The most commonly used technique is the x-y cardioid and hypercardioid. The
microphone pair can be setup with an included angle between 60 and 120
degrees. The angle will determine the apparent width of the stereo image,
the amount of reverberant sound and the bass response. The wider the angle
the more natural the soundfield up to the point where the angle becomes too
great and a hole appears in the center. 90 degrees provides good results
with any cardioid or hypercardioid microphone.