Check the listing for details. Sennheiser MD 421 KOMPAKT Multipurpose Dynamic Cardioid Microphone PROAUDIOSTAR. Condition: Open box. Listed at 224.99 USD. If you’ve heard music, you’ve heard the MD 421 — a legendary Sennheiser microphone featured in countless award-winning performances and productions over the last five decades. Crafted with precise German engineering and decades of audio expertise, MD 421 Kompakt captures every nuance, every detail, and every emotion at any sound level with stunning clarity.