Miniature Cardioid Condenser Boundary Microphone with TB3-to-XLR Output. Audio-Technica has taken its low-profile ES947C cardioid boundary microphone and given it an even smaller footprint, making it a great choice for installations with limited space or where a very clean, inconspicuous look is desired. The miniature ES947C/TB3 still gives you the same clear, highly intelligible audio of its larger sibling, mounting unobtrusively in tabletops, ceilings or panels for conferencing, recording, monitoring and other demanding sound pickup applications.