Cross-Spectrum Microphone Calibration Service - USA - Page 20 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #191 of 368 Old 07-09-12, 05:18 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

I would like to upgrade my current RS mic and built in PC audio for a USB external with a Calibrated EMM-6 from Herb.

I am using an IB for sub and would like to be capable of messuring down to 5hz hopefully. Does someone have a recomendation for an external (USB) sound device with a midi interface if at all possible which can handle down that low? OS is Windows 7 or Linux.

Thank you....
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post #192 of 368 Old 07-10-12, 10:54 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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Ngtybear wrote: View Post
I am using an IB for sub and would like to be capable of messuring down to 5hz hopefully. Does someone have a recomendation for an external (USB) sound device with a midi interface if at all possible which can handle down that low? OS is Windows 7 or Linux.
Tascam US-122/144mkII are popular, have MIDI, and quite flat--look to be down about 3dB at 5 Hz. I may finally buy one as there is a $10 rebate at most music retailers at the moment (and I'm employed which I was not when I started using REW, LOL). You can find the calibration curve for this interface right here.
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post #193 of 368 Old 08-29-12, 12:42 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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JimP wrote: View Post
Is it possible to get the omnimic run through your calibration process and provide a correction file????
Hi Jimp did you get the Omnimic re-calibrated?

Which version do you own?
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post #194 of 368 Old 08-29-12, 09:23 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

No, I didn't.
Got sidetracked with changing out my display and calibrating video.
Not sure If I'll get the Omnimic recalibrated as I was only planning to use it on REW. I can use it on the omnimic software and import the settings which gets me there...I think.
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post #195 of 368 Old 08-29-12, 02:50 PM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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JimP wrote: View Post
No, I didn't.
Got sidetracked with changing out my display and calibrating video.
Not sure If I'll get the Omnimic recalibrated as I was only planning to use it on REW. I can use it on the omnimic software and import the settings which gets me there...I think.

Thanks Jimp

Did you have any feedback (after) from Cross-Spectrum about being able to calibrate your mic?

Which version Mic do you have?
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post #196 of 368 Old 08-30-12, 01:30 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Hey, great forum. Thanks for sharing. Now for my first post: I am curious if someone could speak to the sensitivity of the Dayton microphone, I am hoping to do some very low-noise measurements and wanted to see if there was a suitable mic that wouldn't break the bank. I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?

Also, I was looking at using the Motu 4Pre as my Mic -> USB solution. Any users care to comment?

Really like fooling around with REW; thanks for that! I hope to learn more in the coming months.

Thanks!

EDIT: can REW do simultaneous multi-mic RTA? The Motu 4pre has 4 mic inputs...would be nice.

Last edited by roognation; 08-30-12 at 01:32 AM. Reason: Additional question
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post #197 of 368 Old 08-30-12, 02:16 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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roognation wrote: View Post
I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?
Yeah, you're not going to get a 20 dB noise floor without spending some serious coin. The noise floor on Dayton mics range from 30 to 35 dBA (note the "A") and maybe 40-45 dB. Behringer mics range from around 35 to 40 dBA, perhaps 45-50 dB linear.

To put this in perspective, my quietest ANSI/IEC class 1 mics (1/2-inch BSWA MP201 & PCB 308B02) have noise floors around 15 dBA, 20 dB linear. To get much lower than that on a measurement mic, expect to pay well over $1,000 for a 1-inch B&K/Gras/etc capsule + pre-amp and power supply.
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post #198 of 368 Old 08-30-12, 05:49 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

Hi
Has anyone had their Omnimic re-calibrated, is it possible?
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post #199 of 368 Old 08-30-12, 08:30 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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roognation wrote: View Post
I am hoping to do some very low-noise measurements and wanted to see if there was a suitable mic that wouldn't break the bank. I was hoping to get in to the 20 dBSPL range, but not sure if that is realistic. Anyone care to comment?
I asked similar questions in this thread and didn't get any great answers. However I've just done a bit more searching and perhaps can be a bit more specific than anechoic was above.

