You will want to send a full range signal to the Epicenter®.
Due to how the Epicenter creates the low frequencies, it needs to see a full range signal.
If you just send the Epicenter a subwoofer signal, say 120 Hz and below, it will probably sound garbled, or muffled, not very defined.
If you are using the Epicenter with an aftermarket head unit that has a subwoofer output, and if it is possible to defeat the low pass crossover so that the subwoofer output is sending full range signal, then you could connect the sub output of the head unit to the inputs of the Epicenter.
Also, the Epicenter needs to be in the audio signal path before any EQ’s and crossovers in the system.
Epicenter product pages here