I figured out the sound issue that is happening with the Kia optima sx with the factory amplifier low sound issue. UPDATE!!! I do highly recommend an aftermarket amplifier install it really is night and day with this unit. I used a 5 channel amplifier and 2 rca splitters 1 female to 2 male for the separation of the mid and sub. I ran all 4 door speakers to rear channel of the amplifier. I ran front tweets and center speakers to front channel of amplifier. Sub to sub. I used all of the factory wires including power and remote turn on.
