Please Help! Aftermarket sub very quiet when using Shaker Pro signal
I spent a day replacing the crappy stock subwoofer and amp in my 2013 GTCS. See candersen's post for an idea of how I did it. I added a 500 watt RMS amp and matched sub to the existing Shaker Pro sub box. I ran new 4 guage cable for battery and ground, and I tapped into the existing signal coming into the trunk. To do this, I spliced in an RCA (composite) cable by attaching both right and left + and - to the single + and - signal coming from the head unit to the factory amp. It is somewhat louder than before but nowhere near the thump of a 500 watt sub. Is the signal coming from the stock head unit extremely tame? What can I add to crank the bass back up? I've looked at doing the head unit but I have Sync with nav and my options are limited. Thanks!