Mems mic questions

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Tubetec

Well-known member
Joined
Nov 18, 2015
Messages
5,947
So I harvested a mems mic out of a set of head phones with talkback facility, its the simple 2 wire analog connection .
How would I design a valve input stage with the required voltage for capsule power at the grid and maybe very high input impedance to maximise voltage swing from the capsule ,would a cathode follower work well here ?

Also Ive looked a bit at array microphones, is there any simple way of implementing a beam former from individual mems mics ,or does it all require computer processing at the back end to make it work  ?
 
Tubetec said:
So I harvested a mems mic out of a set of head phones with talkback facility, its the simple 2 wire analog connection .
How would I design a valve input stage with the required voltage for capsule power at the grid
AFAIK MEMS mics require a voltage of about 2.5Vdc

and maybe very high input impedance to maximise voltage swing from the capsule ,
MEMS mics have a low output impedance, so you don't need a very high impedance preamp. The output of a MEMS mic is biased at about Vcc/2, so you need a coupling capacitor and a grid resistor -alternatively you may alter the cathode resistor in order to get an appropriate operating point.

would a cathode follower work well here ?
No, it would just add noise.

Also Ive looked a bit at array microphones, is there any simple way of implementing a beam former from individual mems mics ,or does it all require computer processing at the back end to make it work  ?
Some arrays are simpler than others. Some mic DIYers use the simplest all-parallel array, which improves S/N and a beam that narrows with frequency.
You may want to look at Bessel arrays, that use only weighting (i.e. adjusting the gain of each capsule separately).
But indeed, the best performance is obtained when using both weighting and EQ, which tends to promote digital processing. This is to be approached with a solid knowledge of acoustics and mathematics.
 
thanks for that Abbey,

I did an experiment before with a ps3 eye cam with the array ,I could use a free plugin to steer the beams Voxengo 979 I think I could get a large range of steering of the beams and change the aparent incidence of the sound source by varying delay times of the mics and altering the phasing level and panning of the different channels ,only thing was in four channel mode the mic only worked in 16khz, still usable as ambience mic and once you have the four channels down on tape you could easily change the direct/reflected sound balance later on , I ve always been meaning to do more work on the idea, mems mics and an audio chip that a/d's the channels and makes them available over cable to a daw for instance ,There are Mems also with digital output I believe but again Im a bit clueless about what kind of microcontroller  chip would be appropriate.A nice simple usb based multichannel mic array would be really neat for recording ambiences
 

Latest posts

Back
Top