Is the outside casing just a casing, or is it actually the capsule itself? Reason I ask is because I just purchased 4 of them, all of which have cracked plastic on the outside.... That shouldn't affect the sound, correct? Looks like a few missed hits from drum sticks. The seller swears they don't sound any different but I just wanted to make sure. I couldn't pass up 4 MD421's for $300...