Last one about my SVT-1510HE .... I called Ampeg and a tech said my SWR 350x head should have been fine for this cab (which is rated at 175w RMS 8 ohm) and is not the reason that the speaker blew. He said that the speaker cones were old and were probably dry rotted. What is the life span for speakers? How often would one expect to recone or replace them? I think I bought this cab in 1993.