Are the mains set to small in the 1050? If they aren't, you'll get low frequency sound all the way down. If they are set to small with an 80Hz crossover in the 1050, you will be able to see the roll-off of the crossover, which is not an absolute cutoff - it'll actually appear as a sloping line starting a little above 80Hz.

As for calibrating in stereo mode, you are actually only calibrating the sub with the SMS-1. It can't control any other devices. As such,