To expand on what gonk said, when the toggle is set to HPF/LPF, you'll get a simple, analog x-over on analog inputs played in bypass mode.

For everything outside of that (the 970's stereo mode, 5-channel mode and all the surround modes), now we're playing in the pre/pro's digital domain and the digital x-overs are employed. This means you can set the x-over points to other frequencies for the various speakers in your system.

Personally, I like a x-over setting of 80Hz across the board, so there is no issue with my system being out of calibration when going between the analog and digital bass management worlds.

I assume all of the above applies to your 1070.