Shure KSM137 User Manual page 6

Setting Attenuation
The attenuation switch on the KSM137 lets you reduce the signal level by up to 25 dB
without altering frequency response. This can prevent extremely loud sounds from
overloading the microphone. Set the switch to the desired attenuation levels as follows:
0 dB – Move the switch to this position for "quiet" to "normal" sound levels.
-15 dB – Move the switch to this position when the microphone is approximately
0.75 meters (2 feet) from sound sources such as a kick drum, snare drum, or electric
guitar cabinet.
-25 dB – Move the switch to this position when the microphone is 4 inches (10 cm)
or less from extremely loud sound sources such as kick drum, snare drum, or guitar
cabinets.
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