I measured the input impedance of the AR-11 drivers many years ago.  Recently remeasured the midrange and decided to take a look at the crossover frequency response in simulation for each of the switch positions. I used the AR inductor values including DC resistance and estimated the NPE midrange cap ESR at .1 ohms, the simulator allows these values to be included in the component model but I decided to show it for the caps and not for the inductor: S1, red, is the 0 dB