I have a pair of 7's serial # 7B-32756. One speaker is giving me some trouble. Sound is vibrating from middle driver, the fuse is not blown. Will this speaker be blown or will i have wiring troubles inside the speaker. I'm new to forum and know little about the speakers. I've had them since new (early eighties) and have had no trouble with them until now. Please give me some help on repairing this speaker as new ones are not in the budget at the moment.