HomeProductsSensorsMicrophone kit1/4inch, Free-field, 20kHz, IEPE

M 643+A 811

1/4inch, Free-field, 20kHz, IEPE
The M 643+A 811 is an IEPE 1/4-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.

Description
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Description

Specifications

Parameter	Value
TEDS Function	No
Dimensions	1/4inch
Sound Field Type	Free field
Polarization Voltage	0V（Pre-polarized）
Frequency Response	10Hz - 20kHz ±2dB
Dynamic Range	37.5dB（A）-155dB （1000 Hz 失真<3%）
Noise Floor	37.5dB（A）
Sensitivity mV/Pa (dBV/Pa)	5mV (-46.0dB) ± 2dB
IEC 61094-4 Type	WS3F
Maximum Output Voltage	5.6V
Output Impedance	<50Ω
Supply Power	2mA - 10mA （Typical4mA）
Pressure Equalization Method	Post-equalization
Connector Type	Micordot(M5)
Operating Temperature	-30°C to 85°C
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	10 - 20kHz ± 2dB
Dynamic range	37.5dB（A）-154dB（1000 Hz THD<3%）
background noise	37.5dB（A）
sensitivity mV/Pa(dBV/Pa)	（5±1）mV (-46.0dB) ± 2dB
Maximum Output Voltage	5.6V
Output Impedance	<50Ω
Power Supply	2mA - 20mA（typical 4mA）
Pressure Equalization Method	Post-equalization
Connection	Micordot(L5)
Temperature range	-30℃ to 85℃
Temperature coefficient	-0.012dB/℃
RH	0 - 90% （no condensation）
Humidity coefficient	＜0.1dB（0% - 90% no condensation）
Static pressure coefficient	-0.01dB/kPa
Storage condition	Temperature: 25℃±5℃, humidity: 50%±15%RH (to ensure the long-term stability of the sensor)

Typical frequency response curve

屏幕截图 2026-04-16 153119.png

Dimensions：mm

Dimension parameters
Overall length (with protective grid)	66mm
Diameter (with protective grid)	7mm
Diameter (without protective grid)	6.35mm

M 643+A 835&A 811尺寸.png

Ordering Information

PN	Model	Description
900011-05	M 643+A 811	Free-field measurement microphone kit
900001-08	M 643	Free-field measurement microphone
900010-11	A 811	Preamplifier
730008-000	102C	Customized length_M5_BNC low-noise cable
730008-030	102C030	50Ω_M5_BNC low-noise cable，length 3.0m
730008-060	102C060	50Ω_M5_BNC low-noise cable，length 6.0m
730008-090	102C090	50Ω_M5_BNC low-noise cable，length 9.0m

The measuring microphones we produce are precision sensors, and all aspects related to production are strictly controlled, including material selection, production processes, testing control, and production environment.

图片1.png After years of continuous improvement, we now use special nickel alloy materials as the core material for the diaphragm. Compared to other alloy materials, it exhibits higher sensitivity, lower distortion rate, and more stable long-term performance. The front body of the microphone is made of stainless steel, ensuring that the entire microphone maintains extremely robust structural characteristics even under various assembly conditions.

We adopt advanced production processes and fully automated precision machining equipment, which significantly reduces the accuracy errors caused by secondary clamping in traditional machining equipment. This greatly enhances the dimensional consistency, geometric accuracy, and overall quality stability of the products, providing reliable technical support for demanding application scenarios.

At the same time, we employ extremely rigorous testing and control measures, conducting quantitative testing on any links that may lead to product quality issues, and implementing test sequence control to prevent skip-station situations. The comprehensive MES control enables all data to be traceable, ensuring a high degree of consistency in sensor quality.

The entire production process of all our microphones is strictly carried out in a dust-free workshop, which can minimize the amount of dust in the air, thus creating a stable and pure working environment for the sensors. This ensures a long and stable lifespan for the sensors and maintains their excellent performance throughout daily use.