How to use REW Room EQ with a Denon AVR?

I'm using REW to measure my room EQ with my X4700H. Connected it to front HDMI in Stereo mode. Unfortunately Audyssey seems to work strange in this setup. Was using Audyssey with the mobile app but if I edit the frequency curve for subwoofer there nothing changes with REW. Even more strange the curve edit of the main speakers is visible by measureing the subs! My problem is that I have too less bass from 20-25Hz in REW WHILE playing WITH subwoofers! The mains alone at full range having more bass there! The two subs are placed right behind each of the mains in the corner. I think there is a rolloff from the AVR but I don't know how to setup it better.

Here is a REW of my setup (mains: Heco Astron 500, two subwoofers: Sunfire True Subwoofer). Crossovers 80Hz for the mains and 120Hz for the subs.

Green line mains (fullrange) only
Red line complete system with subs