GRAS EQ 40PM EQset™ Miniature Production Line Microphone

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GRAS EQ 40PM EQset™ Miniature Production Line Microphone

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The GRAS EQ 40PM Miniature Production Line Measurement Microphone is the world's first microphone to incorporate EQset technology.


EQset incorporation in a microphone removes all of the traditional hassle associated with installing, setting up, and replacing microphones in a production line setting. EQset measurement microphones all have flat response curves and fixed sensitivity. Sensitivity variation between individual microphones varies less than 0.2 dB from nominal sensitivity. The flat frequency response is less than 0.5 dB up to 10 kHz, another huge improvement over traditional production line microphnes' ±3 dB across the full frequency range. This provides a number of immediate benefits.


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Product Overview


Cost efficiency—low measurement microphone entry cost, no special hardware needed, and fully backwards compatible with CCP setups.

Ease of use—EQ 40PM-1 is dimensionally identical to the traditional production line microphones, it can easily replace them in existing setups. 

Reduced risk—the extremely narrow pressure response spread (±0.5 dB) greatly reduces the risk of false passes and false failures, which greatly reduces the risk of bad units reaching the customer and the risk of good units being scrapped or recycled.

High environmental stability—the unique design of the EQ 40PM provides this range of microphones with unmatched environmental stability. Deviation on a typical production line is less than ±0.2 dB, so there is no need for corrections due to temperature or humidity.


Freq range: 20 Hz to 20 kHz
Dyn range: 30 dB(A) to 125 dB
Sensitivity: 20 mV/Pa

Product Features

GRAS EQ 40PM with EQset™

EQ 40PM with EQset is designed for use in production line environments, and it provides many benefits over traditional production line- or array-style microphones. Designed to be cost-effective, easy to use, resistant to errors, and environmentally stable, EQ 40PM is the best production line measurement microphone option on the market. Each EQ 40PM measurement microphone has a flat response curve and fixed sensitivity. The tolerance for individual microphone sensitivities is less than ±0.2 dB, and frequency-response variation is less than ±0.5 dB up to 10 kHz. And because EQ 40PM is dimensionally identical to the traditional production line microphones, it can easily replace them in existing setups. 



EQset technology

EQset microphones all have a uniformly fixed sensitivity and flat curve. This reduces measurement uncertainty and greatly simplifies microphone setup, monitoring, replacement, and corrections. EQset means that everything can happen quickly and easily without any individual microphone adjustments or corrections. The simplification of setup and other tasks saves both time in the setup itself and time in operator training. There is, however, one additional benefit that outshines the time savings: EQset all but eliminates the inherent risk of false passes on production lines or correction error for frequencies outside the calibrated frequency in R&D—common issues with other microphones in the market. 


Another benefit of the uniformly fixed sensitivity and flat response curve of each EQset microphone is that because there is no need to make individual corrections for each microphone, there is, therefore, no need to store that correction information on the microphones via TEDS. This enables EQset microphones to be used effectively with systems based on audio sound cards using 48 V phantom power as well as any CCP-based system already in use, so there is no need for price-prohibitive new equipment or retooling of existing CCP-based systems. 


For more info on EQset Technology, view here --> NEW EQset™ Technology (



Environmental stability

The unique design of the EQ 40PM provides this range of microphones with unmatched environmental stability. The deviation on a typical production line is less than ±0.3 dB, so there is no need for corrections due to temperature or humidity over the course of a normal day in a typical production-line environment.



Typical applications and use

  • Production-line testing of audio devices such as drivers, receivers, micro-speakers, and miniature microphones

  • Measurements in confined spaces

When starting up, these microphones have a settling time of approximately 5 seconds for accuracy better than 0.1 dB or 1 minute for full accuracy.




The GRAS EQ 40PM  is a robust, cost-effective measurement microphone designed for use in production line testing of loudspeakers and acoustic transducers. It has a wide frequency range, from 20 Hz to 20 kHz, and a dynamic range from 30 dB (A) to 120 dB.


The cost-effectiveness of the EQ 40PM is a key consideration when setting up multiple production lines. Each EQ 40PM is interchangeable with any other  EQ 40PM without the need for recalibration or additional corrections.


EQ 40PM is a 34 mm long ¼″ microphone that can be used in space-challenged setups where larger microphones would not fit or provide difficulties in testing. Additionally, its small aperture provides an advantage in testing micro-speakers, or miniature microphones. It is good practice to use a microphone with a diameter similar to or smaller than the device to be measured.




This range of microphones is fully compatible with 48 V phantom power setups and CCP-based setups. As such the EQ 40PM can be used in new cost-saving production-line setups or as replacements for less accurate TEDS-based microphones in existing CCP setups. 

Using a phantom power setup along with an analyzer such as the APx500 Flex Audio Analyzer will create a budget-friendly setup that can be expanded or upgraded easily as need arises. 



Calibration—measurement chain 

GRAS EQ 40PM measurement microphones can be calibrated to ensure that down-stream equipment (such as a sound card) is correctly set up using a pistonphone like GRAS 42AP or a hand-held calibrator like the GRAS 42AG Multifunction Sound Calibrator.



Quality and warranty

GRAS measurement microphone sets are made of components from our proven standard portfolio and are all manufactured of high-quality material and branded parts that were chosen and processed to ensure life-long stability and robustness.

All parts are manufactured and assembled at the factory in Denmark by skilled and dedicated operators. 

Thanks to the high quality, our warranty against defective materials and workmanship is two years.


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