Headunit: Philips Cem5000
Subwoofer: Active Sub Blaupunkt Gtb8a

Question:
My Hu using 1 connector which include the basic wires power, ground, front and rear left right speaker. Then another 5 rca left right rear front and mono sub empty.

My active subwoofer only have input for left right rca. So my rca output should plug into mono rca subwoofer and another end point plug into left ?

Or I need a Y connector?

Or I plug into front speaker left right?

Currently using Sub mono rca to input left of the active sub. The signal very weak. Volume need to turn on quite high only the woofer can get the signal and power on.