have a 2013 sahara with the alpine system. When we bought it there was already a Knewood DMX7706S head unit installed. We could not turn it up at all with out the speakers crackling and popping. After upgrading the front dash speakers with a set of Focal Components, and then installing Focal 2-way's in the sound bar, and then redoing the wiring on the head unit, it sounds decent, but lacks bass as in almost not there at all. I know it still has the factory alpine amp and subwoofer but it still should have some bass right?. My brother helped me with the head unit wiring and said that with after market head units and blue tooth systems, you always wire the rear signals to the front and the front signals to the rear, otherwise you wouldn't hear anything on phone calls. He has a few years of car audio installation from Best buy.

any thoughts or known issues when installing after market head units and loosing bass?