What were the 22mm cardioids?
Nice recording but they sound typical cardioid with LF roll-off. There's a couple of JHRoy's recordings on ambisonia with frogs. Also some by others with severe LF filtering. I did the digital filters for Roy's mike so I know what the LF response is.
ambisonia just moved to a new server and some stuff has been lost especially the DTS decodes
. Many of the files were on torrents cos they were huge.Try Ambisonic Info | John Leonard for helicopters with correct LF.
If you know of cardioids with better LF response than the true 50Hz of Shure SM81, I'm interested. But please don't just quote the maker's spec. I have a very short list on Yahoo MicBuilders in my Ricardo directory.
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If you download the *.amb files and use VVMic to simulate cardioids, you'll hear what a cardioid flat to 25Hz sounds like. TetraMic is flat to 25Hz too. The Mk4 only to 27Hz.
Absolutely not. That helicopter shakes my sofas pretty nice. Capsules were Chinese, from MXL-770 microphones. Electronics was mine, with Tamura transformers oversized for such level, so no rol-off caused by them. I wanted to show you the spectrum picture, but my Audacity under Linux was not compiled with mp3 support, unfortunately. I don't have that original anymore, unfortunately, only compressed file left. And I don't have that prototypes, they live in Boston now. But you can download and check it, I am sure it goes well at least from 10 Hz.
Frogs were recorded by my array with Panasonic capsules. No roll-off as well, just a matrix for figure 8 with flatter rear side. But you hear roll-off there, despite of omni capsules. It was the point I meant.
ambisonia just moved to a new server and some stuff has been lost especially the DTS decodes
Try Ambisonic Info | John Leonard for helicopters with correct LF.
If you know of cardioids with better LF response than the true 50Hz of Shure SM81, I'm interested. But please don't just quote the maker's spec. I have a very short list on Yahoo MicBuilders in my Ricardo directory.
What's so special in Shure SM81? It is rated for up to 20 KHz, so capsule is probably 12 mm only, or even smaller. But I suspect it is quite thin, probably 3 microns, while capsules that I used for helicopter were 6 micron thick, but 22 mm in diameter. I don't have precise acoustic measurement equipment, but judging by comparison with Behringer measurement microphone that I used to calibrate my speakers at home, it was flat at least from 20 Hz. Here is the picture I recorded attached, using this microphone back in 2008, you see roll off at highs caused by the microphone, but lows were pretty flat. I don't see any problem to make a mike that goes below 50 Hz.
We don't have recordings recorded simultaneously with both your mikes and mine so all we can do is compare similar recordings. Why don't you try John Leonard's helicopters and tell us which one you think is closest to what you recorded?
If you are simulating fig-8s with pairs of omnis you will have severe LF roll-off.
The SM81 is one of 2 cardioids you can buy today with flat response to 50Hz in free-field conditions. It one of the 2 most extended cardioids you can buy.
If you get to compare your mikes with your SM81, I would really appreciate your comments on the difference in bass response.
What size FFT block are you using with ARTA? Are you windowing? What distance was the source you used to you measure the mikes? What source?
A cardioid -3dB @ 50Hz in free-field will measure flat to 20Hz at 1m from a 'point' source. Most (all?) 'measurements' of cardioids flat to 20Hz are done by the Marketing VP.
There is a discussion of this on the DPA site. A cardioid flat to below 50Hz will show a substantial rise at LF.
Maybe not for omnis .. but I seem to be the only one to do this for fig-8s & cardioids
On a more serious note, there is an excellent PDF book on the Neumann website which is the only accurate and useful book on mike design I've come across. It explains some of the 'problems'.
Also, from your measurement of SM81, you might want to have your ECM8000 calibrated at HF but be careful who you ask to do this.
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Helicopter Recording Spectrums
Not that it means anything ... different helicopters, different flight patterns etc but here are the spectrums of Wave's & John's helicopters analysed as requested.
23s just before the overload on Wave's
21s around the max. level on John's cos his is 48kHz fs
Vert. scale is 50dB. Horizontal scale 10Hz - 20kHz ie B&K 2307 bogroll
Hanning windowing (smoothing)
I've matched levels @ 1kHz but one could argue I should match between 100Hz & 500Hz as I expect both mikes to be sorta flat in that region and there's a lot of helicopter noise there.
If anyone has made direct comparisons of any cardioid with SM81, I'm interested in those that sound more extended. And even more interested if you've made simultaneous recordings that demonstrate this.
Not that it means anything ... different helicopters, different flight patterns etc but here are the spectrums of Wave's & John's helicopters analysed as requested.
23s just before the overload on Wave's
21s around the max. level on John's cos his is 48kHz fs
Vert. scale is 50dB. Horizontal scale 10Hz - 20kHz ie B&K 2307 bogroll
Hanning windowing (smoothing)
I've matched levels @ 1kHz but one could argue I should match between 100Hz & 500Hz as I expect both mikes to be sorta flat in that region and there's a lot of helicopter noise there.
If anyone has made direct comparisons of any cardioid with SM81, I'm interested in those that sound more extended. And even more interested if you've made simultaneous recordings that demonstrate this.
Attachments
Looks like there were different helicopters, but never the less Chinese copy of Neuman capsule goes well on 30 Hz.
I designed that mic and build couple of prototypes back in January 2006. Last time I tried them with Arta (the picture) was back in May 2008. I don't remember all details, sorry.
