I have been reading a few posts here about a guy who has a EP500 and wants advise about setting it up.

OK, so calibrate it ...cool .... turn the knob to bypass as the reciever is doing the bass mgmt, check ...... set to around 80hz, .....
But, why .... why, is it if the user has M80's why do you go an set the mains to small from large.

I find this so contratictory ..... I ask which is best for movies a good bookshelf or a good floorstanding? my replies were the floorstanding, due to the fact they will play lower frequencies, better, balh blah blah ......
What is the differece is the M80's are set to small and or a bookshelf set to small and they reciever sending 80hz and below to the sub ????
Just puzzles me

The difference is that with the M80s you CAN set the crossover lower, whereas a bookshelf 80hz is pretty much it. I found I get better mid/upper bass running my M80s at 40hz set to small to let the sub handle the rest of bass. If I have the M80s set to large they play down to ~30hz along with the sub and the bass can become boomy sometimes.

The reason to set the mains to small is to keep the lowest frequencies sent to the sub and only the sub, this prevents 'double bass'. There is no rule set in stone here, you can set any system up any way you like. I have found some rooms can benefit from the mains and sub doubling up on the lower frequencies to help with nulls.

I completely agree with Jason. Usually I have them crossed at 40Hz for music and 60Hz for movies. The only reason I have 60Hz for because I didn't really noticed a difference between 40 and 60 Hz for movies and that way I put less stress on the M80sa and my modest AVR. One thing that I would add is that might be a good idea to set them as small at least for movies. Before I had a sub, I ran the M80s as large. One day, while watching Iron man at loud volume, I noticed some rattling coming from one of the woofers. I got it replaced but when you have no sub, the LFE is redirected to the mains and in some movies there is some pretty heavy low bass that the M80s can't handle, at least, that's what I thought could have caused that. Since I had a sub, I always set them as small at least for movies.

I was experimenting with this with my M22's and EP350 last week, after I got used to the way they sound. M22's set to Small and cross over at 80Hz. The sound did not improve when I set the crossover to 60Hz, but actually worsened a bit. I noticed a lot less bass. So, I set it back to 80Hz.

I read an article about bass management where the author stated that LARGE and SMALL were terrible label choices.

I think if the system is calibrated properly, you shouldn't notice the difference in frequencies coming from the bookshelfs or the sub. Actually if it is setup properly you shouldn't.
I can see for music, yeh, but not movies.
Way I see it , is if my mains are concentrating on mid range and highs, that frees p some much amp power. I should almost never clip, specially if the lower frequencies are being produced by the 500w amp in the sub, that's what it is therefore after all.

I had the speakers finally back to my brother and a sub, I currenlty am trying to figure out what I need and want right now. and by crossing over at 80hz ( they only go to 80hz ) and a sub I found so much more detail, clarity. Like it has been said, it doesn't take much power to produce 80 - 100 hz and up, I was watching a scene in Behind enemy lines and I can here the shell casings ping as it comes out of the gun. When I switched to large some of the details like that seem to get lost.
I am going to have a reall good vacation week when I get the M80's together and switch between the two sets