Affordable Audio Measurement Microphones
Last month (FRONT of HOUSE, Aug. 2022, page 23), we discussed handheld real-time analyzers, bundled hardware/software kits and Mac/PC-based software systems. This month, we’ll continue our look into audio analysis tools with a focus on basic and high-end professional measurement mics to fit anyone’s budget.
Whatever RTA app you consider, don’t expect to get the best results using your phone or tablet mic. RTA apps work best with a proper measurement mic. These omnidirectional XLR-type condenser microphones are intended for audio and room measurement applications while used with a digital audio interface (with mic preamp).
Most of the following measurement mics are under $99; they typically don’t have calibration files and have a lower SPL rating than the more costly 1/2” capsule mics. These are offered by companies such as: AudioControl, beyerdynamic, dbx, HiFiBerry, PreSonus, Rational Acoustics, Sonarworks and Superlux.
The $149 AudioControl CM-125 (audiocontrol.com) and the Rational Acoustics (rationalacoustics.com) RTA-420 analog measurement mics come with carrying bag, mounting clip, windscreen and individually calibration file on a serialized USB memory stick. Specs include 20 Hz to 20k Hz (±3dB) response, 1/4” diameter capsule and a lower max SPL in the 110 dB (1 kHz @ 1% THD) range.
For specifications of several of these other mics, take a look at our Buyers Guide, “Measurement Microphones: 10 Under $1,000” from the August 2020 issue of FRONT of HOUSE.
Low-Cost Digital Audio Measurement Mics
There is a recent trend for measurement microphone manufacturers to offer lower cost models that include calibration data files and have Apple Lightning or USB connectors.
The MicW (mic-w.com) i437L Kit is an omnidirectional mic for measurement with a Lightning connector for iOS devices (complies with the IEC 61672 Class 2). Max SPL rating is average at 125 dB.
The AudioControl SA-4140i SPL (57 dBA to 137 dBA) and Studio Six Digital (www.studio-sixdigital.com) iTestMic2 (48 to 120 dBA) have Lightning connectors and are calibrated so relative values of each frequency band are accurate.
Dayton (www.dayton.com) and miniDSP (www.minidsp.com) both have budget USB 1/4” capsule mics to work with a laptop and RTA software; they both include a calibration file, but measurement mic tests on the HiFiBerry site seem to justify why they don’t include a calibration file.
The miniDSP UMIK-2 USB reference measurement microphone is 32-bit/44.1 to 192k Hz, with ASIO drivers and a larger 1/2” capsule for a lower noise floor. USB Type C. Maximum SPL (0 dBfs): the 125 dB SPL is average.
Professional Audio Measurement Mics $299-$599
This category includes mid-priced analog omnidirectional measurement microphones, with an XLR output, better build quality and included calibration data files. These microphones are also intended for use in RTA and room measurement uses. Look for 1/2” capsules and a higher dynamic range than 1/4” capsule mics.
The Audix (www.audixusa.com) TM1 Plus omnidirectional test and measurement mic is designed and tested by Audix in the USA. It includes calibration data file, threaded acoustic windscreen, and CA4231 calibration adapter. Frequency response is 20 Hz to 20k Hz ±2dB SPL: 130 dB with distortion <1% 140 dB Max.
Earthworks’ (www.earthworksaudio.com) M23 omnidirectional measurement microphone has a flat frequency response that extends from 3Hz to 23kHz, and a 140dB SPL rating without distortion. The M23 is said to “be immune to most temperature and atmospheric fluctuations; delivering reliable and repeatable results in any environment.”
The Josephson Engineering (www.josephson.com) C-555H is a precision omnidirectional measurement mic that is thermally conditioned for stability in California. These mics are individually calibrated and matched for sensitivity. Frequency Response: 20Hz—20kHz ±2dB Dynamic Range: dB SPL 35—135. It includes a USB stick containing the FRD format calibration data file.
Class/Type 1 Certified Measurement Mics ≥$1,000
Studio Six Digital’s iPrecisionMic ($1,099) is the first Class/Type 1 certified microphone that is also an iOS direct-connect Apple Lightning accessory. Connect iPrecisionMic to any iOS device with a Lightning connector, download the Studio Six Digital AudioTools app, and you have a precision sound level meter, ready for certification.
And Beyond…
DPA Microphones, GRAS Sound & Vibration and NTi Audio each have a series of measurement-reference microphones — with flat frequency response, fast impulse response, and polar characteristics — for all audio test software. There are other more expensive XLR-type high-precision measurement mics available from the traditional audio and acoustic measurement equipment manufacturers — such as Brüel & Kjær — the world’s leading manufacturer of sound measurement equipment.
Certainly not to be overlooked is measurement mic specialist iSEMcon (www.isemcon.com). Its most affordable mic — the iSEMic 725TR ($219) — is designed to interface with iPads and iPhones. In the analog XLR category, one of the company’s most popular mics is the EMX-7150 model ($320), which is also offered in precision-matched pairs, triplets, quads and octet sets.
Next month, we’ll explore interfacing options and preamps for connecting your test mic to your analysis/room measurement system. See you then!
David K. Kennedy operates David Kennedy Associates, providing acoustic and sound design consulting services, with an emphasis on loudspeaker arrays for educational and religious facilities. Visit him at www.d-k-a.com.
