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Old 29th October 2012, 05:39 PM   #28631
gpapag is offline gpapag  Greece
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Default Redefining the superlative form of “too much”

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Originally Posted by RNMarsh View Post
In other words you dont know what you are talking about. Ever used one? Go buy one and use it, then tell me about how naive it is. -RNM
George
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Old 29th October 2012, 05:47 PM   #28632
bcarso is offline bcarso  United States
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Originally Posted by SY View Post
They have some rudimentary specs- as you'd imagine, the bandwidth and dynamic range are limited. They only have one model that makes it to 20kHz and it's only for close miking mouths. The rest are either noise-limited or dynamic range limited (high self noise or low max SPL), as well as bandwidth-limited.

It's a neat idea, one assumes that they're doing it interferometrically, but has a long way to go before it displaces more conventional mike technologies. Nothing there will outperform a decent condenser or ribbon. As Brad pointed out, you still have to have a moving diaphragm, and that's the limiting factor independent of how you transduce the energy.

edit: here's some spec sheets:
http://www.optoacoustics.com/sites/d...-datasheet.pdf
http://www.optoacoustics.com/sites/d...-datasheet.pdf
http://www.optoacoustics.com/sites/d...-datasheet.pdf
The application to MRI patient speech pickup is a good example of the benefits of a nonmetallic transducer, albeit a niche one.

The 1200 looks fairly decent except for bandwidth at the top end. Not sure exactly what "ECM electret" microphones they are comparing it to. I presume they would provide a pattern if asked.

One spec that would be of interest and which can be the downfall of many condensers: what is the effect of temperature on frequency response? I suspect they will have calibrated it and incorporated the correction in software.

Once, when Harman had the closest thing to a pure R&D department, even then once renamed from HAR (Harman Applied Research) to HAT (Harman Applied Technology) , high officials from the automotive group visited the Northridge "campus" and were to get a demonstration of some noise-cancelling hardware. The equipment had worked well prior, and rather than buying expensive microphones used readily available electret condenser capsules, it having been determined that they seemed to work just as well as expensive professional products.

Alas, the vehicle sat in the sun on a rather hot day, and when the president of Harman-Motive got in for the demo, the system was oscillatory. Ooooops.

Later, when HAT became part of Harman-Motive (now Harman-Becker), Brad Plunkett, at that time in charge of HAT's electronics development, chatted with the aforementioned president, and asked him what he thought of HAT. "Oh. You mean The Toy Factory?"

Brad then decided to reconsider a job offer from the Automotive Group. HAT was soon shut down.

Brad Wood

PS: HAR/HAT had come into existence, by the way, based on a mistaken calculation by someone at Ford about the anticipated fuel economies from an active muffler. Ford funded the initial investigation at Harman with a grant of 600k, and this did produce a loudspeaker driver with a cone and surround capable of withstanding exposure to 500 C. So this may have future applications to global warming. [holds forefinger in air]
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Old 29th October 2012, 05:51 PM   #28633
gpapag is offline gpapag  Greece
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Quote:
Originally Posted by scott wurcer View Post
I have not seen a condensor or dynamic mic yet with DC response.
Scott, Kgrlee has answered already here

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Originally Posted by kgrlee View Post
If you block such a hole, the variations of the static pressure will stretch the membrane. As it’s stiffness will change dynamically, so will it’s vibration response (see Leo Beranek). Freq. Response will be constantly changing. Do you want this for an A.F. microphone?

Some sort of considerations, -that is validity for A.F. mics- can be applied on “high tech” sensing constructions too.
Bragg grating sensors (grating engraved in fibers or on plates and membranes) are used for decades in various industrial fields for detecting/monitoring dynamic strain and/or temperature variations.
Fibers and membranes coated with ultra thin (2-3um) piezoelectric material are also manufactured.
They can be made to excel in sensitivity figures or response to extreme frequencies and may manage a flat A.F. response, but will they surpass the overall performance of good existing mics for music-vocals recording ? And if yes, at what asking price? And for whom? (Top recording studios? How many potential customers?)

