The only controls I've seen in the multichannel menus are the ability to turn on/off the:
- surround speakers
- center channel
- sub
I didn't see any ability to adjust subwoofer cutoff frequencies, but you can set the front speaker size from small to large. Perhaps this adjusts the bass cutover in some way. I would suggest looking closer at the manual.
There do not seem to be any adjustments available in 2 channel mode.
Good luck,
Bob