Should I be concerned with some "dimpling" in the rubber surround on one of the Polk Audio DB-651 speakers I just purchased? The other 3 speakers have perfectly shaped rubber surrounds between the frame and the cone. One has a few indentions in it that look like someone poked down on it with a finger and it didn't spring back. Will these work their way out with use and exposure to the elements or should I return the speaker? Thanks.