When you say 'deep', do you mean SLAPPY floor tom sounds (almost like thud) or THUNDEROUS floor tom sounds?
From experience, here's what I found out:
1. The thicker the batter head, the wider the low tuning range.
2. In general, coated heads sound warmer, clear heads sound more 'scooped'.
3. For the reso side, lowering the tuning can give a more open but lower tone. If the reso head is tuned looser than the batter, it gives you a deeper sound (but less punch).
4. Tuning the reso head tighter than the batter gives a perceived higher pitch but actually gives just more punch to the sound.