HPotter,
you may well be right. My speaker however is meant to be a hermaphrodite.
Option 1:
the Fertin runs FR, no EQ. Low end VERY slender.
Option 2:
The Fertin runs from 120Hz northwards. EQ slope 18dB/octave.
The dual Beyma runs from 120Hz souttwards. 18dB/octave, overlayed with baffle EQ of 6dB/octave and a corner frequency of 20-25Hz. Serious low end then.
Talking hot air right now

, will have to see/hear how this comes out.