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Question for mic experts

S

SpamBot

Dec 25, 2008
1,928
12
St. Paul, MN
#1
Today, while looking for a suitable mic with which to record, I remembered the mic I used to use, years ago. This mic was the internal mic of an iMac computer, circa 1999. I got a great sound with it recording into an old version of Audacity.
Well, I went and found that computer in storage, took an hour to open it up (stupid 5 layers of thick plastic) and retrieved the "mic"! The "mic" is in quotes because I'm not sure exactly what I have.
I have attatched pictures, but they are blurry phone pics, so I will describe this thing in detail. The mic end looks like a rubber stopper, because it is designed to plug into a slot inside the computer. It's got a small hole on the end, of course. There are three leads coming off of this that terminate in a plug. The plug was used for an internal connection to a large PCB (Motherboard, I think). I was thinking, why three leads? By my reasoning, they are either because this is a stereo mic, unlikely because of the very narrow opening of the mic, or this is a balanced connection.
What I want to do is use this mic apart from the computer. Do yall think I have a full mic here, or just an element that requires external parts? I didn't want to rip out the motherboard, because I'd like to keep the computer intact, so I'd probably try to build a mic around it if that's the case.
So, how do I figure out what this is? And how to use it? What I'd like most would be a link to a site talking ALL ABOUT this sort of thing, because I'd really like to learn about this.
 

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#2
While I'm not sure of anything specific to that mic, what I can tell you is if it is a self-contained mic then you should be able to alligator-clip its leads to an XLR plug, and by trial and error find the connection which results in an audio signal through any ordinary mic preamp. If no combination of alligator clip and XLR pins results in audio through a mic pre, then it's not a self-contained mic. The only exception I can think of is if one of the leads is for power, but that seems unlikely with such a small mic.
 
#3
I'm not an engineer, but here are my best guesses...

A basic mike like that will probably have a positive and a negative lead...my guess would be that it probably gets some unknown amount of voltage from the board it was connected to. Mikes normally come in two types: Dynamic (no battery or power required) and Condenser (internal power or phantom power required). This mike appears to be too small to have a diaphragm that sound waves can move (dynamic) so my guess is that it's powered. What that amount of power is would be hard to guess without the ability to test the board when it's turned on.

Bongomania's suggestion makes sense to me - at least you can give it a try. Whichever lead on the XLR is ground would go to the negative side of the mike - the other lead would go to one of the other two XLR pins. (Polarity shouldn't matter - just find the XLR ground pin and use it for one of the two connections.)

But the fact is it's not worth messing with. There are plenty of good, inexpensive mikes that don't require hours of time messing with them.

I don't know of a website that goes into detail on microphone design, but you can search for one very easily.
 
#4
That is a condenser mic of the cheap variety that are commonly found built into computers. The extra lead is almost certainly power from the mother board and who knows what voltage it will be (12v, 5v or otherwise).

Pilgrim is right that it's a waste of time to screw with it. You can go to Best Buy or Circuit City or any of a million online stores and buy a better mic than that for less than $10 and it will have the lead ready to plug into your computer's sound card.
 
#5
Whether it's a waste of time or not (If you say so, it is) I want to play with this some more. At any rate, on closer inspection, There's only a small cylinder embedded in the rubber, probably the element and not the full mike. Also, I cracked open the plug, and the leads are colored red, white and black. I'd imagine that black is ground. Is there a standard for what lead would be power and what would be the signal lead?

I understand completely that this is not an efficient use of my time and money. However, I have a drive to figure this thing out, and would like to see it through, even if only for a few days.
 

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