Pad Switch; Proximity Effect - Shure pg27 Instruction Manual

Pad Switch

Proximity Effect

Unidirectional microphones such as the PG27 progressively boost bass frequencies by 6 to 10 dB below 100 Hz
when the microphone is at a distance of about 6 mm (1/4 in.) from the sound source. This phenomenon, known as
proximity effect, can be used to create a warmer, more powerful sound.
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The pad switch helps prevent distortion from extremely loud sources, such as when
close-miking horns or drums.