Sennheiser Sub-Miniature capsule HM 401

The HM 401 sub-miniature capsule is the equivalent to the well-known sub-miniature microphone MM 301 in weight and dimensions. It can, therefore be built in to equipment in a similar manner to the Microphone where there is only a very small space e. g. in spectacle hearing aids and small hearing aids which are worn behind the ear. The acoustic output of the earpiece is a small tube which is built in to the narrow side of the earpiece. The earpiece is designed to operate in wide changes of temperature and humidity, and this allows it to be used in the tropics

Technical Data

Frequency range with 2 cm coupler ....................... 200 to 3,000 Hz (at the ear a frequency range up to approx. 5 Khz

Sensitivity at 1,000 Hz and a power of 0.3 mW  ....................... approx. 120 dB rel 2 x 10-4 dyne/cm2

Maximum input power  ....................... approx. 1 mW

Distortion at 1mW at 400 Hz  .......................  ≤ 10 s/q

Impedance (at 1000 Hz) ....................... choice between 300 and 2 k Ω

D C  ....................... Approx. 1.1 mA at Z ⇋ 300 Ω | Approx 0.4 mA at Z ⇋ 2000 Ω

Dimensions ....................... 7.2 x 11.5 x 4.4 mm

Weight ....................... Approx. 0.8g

Placed beside a Dime to show size reference