Stage monitors are placed in the rear null of the vocal mic's polar pattern to maximize gain before feedback

The acoustic feedback path in a monitor system runs from the monitor speaker into the microphone and back through the amplifier. To maximize gain before feedback, the monitor must be placed in the direction where the mic’s sensitivity is lowest — the rear null of a cardioid pattern. In practice this means placing the monitor in front of the performer and behind the microphone, with the mic’s front face pointed toward the performer’s mouth (away from the monitor). The mic stand then sits between the performer and the monitor speaker. Two monitors placed apart and aimed to intersect at center stage create comb filtering and poor coverage; the correct technique is to place two monitors together with their rear corners touching and splay them to cover the stage area, avoiding the interference pattern.

Examples

A monitor floor wedge is placed directly in front of the vocalist, angled up toward their face. The mic faces the vocalist — its rear faces the monitor. This configuration gives maximum feedback rejection and maximum monitor level before howling.

Assessment

A monitor engineer positions two wedge monitors symmetrically, one left and one right, both aimed at center stage. The engineer gets frequent feedback. Why? How should the monitors be repositioned?