I am wondering why you have the crossover set to 70Hz at the sub instead of bypassing it entirely. With the 1070 doing bass management, there's no need to use the sub's crossover at all.

Analog bypass skips the bass management entirely, although I believe that the rear panel toggle switch will work for stereo analog inputs just as well as it will for the 7.1 Direct input (in which case you'd want to set it to "HPF/LPF"). Bypass with digital inputs skips DSP, including bass management. If you're using a digital input, try using straight stereo mode.