Werner Jagusch crossovers

Jagusch uses a transformer or autoformer to attenuate the compression driver.
The following is pure assumption: There are no parallel resistors on the attenuator taps so every tap will reflect a different impedance to the filter, thereby changing the high pass frequency with attenuation. There is an L-Pad wired in but I can't tell from the Ebay pictures how. Maybe it is supposed to take care of that.
Have you tried contacting Jagusch and asking him?