If they were both 15" subs and the same amp was used and the box is the best it can be for each of the subs, and the same wires where used why would there be any difference. Just wondering why would there be any difference between the 2 subs. Not naming any subs to compare, just as a curious why one would hit harder then the other one, or could it just be the size of the magnet that's making it hit harder?