Earthworks M23 – 23kHz Measurement Microphone


The M23 is a cost effective reference microphone for SMAART, MLSSA, Spectrafoo software, TEF and RTA, and all “audio band” measurements. It has a flat frequency response, fast impulse response and exceptional polar characteristics. 9Hz – 23kHz flat frequency response. Omnidirectional polar pattern. Handles up to 140dB SPL without distortion.

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Earthworks M23 is an affordable omnidirectional measurement microphone with flat, 3Hz-23kHz frequency response, exceptional polar characteristics and super-fast impulse response

When David Blackmer founded Earthworks, his goal was to create the best-sounding speakers the world would ever hear. Drawing on his immense design acumen from his days as founder of dbx and creator of innovations such as over-easy compression (still ubiquitous in the studio), Blackmer realized that in order to measure the response of such speakers, his test equipment needed to far surpass the performance on any test microphones available at the time—and thus Earthworks range of measurement microphones were born (which also laid the foundation for all subsequent Earthworks microphones). The M23 is a 23kHz omnidirectional microphone that offers an affordable entry to precision testing. It has a flat frequency response that extends from 3Hz to 23kHz, an exceptionally consistent polar response, and 140dB SPL rating without distortion and no handling noise. Immune to most temperature and atmospheric fluctuations, the M23 delivers reliable and repeatable results in any environment.

Earthworks M23 omni measurement microphone in one take:

  • 3Hz – 23kHz flat frequency response
  • Cost effective measurement microphone
  • Improved version of the SMAARTMIC previously offered by EAW
  • Ideally suited for acoustical measurements sound system setup and troubleshooting, room acoustics, or any application where an accurate free-field measurement microphone is required
  • Omnidirectional polar pattern
  • Flat frequency response, fast impulse response and exceptional polar characteristics
  • Used by SMAART, MLSSA, Spectrafoo, TEF and RTA in addition to acoustic measurement systems manufactured by dbx, DEQX and others
  • Meets or exceeds ANSI Type 1 and applicable IEC 61094 requirements
  • Each M Series microphone is delivered with its own calibration chart providing its individually measured open-circuit sensitivity and the frequency response curve
  • Electronic Calibration File available
  • Operating Temp Range: -20 deg. C to +60 deg. C ( -4 deg. F to 140 deg. F)
  • Storage Temp Range: -40 deg. C to +80 deg. C ( -40 deg. F to 176 deg. F)
  • Humidity: Up to 90%
  • Re-calibration recommended every five (5) years

Flat frequency response

Designed and calibrated for measurement tasks, the Earthworks M23 is a pre-polarized condenser microphone directly coupled to a wideband, low output-impedance preamplifier. It features a linear free-field frequency response from 3Hz – 23kHz, very low handling noise, uniform polar pattern, and very high SPL handling capabilities. Taking into account the subtleties of acoustic behavior, particularly the change in sound characteristics based on atmospheric characteristics, the M23 features temperature-compensated electronics, which removes the transconductance of the input FET (Field Effect Transistor) from the overall gain structure. This means that the sensitivity remains very stable when the microphone is subjected to variations in ambient temperature.

Used with all the industry standard acoustic measurement systems

Extremely fast impulse response and linear phase response make the M23 ideal for use with high-quality FFT-based real-time audio system measurement software like SMAART, SIM, REW, Electroacoustics Toolbox, FuzzMeasure and others, as well as for use in PA system alignment and loudspeaker design.


The Earthworks M23 is excels at sound system setup and troubleshooting, room acoustics, or any free-field measurement application. The wide linear minimum-phase response and fast well-damped impulse response make the M23 an excellent microphone for room acoustics measurements, especially time domain measurements. The M23 also provides precision response for high-end loudspeaker design and quality control, scientific research, measurements of ultrasonic or subsonic transducers.


Hand-tuned and tested

Every M23 is individually hand-tuned and tested and delivered with its own calibration chart providing its individually measured open-circuit sensitivity and the frequency response curve. A computer file containing the frequency response data for importing directly into measurement software is available from Earthworks, Inc. upon registering your new microphone. A mounting clip and a calibrator adapter are included with the microphone.

The Earthworks M23 omnidirectional measurement microphone is designed for to exceed the most stringent requirements for those who demand the very best. For more information, call or chat online with your Westlake Pro Sales Consultant today.


Earthworks M23 specifications: 

  • Frequency Response: 3Hz to 23kHz ±1/-3dB
  • Polar Pattern: Omnidirectional
  • Sensitivity: 34mV/Pa (-29dBV/Pa)
  • Power Requirements: 24 – 48V Phantom, 10mA
  • Max Acoustic Input: 140dB SPL
  • Output: XLR (pin 2+)
  • Output Impedance: 65 ohm balanced (between pins 2 & 3)
  • Min Output Load: 600 ohm between pins 2 & 3
  • Noise: 20dB SPL equivalent (A weighted)
  • Dimensions L x D: 6-1/2″ x 7/8″ (165 x 22 mm)
  • Weight: .35 lb. (160g)

Additional information


20dB SPL equivalent (A weighted)


165mm x 22mm (6.5 x .860 inches)

Max Acoustic Input

138dB SPL

Polar Pattern



34mV/Pa (-29dBV/Pa)

Output Impedance

65Ω balanced (between pins 2 & 3)

Power Requirements

24 – 48V Phantom, 10mA


XLR (pin 2+)


.35 lb. (160g)

Minimum Output Load

600Ω between pins 2 & 3


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