if i have one 12" sub in a ported box with a 500 watt amp to it and i get another identical sub and amp how many more db's am i going to gain? right now i can hit 127 in the front seat
on average ppl gain 3 dbs wen the double power and add another sub....also it depends wut car u have tht will make the difference but i would have to say a minimum of 3 dbs