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The MEMS revolution - The perfect microphone membrane?

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The MEMS revolution - The perfect microphone membrane?

Postby Butters » Thu Jan 11, 2018 10:57 pm

Interesting SOS "on Test" article in January 2018 issue , on the MEMS microphone technology used to support the IK Multimedia ARC software, and being used within billions of portable devices.

Interesting section on how the diaphragms are made ( must be similar to substrate doping techniques discovered decades ago to make silicon semiconductor pnp/npn transistors and diodes, etc.)

Once this technology filters "UP" to become professional studio specification /quality, then hopefully we may see almost flat, if not neutral sounding microphones. Hopefully much cheaper (electronics permitting). Not sure how this will be received by the musical establishment? Maybe another digital vs analogue debate? clean vs sterile - with the old microphones having inherent design flaws providing musicality (or should that be subjective distortion?).
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Re: The MEMS revolution - The perfect microphone membrane?

Postby Hugh Robjohns » Thu Jan 11, 2018 11:40 pm

MEMS devices, and MEMS microphones in particular, are an interesting technology and already widely used in mobile phones and many other hi-tech applications where their diminutive size and precisely repeatable manufacturing process lend themselves very cost-effective solutions.

However, the technology is still some way off being 'the perfect microphone' for music recording applications. Currently, all MEMS microphones are omnidirectional and, while arrays of multiple spaced elements can be processed to provide varying degrees of directionality, the processing involved to achieve useful directionality necessarily compromises the technical performance to some degree, which is still substantially inferior in comparison to conventional capacitor mic capsules.

Fundamentally, MEMS capsules have a relatively poor low frequency response combined with a substantial and narrow HF resonance peak around 15-20kHz. Signal processing can help correct these features to a degree but again it further compromises the already fairly extremely poor signal-to-noise ratio. Harmonic distortion is also significantly worse than conventional capacitor mic capsules for a given max SPL.

No doubt this ingenious technology will be developed further and will continue to improve in the years to come... But I doubt anyone will be rushing to sell their U87s any time soon. ;-)

The decision to use a MEMS microphone capsule for the ARC's room measurement makes a lot of sense because the application requires an omnidirectional polar pattern, doesn't require low noise or high SPL handling, and isn't too worried about distortion. But what it does demand is very low cost and very high consistency between mic elements to avoid the need to test and calibrate every single mic supplied with each the system. And that fits the MEMS profile very well indeed.

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Re: The MEMS revolution - The perfect microphone membrane?

Postby Butters » Fri Jan 12, 2018 12:04 am

Hi Hugh,

Sounds like MEMS technology is a long way off from hitting the shelves.
Might as well go out and buy that U87 I promised myself. If only I had the capital :-(
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