It is a good idea to aim to have the bulk of your sub-bass and bassdrum one octave apart from each other.
First you have to decide which one you want as the main body for the low end of the track. In drum & bass and dubstep this is nearly always the sub bass.
Now look at the sub-bass in an analyzer and see where it’s main body is located. If this is around 50hz, then the main body of your bassdrum should be twice as high = 100hz.
A good approach is to first choose a bassdrum sound that roughly hits that area and then fine-adjust that with EQ.
This way the bottom end of your track will sound better and the track itself plays louder.