Are the older Shure microphones model 545S-Unidyne 3 undirectional dynamic microphone and the 545S impedance microphone the same microphone with a different description or are they two different mics?
545S is the model number. Unidyne III is the design of the mic element. The 545 models have always used the Unidyne III element. Therefore, a 545S Unidyne III is the same as the 545S.