alot of SQ cars cross their subs over at 40hz or lower for SQ judging. Get enough of anything and they can cover that range easily. Beyond the organ track not much test dynamic capablities on your subs, just getting them to sound like they are upfront and not draw attention is good enough. That's not what this thread is about however, but like it or not the term SQ sub is a misnomer. Given an install that keeps the frequency response relatively flat it's pretty hard to **** up subbass in a car. Cabin gain lets almost anything get loud enough to blend properly with any regular midbasses's total output. If you want to get 60db's over your frontstage and not have the subs distort, that's another story, but that's not actual "SQ".