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Audio measurement gear

amirm

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Will you be showing measurements of your own space as real-world examples?
What you saying? That I can't be an overweight doctor telling you to keep your weight down??? :D
 

RayDunzl

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I suppose it is a bit much to ask of The King of Audio.
 

c1ferrari

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Ray,

You are a clever writer -- most astute!
:cool:
 

RayDunzl

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c1ferrari

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Yeah...good stuff! :cool:
I know the DOD have their fingers in there...someplace.
o_O
 

c1ferrari

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To be clear, the UMIK-1 is about $100 USD from CSL with an individual calibration file. They do not provide the absolute reference, but you can get that by downloading the file for the mic from the miniDSP site (miniDSP sells them but does not individually calibrate them for on- and off-axis response that we typically use). See http://cross-spectrum.com/measurement/calibrated_umik.html

Cross-Spectrum Acoustics Calibrated MiniDSP UMIK-1 isn’t available at this time -- Sold Out.
:eek:
 

DonH56

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Depends on what you consider "standard", I suppose. For me the calibration made a significant difference in accuracy at frequency extremes, especially at LF (would not cal a subwoofer without a calibrated mic, but can't hear 20 kHz anymore so that was less an issue for me).

That said, the standard UMIK-1 from miniDSP has a cal file, so is close, just not individually calibrated. I have not compared the cal files recently so don't remember how far off it was, nor do I recall the uncal'd response, and I don't have ready access to that data at the moment. IIRC there was a fairly significant difference (few dB) between the miniDSP and CSL calibration files.

Found the cal plots for my UMIK-1 -- notice rolloff at LF and peaking around 10 kHz.

upload_2016-11-4_22-1-29.png


IIRC it was out of stock when I first checked but they got more in a week or two. The UMIK-1 has lower noise floor than the other USB mic they offered at the time.
 

RayDunzl

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... the standard UMIK-1 from miniDSP has a cal file, so is close, just not individually calibrated.

That would be news to me.

--

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:

40638d1361198737-minidsp-umik-1-microphone-cf-umic-190-439.jpg


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.

--

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
 
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c1ferrari

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I thought I'd acquire the Cross-Spectrum UMIK-1 as it arrives with cal files, etc., which differentiate it from the MiniDSP-sourced UMIK-1.
I'll check in every few days until I can score one.
:D
 

DonH56

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RayDunzl is probably correct. It seems like a few years ago miniDSP switched to individual cal files? I am not sure; I do know when I started looking, they told me it was a "batch" file for a group of microphones and not an individual file. It was also for only on-axis measurements.

My Earthworks is extremely flat out of the box. It came with a cal plot and report but no file. I think you can now get an actual file from Earthworks when you buy the mic (or after).

There are measurement mics that are (hopefully) designed and manufactured to be intrinsically flat, like my Earthworks, and then calibrated mics like the UMIK-1 that have been measured and compared to a reference mic to produce a calibration file so you can compensate their inaccuracies. Either should be fine for audio stuff, and the calibrated mics are generally much cheaper.
 

c1ferrari

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I think Mike's in BC, Canada...I'm in SoCal -- if we were closer, I'd have lent him my Rohde & Schwarz UPV.
Perhaps, it would have been useful.
:)
 

c1ferrari

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Well, the UMIK-1 has finally arrived! Hope to play with it, soon. :)
 

Purité Audio

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My new milli volt meter, for level matching down to 0.1 dB
 
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