The bass and treble "tone" adjustments will boost or cut the frequencies around 100-200Hz and 1-2kHz, or something like that. I don't know the exact frequency ranges, but it's not your subwoofer. It's because people are impressed by "bass" around 150Hz and think treble is in the lower kHz range, based on what they can hear being changed.
I'd leave them alone unless you have a personal preference that emphasizes things in those frequencies.