It's low end ought to be pretty much the same, maybe a bit more. Three 15"s is more surface area, after all. The thing is, if you want a real 10 Hz sensation, you are going to need a lot of bass, more than any single sub can give you. There is also the matter of distortion, yeah, a sub can output 10 Hz, but how cleanly? The very few subs that can do that, can not do it very cleanly at any worthwhile output levels. I wouldn't worry about 10 Hz unless you intend to have a whole stack of subwoofers.