Hi. we have BL 7-4 and made a 12v trigger to turn on. this works good. when we wired the 2 RCA plugs for line level sound input.. we sent both L and R to the speaker..but it did sound very loud.. compared to the 2 BL 8000’s with same input. QUESTION: when we send signal to BL7-4 should we only send one of the sides .. Left OR Right? not both..correct?