The predecessor to the SM57, the 545SD Classic Unidyne® Instrument Microphone is a dual-impedance, unidirectional, dynamic microphone.
Shipped connected for low-impedance operation, the 545SD features a silent magnetic reed on/off switch with lock-on option. A favorite for instrument pickup and recording, the 545SD can also be used on lecterns in public address systems.
Frequency Response 50 to 15,000 Hz
Polar Pattern Cardioid (unidirectional)--uniform with frequency, symmetrical about axis
lmpedance Dual. Microphone rating impedance is 150 ohms (250 ohms actual) for connection to microphone inputs rated at 19 to 300 ohms and "High" for connection to high-impedance microphone inputs. Wired for low impedance as supplied.
Output Level LOW @ 1,000 Hz: Open Circuit Voltage* -58.0 dB (1.3 mV); HIGH @ 1,000 Hz: Open Circuit Voltage* -35.0 dB (17.6 mV) *0 dB = 1 volt per Pascal (1 Pa = 94 dB SPL)