first find out if the subs are DVC or SVC, dual voice coil or single vioce coil, respectivly.

with two subs you car get a final 1 OHM by using these:

a pair of 2OHM SVC
a pair of 4OHM DVC

you cannot get a 1OHM load with a pair of 8OHm subs, DVC or not.