From the DPA University site...http://www.dpamicrophones.com/eng_pub/MicUni/Main.html
Two first order cardioid microphones spaced 20 cm and angled 90° creating the stereo image.
DIN stereo uses two cardioid microphones spaced 20 cm apart and angled at 90° to create a stereo image. The DIN stereo produces a blend of intensity stereo signals and time delay stereo signals, due to the off-axis attenuation of the cardioid microphones together with the 20 cm spacing. If used at larger distances to the sound source the DIN stereo technique will loose the low frequencies due to the use of pressure gradient microphones and the influence of the proximity on these type of microphones. The DIN stereo technique is more useful at shorter distances, for example on piano, small ensembles or used for creating stereo on a instrument section in a classical orchestra.