Tip #7:
Microphone Techniques for Lectern and Stage

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A microphone positioned above or near a reflective surface receives a direct signal from the sound source, and a reflected signal from the surface. Because sound takes time to travel, the reflected signal arrives at the microphone later than the direct signal. The direct and delayed signals combine at the mic diaphragm. This causes an uneven frequency response (see below) called a "comb filter effect," which results in an unnatural sound quality.

The figure above shows a poor way to mike a person at a lectern. The microphone is too far away from the mouth, resulting in pickup of reflected sound from the lectern’s surface. This will result in an audible comb-filter effect, which sounds hollow or tonally colored.

The figure below shows a better way to mike a person at a lectern. The microphone is close to the mouth (about 8 inches). The sound reflected from the lectern arrives toward the rear of the mic, where sound is rejected. This will greatly reduce the audible comb-filter effect.

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The figure below shows an effective way to mike an actor on a stage. Use a boundary mic, which is designed with the mic capsule on or very near the reflected surface.  In a boundary mic, the reflected path is nearly equal to the direct-sound path length, so the direct and reflected sounds are in phase. This will greatly reduce the audible comb-filter effect. To reduce feedback, use a Crown PCC-160 boundary mic, which is directional. For maximum clarity and gain-before-feedback, use a wireless lavalier mic on the actor.

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