George
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Old 29th October 2012, 08:01 PM   #28634
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Originally Posted by gpapag View Post
Do you want this for an A.F. microphone?
Somebody who want to use his loudspeaker as a barometer ?
To be serious, anything under 16hz is an audio nuisance, source of distortion (CM), lose of available power (a lot with loudspeakers).
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Last edited by Esperado; 29th October 2012 at 08:04 PM.
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Old 29th October 2012, 08:11 PM   #28635
dimitri is offline dimitri  United States
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Quote:
If you shine a light on a vibrating diaphram
Richard, this solution is interesting enough...

David Schwartz Laser-Accurate microphone

Quote:
Using a laser to measure the deflections that sound waves make as they travel through a steady stream of smoke, this wholly new type of mike eliminates virtually all mechanical interference with the sound.
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Old 29th October 2012, 08:27 PM   #28636
bcarso is offline bcarso  United States
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Originally Posted by dimitri View Post
Richard, this solution is interesting enough...

David Schwartz Laser-Accurate microphone
I remember this. I believe he said he got the idea talking across a table to his wife
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Old 29th October 2012, 08:50 PM   #28637
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Quote:
Originally Posted by dimitri View Post
Richard, this solution is interesting enough...
David Schwartz Laser-Accurate microphone
If you use the reflexion of a laser on a reflecting vibrating plate, and measure the displacement of the reflexion, you just need to increase the distance of the measuring target to amplify the signal.
The target can be an array of 16 000 000 of photo-diodes (24 bits), so it is only digital: 0 noise. The simple geometrical error introduced by the curve/ tangent error of the target, if the array is flat, can be compensated by DSP calculation.
As the mirror can be very little, little inertia, no partial resonances to fear. All that is less difficult to reach that what is done in a digital reflex body. Both on a mechanical and electronic point of view.
Here, we have a real digital mike.
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Old 29th October 2012, 09:53 PM   #28638
gpapag is offline gpapag  Greece
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Originally Posted by bcarso View Post
I remember this. I believe he said he got the idea talking across a table to his wife
You can find this on ship engines as a sensor for checking the amount of oil fumes inside the crankshaft box vent or close to the valve’s housing.

If you check for MEMS microphone or Fiber Optics vibration detector at freepatents online, you will see interesting ideas. Nothing to be too excited for serious audio applications except the possibility for direct digital conversion and noise pick-up immunity at the interconnect wiring.
But there are always the “old boys” that have some very interesting solutions (e.g): http://www.neumann.com/img/Linkgraph...lution-D_E.pdf

George
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Old 29th October 2012, 09:55 PM   #28639
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Originally Posted by RNMarsh View Post
In other words you dont know what you are talking about. Ever used one? Go buy one and use it, then tell me about how naive it is.
Actually I've designed and used such a beast in da early 80s. It was part of a Scanned Laser Doppler Velocimeter for looking at breakup behaviour of speaker cones.

Lasers (& optic stuff etc) are not magical devices but are subject to the same S/N ratio & bandwidth considerations as more mundane technologies.

I've read the Optimic bumph and am frankly quite sceptical ... but it might be NIH syndrome on my part as I've never tried one in the flesh

Mr. Marsh, presumably you've used an Optimic and compared it to common or garden AKG 414s, Schoeps MK2, B&K 4179+2660 and the like. Can you tell us how it compares in terms of S/N, overload & response?
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Old 29th October 2012, 10:17 PM   #28640
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Originally Posted by gpapag View Post
If you block such a hole, the variations of the static pressure will stretch the membrane. As it’s stiffness will change dynamically, so will it’s vibration response (see Leo Beranek). Freq. Response will be constantly changing. Do you want this for an A.F. microphone?
Not so. A B&K omni has its main resonance at the top of its frequency range so can use very stiff diaphragm materials like Ni. You can work out the pressure changes necessary to move a Ni diaphragm into the plastic range (ie it stretches) and human beings will have given up long before that.

The stiffness doesn't change.

Even lesser omnis with 'plastic' diaphragms can be used at great depth in diving chambers and at great altitude.

There's a pdf book on the Neumann website that explains this and other stuff. It's the only useful & accurate book on mike design I've come across.

But don't take my pontificating at face value. Used B&K 4133/4s are available on eBay. I can vouch from experience that they retain their calibration for decades as long as they haven't been damaged or dismantled.
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