Polar Patterns and Placement

An omnidirectional microphone picks up equally in all directions; it has the most natural tone and no directional rejection. A cardioid picks up mainly from the front and has its null directly behind, at 180 degrees, and is widely used in live sound. A supercardioid has a narrower front pickup and a small rear lobe, with its deepest rejection near 125 degrees off axis. A hypercardioid is narrower still, with nulls near 110 degrees and a larger rear lobe. Shure accordingly recommends placing a floor monitor directly behind a cardioid, but to the sides and slightly behind a supercardioid or hypercardioid, because a wedge placed directly behind those patterns sits in their rear lobe.

Directional microphones also show proximity effect: the low frequencies rise as the source moves closer. The effect comes from the pressure-gradient operation of these capsules and is strongest on bidirectional microphones, while a pressure omnidirectional microphone shows none. A singer working close to the grille gets a boost below a few hundred hertz, and the tone thins again when the singer moves back. Proximity effect can be used deliberately or compensated. Moving a microphone by a few centimetres changes its tone, its isolation and its gain before feedback more than equalization can later in the chain.