The question was about tracking, not whether or not the lowest notes/harmonics were audible.Recognizing notes, sure. Accurately playing a low low B octave at 15 Hz ? Riiight.

FWIW, my Micro-Pog's lower octave tracks flawlessly all the way down, but yes, the audiblility of the notes begins to vanish below a certain range.
RE: Deep Impact.
Audible? Debatable depending on amp. Gargly? Not at all. You might want to pay more attention to my actual (and your original) point.