Measurement Mic. Diy Help

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Dear, Gurus
I want to diy a precision measuring mic (thr ones that require an electret microphone); I have read a few articles and guides but they are pretty old, and I was just not able to find Panasonic WM61A nor WM61AY nor any of the alternatives. I searched the net but I could not find any new guides. Is the diy electret measuring mic died with that panasonic model going obsolete?
I would really like to make one and ask you of recommending an alternative to the panasonic model or maybe a new guide completely. I could buy from both digikey.in and mouser.in or also from amazon.in and ebay.in.
Thank you.
 

PRR

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Panasonic WM-61A Mic Capsule to be discontinued

> not able to find Panasonic WM61A nor

They can be found, but not from P-Sonic and maybe under another number.

DigiKey lists two alternates from PUI, a long-time mini-mike supplier who probably contracts Asian factories for P-Sonic work-alikes. The $2 model looks good to me. More looking-around would be wise.

This CUI is very flat, though they don't plot below 100Hz.

This eBay vendor is offering JLI mikes with graphs that are very flat for a good price.

Making a small f-l-a-t omni is not rocket science. They have become a commodity, like resistors. The design tends to a bass-droop and a top-ring. Some have more of both for better speech intelligibility. Others let the bass run below 50Hz, and mini-capsules tend to have enough damping to control (not eliminate) the top-ring.
 
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DigiKey lists two alternates from PUI, a long-time mini-mike supplier who probably contracts Asian factories for P-Sonic work-alikes. The $2 model looks good to me. More looking-around would be wise.

This CUI is very flat, though they don't plot below 100Hz.

thank you.

This eBay vendor is offering JLI mikes with graphs that are very flat for a good price.

the shipping is about 20 times the product, could not afford it.

Making a small f-l-a-t omni is not rocket science. They have become a commodity, like resistors. The design tends to a bass-droop and a top-ring. Some have more of both for better speech intelligibility. Others let the bass run below 50Hz, and mini-capsules tend to have enough damping to control (not eliminate) the top-ring.

could you recommend some guides?

And I am sorry for being late almost abandoned the thread. I downloaded a ton of datasheets from mouser.in and after a while after after reading 23 datasheets I found this:

AOM-5024L-HD-R PUI Audio | Mouser India

what do you think? is this good enough? please do reply...
thank you.
 
Just FYI. I recently spoke to a guy deep into this part of the industry (a measurement mic mfg) and he said that the Panasonic mic element was the foundation of most low cost measurement mics on the market and that Panasonic's decision to end production was a huge hit to a lot of OEM's.

He also said that as of this time their isn't a replacement with the sample to sample consistency and reliability that the Panasonic unit had, thus this segment of mic OEM's is still looking for a solution. Many of the better OEM's are now buying larger batches, testing each element and tossing the outliers.

Not a pretty situation, but a DIY'er can buy (10) or so and sort through them with the proper measurement equipment.
 
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However, without a reference how do you select good elements? Things like reciprocity measurements are not really possible with an active electret. To my knowledge no one has made an electrostatic actuator for this type of microphone. it would be interesting to try to make one.

Free field measurements need reference mikes. This is expensive but a good way. However there are a ton of pitfalls in even comparing measurements between microphones if the physics of how they interact with the acoustic fields aren't addressed.

I could see someone setting up a service testing elements and sorting them. But it would be time consuming and not cheap. Is there enough interest to get this off the ground? (I have the essentials but would need to find a high school student with appropriate skills and patience to do it.)
 
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There were people around that would calibrate your diy mic, though I don't remember the details. I know there was one here in Aus, and pretty sure there was someone offering the service in the US, though I can't remember how expensive it was. Now that relatively cheap calibrated mics are available, it may no longer be worthwhile.

If you have a VERY flat mic (like the panasonic WM60AY) then one way to get an idea of how accurate it is (in the higher frequency ranges) is to measure a reputable tweeter and compare to manufactures published curves. If the results are very close (as they were in my case) then you can probably safely use it uncalibrated.

It all depends on what you are trying to achieve. If you mainly want it for crossover modeling, provided it doesn't have any big anomalies in your crossover region you will probably get decent results with an uncalibrated mic, provided you don't put too much empahsis on "correcting" for spl differences in the upper or lower octaves where you may be getting incorrect readings from your mic. You would be better off trusting manufacturers (or simulations in the lower octaves) curves there.

Tony.
 
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Free field measurements need reference mikes. This is expensive but a good way.

I had good luck with the spark discharge method for 500Hz - 20kHz once I found the right literature. For absolute SPL and low frequency response I used a homemade piston chamber and a medical pressure gage ($15) which is calibrated and goes to DC. It was strain gage based and had response out to 3k or so. They sold our mic business before I could cross calibrate.
 
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I too have been looking long for a microphone suitable for my budget DIY stuff, had just a look at Mouser and checked through only a few, especially the brand CUI Inc. seemed to have a few new interesting microphones, some of them are already in stock at Mouser.

CMC-4015-25T CUI | Mouser Europe
CMC-6027-24T CUI | Mouser Europe
CMC-6027-32T CUI | Mouser Europe

Attached PDF's of the 3 above link examples, perhaps someone with better understanding on microphones could comment on these.
 

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Out of those the second one looks the best. The third one I'd rule out completely.

The problem is knowing whether the posted FR curve is representative or not (ie what is the variability sample to sample). If it is then for any normal crossover work in the 300 - 5 Khz range I think it would be fine.

