Jecklin disk

A Jecklin Disk is a sound-absorbing disk placed between two microphones to create an acoustic "shadow" from one microphone to the other. The resulting two signals can possibly produce a pleasing stereo effect.

Always, a matching pair of omnidirectional microphones are used.

The technique was invented by Jürg Jecklin, the former chief sound engineer of Swiss Radio. He referred to the technique as an "Optimal Stereo Signal" (OSS). In the beginning Jecklin used omnidirectional microphones on either side of a 30.5cm ring of about 2cm thickness, which had a muffling layer of soft plastic foam on each side. The capsules of the microphones were above the surface of the disc just in the center, 16.5 centimeters apart from each other and each pointing 20 degrees outside.

Jecklin found the 16.5 centimeter ear spacing between the microphones too narrow. In his own paper he notes that the disk has to be 35 centimeters in diameter and the distance between the microphones should be 36 centimeters.

Jecklin's German from his script: "Zwei Kugelmikrofone sind mit einem gegenseitigen Abstand von 36 cm angeordnet und durch eine mit Schaumstoff belegte Scheibe von 35 cm Durchmesser akustisch getrennt." That means: Two omnidirectional microphones have a distance from one to another of 36 cm pointing parallel to the front and a separation between them of a foam plated disk with a diameter of 35 cm.