Spl meter and more....

[DanDan]

I have compared UMIKs plus their individual Cal File here against a Bruel & Kjaer 2250 internal Mic. They were remarkably close. A blurred memory but on another forum some time ago some of us managed to sort of remotely compare these versus another product plus Cal File. The UMIK +Cal File seemed to have way better FR flatness. I think the spark thing may be just absolute Level Cal. Speaking of which, both UMIKs were 1.8dB off absolute 94dB, when measured with a B&K Calibrator.
The iPhone apps are great for Noise Work. It is not exactly cool to wander around a nightclub in full swing with a megabuck SLM, or a neighbourhood. Using a PMik ups the game, particularly if the app allows Calibration against a known source.
There is a German company who are selling what appears to be an intermediate grade of mic, much cheaper than the DPA, Earthworks, etc. http://www.isemcon.net/ashop/
DD

 

[Matthew J Poes]

I have compared UMIKs plus their individual Cal File here against a Bruel & Kjaer 2250 internal Mic. They were remarkably close. A blurred memory but on another forum some time ago some of us managed to sort of remotely compare these versus another product plus Cal File. The UMIK +Cal File seemed to have way better FR flatness. I think the spark thing may be just absolute Level Cal. Speaking of which, both UMIKs were 1.8dB off absolute 94dB, when measured with a B&K Calibrator.
The iPhone apps are great for Noise Work. It is not exactly cool to wander around a nightclub in full swing with a megabuck SLM, or a neighbourhood. Using a PMik ups the game, particularly if the app allows Calibration against a known source.
There is a German company who are selling what appears to be an intermediate grade of mic, much cheaper than the DPA, Earthworks, etc. http://www.isemcon.net/ashop/
DD

How did you get the Umik to fit in your calibrator?

Others have found it to be a little small. The Dayton usb mic is way too small. You have to use some material to build it up. I used a small piece of rubber and some Teflon tube I had. It made what seemed like a tight fit and changed the results. I was able to later confirm this was working pretty close for calibration once I had the 1/2” mic either a proper iec capsule. I no longer recall the SPL accuracy but remember it was close.

For a good cheap mic, I think the best intermediate grade mic is this:
http://www.mic-w.com/pro.php?id=13

It’s a Chinese made measurement mic using P48. It’s a consumer division of a lab mic manufacturer. I have one that I received with a NIST certification of the response. It’s flat well past 20khz and correctable out to 34khz. Self noise is low enough that mic preamps are noticeably a weak point. It takes any standard 1/2” IEC capsule that is pre-polarized.

BSWA is who makes these mics and capsules. I now have a second capsule from BSWA with serialized calibration file from the US dealer. It’s slightly quieter with lower bass extension.

They don’t say this but having talked to the folks at the US dealer, who sell better name brands, these are direct copies of a well known German capsule and look nearly identical. The price is about 1/4th the other brands and the quality is very good.

Since I had access to an Earthworks M20 for direct comparison, they are similar in accuracy. The MicW is significantly quieter for about the same price. However because it’s a 1/2” capsule it is more directional at high frequencies.

 

[DanDan]

Very interesting. I had seen those little i Mics advertised around here, but not the bigger ones.
You are right, most of the common mics used for measurement are smaller than standard. The PMik is bigger and that is what I used the Calibrator for.
Testing the UMIKs was done by comparison. Pink Noise. Two I tested were both 1.8dB different to the B&K SLM. Oddly, both exactly 1.8dB. I can remember if it was up or down, and I found it possible to get complete agreement by simply rewriting the Cal File first line.

 

[Matthew J Poes]

Very interesting. I had seen those little i Mics advertised around here, but not the bigger ones.
You are right, most of the common mics used for measurement are smaller than standard. The PMik is bigger and that is what I used the Calibrator for.
Testing the UMIKs was done by comparison. Pink Noise. Two I tested were both 1.8dB different to the B&K SLM. Oddly, both exactly 1.8dB. I can remember if it was up or down, and I found it possible to get complete agreement by simply rewriting the Cal File first line.
DD

Thats how I fixed the Dayton. I did enlarge the head with material, but I also did exactly as you did using 3 different "known to be accurate" mics and a calibrator, then using pink noise as well as pure tones. I had thought that if one of the mics response wasn't accurate in this little test, a pure tone at 1khz, 500hz, and 5khz, for example, might also give me a good sense.

 

[Kerry Armes]

I know this is an old thread but I will add my two cents about the OmniMic. The factory calibration file is rubbish. I had mine calibrated by Cross Spectrum Labs and the two curves are not even close. I do like the OmniMic for it's simplicity and how easy it is to get setup to take measurements. For crossover design design, absolute SPL accuracy is of way less importance than relative SPL accuracy, so OminMic after calibration becomes accurate enough to do crossover design but isn't the most accurate for say, taking precision measurements for 1 meter 2.83 volt infinite baffle or doing some of the types of subwoofer testing Matt does.