Tip about the B&K mic numbers, Odds are Free field, Evens are Pressure field.
Strangely, the newer B&K mics don't do this any more.
Interesting concept Dave, I've been down a similar path. Was looking optimistic at 1 degree step rotation but was too time consuming and ended up using larger steps by comparing the polar plots for nearly the same result. Fine & course steps.
Good luck on your project.
That should read steps near the "pole" are smaller than steps near the "equator"
I didn't know the odds/evens tip, thanks.
Why don't mic manufacturers have some sort of rational scheme to identify their capsules?
And why do most have such useless websites?
NTK over at AudioScienceReview has done a lot of simulator trials on this, it's still not entirely clear to me the best scheme
David
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I’m curious how you are going to address the obvious challenge on the mechanical part of the measuring system. That seems more complicated than the normal stepper motor driven turntable and that in two axis.
I realise now that I overlooked the possibility of an option 3.
Use a B&K style pre-polarised capsule and a B&K style classic pre-amp but make up a custom power supply interface to work with standard equipment.
This looks like it should be reasonably simple, - just omit the 200 V polarisation entirely, provide +-15 V to power the pre-amp (maybe battery, skip need for phantom power), convert from proprietary B&K (LEMO) connectors to XLR.
Easy!(?) and there's a fair supply of second hand equipment with this style interface available as people convert to IEPE (AKA CCP, Deltatron or whatever).
I also realise there is an option 4 too.
Use IEPE equipment and convert to XLR.
Anyone tried this?
David
Thanks, I only recently became aware of this but that's what I had in mind in the previous post when I wrote
"there is an option 4 too.
Use IEPE equipment and convert to XLR."
In the end I ordered a MicW M215 measurement microphone after I found a reasonable deal.
About the same price as the iSemcon with the necessary IEPE to P48/XLR conversion included, probably cheaper once the postal cost to Australia is added.
The MicW frequency response extends to >31 kHz which is nice to spot tweeter resonances.
Also the noise floor is lower and the max SPL more.
But best of all, the MicW is Class 1, which is nice even if I don't really need it.
It's a metal capsule like B&K so stability should be better.
That is desirable, just on principle, even if the plastic electrets aren't too bad.
But I am still interested in mic buffer circuitry, in case I ever see a cheap B&K capsule.😉
Best wishes
David
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Is a 1/2 inch omnidirectional enough for the NFS to work properly at higher frequencies? The pressure buildup in front of a 1/2 inch starts at lower frequencies than with a 1/4 inch. But you probably do not intend to measure far above 1k I presume.
MicW seems to be a BSWA brand. Didn’t realize that. Anyway, I won’t hijack this thread anymore with mike suggestions. Hope you’ll post your progression, I appreciate your contributions to this!
MicW seems to be a BSWA brand. Didn’t realize that. Anyway, I won’t hijack this thread anymore with mike suggestions. Hope you’ll post your progression, I appreciate your contributions to this!
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The 1/2" is fine, Klippel recommend a capsule of this size (except Deutsche rather than Chinese)
I intend to measure to 20 kHz but the field separation is only used below 1 kHz, above that it's time windowed.
Yes, I don't know about them myself until recently.
Seems to be so they can keep BSWA as a "premium" brand.
But the MicW 215 looks to have their top of the line tech at a "consumer" price.
On the contrary, I, for my part, appreciate your contribution in return.
When the mic arrives in a few weeks I hope to collaborate with William Cowan to do a comparison with his Earthworks M30.
Any recommendations on how best to do this?
I will post any results, and also plan to post a mock up of the NFS scanner mechanics.
Best wishes
David
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Dave, I've found a ready-made solution to this. The NTI M2010 has an ACO Pacific 7052 metal capsule with XLR input and 48V phantom power. I've verified with NTI that it can be hooked up to a standard USB interface. There is a place in Canada that has hundreds of these and they're selling them on ebay for $255 ea at current exchange rates.
What place in Canada? I checked ebay and Toronto Surplus has a few but not a lot.
Your $255 becomes ~$400 Australian, which is still not bad, if postal fees aren't extortionate.
So thanks for the heads-up
I did eventually collect the MicW clone of a B&K, and had a session with William Cowan to compare it with his Earthworks.
That was useful (and fun, thanks William) to learn the MicW rolls off a little earlier but it follows the calibration quite accurately.
So the roll off can be equalised out, and the stability should be excellent.
Still tempted to buy another mic as a cross check and reference😉
Best wishes
David
Dave,
Toronto surplus is selling them. On the Toronto surplus website it shows they have 245 in stock. I'm guessing they will be there for quite some time!
I ordered two of these over the phone but I don't have them yet. They matched their eBay price (which has been declining due to the strengthening dollar) and they didn't charge sales tax (as eBay does). I also asked for pictures of the diaphragms and they said no problem (see below/attached for these).
NTI also told me they can send the original calibration data from the factory, and that data will likely be valid if the mics haven't been "knocked around." If the two mics do not match with compensation applied I will get one calibrated. That is of course assuming they actually have the data and send it to me!
Like you, I'm thinking it's better to have two stable microphones to cross check. In the past I used a mitey mike, and later a CSL calibrated Dayton EMM6 and an M23. I've never had any issues, except once applying the calibration incorrectly on a big project, which caused huge problems for me. This is one of the reasons I would like the mic to be flat on it's own and require minimal compensation.
I did see your post on the MicW and how you compared it to William's M23. Good to know the MicW's calibration seems good. The MicW 1/2 inch measurement mics seem like a really good deal, I just wish there was more anecdotal information about them. For example I haven't seen any information about whether a compensation file can be obtained. And other than your anecdote I haven't seen any comparisons to other calibrated mics. And of course there are always concerns about stability. My gut says they're good, but only time will tell!
Toronto surplus is selling them. On the Toronto surplus website it shows they have 245 in stock. I'm guessing they will be there for quite some time!
I ordered two of these over the phone but I don't have them yet. They matched their eBay price (which has been declining due to the strengthening dollar) and they didn't charge sales tax (as eBay does). I also asked for pictures of the diaphragms and they said no problem (see below/attached for these).
NTI also told me they can send the original calibration data from the factory, and that data will likely be valid if the mics haven't been "knocked around." If the two mics do not match with compensation applied I will get one calibrated. That is of course assuming they actually have the data and send it to me!
Like you, I'm thinking it's better to have two stable microphones to cross check. In the past I used a mitey mike, and later a CSL calibrated Dayton EMM6 and an M23. I've never had any issues, except once applying the calibration incorrectly on a big project, which caused huge problems for me. This is one of the reasons I would like the mic to be flat on it's own and require minimal compensation.
I did see your post on the MicW and how you compared it to William's M23. Good to know the MicW's calibration seems good. The MicW 1/2 inch measurement mics seem like a really good deal, I just wish there was more anecdotal information about them. For example I haven't seen any information about whether a compensation file can be obtained. And other than your anecdote I haven't seen any comparisons to other calibrated mics. And of course there are always concerns about stability. My gut says they're good, but only time will tell!