Setting Attenuation; Load Impedance; Power Requirements; Specifications - Shure SM27 User Manual

Setting Attenuation

The attenuation switch lets you reduce the signal level without altering
the frequency response. This can prevent extremely loud sounds from
overloading the microphone.
For "quiet" to "normal" sound levels.
0 dB
For use with extremely loud sound sources such as
-15 dB
drums, horns, or loud guitar cabinets.
Integral Pop Filter
The microphone grille consists of 3 separate mesh layers that act as an
integral pop filter. This helps reduce wind and breath noise. Depending on
the performer, an external pop-protection screen or windscreen may be
necessary when close-miking vocalists.

Load Impedance

Maximum SPL capability, output clipping level, and dynamic range vary
with the input load impedance of the preamplifier to which you connect
the microphone. Shure recommends a minimum input load impedance of
1000 Ω. Most modern microphone preamplifiers meet this requirement.
Higher impedance results in better performance for these specifications.

Power Requirements

This microphone requires phantom power and performs best with a 48
Vdc supply (IEC-61938). However, it will operate with slightly decreased
headroom and sensitivity with supplies as low as 11 Vdc.
Most modern mixers provide phantom power. You must use a balanced
microphone cable: XLR-to-XLR or XLR-to-TRS.

Specifications

Type
Electret Condenser
Frequency Response
20 to 20,000 Hz
Polar Pattern
Cardioid
Output Impedance
140 Ω
Sensitivity
at 1kHz,open circuit voltage
-37 dBV/Pa[1]
4
Maximum SPL
1 kHz at 1% THD[2]
2500 Ω load 138 dB (152 dB, PAD ON)
1000 Ω load 133 dB (147 dB, PAD ON)
Signal-To-Noise Ratio[3]
84.5 dB
Dynamic Range
at 1kHz
2500 Ω load 128 dB
1000 Ω load 123 dB
Common Mode Rejection
20 Hz to 20 kHz
>55 dB
Clipping Level
20 Hz to 20 kHz, at 1% THD
2500 Ω load 7 dB
1000 Ω load 1 dB
Self Noise
equivalent SPL, A-weighted, typical
9.5 dB
Polarity
Positive pressure on diaphragm produces positive voltage on pin 2 with respect to pin 3
Weight
642 g(22.6 oz.)
Switch
Attenuator -15 dB
Low Frequency Response Flat, –6 dB/octave below 115
Hz, or –18 dB/octave below
80 Hz
Connector
Three-pin professional audio (XLR), male, balanced
Power Requirements
48 V DCphantom power, 5.4 mA
[1] 1 Pa=94 dB SPL
[2] THD of microphone preamplifier when applied input signal level is equivalent to cartridge output
at specified SPL
[3] S/N ratio is the difference between 94 dB SPL and equivalent SPL of self-noise, A-weighted