So I did a bit more testing - with an envelope into CV1, dial fully open, frequency full counter clockwise I get nothing. If I double up an envelope into the Cv2 input still nothing. I need the frequency pot about half way open to get the envelope opening the filter.
I can't say I'm disappointed as the low end is so huge and it has some mad extended range (maybe I could use as an lfo when self oscillating?), just wondering if that is normal behaviour for this?