The M149 Switchable Tube Microphone from Neumann is a variable dual-diaphragm microphone. The K 49 capsule, well known from the legendary U 47 and M 49 microphones, is followed by a tube functioning as an impedance converter. In contrast to earlier concepts utilizing a transformer, the tube is complemented with a transformerless output circuit design. The M 149 Tube can thus feed long microphone cables without any coloration.

Two slide switches are located below the large, acoustically open headgrille. The switch at the front allows selection one of nine directional patterns. The slide switch at the rear operates a seven-step high pass filter, allowing very fine adjustment of the cut-off frequency.