Cross-Spectrum Microphone Calibration Service - USA - Page 9 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #81 of 366 Old 07-15-09, 07:12 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Well, then that makes sense, especially if you want absolute correct level matches, also when designing/confirming crossovers. But, as Anechoic mentioned, most users simply want correct FR and Polar response (the two things I looked for). I haven't built speakers in a LONG time. It would be fun to do it again, especially with all the software available.

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post #82 of 366 Old 07-22-09, 05:26 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately, like what you would use one of these for:

http://www.galaxyaudio.com/CMC200.jsp

Maybe I've overlooked something here, but from what I've read the ECM8000 has a wider frequency range (15 Hz to 20 kHz) than the Galaxy CM-140 (31.5Hz to 8KHz), so why would you want to use the Galaxy to do room measurements beyond typical SPL readings?

What I'm getting at is this: Is it worth it to own one of each and have them both calibrated: the ECM8000 with its cal files to correct for frequency response and polar data, and the Galaxy CM-140 to check for SPL? I'd still like to do SPL measurements (level matching systems like my car stereo and headphones, checking noise levels, etc.) w/out having to hook up a whole rig to do this.
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post #83 of 366 Old 07-23-09, 09:04 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Hi Dan,

I have a comparable SPL meter to the one above, but from TENMA. It has the same specs and I only use it for level matching with pink noise. As for doing SPL measurements outside the freq range of this meter, for a stand alone product you can look at Goldline products, but they are expensive.

http://www.parts-express.com/pe/show...number=390-815
http://www.parts-express.com/pe/show...number=390-805

So, if you have a laptop with REW, that may be the better choice IMO. The 2nd one above from Goldline is an incredible piece, but you can buy a laptop, calibrated ECM8000, and outboard sound card with phantom voltage for less then the Goldline unit.

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post #84 of 366 Old 07-23-09, 10:12 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Quote:
When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately
The calibration comes in the form of a calibration file in easily read text form.

Quote:
Maybe I've overlooked something here, but from what I've read the ECM8000 has a wider frequency range (15 Hz to 20 kHz) than the Galaxy CM-140 (31.5Hz to 8KHz), so why would you want to use the Galaxy to do room measurements beyond typical SPL readings?
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).

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post #85 of 366 Old 07-23-09, 03:04 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Quote:
brucek wrote: View Post
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).
Oops, typo there, it would show -10dB, the cal file contains the actual response of the mic/meter.
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post #86 of 366 Old 07-23-09, 05:36 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

First of all, thanks for all the replies here from other members, your input has been very helpful.


Ray,

I checked out that TENMA meter.

http://www.mcmelectronics.com/produc...72-945-/72-945

All the specs are very similar to the Galaxy meter and actually comes with some nice extras like a hard carrying case, AC adapter, and a USB cable. It seems like the USB connection might actually make connecting it to a computer a little easier. Have you ever used it as a test mic in the REW application?

For all,

Going back to my question about the calibration... I now understand that a cal file is included to show the frequency deviations to adjust inside REW, but I was also hoping to know if the SPL meter calibration can be done for the SPL measurement itself, much like what the Galaxy CM-C200 is used for, to calibrate it at 94 dB and 114 dB.

http://www.galaxyaudio.com/CMC200.jsp

The SPL level calibration device would be nice to have, but it's about $180-$250 on it's own, depending on where you look. I think it would be really handy to have something that could function as a calibrated, standalone SPL meter as well as being able to use it with REW or other programs.
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post #87 of 366 Old 07-23-09, 06:53 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Dan,

Tenma also makes an expensive calibrated model:

http://www.mcmelectronics.com/produc...635C-/72-6635C

This is more comparable to the Galaxy version, but the model you are looking at is just fine (there is another version of the one you are looking at for a bit more money that can do data logging:

http://www.mcmelectronics.com/produc...72-947-/72-947

None of them IMO is a flat as using an ECM8000 (calibrated), which is what I use for REW, but it really should be fine if you can get a cal file for it and take that into account as mentioned above.

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post #88 of 366 Old 07-24-09, 12:35 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Quote:
VintageGold wrote: View Post
When an SPL meter like the Galaxy CM-140 or RS unit is calibrated, does the calibration process simply provide a cal file like what's used for the ECM8000 or is it actually being calibrated so it, as a standalone instrument, measures dB's more accurately, like what you would use one of these for:

http://www.galaxyaudio.com/CMC200.jsp
brucek addressed the rest of your post, but I just wanted to mention that I can do either/both types of calibration (frequency response correction curves and level/sensitivity adjustments) for SLMs with 1/2-inch type microphones.
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post #89 of 366 Old 07-28-09, 04:00 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Hi All,

Just a friendly reminder that prices will change starting on Saturday, Aug 1. If you want measurements at extra angles without paying extra, speak now or forever hold your piece.

That said, I will let slip that it won't be a total loss for HS readers if you miss the deadline. Stay tuned...
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post #90 of 366 Old 07-28-09, 04:09 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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...
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