The Shure MX391/O is a miniature omnidirectional boundary microphone designed for surface-mount installation in professional conference rooms, boardrooms, and multimedia spaces. This low-profile unit captures audio across a 50 Hz to 17 kHz frequency band with -45 dBV/Pa sensitivity, delivering 105 dB dynamic range and a 120 dB SPL maximum at 1% THD. The microphone operates on 11–52 VDC phantom power at 1.5 mA current draw, outputting balanced audio through an XLR male connector. Its compact 75 mm diameter × 22 mm height form factor and integrated 3.0 m cable with female XLR termination enable direct connection to mixing consoles and preamplifiers without additional adapters.
Technical Specifications
• Polar Pattern: Omnidirectional
• Frequency Response: 50 Hz to 17 kHz
• Sensitivity: -45 dBV/Pa (1.78 mV) at 1 kHz
• Output Impedance: 150 Ohms nominal (200 Ohms actual)
• Maximum SPL: 120 dB SPL at 1% THD, 1 kHz
• Dynamic Range: 105 dB
• Signal-to-Noise Ratio: 66 dB at 94 dB SPL
• Equivalent Output Noise: 28 dB SPL-A
• Clipping Level: -6 dBV (1.56 V) at 1% THD
• Phantom Power: 11–52 VDC
• Current Consumption: 1.5 mA typical
• Connector: XLR male audio output
• Cable: 3.0 m (10 ft) attached with female XLR termination
• Dimensions: 75 mm (diameter) × 22 mm (height)
• Weight: 118 g (4.2 oz)
• Housing: Black metal
– Key Features
• Balanced, floating differential output on pins 2 and 3 (positive pressure produces positive voltage on pin 2)
• Low-impedance output at 150 Ohms nominal
• Discreet boundary-mounted form factor minimizes visual impact
• Durable metal construction for permanent installations
– Typical Applications
• Conference room and boardroom audio capture
• Multimedia presentation spaces
• Table and lectern surface mounting
– Compatibility & Integration
The MX391/O connects directly to any audio mixer, preamplifier, or console equipped with XLR input and phantom power delivery in the 11–52 VDC range. The integrated 3.0 m cable supports standard surface-mount accessories and AV system integration.
