The U851A from Audio-Technica is a boundary microphone for surface-mount applications. It operates in a cardioid/half-cardioid polar pattern, though its condenser-element is switchable. Offering a frequency range of 30 Hz to 20 kHz, this microphone works with an AA battery as well as phantom power, and boasts an SPL of 123 dB to 133 dB depending on the method of power used.
