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Question about electret cardioid mechanics

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School

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Supposedly a cardioid mic cancels out sound beyond a certain field of around 130 degrees.

Is this electrically canceled or is it a physical thing?

I want to put a cardioid in the soundhole of an acoustic guitar. But I only want it to pick up the sound from the strings, and not the boominess of the acoustic body.

My concern is that the boominess could overcome a physical cancelation, via the side vents.
 

Nigel Goodwin

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It doesn't 'cancel out', it's just less sensitive from that direction.

Electret mikes are commonly used in guitar bodies, don't over think it - stick the mike in and see what happens.

From a sound engineers point of view, they are an absolute nuisance, an incredibly huge source of acoustic feedback (you don't use omnidirectional mikes like electret ones on stage if you can avoid it).
 

School

New Member
Nigel, thanks for the reply.

I've been digging into this, and using a cardioid doesn't seem to be the best solution. Everyone seems to use the omni electrets.

Are you familiar with using mics on the soundboard?
I wonder if I put one at say the upper left corner, and one at the lower right corner, if I might get a good balance of sounds/tones. And then blend that with a bridge piezo mic maybe.

Oh, and as far as soundboard mics, i'm thinking specifically of putting them on top of the sound board.




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Nigel Goodwin

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Nigel, thanks for the reply.

I've been digging into this, and using a cardioid doesn't seem to be the best solution. Everyone seems to use the omni electrets.
I thought all electrets were omni anyway?.

It's a comon feature on loads of guitars, have a look inside those in your local guitar shop and see where they are fitted :D
 

audioguru

Well-Known Member
Most Helpful Member
Cardioid electret mics have ports at the rear. These ports pickup reverse-phased sounds from the sides and from the rear which combine with in-phase sounds from the front and partially cancel sounds that are off-axis.

If you insert a cardioid electret mic in a hole in a guitar then the rear ports will pickup the sounds from inside the guitar.
 
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