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Re: I must be doing something wrong

The cal files for your meter look kosher. Try checking in the REW forum to make sure there isn't something wrong with the software settings.
I tried RS meter with generic calibration and got the same weirdness. This rules out the bad meter theory. I am taking this to the REW forum.

Thank you for all the help
 

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A couple updates to calibrated mic/meter sales:

  • I've started shipping calibration files on 128k USB thumb drives rather than mini-CD's. For those concern about virii that might have been infected the drives at the factories, my script reformats the drive prior to copying over the cal files so that should mitigate the danger.
  • Meter/mic shipments will be backordered for a couple weeks while I send my reference microphone to calibration lab for its biennial NIST-traceable calibration. I have a few mics and 1 meter in stock, but after that it may be a week or so before shipments resume.
  • Also, after careful consideration I've decided to drop the Basic and Premium options and to just sell Basic+ & Premium+ mics. I sell something like 10 Basic mics and 1-2(!) Premium mics per year, so for me the extra options (and having to spend time explaining those options) just isn't worth it.
 

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Hi Anechoic,

I'm interested in the Dayton mic. You mentioned on another page that the Dayton mic was flatter and more reliable than the Behringer. My question is, does it really matter if there are variations between these models if you are going to apply a correction file to correct the response?

So in other words, why spend $200-300 on a mic, when a cheapie, relatively speaking with a correction file can get close or similar results? Just need to understand the need for expensive mics.

All I want is to measure the room, set speaker and subwoofer levels correctly (currently using a Radioshack meter) and I want my measurements to be repeatable, so I need some accuracy. I've never used REW, but I'm almost made up my mind on the Dayton mic (if you could please tell me whether it should or needs to be calibrated) with Tascam US-122 MKII (USB sound card with phantom power).
 

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Hi Anechoic,

I'm interested in the Dayton mic. You mentioned on another page that the Dayton mic was flatter and more reliable than the Behringer. My question is, does it really matter if there are variations between these models if you are going to apply a correction file to correct the response?
In theory it shouldn't matter. However having to make large adjustements (especially at the lower frequencies) may cause distortion problems, so if folks want to minimize and potential problems, they should go with the mics that are flatter out-of-the-box (typically the Daytons, although that's not as true now as it was a few years ago).

So in other words, why spend $200-300 on a mic, when a cheapie, relatively speaking with a correction file can get close or similar results? Just need to understand the need for expensive mics.
Flatter (meaning: more expensive) mics allow you some flexibility, the most important being that you can use it with any analyzer without needing a calibration file. The more expensive mics also have other features such as lower noise floors, higher SPL limits, better insensitivity to temperature & humidity variations, higher sensitivities and so on.
 

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Thanks for answering my question Anechoic. So in your opinion, for measuring frequency response in the room, would you choose the Dayton over the Behringer and would you still have it calibrated, or would you rather rely on a correction file? Just trying to make up my mind which is better for the application.
 

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Thanks for answering my question Anechoic. So in your opinion, for measuring frequency response in the room, would you choose the Dayton over the Behringer and would you still have it calibrated, or would you rather rely on a correction file? Just trying to make up my mind which is better for the application.
(keeping in mind that I'm selling calibrated Daytons and Behringers and it's in my interest to convince you to buy my mics rather than buying them from others)

I would wholeheartedly recommend against buying an uncalibrated Behringer ECM8000. There is too much variability - you never know when you may wind up getting an ECM8000 with a frequency-response like this. Not to mention that a good percentage of ECM8000's have problems out of the box.

The Dayton mics straight from PE come with a 20Hz - 20kHz calibration file. I think my cal files are more accurate, but it you're looking to save some money, the factory cal curve is certainly good enough.

The mics I sell come with 90-degree correction curves and for room measurements I recommending pointing the mic at the ceiling (tilted slightly toward front speakers) and using the 90-degree correction curve. The off-the-shelf Dayton only comes with 0-degree correction curves, which can be useful might might require some experimentation for room acoustics purposes. My calibrations are also performed from 5Hz to 25 kHz, if you care about the lower bass, the factory Dayton curve may not be sufficient.
 

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Thank you for the in-depth reply! I don't require 5 Hz measurements .. and I'm not a speaker designer, just want to measure my room, check before and after and make sure the results are accurate.

I sent you a PM. Thanks.
 

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Thank you for the in-depth reply! I don't require 5 Hz measurements .. and I'm not a speaker designer, just want to measure my room, check before and after and make sure the results are accurate.

I sent you a PM. Thanks.
It may be that the factory Daytons from PE will work for you, especially if you're just making before & after comparisons.
 

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I want to add my thanks and appreciation to the quality service that Cross-Spectrum is providing. I had read some threads a while back discussing the Behringer mics and their use with REW, and the need to have a calibration file. I filed that away for future use and finally got around to ordering one the other day. I provided my HTS user i.d. on the PayPal order. Within a few minutes, Herb emailed me to let me know that the HTS discount doesn't apply to the Behringer's, and asked me whether I wanted to convert the order to a Dayton.

Since I was a little behind the curve in terms of my research, we exchanged some additional emails discussing the relative merits of each. That discussion convinced me that the Dayton was probably better technically, and a better deal financially. Herb changed the order the order as a result. I think that was fantastic.

Thanks for the great service. :T It's something that I greatly appreciate. I would recommend Cross Spectrum's service wholeheartedly.

I'm looking forward to another round of REW measurements and tweaking in the next couple of months. It will be interesting to compare results with the newer more accurate equipment with what I got with the Radio Shack meter.

Rog
 

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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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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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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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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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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.
 

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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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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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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.

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 :).

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.

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

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.

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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