I try to get my bass to sit within 100 (or 200) Hz and 2,000 Hz (maybe 2,400 Hz, if I'm feeling it). I use EQ to "enforce" this restriction, stopping the bass from clashing with the leads. The sub (< 100 Hz) is for the kick, and 2,000-18,000 Hz is for the leads. Sometimes, I split the bass into 100-600 Hz, and 600-2000 Hz, either doubled up playing the same notes, or as separate parts. I've found this wide range makes for basses that are both deep, and also clear/audible (especially on lower-end systems). I don't pretend to know the "right" answer, though. Does anyone else share this approach? Does anyone target bass frequencies differently? If so, how come?