I used to work briefly in the field of acoustics, but never heard of this.
What they do, is calibrate SPL before and after each job as well get the microphones calibrated after a couple of years (can't remember how many).
So stability isn't really in an issue.
Actually, I have never seen any major stability issues with just even the cheap measurement microphones.
The Indian Standard IS 15575 (Part 1) is allegedly lifted directly from IEC 61672-1 and is more readily available.
A non-scientific and anecdotal data point on cheap microphone stability: I did a test on a Radio Shack SPL meter this summer, letting it sit in my basement at 62 degrees F then in my 80+ degree F shop. I got something over a 0.5dB change in sensitivity. Obviously that's not a big change, and if you calibrate before each measurement it's not a big deal, but it makes me wonder what repeated temperature cycles would do to the capsule.
I wouldn’t put much faith in that, the capsules in the Radio Shack SPL meters are absolute garbage (it was a $30 SPL meter that should have been $15 but didn’t really have any competition during most of its sales-life.)
I still have at least one collecting dust somewhere in my home.
Nice bit of info. on the IS vs IEC.
I still have at least one collecting dust somewhere in my home.
Nice bit of info. on the IS vs IEC.
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The real 'measure' of a measurement mike is its calibration. I used to design the beasts and say, "A good measurement mike's calibration tells you how bad it is. A crap measurement mike's calibration tells you how good it is".
There are some good inexpensive calibration houses out there but also a couple of real cowboys which I won't call out in public.
One inexpensive measurement mike whose calibration I trust, is that supplied with Clio .. but its not XLR P48
Hebden Mikes used to make one of mine but I'm not sure it is still available.
The Panasonic WM61 was good cos it was probably the most consistent and flat of the small 6mm electrets. Early Behringer ECM8000 were useful without a calibration curve cos they used this. Alas, they switched to a lesser capsule to save perhaps $0.05 and I wouldn't use a modern one without calibration today.
In Cooktown, Oz, 100% RH & 30+C for many months, you probably want re-calibration every 12 mths. But a nicely kept mike in Oxford, UK may hold its calibration, sensitivity & response, to 0.2dB for 5 yrs. This is real experience & data on electrets.
To put this into perspective, our UK factory used about a dozen B&K 4133/4s which were calibrated annually. In 20+ yrs, I never saw a >0.2dB change in response unless there was obvious damage.
There are some good inexpensive calibration houses out there but also a couple of real cowboys which I won't call out in public.
One inexpensive measurement mike whose calibration I trust, is that supplied with Clio .. but its not XLR P48
Hebden Mikes used to make one of mine but I'm not sure it is still available.
The Panasonic WM61 was good cos it was probably the most consistent and flat of the small 6mm electrets. Early Behringer ECM8000 were useful without a calibration curve cos they used this. Alas, they switched to a lesser capsule to save perhaps $0.05 and I wouldn't use a modern one without calibration today.
In Cooktown, Oz, 100% RH & 30+C for many months, you probably want re-calibration every 12 mths. But a nicely kept mike in Oxford, UK may hold its calibration, sensitivity & response, to 0.2dB for 5 yrs. This is real experience & data on electrets.
To put this into perspective, our UK factory used about a dozen B&K 4133/4s which were calibrated annually. In 20+ yrs, I never saw a >0.2dB change in response unless there was obvious damage.
Where is your *.CAL file from?
In general, the smaller the capsule, the flatter it will be at HF. I used to say it was impossible to make 6mm capsules with poor HF but recent experience says I was wrong.
AOM-5024 makes a good music recording mike but will be wonkier than the 6mm capsules for measurement.
A 6mm electret omni with the consistency of WM61 has yet to emerge but Henry Spragen suggests a JLI replacement is promising
audioimprov.com/AudioImprov/Mics/Entries/2017/12/13_A_Simple_Reference_Mic.html
Now you really make me want a good mike calibration device!
Aah, i think that explains the big difference i saw in a pair of ECM8000's i bought back around year 2000, versus three i bought last year.
The old ones seemed relatively good without cal files, compared to my EMX-7150.
New ones, not so much..
Ok, in that case I would recommend the MicW M215, about $550 NZ.
It's what I chose when it was my own money and I wanted a better mic.
Just an FYI, several people have mentioned the Brüel & Kjær (usually abbreviated to B&K to avoid the awkward Unicode characters)
They are the traditional benchmark for measurement mics but don't actually meet your criteria, they have no XLR / Phantom powered measurement mics.
Hence my recommendation of the Microtech Gefell, they are practically the only choice for B&K comparable stability in XLR.
So if you do luck onto that other mythic find, a reasonably priced B&K, then you should send it to me to take care of.
Best wishes
David
DPA are the 'music' branch of B&K and are XLR P48V. There's a couple of DPA mikes which will take B&K 1/2" capsules. The calibration curves are supplied with the capsules. $$$ of course
I like 6mm electrets (like WM61S) but mounted in 1/2" tubes cos I have loadsa experience with 1/2" B&K mikes and 'know' what they do off-axis.
Send it to me at Cooktown Recording and Ambisonic Productions to check its calibration first and I'll send it on to DaveSo if you do luck onto that other mythic find, a reasonably priced B&K, then you should send it to me to take care of.
Hi Richard
DPA are the 'music' branch of B&K and are XLR P48V. There's a couple of DPA mikes which will take B&K 1/2" capsules. The calibration curves are supplied with the capsules. $$$ of course
Yeah, I know about DPA but their bodies don't take the best (that is, most stable) measurement microphone capsules, only the second tier electret capsules.
