STRDG-720 - Small/Large speaker

[fsavoie]

I just got a sony STRDG-720 in which I have the option to select for my front speaker if they are small (satelite) or large one. My current setup is using a ps3 as the player (CD and Blu-ray/dvd) and my front speaker are infinity satelite speaker with a passive subwoofer (both front speaker wires goes from the receiver to the sub, and from the sub to the speakers). I also have a "real" subwoofer connected in the receiver's sub output. When I listen to a music CD, the sound is much better in my front speaker set on "large" in the receiver. Both subs are working great and the music is good. But if I watch a movie with that setting, its like if the receiver is almost ignoring my "real" sub and only using the passive one... so I have to change my option for "small" in the receiver to enjoy good bass as when I was listening a music CD. Is there something I don't get or is there a setting that I could modify that would allow both sub working fine during a movie like for music cd?