I’m not sure how to treat the series resistors in this design. Do I add the resistances in with the impedances and look for the frequency where the sum of R+Ic is equal to the impedance of the inductor+its R? Is there more to it. Why would one design it this way? Thanks

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They are all response plots. They are overlays using different amounts of resistance. The top two attachments are showing the effect of introducing one of the two resistors and the third shows both at once.

For the most part, the first resistor (second attachment) sets the level of the treble and it has a minor effect on the Q. The other resistor (first attachment) mainly affects the Q, and it also cuts from second order to first.

The software is Vituixcad.