Cross-Spectrum Microphone Calibration Service - USA - Page 10 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #91 of 366 Old 07-28-09, 04:25 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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JimP wrote: View Post
Anechoic,

Where can we find your current prices for either buying a ECM8000 with calibration or having our own ECM8000 calibrated. I'd want it accurate to either 10 or 15 hz...
Click on my name to find prices for pre-calibrated ECM8000 sales. Having your own mic calibrated is $55 for basic calibration, +$10 for polar measurements, +$10 for noise floor/sensitivity. Extra angles are free, but as of Sat, extra angles will be $5 per additional angle. The new price structure for mic sales (again, starting Aug 1) is described here.
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post #92 of 366 Old 08-09-09, 06:46 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

I had Herb (Cross Spectrum Labs) test an E-V RE510 for me a few months ago and was very satisfied with the service. The mic, not so much. Herb is the real deal.

Herb, are you able to test mics at frequencies other than the standard third-octave intervals? The reason I ask is because I use a program called Voxengo Curve EQ to approximate the inverse of a mic's measured frequency response and thus "flatten" it, and it has more and different frequencies available on its EQ than the third-octave values.

Thanks.
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post #93 of 366 Old 08-09-09, 06:52 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Thanks for the kind words.

I can do 1/6 octave.
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post #94 of 366 Old 08-17-09, 12:50 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

For those on the fence about getting the calibrated ECM-8000, I recommend going for it. I received mine Friday (thanks for the fast service from Cross Spectrum) and there is quite a bit of difference between it and the generic curve from this website. (To be fair, that generic curve is from one mic and Cross Spectrum has posted the variation among samples of the ECM-8000).

I suppose it all depends on how accurate you want your calibration to be. But, that is why we do this, right?

Hug your pet today!
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post #95 of 366 Old 09-14-09, 12:18 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

BTW everyone, if you're in the Boston area, the Boston Audio Society will be holding a "microphone measurement clinic." A bunch of us who do various sorts of measurements (including Joe DeMarinis and possibly someone from Listen Inc.) will be there to talk about mic measurements and actually do some mic measurements. The plan right now is that Joe will be handling the mid-to-high frequency measurements and I'll be doing low-frequency measurements with my low-freq calibration rig.

We're looking at Nov 21 or 22, and when we settle on a date, it will be posted on the BAS website.
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post #96 of 366 Old 09-19-09, 04:22 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

FYI, in case anyone was wondering just how accurate my calibration process is, I did I little test to see how my measurement compare with mic calibrations performed by a NIST-traceable lab. I have several professional measurement microphones that are regularly calibrated by Scantek.

One of my more top-of-the-line microphones is a BSWA MP201. Scantek has calibrated this a couple of time using an electrostatic actuator (to get the pressure response) and then applying a free-field correction per ANSI/IEC standards. One such result is shown below (I do have a more recent cal, but I can't find the plot right now. FWIW, the mic FR didn't change):



So I took the data points off that plot, measured the MP201 using my freefield method (which is basically the substitution method using another calibrated mic) and plotted a comparison:



No tricks, no adjustments, no massaging the data, that's what I got using the same software, hardware and scripts I use to generate curves for all the mics I sell. There is a discrepancy at 20 kHz; the problem at those high frequencies is that the wavelengths are so small that every little thing can effect the result, including the microphone mounting method. Without knowing the exact free-field correction process Scantek uses I can't say who is more/less correct but I will note that both measurements are will within ANSI/IEC accuracy standards (which get larger at higher frequencies).
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post #97 of 366 Old 09-19-09, 07:26 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Very nice Herb!!! It gives a lot of confidence in your technique and calibration skills (not that we did not have it before). Thanks again for such a great service!!!

Ray


Happy Listening!!! Listen with an open mind and heart!!!
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post #98 of 366 Old 10-19-09, 10:36 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Now this is a great excuse to take the Downeaster to Boston. 2 hours from OOB to Boston, listening to podcast, reading....
Most people I knew from my last meeting I went to at BAS are long gone either in the audio world or dead.

Think I will bring my mic with me too, maybe re-enlist in BAS.

Last BAS I went to, a bit fuzzy... either Acoustic Research, doing car audio tests with a PDP11, or some microphone clinic at BBN, I remember most of us were spending thousands on audio gear mass produced, and the speaker emphasized a microphone is mostly hand made, for only 700.00 or so. (circa 1978ish).
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post #99 of 366 Old 10-19-09, 11:04 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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nerdful1 wrote: View Post
Now this is a great excuse to take the Downeaster to Boston. 2 hours from OOB to Boston, listening to podcast, reading....
Most people I knew from my last meeting I went to at BAS are long gone either in the audio world or dead.

Think I will bring my mic with me too, maybe re-enlist in BAS.
We'd love to have you. The only problem is that it looks like we're going to have the meeting in Winchester, so getting from North Station to Winchester might be a bit of a haul. Although there is a commuter rail stop in Winchester, so I'm sure I or someone else could give you a ride to/from the station.
Quote:
Last BAS I went to, a bit fuzzy... either Acoustic Research, doing car audio tests with a PDP11, or some microphone clinic at BBN, I remember most of us were spending thousands on audio gear mass produced, and the speaker emphasized a microphone is mostly hand made, for only 700.00 or so. (circa 1978ish).
Wow, you are old!
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post #100 of 366 Old 10-20-09, 04:25 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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brucek wrote: View Post
The calibration comes in the form of a calibration file in easily read text form.


The calibration file extends the accuracy range to 20KHz for the Galaxy, just as it does for the ECM8000. So, if your Galaxy was down by 10dB at 20KHz, then the file would show +10dB for the 20KHz entry. This would render the reading flat once the calibration was added in REW (or manually).

brucek
Sorry I don't understand... why the mic need a calibration? It's not perfect yet?
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