As some of you know, I'm an advocate of using the large setting for all speakers-if they can handle that-for surround *music* systems as recommended by so many professional 5.1 mixers. But that is not exactly what I am discussing here. What I was curious about was why the engineers that designed these automated parameter setting systems i.e. Pioneer's MCACC, Yamaha's YPAO, etc, would allow so many people's rear and center channels in their home theater systems to be set to large if that wasn't the better way to do things. But there are many people that advise ignoring this and manually re-setting them to small "because that's what they should be set to". Not to imply that computers or engineers are infallible, but I would like to know the rationale behind that manual re-setting advice. Because wouldn't trained audio engineers know a little bit more about this issue than the casual audio hobbyist? And as far as these systems' microphones being inaccurate as I've seen some people suggest, that can be (mostly) taken of by including correction formulas in the MCACC/YPAO/etc software. And a company doesn't want to have to deal with a multitude of lawsuits that involve their customers' speakers being fried, so I think they would design these systems very carefully. BTW: I think the thinking behind the holy grail of crossovers (if a system even needs one at all), 80Hz, is because the huge majority of people will NOT buy a set up disc and a sound level meter, so a crossover was chosen that is a good compromise between sound quality and speaker longevity (and maybe a bit of smart marketing too: potential 5.1 customer "No WAY will I put five full-range speakers in 3 cubic foot cabinets and a subwoofer in my living room! And look at the cost!!!"). Anybody else have any thoughts on this?