I own a pair of Magnepan MMG. It has been working fine until I turned on my system today to listen to music. I notice one side was louder (clearer) than the other. So I adjust the balance from left to right. The left speaker sounds fine but the right one lack highs and sounds very hollow and muddy. I don't know what the problem is could it possibly be the quasi-ribbon tweeter? If so is there a way to fix it? BTW, it is powered by a Marantz MM9000 amp using a Sony STR-2ES receiver as pre/pro.