I am trying to install a sub into my car without buying a headunit and I am having trouble wiring it up with the adapter. I didnt know if you wire it from the stock radio or if you can just tap into the rear speaker. Whats is the best setup for this?

 

Its possible to tap into the rears, I did but my rears were blown so i just pulled the wire through the rubber going into the door and added wire and ran it to the back, look up a wiring diagram and go to the back of the headunit and match up left positive and negitive with the wires on the adapter, same on the other side.

 

i would tap into the rears as well, thats probly gonna be the easiest...

 

You can also use a PAC interface which will also give you front and rear rca. I am running JL 300w for mids & highs and two JL 500w amps for each JL sub. All with stock radio.