AK... active capsules are part of the variable miniature microphone system. Together with the KM 100 output stage AK... active capsules form a complete microphone. AK 30 and KM 100, for example, make up the KM 130.
AK 40 is a pressure gradient transducer with cardioid characteristic. The frequency curves are very even and parallel to 0° sound incidence. Sound sources within a pickup angle of ± 135° are transmitted without coloration.