Earthworks (least expensive model M23 ~$450) is spec'd at 22 dBA self noise.
DPA 4006A is spec'd at 15dBA typical 17 dBA max (though they also list 27-29 dB per ITU-R .468-4, I'm not sure what that means at the moment)-this is a $1925 mic. (!)
B&K 4955 is spec'd at <6.5dBA self-noise, but their (and, it appears, THE) ultimate setup is 4179+2660pre, the 2179 is spec'd for -5.5dBA. But this stuff isn't available at retail so is probably "If you have to ask, you can't afford it" sort of pricing.
The GRAS that anechoic mentioned is here. I haven't looked at it in any detail.
ACO stuff looks to be here and here, I again haven't reviewed it or looked for pricing (would be glad to see it if you look into it).
Looks like you can get the "SoundFirst SF101a" from http://www.testmic.com/ at 13dBA for $890, they say the SF111a should be ~10dBA for $1415. Also interesting what that site says of their Josephson mic: "This is the mic that many manufacturers copied the body from, but not the performance." It does indeed look much like the Behringer and Dayton mics most of us 'round here use.
I also found LinearX M53 for $350 at 18 dBA.
There's also some stuff from Scantek that I haven't looked at much.

So predictably the costs appear to be pretty well exponentially increasing the lower the desired noise floor beyond an "average" level.

There was also some discussion of preamp noise levels there, however it looks to me that they are all rated in dBFS so as long as you don't have a lot of dynamic range in the measurement I'm guessing reducing the input gain will mitigate that problem.
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post #200 of 368 Old 08-30-12, 10:22 AM
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Re: Cross-Spectrum Microphone Calibration Service - USA

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aackthpt wrote: View Post
DPA 4006A is spec'd at 15dBA typical 17 dBA max (though they also list 27-29 dB per ITU-R .468-4, I'm not sure what that means at the moment)-this is a $1925 mic. (!)
ITU-R .468 is another frequency weighting curve, similar to A-weighting.

Quote:
B&K 4955 is spec'd at <6.5dBA self-noise, but their (and, it appears, THE) ultimate setup is 4179+2660pre, the 2179 is spec'd for -5.5dBA. But this stuff isn't available at retail so is probably "If you have to ask, you can't afford it" sort of pricing.
Yep. My old firm has that setup, it's used for measuring noise levels at very remote locations where there are no man-made noise sources for dozens of miles. I don't remember the pricing, but I'm guessing it's at least in the $2,500 range. It was only used for very special occasions .

Quote:
ACO stuff looks to be here and here, I again haven't reviewed it or looked for pricing (would be glad to see it if you look into it).
I have the ACO Pacific price list, current as of last winter, if someone has a specific question, let me know. I own the 7052, the noise floor for my capsule is in the low 20's, which is typical for a Type 2 mic.

There's also the used-equipment inventory at Modal Shop.

Quote:
I also found LinearX M53 for $350 at 18 dBA.
That's a really good price if that spec actually holds up.

Quote:
There's also some stuff from Scantek that I haven't looked at much.
That's where I got my BSWA MP201 from, the 1/2 inch Class 1 mics will all have noise floors in the 15-17 dBA range. They also off Class 0 mics that probably have lower noise floors (probably not lower than around 8 dBA though), but you don't want to know that pricing.

Quote:
There was also some discussion of preamp noise levels there, however it looks to me that they are all rated in dBFS so as long as you don't have a lot of dynamic range in the measurement I'm guessing reducing the input gain will mitigate that problem.
With regard to IEC/ANSI-rated equipment, the mic usually determines the noise floor moreso than the pre-amp unless the mic floor is really quiet (~5 dBA or lower).

Also remember that the noise floor of the mic will have to be at least 8 to 10 dB lower than the noise level to be measured, so to measure noise levels at 20 dBA, the mic will need a noise floor of 8 to 10 dBA.
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