Do cabs have fuses in them? Are heads calibrated to cabs? I know that tubes and fuses are changed but I'm curious if heads are setup specifically for different cabs. I don't mean any Eqing and I'm not referring to mating amps and cabs of similar ohms. a guy at my church doesn't want me to hook my SWR amp through his swr cab (6x10) because he said something about sound waves and something being calibrated and if I hook my amp up it was mess something up. (his cab and my amp are both 4 ohms).