Microphones in parallel to reduce noise

Assuming they are the bufferless version, aren't they all simply in parallel? ...Jim Thompson

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The 10 noise signals ( from the internal JFET pre-amps) are un-correlated while the sound arriving at each co-sited mic will be heavily correlated. So the output signal will be 10 times that of one mic, while the self noise will be only 3.16 times - so a 10 dB improvement is possible.

I suspect the mics are arranged to create a directional pick up pattern too.

BTW

Dynamic mics have much less self noise than typical electrets - cos there is no internal pre-amp. Means it is easy to get a 10dB or more improvement, just by using one instead.

..... Phil

Electret mikes usually have built-in FET stage. Are you sure they are combined in parallel, not in series?

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

They are available WITHOUT the FET. I have an RFQ on my desk requesting a complex chip that will use Electrets sans FET's. ...Jim Thompson

Right. Some of ours come with FETs, some not. Some "dynamics" are really electrets in drag.

"Jim Thompson" Vladimir Vassilevsky

The kind with inbuilt JFET pre-amps are about a million times more common.

PLUS, to comply with the OPs post they cannot be naked condenser capsules.

.... Phil

Ok, each mic has a surface mount network around it for frequency shaping. and each one has a internal fet. Until I can dig into it in the morning I don't know the values, 805 parts that I cant see until I get a microscope. A bit of probing reveals the outer ones are tailored to low freqs, inner ones to highs, and gain increases towards the centers of the array.

Steve

So tomorrow I look at the bias string.. Ok. I didn't have time to do much probing. I did sweep the response of each one by injecting a sweep.

Steve

"krw"

... Phil

If this is work, it should probably stay there, for the benefit of your employers and clients.

RL

BIENT ** =A0noise pickup, =A0not self noise !!

ought to

Mixer front ends still add thermal noise, "pal", and yes, its a conference mike.

Steve

In fact, you are. You and DimBulb; a perfect pair.

"krw"

Why don't ya go drop dead -

you VILE LYING pile of sub human GARBAGE.

.... Phil

What sort of 'unit' ?

Why do you think it would make the unit noisy unless designed by a cretin ? Plenty of them about of course ! ;-(

You mean the inverting 'virtual earth' type ? Yes, avoiding that structure *would* avoid excess noise.

Join the AES. Or come round and look at my data library which has some excellent app notes / books on that and similar subects.

Graham

Very likely.

But dynamic capsules cost more !

Graham

Quite so.

How many Gigaohms input impedance will the complex chip have ?

Graham

Uh ? What's a 'mixer front end' ? Obviously you're not an audio professional and haven't a clue about current practice. You can make a mix stage today using inexpensive off the shelf parts that has 100dB or more dynamic range quite easily.

So what's the mix stage chip ?

Graham

Provide a link to one of these 'electret dynamics' or SHUT UP !

Graham

"Eeysore is Baaaaakk"

.... Phil