I think that is backwards...
you want each segment of your speaker setup to begin rolling off 'approximately' 10Hz sooner than the lowest frequency of the next segment...
for instance a subwoofer to a bass bin... the subwoofer would begin rolling off around 40Hz at its upper cutoff, and the Bass Bin would begin it's roll off around 50Hz at it's lower cutoff. set the roll off to 6db... but you can try 12db and 18db very easily to see if the slope is more or less to your liking. The reason you are doing this is because as the two signals cross over, they 'Sum' and cause a bump in response. if you aren't careful, you can cause yourself issues with unnecessary 'peaks' in frequency response at those XO points if they overlap by to much.
this of course is merely generality, your specific needs might be different.