Still perfectly adequate for DIY measurements of course, just not what the OP asked.
And they are still really expensive, top dollar for second tier is not an attractive option.
Best wishes
David
How did the cyclone affect you? I assume that since you can post it can't be too bad, but all fine?
DPA are the 'music' branch of B&K and are XLR P48V. There's a couple of DPA mikes which will take B&K 1/2" capsules. The calibration curves are supplied with the capsules. $$$ of course
Yeah, I know about DPA but their bodies don't take the best (that is, most stable) measurement microphone capsules, only the second tier electret capsules.
Still perfectly adequate for DIY measurements of course, just not what the OP asked.
And they are still really expensive, top dollar for second tier is not an attractive option.
Best wishes
David
How did the cyclone affect you? I assume that since you can post it can't be too bad, but all fine?
I don't remember where I got it, but it's from the internet. Maybe someone just digitised the curve in the datasheet.
I'd say beware, for that looks like it has been copied and pasted from one of PUI's sheets. The drawings and figures are just the same, except that the Chinese "FREQUNENCY" response is something much flatter, possibly done with the intention of tapping into the market that once belonged to Panasonic.
And what is 'Ordinary temperature / humidity / air pressure anyway ?
Sorry Sir, but that's a lot of red flags .....
Many years ago when I owned a DBX 2020 automated 1 octave equalizer,
its test mic. was a simple little plastic electret. Its inside unit calibration was
performed by a '14pin IC looking device' with 4 micro-pots being simple four band EQ.
I can only assume that the highest region EQ would have been very narrow band.
its test mic. was a simple little plastic electret. Its inside unit calibration was
performed by a '14pin IC looking device' with 4 micro-pots being simple four band EQ.
I can only assume that the highest region EQ would have been very narrow band.
I didn't say this was THE ONE. Only that Henry thought it looked promising. For a complete picture, loadsa other gurus need to have compared this with their 'measurement' mikes. WM61A's reputation was built up over years.
We DO know that the present ECM8000 capsule isn't it.
I would like to know what Earthworks use unless they have the World's last remaining stash of WM61As .... Oops! Shouldn't have said that! Us small mike makers need to stick together and keep da Voodoo from da unwashed masses.
(For others)
That’s from 6.3.3 (temp.) and 6.4 (humidity/dewpoint) pg. 26:
https://law.resource.org/pub/in/bis/S04/is.15575.1.2005.pdf
+/- .5db difference between class 1 & 2, and even then under * unknown and likely harsh environmental conditions typically mitigated by testing indoors.
I find that to be nearly useless.
Microphones pedaling marketability based on “class 1” vs “class 2” in and of itself with respect to environmental deviation (as opposed to simply general deviations in linearity) for indoor testing with loudspeakers - are no longer something I will concern myself with. (..maybe outdoor and humidity/dewpoint though - in those use-cases.)
*you don’t really know at one point (temp. or humidity/dewpoint) there will start to be any deviation, moreover you don’t even know if there will be a difference between class 1 & 2 - for any mic..
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I won't go into my opinion of Class 1 vs 2 but if I was making mikes commercially again, I would get into bed with Primo or Transound and help improve their ELECTRETS.
IN PRACTICE, modern electrets are MUCH more reliable and consistent compared to capsules that need a polarizing voltage. B&K and SHURE led the way in the early 80s and I was jealous cos there was no way Calrec could afford the technology.
IN PRACTICE, modern electrets are MUCH more reliable and consistent compared to capsules that need a polarizing voltage. B&K and SHURE led the way in the early 80s and I was jealous cos there was no way Calrec could afford the technology.
Another route worth checking, if the price of s/h B&K 4133 or 4191 capsules is sensible, is making your own bodies & preamps. Make sure the capsule comes in the little wooden box, the calibration curve is included and the capsule looks undamaged.
But I gotta say the thread on those capsules is very fine. The main 'reference' at Calrec was a 4133 with our own electronics. But we persuaded B&K to sell us their own housing/body with the thread. As Clem Beaumont, my mike mentor, was a clock and watch maker in his spare time, this sames something about the difficulty of cutting that thread.
We wanted our own electronics cos we sometimes used the mike for recording and ours was nearly 10dB quieter.
But I gotta say the thread on those capsules is very fine. The main 'reference' at Calrec was a 4133 with our own electronics. But we persuaded B&K to sell us their own housing/body with the thread. As Clem Beaumont, my mike mentor, was a clock and watch maker in his spare time, this sames something about the difficulty of cutting that thread.
We wanted our own electronics cos we sometimes used the mike for recording and ours was nearly 10dB quieter.
I still have my Panasonic WM61A. It was flat but has a lot of noise at low frequencies.
Ed
I once did a kind of comparative test with a rather cheaper IMG ECM-40 and a somewhat more expensive iSemcon EMX-7150, which might be of interest here. The whole thing is in German, a translation programme may help:
https://www.diy-hifi-forum.eu/forum/showthread.php?21398-Vergleich-ISEMcon-EMX-7150-mit-IMG-ECM-40
Best regards
Michael
https://www.diy-hifi-forum.eu/forum/showthread.php?21398-Vergleich-ISEMcon-EMX-7150-mit-IMG-ECM-40
Best regards
Michael
