Two sound pressure microphones are arranged at a distance of 165 mm. This distance results in the correct delay time difference between the two channels. The two microphones are separated by an acoustically muffled disc of 300 mm diameter. The effect of this disc is as follows: as the frequency increases, the two microphones are more and more separated. Below the value of approximately 200 Hz, the two microphones record the same. The acoustic muffling of the disc results in a frequency response difference of the two channels depending on the angle of impact of the sound. In addition, there is a sound diffraction around the disc rim which is dependent on frequency and angle.
The microphones are pushed from the rear through the holding clamps of the OSS disc. Take care that the microphone capsules on both sides are located at a distance of approx 8 cm directly above the disc center. This can be checked by means of the pulled-in measuring cord. In this case, the angles of the microphones are drawn slightly towards the outside.