He means L + R RCA line in. There is no LFE RCA input jack on the PSW10.http://www.hometheatershack.com/forums/33933-rca-y-cable-how.html#ixzz11qr2z4m9
http://www.axiomaudio.com/sub_setup.htmlMake sure you connect a single RCA coaxial cable from the "Sub Output" jack to either the left or the right line-level RCA input on the subwoofer. You don’t need to use a Y-adaptor to connect both jacks. But you do want to set the subwoofer’s crossover to its maximum rotation so you remove it from the circuit. This is done to avoid "cascading" two crossovers, which might cause uneven and erratic deep bass output.