Originally Posted by radicalwalrus
Are most cabs that are the same size the same ohm?
To answer this more general question, no. In fact some manufacturers will offer a given cab, usually 210s and 212s, in both 4 ohm and 8 ohm versions.
So you really have to read the jack plate on the cabinet to see what its nominal impedance is (2, 4, 8, or 16 ohms, most common by far for bass are 4 and 8 ohm cabinets).