M 661

1/2inch, Free-field, 16kHz
M 661 is an IEPE 1/2-inch prepolarized free-field measurement microphone, which is used to measure the undistorted true sound pressure of the microphone before it is placed into the sound field. The main part is made of stainless steel so that it has good toughness and long-term stability.

Specifications

Parameter	Value
Dimensions	1/2inch
Sound Field Type	Free field
Polarization Voltage	0V（Pre-polarized）
Frequency Response	3.15Hz – 16kHz ± 2dB 12.5Hz – 10kHz ± 1dB
Dynamic Range	18dB（A）-135dB （1000 Hz 失真<3%）
Noise Floor	＜18dB（A）
Sensitivity	（50±10）mV/Pa (-26.0± 2) dB re 1V/Pa
Standard	IEC 61094-4 类型，WS2F
Typical Capacitance	＜18.0pF
Pressure Equalization Method	Post-equalization
Operating Temperature	-30℃ ~ 85℃
Temperature Coefficient	-0.012dB/℃
Humidity Coefficient	<0.1dB (0% - 90% no condensation )
Relative Humidity	0% - 90% no condensation
Static Pressure Coefficient	-0.01dB/kPa

Specifications

Types of Acoustic Fields	Free Field
Polarization voltages	0V（Prepolarized）
Frequency range	3.15Hz – 16kHz ± 2dB 12.5Hz – 10kHz ± 1dB
Dynamic range	17dB（A）-135dB（1000 Hz THD<3%）
Background noise	17dB（A）
Sensitivity mV/Pa(dBV/Pa)	50mV (-26.0dB) ± 2dB
Capacitance Typical	16.0pF
Temperature range, operation	-30℃ to 85℃
Temperature range, storage	Temperature：25℃±5℃，Humidity：50%±15%RH（Ensure the long-term stability of the sensor）
Humidity range non condensing	0 - 90% non condensation
Humidity coefficient	<0.1dB（0 - 90% no condensation）

Typical frequency response curve

Dimensions

Height including protective cage	17.2mm
Diameter with protective cage	13.2mm
Height excluding protective cage	16.2mm
Diameter excluding protective cage	12.7mm
Front-loaded extreme fit thread	11.7mm - 60UNS
Protective cage engaging thread	12.7mm - 60UNS