Since I listen to alot of 5 ch stereo I'll bet the large setting is ok b/c my rears are set to small which means all the low bass is still getting to my subwoofer. I need to listen more when it comes to movies in dolby digital or DTS. That seems like what is being said. Small with movies-large with music depending on speakers and room too. In my case I think that's the way to go.