The Shure SM81 is a small‑diaphragm condenser microphone often used for acoustic instruments, overheads, and other detailed sources where a neutral, accurate sound is important. It has a wide, flat frequency response from roughly 20 Hz to 20 kHz, giving it a natural tone with minimal coloration, and its cardioid pattern helps focus on the intended sound while reducing pickup from the sides and rear. The mic includes two onboard controls: a three‑position low‑cut filter to manage rumble or proximity effect, and a –10 dB pad for handling louder sources without distortion. As a condenser, it requires phantom power (12–48 V), and its low self‑noise makes it suitable for quieter instruments as well as high‑SPL ones. Built with a rugged metal body and known for its reliability, the SM81 has become a long‑standing staple for engineers who need a consistent, accurate microphone for strings, cymbals, pianos, and other acoustic sources.