The bass was light so I added a textbook 6dB baffle step to lower the response above 600 Hz or so to get a better balance.
The green curve is the driver itself.
To flatten the impedance a zobel network is used calculated values are 4.7 Ohms and 36µF, the things I had in the drawer was way off at 6.8 Ohms and 20µF. Still it works well with an impedance ranging from 3.5 to 5 Ohm from 120 to above 10 000 Hz, pink curve where as before it reach 12 Ohm at 10 000 Hz.
Calculated baffle step compensation is a 4 Ohm resistor and a 1.1 mH coil, here I got closer at 4.7 Ohm and 0.7 mH, blue curve.
The sound took a huge step towards a more balanced sound, I am sure that there is room for improvements by tweaking various values. I will perhaps get back to that after tweaking the room accoustics.