MPA401 1/4” Free-field Microphone Set

MPA401 is a combination of MP401 microphone and MA411A/B preamplifier, which can be separate into MP401 and MA411A/B according to user’s application.

MP401 is a 1/4" free-field microphone, suitable for measurement in free-field and semi free-field without reflection. It is prepolarized microphone without external polarization voltage and suitable for ICCP-powered preamplifier. It is complying with IEC 61094 WS2F standard.
MA411A/B is a 1/4" ICCP-powered preamplifier, suitable for prepolarized microphones.

 Optional TEDS is available for most of BSWA preamplifier to support read microphone information directly by data acquisition equipment, including microphone model, serial number, sensitivity, etc. BSWA TEDS microphone supports the IEEE 1451.4 standard. The v0.9 version is used by default to be compatible with more data acquisition equipment. The v1.0 version can also be selected according to user’s requirements.


      ● 1/4” free-field microphone

      ● Sensitivity (@250 Hz): 5 mV/Pa (-46 dB re 1V/Pa)

      ● Frequency response: 10 Hz ~ 40 kHz (±2 dB), 6.3 Hz ~ 50 kHz (±3 dB)

      ● Dynamic range: 35 dBA ~ 155 dB

      ● Polarization voltage: 0V (prepolarized)

      ● Pressure equalization: rear-vented

      ● Optional TEDS (IEEE.1451.4)



      ● High precision general purpose acoustic measurement



● About The Microphone Set

The output impedance of the working standard microphone can reach more than GΩ level, so it cannot be directly connected to the data acquisition equipment. The preamplifier must be used to reduce the output impedance to below 100 Ω. The traditional condenser microphone also needs the preamplifier to provide an external polarization voltage of 200 V to charge the capacitor, or coat the rear plate with electret material that can store charge to replace the polarization voltage (prepolarized).

Anyway, different microphone types need to be matched with corresponding preamplifiers to work. BSWA offers the microphone set that consists of microphone cartridge and preamplifier, is reliable and robust. The microphone set is assembled in a clean-room environment, reducing the potential measurements errors cause by the interface contaminating.

● Compatibility

BSWA MK series external polarization microphone needs to be matched with MV series traditional 200 V preamplifier and MC7xx series conditioner; while MP type prepolarized microphone need to be matched with MA series ICCP preamplifier and MC1xx series conditioner. The connection thread between the microphone and the preamplifier complies with WS2 (1/2”) or WS3 (1/4”) standard, and the same type of microphone or preamplifier can be connected to each other.

● Preamplifier’s Impact

The preamplifier not only reduces the output impedance, but also has a certain impact on the performance of the microphone, as described below:

1. Sensitivity: Preamplifier always lowers the sensitivity of the microphone. The typical attenuation value is about 0.3 dB.

2. Self-generated noise: The output noise of the microphone is thermal noise, and the preamplifier will bring a certain amount of electrical noise. Therefore, the total output noise of the combination of microphone and preamplifier is the sum of thermal noise and electrical noise.

3. Maximum output voltage: The maximum output voltage of the microphone is the product of its maximum sound pressure level and its sensitivity. This value often cannot exactly match the maximum output voltage of the preamplifier. The maximum output voltage of the combined microphone and preamplifier is determined by the smaller of the respective maximum output voltages of the microphone and preamplifier. Therefore, if the maximum output voltage of the preamplifier is smaller than the maximum output voltage of the microphone, the dynamic range of the microphone will be reduced.

4. Frequency response: The MA series ICCP-powered preamplifier has certain attenuation at low frequency, but it can still meet the general requirements from 20 Hz to 20 kHz.


Diameter 1/4"
Standard (IEC 61672) Class 1
Microphone MP401
Sound Field Free-field
Preamplifier MA411A/B
Open-circuit Sensitivity (mV/Pa) (±2 dB) 5 (-46 dB re 1V/Pa)
Frequency Response (Hz) 10 ~ 40 k (±2 dB), 6.3 ~ 50 k (±3 dB)
Dynamic Range (dBA ~ dB) 35 ~ 155
Maximum Output Voltage (Vp) ±8
Self-generated Noise (dBA) 35
Output Impedance (Ω) < 30
Pressure Equalization Vent Rear vented
Power Supply ICCP (2mA ~ 20mA, 4mA Typ.)
Operating Temperature Range (°C) -30 ~ 80
Operating Humidity Range (%RH) 0 ~ 95
Temperature Coefficient (250 Hz) (dB/°C) -0.02
Pressure Coefficient (250 Hz) (dB/kPa) -0.007
Influence of Humidity (dB) <0.1
Dimensions (mm) Ø7 × 63.3 (with MA411A), Ø7 × 58.3 (with MA411B)
Output Connector SMB / 10-32 UNF
Weight (g) 7.7
TEDS Version MPA461

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