I have a Yamaha YST-SW300 sub. It has a dial on the side with Music on one side and Movie on the other. If I adjust it all the way over to Movie I get more of a rumbling bass effect whereas if I set it to Music, the bass is tighter. Can anyone tell me how this works? I know that all subs don't have this feature. Wouldn't a good sub simply play as close to the source intended and not have to regulate it as my sub does? Thanks in advance.