What are the importance differences between the SM5B and SM5C?
SM5C impedance is 38 ohms; SM5B impedance is 160 ohms.
SM5C output level is 6 dB less than the SM5B. (SM5C is -64 dBV at one Pascal SPL.)
SM5C has a steep roll-off below 100 Hz; circa 10 dB per octave.
SM5C has a hum-bucking coil that provides an additional 4 dB of hum field rejection.