I feel like an idiot I am trying to install a sub in my 2011 tc (alpine system) but have no clue which set of RCAs is for the sub. So if you have the head unit in the car screwed into the dash and there are three sets on the back of it going in order from top down 1 2 or 3 which do you plug the rca's for the amp into?

 

The bottom set is the one for the subs, just make sure you turn the output on in the menu

 

If you can get the radio out of the dash they should be labeled. F , R, and SW should be stamped somewhere around the RCA outputs.