SPL is the displacement of air but there is a lot more to it than that, i know somewhat about it but i will let zac tell you about it because he knows a lot more than me, people tend to say "oh, that sub has more xmax meaning it will be louder than the other" which is completely wrong, it may have potential but there are way to many factors for me to even get started on, and what you are saying is completely possible, ive seen 1 higher model 10" take down 2 lower model 15" many times