Re: mic for low frequencies

[Irish]

Suppose the sensing beam overloads the system and overshoots the cell?

Ah, now you're trying to be practical!
I can see someone spending a lot of time adjusting the distances between the source and the photocells, and between the two photocells, to keep the signal in the straight-line part of the s-curve.

Or how's bout send two tones into the photothings. The photothings will change the sizes of the two signals versus light.

And an AM demodulator plug-in to get the signals back out?

It might just work.

PO'L

[steve]

In the off-chance that Kinshoro is still looking for a practical alternative to the knowles acoustics sp0103be3, I'd like to pull the suggestion of a Panasonic WM-034BY (or equivalent) closer to the end of this meandering topic.

[kozikowski]

<<<Ah, now you're trying to be practical!>>>

Yes. Cut that out [smacking face with upraised palm].

<<<I can see someone spending a lot of time adjusting the distances between the source and the photocells, and between the two photocells, to keep the signal in the straight-line part of the s-curve.>>>

Or maybe not. Successful systems are more or less self-calibrating. Point the system somewhere and create a special tone or disturbance. You might be able to do that with a bright flashlight (electric torch). Take a picture of the setup. The camera flash is the zero point. Phototransistors will not care.

OK, guys, that's zero. Any deviation from this instant in time is signal and valuable information. As long as you stay sorta on the straight-line portion of the system, it doesn't matter. You might well find out later that you "zeroed" the system 2/3 of the way off center. Who cares?

The limit on frequency response should be well up in the KHz range. Phototransistors don't have the sloppy response that photocells do.

If your head doesn't hurt yet, you recalibrate the system at the end and automatically generate a correction factor applied to the envelope tool.

Is the original poster still awake?

Koz