"The optional RTA-M real time audio analyzing mic is the perfect accessory tool for the DriveRack PA series (PA, PX, PA+, PA2) and 260. Used in conjunction with the System Setup Wizard and Auto EQ Wizard the RTA-M is ideal for optimizing the sound quality of even the most difficult of acoustic environments. Features Polar Pattern : omni-directional Element : back electret-Condenser Frequency Response : 20 Hz - 20 kHz Impedance : 250 30% (at 1,000Hz) Sensitivity : -63 dB +-3 dB ( 0 dB=1V/ microbar 1,000 Hz indicated by open circuit ) Operating Voltage : phantom power 9V-52VDC"