Two first order cardioid microphones spaced 17 cm and angled 110° creating the stereo image.

The ORTF stereo technique uses two first order cardioid microphones with a spacing of 17 cm between the microphone diaphragms, and with an 110° angle between the capsules. This technique is well suited for reproducing stereo cues that are similar to those that are used by the human ear to perceive directional information in the horizontal plane. The spacing of the microphones emulates the distance between the human ears, and the angle between the two directional microphones emulates the shadow effect of the human head.

The ORTF stereo technique provides the recording with a wider stereo image than XY stereo and still preserves a reasonable amount of mono-information. Care must be taken when using this technique at larger distances, as the directional microphones exhibit proximity effect and will result in low frequency loss. You could add low frequency with an Equaliser to desired taste.