AK… active capsules are part of the variable miniature microphone system. Together with the KM100 output stage AK… active capsules form a complete microphone. AK30 and KM100, for example, make up the KM130.
AK31 is a free-field equalized pressure transducer. The sensitivity in the free sound field is flat up to 20kHz. In the diffuse sound field there is a roll-off above 5kHz.
