My '11 sub amp was shorted out at purchase. Dealer replaced it. If I remember right on the alpine....it was a simple on/off switch in the settings. Deeper than that is crossover stuff but that is fine tuning once it is working. Should be pretty obvious if working or not. Really fills up the space in the back with more full sound. Oh, ensure the sub volume is set to 15 (max) as overall it is kinda weak. Good luck with your puzzle ;-0