With the options of large and small, a crossover point of some sort has to exist. If the manual doesn't say what crossover point is being used, the only way to know for certain is to contact Pioneer and ask (which, as you say, is easier said than done) - it would be logical for the crossover to be 80Hz, but that doesn't mean that's what is being used. With all channels large and the sub on, then the only data that the sub gets is the .1 track.