XY stereo set-up is a coincidence stereo technique using two cardioid microphones in the same point and angled at 90° to produce a stereo image. Theoretically, the two microphone capsules need to be at exactly the same point in space to avoid any phase problems due to the distance between the capsules. As this is not physically possible, the nearest approximation is to place one microphone on top of the other with the diaphragms vertically aligned. In this way, sound sources in the horizontal plane are picked up as if the two microphones were placed at the same point. However, channel separation is limited, and wide stereo images are not possible. But the XY stereo method is highly mono-compatible and is used in broadcasting situations where listeners might be listening to stereo audio on mono equipment.

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