... the standard UMIK-1 from miniDSP has a cal file, so is close, just not individually calibrated.
That would be news to me.
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The UMIK-1 comes from HongKong (MiniDSP Direct) with an on-axis calibration file - downloaded by serial number.
I didn't understand initially, but in this case, a "calibrated" mic means not a perfect piece of hardware, but one that comes with a file the measurement software reads to "correct" the data it outputs.
Here's mine for serial #700-4591...
Cross-Spectrum imports a few, makes their own set of calibration files for each, and sells that service along with having the mic in stock in the U.S. (or not). Their bulk-buy and shipping cost savings makes their price just a few ($5? $10?) more after shipping.
I bought mine from HongKong, and it got to me in little more than the time it took to fly from HongKong to New York, and overnight on to Tampa. I don't think it was more than 48 hours. I bought a convolver separately and it missed all the connections and sat forlornly in Customs and took some days longer to get here.
Somebody curious collected a series of the stock calibration files and made this comparison:
I can see when I've forgotten to specify the use of the cal file in REW when looking at a trace of my already corrected response - it's a little hot up top.
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Somebody wrote a conversion utility to adjust the on-axis cal file to 90 degrees:
"It turns out that the delta between 0 degree and 90 degree measurements on UMIK-1s are extremely consistent, based on 10 measurement samples from Cross Spectrum Labs. So, I wrote a utility to translate the 0 degree calibration files from MiniDSP to 90 degree files."
https://www.minidsp.com/forum/umik-questions/10088-translate-0-degree-calibration-to-90-degree