Check to hear if it is one speaker or more that is noise or if it is something in or on the cabinet. Look for loose screws, nuts, wires, frames, casters, handles....anything.
Only way to get the original sound is to have them reconed. MWA is supply wonderful faithful parts these days. Sometimes Image parts are better but mostly MWA does a great job. I can recone them for $50.00 each or less depending on how many. I am in the metro Detroit area.