Serial Number 64532 (Early 1970s)

Closed-Housing Directional Design [1]At the time of its release, directional cardioid microphones typically relied on rear air-entry ports to shape their pickup pattern. Sennheiser engineered the MD 421 with a smooth, closed acoustic housing. This allows the user to hold or mount the microphone anywhere without blocking critical rear ports, maintaining its strict directional pickup regardless of handling. [1]High Feedback & Hum Rejection [1]

• Cardioid Directional Characteristic: Engineered with a distinct front-to-back ratio of approximately 18 dB at 1000 Hz. This design provides maximum insensitivity to unwanted sound from the rear (180°), making it highly effective at preventing feedback near loud stage speakers. [1, 2]
• Hum Compensation Coil: Built with a specialized hum-bucking coil wired in opposite polarity to the converter coil. This design element explicitly cancels out low-frequency magnetic stray fields, preventing interference from nearby lights or power supplies. [1, 2]

Adjustable Bass Control [1]The microphone includes a 5-position bass roll-off/tone switch integrated into the housing. [1, 2]

• "M" (Music): Provides a completely flat, linear frequency response across the low end.
• "S" (Speech): Intentionally cuts the low-frequency response by approximately 6dB below 500 Hz to clear up vocal muddiness and combat proximity effects.
• Intermediate Steps: Three unlabeled indentation steps allow fine-tuning between the two extremes. [1, 2, 3]

Production CalibrationEvery vintage MD 421 was custom-calibrated at the factory in Germany. Each unit left production packed with its own individual, date-stamped frequency response quality-control sheet to guarantee it fell within published standard performance limits

Gently used in home studio environment, no smoking. Slight dent on grille that does not effect performance.

DOES NOT INCLUDE THE DIN-XLR ADAPTER CABLE, these can be easily purchased online.