The Optimized Cardioid Triangle (OCT), is a microphone array for front-channel reproduction, initiated by Günther Theile & Helmut Wittek
OCT is an array designed for the three front channels only. The system offers high separation between left-center and right-center. An additional configuration for the surround channels should be chosen carefully.
A cardioid microphone is used for the center channel placed only 8 cm (3.1 in) in front of two higher directional cardioids for left and right channels, pointing outwards. The spacing between the left and right microphones is the key to the desired recording angle. Distances between 40 cm (15.7 in) and 90 cm (35.4) are recommended from the designers, resulting in recording angles from 160° to 90°.
One or more pressure (omnidirectional) microphones can be added to the system to compensate for the missing low frequency from the pressure gradient capsules for the cardioids.
The OCT2 variation suggests that the center microphone should be placed 40 cm (15.7 in) in front of the left/right microphone base line, giving larger time differences and spaciousness more like the Decca Tree.
If you want to try this setup with DPA mics, we suggest the following microphones and accessories. d:dicate™ 4011A Cardioid Microphone d:dicate™ 4011C Cardioid Microphone S5 Surround/Decca tree mount