So, what's the general opinion on the best sealed enclosure size for a 15" D2? Seems like a lot of people prefer 2.4cf? Also, is that before or after sub displacement, and what is the displacement of a 15" D2? Also, does polyfill do anything besides making the sub think the enclosure is larger? If that's all it does, why not just build the enclosure larger in the first place? Basically all this is the long way of asking, how big should my enclosure be??? Thanks~