Don't have an answer on XLR mics but just some interesting asides. We make product noise measurements with a $5k Quest (3M) SPL meter. It had a B&K electret cartridge. I use the word "had" because somebody dropped it (not me) and completely destroyed it. Actually bent the mic housing. We weren't willing to spend the $1k+ that B&K wanted for a new one, so it sat for years. I decided to take a chance on a similar cartridge from these people- https://cnaihua.en.alibaba.com/mini...12bHt93kR&from=detail&productId=1600734634707 It turned out to be 1/10 the price and performs just as well. I also bought an iSV1611 USB mic from them. We mostly retired the SPL meter and use the USB mic for everything now. For my home stuff I found and refurbed a General Radio Reciprocity Calibrator- https://www.conradhoffman.com/GR1559B.htm That's geared towards the GR piezo-ceramic mics. They actually have very good response and were made as measurement mics. They're common on eBay, but I wouldn't trust one without extensive testing. Many have lost sensitivity or are damaged in other ways. OTOH, they don't usually cost too much. Hint- you can buy a completely obsolete GR SPL meter that has one and just throw away the meter. Something like a model 1551C that you can't get batteries for anymore is a good candidate. The piezo mics have a healthy output signal that's easy to amplify. FWIW, I used to like building speakers. The flattest speaker I ever built was also the worst sounding!
I did a bit more reading:
Apparently the problem with electret’s (regardless of mic’s class 1 or 2 marketing) is not related to freq. deviation with respect to environmental issues,
-instead electret’s can have a problem with loss in sensitivity (broad-band) from dew-point/condensation issues. Condensation lowers the surface charge and reduces overall sensitivity.
Notably this often happens from a rapid change in temperature (pulling out of storage from a colder room) with moderate to high humidity, which could be localized (like simply breathing close to the mic.).
So if using an electret-based mic., keep it at roughly the same temperature for storage as in-use and avoid using it in very high humidity or even breathing very close to it.
-even then though, this is really about mic. sensitivity lowering and causing an incorrect Spl-reading: critical for Spl-meters, but not so much for loudspeaker design (as a practical matter).
Thanks for this Michael. Google Chrome did a very good translation to English. What this tells us is
- ISEMcon use a good and quite consistent capsule for EMX-7150
- IMG ECM-40 use a transformer like some early versions of Behringer ECM8000
- EMX-7150 is good for THD at high levels too
- Most importantly, both companies do good calibration which can be relied on
Well, everything else? I measured the on-axis 1 meter response and got it near perfect. No doubt there were baffle step issues, phase issues and off axis issues. I also don't think flat high frequency response is pleasant. I don't think you'd actually like live music in your living room long term. Some roll-off is gentler on the ears. There are just a lot of factors in building a good speaker, which I eventually managed to do.So, if it was actually 'flat',
what do you think made it sound so bad
Don't worry about that Conrad. ALL serious speaker designers have this experience when they start.
When you first have the means to measure Frequency Response, you are all excited cos the best speaker in the world must result
Then you spend the rest of your life finding out why this isn't so
The best conventional speakers DO have 'flat' on-axis response but they have loadsa other good stuff, hand carved from solid Unobtainium & BS by Virgins too.
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My experience doesn't quite tally with "no frequency response changes". But I certainly agree with your recommendations for storage and use.
Sadly, in Cooktown, Oz, just hit by Cyclone Jasper this week, this is not practical
Well short term there might be a freq. response change with humidity as the moisture interacts with different areas of the diaphragm, after drying though it shouldn’t unless enough dust was deposited on the diaphragm during that moisture build up.
-of course this would to some extent be true for any microphone (including dynamic mic’s).
This isn’t the same as a long-term loss in Sensetivity due to a loss in surface charge for those mic’s (electret’s) that don’t need a separate power source (battery or wall-power) for creating/maintaing the charge (as you would find scaled-up with an electrostatic loudspeaker).
When an electret mic. like Earthworks M23R states in the manual (needs calibration about every 5 years), it’s that charge that (potentially) needs refreshing.
-of course this would to some extent be true for any microphone (including dynamic mic’s).
This isn’t the same as a long-term loss in Sensetivity due to a loss in surface charge for those mic’s (electret’s) that don’t need a separate power source (battery or wall-power) for creating/maintaing the charge (as you would find scaled-up with an electrostatic loudspeaker).
When an electret mic. like Earthworks M23R states in the manual (needs calibration about every 5 years), it’s that charge that (potentially) needs refreshing.
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This is just from reading multiple articles and posts by others. I haven’t experienced either *problem (that I know of), even though my interior environment approaches 70% humidity on some days along with 40 degree changes long-term.
I keep my mic’s in their boxes and every time I’ve pulled them out the temperature “swing” has been negligible from storage to use. Also, they are rarely used.
*the Radio Shack Spl meter definitely did loose sensitivity over time, and it didn’t have its own case.
I keep my mic’s in their boxes and every time I’ve pulled them out the temperature “swing” has been negligible from storage to use. Also, they are rarely used.
*the Radio Shack Spl meter definitely did loose sensitivity over time, and it didn’t have its own case.
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Here are a couple of plots that may be interesting. The source loudspeaker was an SB Acoustics D19ST-C000-4, flush mounted to a large baffle, driven full range. The front tip of the microphones under test were placed at the same location, within about 1mm. No cal files were applied in any of the plots and no eq was appled to the D19.
This first plot shows my Earthworks M23 in green, my Clio mic in red and two WM61 mic capsules mounted in long brass tubes. The Panasonic mic capsules differ in age by some 20 years. The yellow one is the newer of the two. I bought a packet of "NOS" WM61s off Fleabay, and their performance was way off. They looked quite different to the original capsules too.
This plot shows my M23 and a MicW M215. Note that this trace is 2dB/
This first plot shows my Earthworks M23 in green, my Clio mic in red and two WM61 mic capsules mounted in long brass tubes. The Panasonic mic capsules differ in age by some 20 years. The yellow one is the newer of the two. I bought a packet of "NOS" WM61s off Fleabay, and their performance was way off. They looked quite different to the original capsules too.
This plot shows my M23 and a MicW M215. Note that this trace is 2dB/
I find the above plots of a
Was this measured > indoors, outdoors or anechoic ?
almost too flat to believe. (4" driver ?) It must be exceptional !
Was this measured > indoors, outdoors or anechoic ?
That was one of my takeaways from this session. This little tweeter is really good, especially for its $25 price!
That said, I did look at the published curves for all the tweeters I had and selected the flattest one. This test also shows the benefit of a large baffle, in this case 1000mm x 1200mm. Measured indoors. The first reflection was gated out.
That said, I did look at the published curves for all the tweeters I had and selected the flattest one. This test also shows the benefit of a large baffle, in this case 1000mm x 1200mm. Measured indoors. The first reflection was gated out.
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I have used these WM6x mic capsules as well.
I actually milled and turned a whole aluminium microphone for one, many many years ago
(the top one)
The main issue is not if they perform well on paper, or from measurements from a few.
The main issue, is that beforehand you just don't know how they will perform.
The particulars ones someone might have might be all great, or maybe not.
Or in fancy words, we just don't have any clue about the (standard) deviation.
Fact is that after you made a nice mic, you still have to get it calibrated.
Since you have no clue how it performs.
Btw, with my own diy microphone experiment, I actually discovered that the generic (cheap) microphone shape doesn't make much sense.
A part of the 8-20kHz hump is mostly because of the baffelstep of the tube where the capsule is mounted.
One of the reason I made mine as thin as possible and much longer.
I could very clearly measure the difference with the same capsule.
In a good design they compensate for that already.
