Microphone Cartridges

4191 1/2-Inch Free-Field Microphone

4191 1/2-Inch Free-Field Microphone

Type 4191 is designed for high-precision, free-field measurements where a wide bandwidth is required. Being externally polarized, Type 4191 must be used with a classical preamplifier.


  • Precision measurements to 40 kHz
  • Premium class sound level meters
  • Equipment complying with IEC 61672 class 1


At higher frequencies reflections and diffractions causes a pressure increase in front of the diaphragm of a microphone. If not corrected for, this would result in an increased output voltage. A free-field optimisation means that the frequency response of the microphone has been designed in such a way that the free-field response at 0 degrees incidence is flat. This microphone is optimised for use with the protection grid in place.

Free-field microphones are commonly used for sound measurement in an anechoic chamber or far away from reflecting buildings, etc. Another area for free-field microphones is for general electroacoustic measurements like loudspeaker and microphone measurements.

With an upper frequency of 40 kHz, Type 4191 is especially suited all high-precision electroacoustic measurements as well as general acoustic measurements where a robust and stable free-field microphone is required. Despite the 40 kHz upper frequency, this microphone is optimised to operate with the protection grid in place.


A press-fitted, stainless-steel diaphragm ensures superior long-term stability and mechanical robustness – Type 4191 will withstand the 1 m drop test of IEC 60068-2-32.


Type 4191 requires an external polarization voltage and must therefore be used with a classical preamplifier. Externally polarized microphones may be used at higher temperatures without severe changes in sensitivity.

Type 4191 is available in TEDS combinations with the classical Microphone Preamplifier Type 2669. The TEDS microphone is considered one unit and has been sealed in a clean environment. The TEDS is programmed with the loaded sensitivity of the actual cartridge and the data is therefore readily available. The default TEDS template is to IEEE P 1451.4 but TEDS to IEEE 1451.4 is available on request.

Capacitance: 18 pF
Diameter: 1/2
Dynamic range: 20 – 162 dB
Frequency range: 3.15 – 40000 Hz
Inherent noise: 20 dB A
Lower limiting frequency -3dB: 2 Hz
Optimised: Free field
Polarization: Ext polarized
Polarization voltages: 200 V
Pressure coefficient: -0.007 dB/kPa
Sensitivity: 12.5 mV/Pa
Standards: IEC 61094-4 WS2F
Temperature coefficient: -0.002 db/ºC
Temperature range: -30 – 300 C
Venting: Side
Weight: gram
Sound field: Free-field
Input type: Classic
Microphone type: Free field