If they have good consistency you may even be able to make a generic calibration file from the posted response curve, however you would really want to try to compare against a measurement with a calibrated mic before trusting it. Of course if you have access to a calibrated mic you could make a proper calibration file :)

I think it would work fine with preamps designed for the panasonic mic's

Tony.
 
Thanks Tony, I guess we have to order a bunch to get an average FR, any voluntaries? :)

Anyhow, when I searched the web for some month ago I came up with another measurement microphone which comes in a "ready" package, the mic is Superlux ECM999
Can be ordered from Thomann and other places for a bit under 40€
Superlux ECM999 - Thomann UK
Have seen these also on AliExpress but at no price advantage.

Seems like the Superlux microphones are originally from Taiwan.
http://www.superlux.com.tw/index.do

ECM999
Superlux - ECM999

Sensitivity: -37dBV/Pa (14mV/Pa) 1Pa=94dB SPL (at 1,000 Hz Open Circuit Voltage)
Rated impedance :200Ω
Minimum load impedance: 3,000Ω (Obs! in the PDF it says min. 1kOhm)
Equivalent noise level: (A-weighted) 22dB
Max. SPL (1 kΩ load) :132dB SPL (THD≦1% 1kHz)
Dynamic range (1 kΩ Load) :106dB
Environmental conditions:
Polarity: Pin 2 output positive voltage (related to pin 3) when diaphragm receives positive pressure. (Diaphragm moving inward)
Connector: 3 pin male XLR type
Finish: solemn black finish
Weight: 150g (5.30 oz.)
Current consumption: 0.5mA
Noise ratio-to-Signal :70 dB
Power supply :9~52 V Phantom
Dimensions :Φ21.0x193.0mm (0.83x7,56n.)
Frequency Response :20~20000Hz

I noticed there's some discrepancies on the frequency response given in various PDF's for ECM999, see attached picture. :(

Another alternative could be ECM888B
Superlux ECM 888 B - Thomann Suomi
Superlux - ECM888B

Somewhere I saw a pretty good mic shootout test where the ECM-999 did quite well, at least for its price, have been surfing the net for a while to find the test again but I just can't find that link right now.
On the other hand, a lot could be saved buying an electret capsule for only couple of €$£ and save the money for a calibration, also the shipping cost for a tiny electret capsule is probably much cheaper, if it has to be shipped by post for calibration.
 

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Some day ago skimmed through eBay for calibrated mic's, just thought I would attach some pictures of an "interesting" case, the asking price was ~700 US$, but as one can see from the calibration graph the mic (Type TL7405) has a 10dB droop from ~2kHz and above, ie. not much better than one of the electret capsule I found earlier, maybe this one has other qualities?
 

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The upper curve is the correct free field response (what you normally do for speakers). The calibration is using an electrostatic actuator which creates the equivalent of a pressure response. The difference is due to the physics of the size and shape of the capsule in free space. The mfr has a specific correction curve for the microphone diameter and the electrostatic coupler based on the physics.

Any microphone disturbs the sound field around it. The B&K mike book has a good description of the phenomena. https://www.bksv.com/media/doc/be1447.pdf Section 2 I think. Lots more than you may want to know.
 
Making a small f-l-a-t omni is not rocket science. They have become a commodity, like resistors. The design tends to a bass-droop and a top-ring. Some have more of both for better speech intelligibility. Others let the bass run below 50Hz, and mini-capsules tend to have enough damping to control (not eliminate) the top-ring.

Could you point me to a tutorial, please.

Just FYI. I recently spoke to a guy deep into this part of the industry (a measurement mic mfg) and he said that the Panasonic mic element was the foundation of most low cost measurement mics on the market and that Panasonic's decision to end production was a huge hit to a lot of OEM's.

He also said that as of this time their isn't a replacement with the sample to sample consistency and reliability that the Panasonic unit had,

Thats sad. I began to look for calibrated mics but the ones that are recommended are in the range of 11K to 28K INR: too high for me because my sole reason at first for diyaudio was cost efficiency.


I too have been looking long for a microphone suitable for my budget DIY stuff, had just a look at Mouser and checked through only a few, especially the brand CUI Inc. seemed to have a few new interesting microphones

please take a look at this too. After about a couple of hundred datasheet download I found this, its really cheap but almost very flat.

CMA-6542PF CUI | Mouser India

NB I am sorry for being very late till last I replied to this thread.
 
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The mike looks good. Decent SNR and supposedly extended bass is unusual. Consistency may be an issue. The sensitivity is listed at +/- 3 dB which is a lot. It means anything that works can ship. I don't think CUI makes them. They are sourced from China.

The best current vendor for mikes would be Primo with the Japanese obsession for quality. Still not all extended for HF or LF.
 
The best current vendor for mikes would be Primo with the Japanese obsession for quality. Still not all extended for HF or LF.

The Primo (?) small omni capsule sold as the Nakamichi CP-3 had an excellent HF response. The CP-1 and CP-2 were definitely Primo products. IIRC EM-21 and EM-23. The consistency is excellent still holding spec after 40yr.
 
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Has no one found a way after the Panasonic WM61A got eol? What do you use guys, you buy branded calibrated mic or find one mic electret close to Panasonic WM61A and diy a mic?
I would also like to ask if there is a way to calibrate with software tools an uncalibrated mic electret?
Thank you
 
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