Thks for the input eric and others.

Eric please clarify if the bass is turned up in the sub? Or out the mains?

As i see it, With
front = large
and sub = L+R/Sub

When you go from 40-200HZ the bass level Should go up, (in the subwoofer that is) That is a sign of a working system.

The reason being is that, When sub set to (L/R + Sub) The output from the fronts are suppose to be redirected to the sub, and the higher the X-over the more that is redirected to the sub.

Eric can you please do the setting with the x-over with the SUB set to NONE?

Also if you can repeat your test and find where the bass is being increased. either the fronts/ the sub / or both. And easy test is to unplug/disconnect the sub and repeast your tests. That will isolate the fronts to see if the boost is in the fronts, Then do the same with the Fronts, to see if it increase in the sub outputs.

Pehaps there is an issue here as well.