I dont know why but Ford built most explorers with a premium sound syst that are intertwined....This means that if you up-graded anything (from cd deck to speakers to subs and amp) you have to rewire EVERYTHING. If you blow one speaker, all four have to be replaced. I had soundtrack install a Kenwood 745 watt amp with 2 12" rockford fosgate subs...they had to re run wire and bypass the pre amp and the 6" sub....So if you are installing your own system in an explorer, expect a good amount of time and be patient!!