Anybody own a component that sounds better with the cover off?

I'm not a big tweaker at all but recently I've been figuring out a problem I've have with my Lamm LP2 and now that it's fixed I've been listening with the cover off and then on and then off again and it just sounds better with it off. Things just seem tighter sounding. More precise. 

I've gone back and forth so I don't think I'm imagining it. It's not like I'm putting crystal on top of the speakers or anything :)