Schoeps MK 21
The Schoeps MK 21 is a wide cardioid capsule for the Collette CMC 1 and CMC 6 series. The directivity of the wide cardioid lies between the omni and the cardioid and the idea behind their development is to combine the advantages of these two patterns.
The low-frequency behaviour of the MK 21 is better than that of the cardioid, and proximity effect is less pronounced. The wide cardioid polar pattern is extremely consistent across the frequency range and laterally-arriving direct sound and reflections are picked up without added coloration. The MK 21 is a very well-liked capsule and it's preferred when a slight directional effect and a warm, natural sound image are desired. Over the years it has become an integral part of the audio engineer's toolkit.
When used as a spot microphone, the distance from the sound source should be slightly smaller than when using a cardioid due to lower directivity index, preventing it from generating large enough level differences for X/Y use, though MS and near-coincident spacings are often successful.