I've tried this before, so I thought I'd try it again. I start with the Default Program 199 on my Kurzweil K2661 synthesizer and modify it to use the Sine keymap and remove touch sensitivity. I program the mod wheel to control volume. That makes for a nice keyboard sinewave generator which sounds far cleaner than my B&K generator. Today I sent digital from optical out through C02 converter to coax, then into coax digital input 2 on my Tact, thus it was unnecessary to run Masterlink as I usually do (and for some reason Masterlink was not locking onto output from C02, perhaps bad short cable).
Playing around, it was easy to hear all the way down to C0 (16.35 Hz), or at least that last note can be unambigously felt. Various rattles between the upper 20's and up in the walls, fireplace, and stuff; I need to make a map of all the rattles and fix them. There clearly is a broad depression in the area between A2 (110) and A4 (440). That was why I had previously run subwoofer up to 165, but that was not an effective strategy. Still, I wouldn't say that A2 or A3 is inaudible, just noticably lower than A1 or A5.