My 4x12 had been working fine for about 5 years. One day we load up our gear into the trailer and head off to play. Unfortunately weather did not cooperate, and the gig was cancelled w/o ever even opening up the trailer. After unloading the gear back into our practice room (as we have done a thousand times w/o issue), my cabinet suddenly has no low end. It's hard to say if the volume is reduced or not, since half of the audible spectrum simply isn't there. I've tried my amp with different guitars, cables, 4ohm/8ohm/16ohm outputs, etc....I have definitively isolated the problem to the speaker cabinet itself. So, what could cause a speaker cabinet to still function, but not have any low end? I opened the thing up, and there is no apparent damage to any of the speakers or wiring. I'm at a loss, and we have a gig Friday night. I've resigned myself to getting either new speakers or a whole new cab, but this seems like it should be easily fixable.