The Sennheiser e 901 is a boundary condenser microphone designed mainly for kick (bass) drum, and also suited to grand piano. It simply lies inside the kick drum or piano with no stand needed, resting on a slip-free, damping rubber pad. The pre-polarised condenser capsule with half-cardioid pickup and a frequency response optimised for low-frequency instruments delivers a dry, defined kick sound with a fast, clean attack, and it handles very high sound pressure levels without distortion. An integrated preamplifier feeds a standard gold-plated 3-pin XLR connector and requires 48 V phantom power. Sensitivity is 0.5 mV/Pa and nominal impedance below 100 ohms. The rugged metal housing measures 126.5 x 105 x 26.5 mm and weighs 550 g. Frequency response is 20 - 20,000 Hz. It is a practical choice for drummers, live engineers and studios wanting a consistent kick sound without positioning a mic stand.