Matched microphones are strongly recommended for stereo techniques. Two mics of the same make, model, and vintage can each sound slightly different due to unavoidable component and manufacturing inconsistencies. Matched pairs undergo additional testing by the manufacturer in order to pair together mics with the most similar performance, resulting in more accurate stereo imaging. Bi-directional microphones really reject sound sources positioned to their sides. This results in a lot less overlap or common pick-up between the mics. Blumlein pairs can produce very natural, realistic images that are wider and more spacious than XY coincident pairs. In order to be reproduced on stereo loudspeakers or headphones, an MS array needs to be decoded to stereo using a sum and difference matrix, the process is known as matrixing. Raw MS tracks can be recorded and then matrixed to stereo at a later time. Or they can be matrixed prior to the recording device to record LR stereo tracks.