Does anyone know the input impedance of an unmodified Sunn 215B cabinet?
...you Can simply plug a cable into it and measure the resistance with an ohmmeter at the cable end, that will tell you the resistance (ohmage) of your speaker cab!
Well, not really. What you are measuring with the above method is the DC resistance of the voice coil,
not the actual impedence of the cabinet. This measurement doesn't account for the reactance of a working speaker in action. It will usually be lower than the actual impedence of the cab, but it's relatively close. The impedence cab is either 16 ohms (doubtful) 8 ohms, or 4 ohms, whichever the voice coil's DC resistence is closest to.