Our school has 4 JBL stage monitors. We need all four of them for the upcoming show. Problem: in previous shows, I always find two of them that sound just...dumb. They sound almost like a speaker only receiving half of its biamp single (no, I'm not biamping these). One is lacking highs and sounds muffled, and one is lacking lows and sounds like a tin can. This is what I KNOW... It IS the speakers (I've replaced all cables, patches, board channels etc etc). I haven't had time when I find problems to FIX the problem...or troubleshoot it, because I've always been in time crunches. WHAT can I do next week when I have the space reserved purely for fixing this among other things? What can I do to "fix" them or find the problem? One though I had is that perhaps an internal switch got flipped or a driver is blown? (We have no limiting on our aux sends for effects).