The holder ensures that two cardioid microphones (CCM/MK 4) have the exact distance and angle to each other for the ORTF method.

An ORTF-like technique is achieved by using open cardioids (CCM / MK 22). However, due to the lower directivity of the open cardioids, the level difference becomes smaller and thus the recording angle becomes larger. The holder STC 22 is slightly longer to compensate for this with larger time differences. Thus, the same recording angle as in the ORTF technique is achieved.