purty shure ya need an o scope to see cancellation but i'm not shure... thats what we used... i'll give you a simple explanation of why you "CAN" get better sound quality with multi sub setups... cause like a 2 way component the fewer frequencies that a speaker (or sub) has to respond to, the more accuratly it can reproduce the ones it does have to respond to... now different sizes have different resonance so are better suited to produce different frequencies... so it is logical ,if you are going to have 2 subs produce different frequency ranges, to have the subs different sizes.... i have so many 10's cause its purty close to equal with the 1 13 in terms of output and the lines are blured a bit so all of the subs play the frequencies they are weakest in... and the 13 is reverse mounted to avoid phase cancellation in the frequencies that they share