For most purposes, use the narrowband files. Herb supplies the calibration files in a narrowband version and a 1/3-octave version. ![]() Typically, you would use the 0 degree file when performing speaker measurements, with the microphone pointed directly at the speaker, and the 90 degree file while performing room measurements, with the microphone pointed towards the floor or ceiling. Polar response chart of my EMM-6Ĭalibration files for angles of 0 (on-axis), 45, and 90 degrees are supplied. You can see samples of the full sheet on Herb’s website for the Basic+ and Premium+ levels. Here is the plot of the 0, 45, and 90 degree curves of my EMM-6:įigure 2. In addition to the electronic calibration files, you also get the printed sheet as a PDF document. My files came on a CD, but Herb has recently switched to supplying the files on a USB thumbdrive. (The older Basic and Premium variants are no longer offered.) What you get, in addition to the microphone and accessories supplied by Dayton, is a printed sheet with the measurements of the microphone plotted, and a set of electronic calibration files. Herb provides calibrated microphones in two variants, called Basic+ and Premium+. Each individual microphone will vary – less for more expensive microphones and more for cheaper ones – and so calibration files must be generated individually for each microphone. All measurement equipment must be calibrated, and more expensive microphones like the Earthworks M30 come from the manufacturer with a calibration chart and (recently) an electronic calibration file. Note that calibration is not something that is done only with inexpensive microphones. This is great, for most of us! Why? Because it’s much cheaper to get an “inaccurate” microphone with a compensating calibration file than it is to get a truly accurate microphone. The result is a measured response that is the same (or close to) what you would get if you had a perfectly flat microphone. For example, if the calibration file says that the microphone is 5 dB down at 20 Hz, then the measurement software will add 5 dB to whatever value it calculates as the acoustic SPL at 20 Hz. The measurement software corrects the raw response calculated from the measurement sweep using the data in the selected file. Exactly where you do this depends on the program, but the screenshot below shows the calibration selection in FuzzMeasure Pro. This file is then loaded into the measurement software so the software can compensate for inaccuracies in the microphone. Instead, the microphone’s frequency response is measured and captured as data in a file. ![]() Nothing is actually done to the microphone itself. The first thing to explain is what it means to “calibrate” a microphone. ![]() In this article I’ll review the CSL-calibrated EMM-6 and compare it to an Earthworks M30 to see how it measures up. So it’s good to know that there’s an inexpensive alternative to a high-quality measurement microphone like the Earthworks M30. Perhaps because it’s not a part of the system per se, the price of a basic acoustic measurement setup can be something of a barrier to audiophiles. Some time later, Parts Express began selling a similar microphone branded as the Dayton EMM-6, and Herb decided to also offer those as a calibrated unit. Herb found that calibration of the Behringer ECM-8000 microphone was sufficiently popular that he began to purchase the microphones in bulk and sell them as calibrated units (so, rather than buying an ECM-8000 and shipping it to Herb for calibration, you would just buy the ECM-8000 directly from Herb). That is, their frequency response, while “flat enough” for casual full-spectrum measurements, isn’t accurate enough for use in speaker design or fine-tuning equalization and in-room system response.Ī few years ago, Herb Singleton from Cross-Spectrum Labs (CSL) began offering an inexpensive microphone calibration service. While relatively cheap measurement microphones like the Behringer ECM-8000 and Dayton EMM-6 are a tempting proposition for anyone interested in making acoustic measurements of loudspeakers or listening rooms, they have an Achilles heel: they aren’t flat.
0 Comments
Leave a Reply. |