I assume they have two inputs for use with non-AV receivers, where all you have is preamp-out signals (stereo). If you only use one of the two pre-out jacks you only get the bass from one channel... so the sub lets you run both signals in and it mixes them to create a single bass signal which covers both channels.


M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8