The Sennheiser MD 421 II is a cardioid, dynamic microphone popularized by the recording and broadcast industry.

The MD 421 II is favored for its ability to handle a variety of applications due to its flexible bass control. The microphone features a 5-position bass roll-off switch and frequency response of 30-17,000 Hz. The cardioid polar pattern effectively rejects off-axis noise due to room acoustics and noise. The cardioid pattern also provides effective feedback rejection often caused by monitors positioned within close proximity.

The MD 421 II features a dynamic capsule allowing even signal response whether close-up or at a reasonable distance. This is particularly useful for broadcast, where announcers and DJ’s can refrain from remaining absolutely stationary.

Due to the microphone’s dynamic capsule, the MD 421 II handles high sound pressure levels, suitable for miking instruments high in transient (peak) response.