Speaker covers on or off??

[Weatherman]

Speaker covers are needed for several good reasons.

They disperse the sound waves (a property of any waves) making a more natural sound. Sound straight from a speaker is more unidirectional than sound being passed through a physical barrier. This is especially true for mid to high frequencies. Some speaker systems use a horn to disperse sound, however, this is not recomended for a small home theater system. The barrier acts to fill the room with sound.

Some problems arise if the covers are off. Since the waves tend to travel essentially in one direction, the chances of unwanted echoing off a wall or couch are higher. This will cause a "stadium effect". This is most notable during scenes where there is a lot of talking. Subwoofers don't need dispersion baffles or covers because of the omnidirectional nature of low frequency waves. Without covers the channels will not mend. For instance if a helicopter moves from left to right it will not be as smooth with the covers off. The left and right channels will be more noticable. Covers make for a smooth transisition for action scenes and background music.

High end home theaters have the same material (similar to the covers on your speakers) on the walls and ceiling to mitigate the problem of echoing and feedback.

If your watching a blu-ray with crappy sound what's the point!?

Hope this helps.