I think that theoretical calculations may be helpful, but eventually, each particular setup will have its own characteristics, depending on room size, the components, placement, and even the furniture (and so on). In my experience, the importance of bass directionality increases proportionally with room size. Using test tones, in my smallish living room, I could not identify the source below 70 Hz or so. Again, with test tones, the very lowest limit where I could hear a signal was 20 Hz, but this can vary from person to person and the equipment also makes a difference. At 16 Hz, I could clearly see the woofer's cone moving, and feel some physical air pressure, but no sound (at least for me). I think with real music these low frequencies are seldom "audible" per se, what they most often do is to "round up" or to "fill" the sound of the instruments (complementary harmonics? I'm not sure).
Anyway, this is just MY experience from the period when I was concerned with these questions spending hours with measurements and tinkering. Lately I just try to enjoy the music :).
Anyway, this is just MY experience from the period when I was concerned with these questions spending hours with measurements and tinkering. Lately I just try to enjoy the music :).