Something on top of a speaker=okay?

Best way to know is experimenting. Try with and without and also move it to the other channel. And try different music before you draw a conclusion. In my opinion, yes it will make a difference, but is that difference an improvement? Your ears are the final judge. 

Good luck 

I tried a couple of these and they sounded like...

DeKay

Hey…at least he’s not suggesting we tape AAA batteries to our cables!

I don't know.  I might be concerned with the taxidermy chemicals being bad for the drivers.

And my posting asking if the air pressure in the listening room makes a difference got deleted?