Anatoliy
I designed that mic and build couple of prototypes back in January 2006. Last time I tried them with Arta (the picture) was back in May 2008. I don't remember all details, sorry.
Anatoliy
Details of records: when I recorded that helicopter I put microphones about 1 meter (3 feet) from the wall, under the roof edge of my barn. I wanted to record the rain. That curve in the room was recorded on a distance about 5 meters from woofers, about 2.5 meters from the rear wall. Sub is under the left wall (opening in the floor) about 2.5 meters left. I did not test the mic then, I replaced the amp for the sub, and measured relative levels of the sub, woofers, and line arrays in the wall.
Yes, if not to equalize properly the difference in response of front and rear capsules.
You can't fool the physics, but you can model a pressure gradient mic from 2 pressure capsules.
Again, I don't see what's so special in them. Judging from datasheet, they were measured on 1 meter. You can measure mine on the same distance, and may get probably even better results.
I don't have SM81. But I will probably need to find some lab to measure some mics. I am going to make some array from optical capsules. And to finish a stereo mic prototype with pair of Chinese copies of Numan capsules. If Scott Wurcer is serious about the lab, I may go there.
Nicht sprechen.
It was not SM81 measurement. If was testing of my speakers using my own mic prototype.
PS: Sorry John for microphone & helicopter off-topic!
Got small speakers to reproduce this 'copter LF sound at same/realistic levels?
A music source that all can hear with bass prominant, deep and clear is this album/CD : Hellecasters Jam Tracks by Will Ray.
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Yes. But you also need to provide 6dB/8ve bass boost from quite a high frequency, from above 1kHz. Have a look at the B&K info on their Sound Intensity probe. A flat response fig-8 is actually a particle velocity device though it is usually actuated by pressure-gradient.
If you send them to Cooktown, I'll be happy to check this.
Wanna make a small wager on this? Maybe a bottle of Burgundy? I'll have to ask Brad or Scott to sponsor my side of the bargain
I measured a lot of mikes in da previous millenium and even some in this. Haven't found any evidence of cardioids more extended than SM81 so yours will be the first in more than 3 decades. It will be the most extended conventional cardioid in the known universe.
Anyone used other cardioids with SM81 to record the same musical event?
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we had like tickets printed by government from thin air.
The uncomfortable reality (current version):
We have like money, printed by central banks from thin air.
Sure.
(see attachment)George
Attachments
I agree, of course about with what you wrote about Cardiod mikes. It is inherent to their principle of construction: acoustic short circuit of distant long lengths waves.
On this point of view of bass reproduction, artificial heads with omnis are OMHO better.
I don't 100% agree with your comment about ORTF miking. Yes, it depend greatly from the linearity of the mike's response curve at 60°. That's why ORTF was using paired Shoeps mikes, near flat at this angle. And i do not agree, as well, with the "reduced width of musical scene".
What i don't like is more that the instruments in the stereo area are a little 'out of focus' (see what i mean ?) while well positioned.
I believe it is due to the mikes disparities, because, when you do the same effect in an artificial way (pan pot+delay) you don't suffer from the same problem.
Yes, they are not ideal for focusing the central instruments, but an other front mike can add a little presence to them.
About all [FONT=Verdana, Arial, Helvetica, sans-serif](M-S) i had tried or listen to, i was always disappointed. Something not natural and near disagreeable. They are largely used in Europa for movie shootings. Movie mixing engineers used to play (stupid) with 3 desk's slides, while i was decoding them first and use the pan pots to reduce stereo image, instead. Same effect, easier.
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Wouldn't the response at zero/on-axis be peaked if flat at 60 degrees? [unless very small diameter] Thx-RNM
SM-81 has almost uniform frequency response from any direction on 1M distance, according to the datasheet. http://www.shure.com/uploads/specification_sheet/upload/84/us_pro_sm81_specsheet.pdf
Schoeps MK4 have quite little diameter electrostatic cartridge.
The front response have a little elegance around 10Kz. A nice mike for acoustic guitars.
I don't have directional curves, right now, but, indeed, they insist on their web site about constant directivity curves.
Thanks Wave but I designed some subs for the Bradford Computer Organs just to do 32' stops. The biggest installation was in the nave at Worcester Cathedral. At an organ recital, a 2 ton stone block was shaken off the ceiling. Fortunately no one was near.may be you just need to buy some bigger woofers and stop your haunt for microphones with extended bass?
Probably the most spectacular demo of my Powered Integrated Super Stuff.
I probably won't build this in Cooktown, but when you got speakers that do 16Hz with substantial acoustic power, you sorta want recordings that capture that.
So Mr. Marsh, I don't only design teeny speakers without bass.
When we tested this for the first time, we (literally) raised the roof in the factory.While I have the greatest respect for Dip. Ing Wuttke of Schoeps & his designs (Gerzon believed only 3 companies could make the Soundfield; Calrec, Schoeps & ANother) he will be smiling at your confidence in his capsules
But as I said, its a huge subject and I would use a modified ORTF if I had to make something sound like a Soundfield from 'conventional' mikes.
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I've been there. Now I want such subs for all audio engineers who do mastering, to hear and remove that disturbing content that shakes my sofa each time somebody "pops" an air into the mic.
Don't know for now, but, long time ago, ORTF was testing all the mikes against very severe specifications. They had special models engraved for them with special plugs. That was a big market for Schoeps, at the time.
I had too in my studio, a very old electrostatic i beloved: SCHOEPS CLASSICS: 1953 - The CM 51
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