Optimum Stereo Signal Recording per "Jecklin Disk" specifications.
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 appromately 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.