In alt.home.repair, on Sun, 5 Aug 2018 10:24:39 -0000 (UTC), Bruce
Esquibel wrote:

In sci.electronics.repair micky wrote:

And what is it equalizing?

A number of car stereos have a setup that is used when first installed to
automatically set the volume and eq (bass/treble) for each speaker so it is
optimized.

When in that mode, the radio plays a number of tones and white noise one
speaker at a time to figure out the best pattern for the driver. That
microphone is used to listen to those tones. You aren't in the car, you
place the mic where your head would be and get out of the car and let the
radio run the tests.

You don't leave it in circuit, after the radio does it's thing, it's
removed.

Thanks, Bruce. (and thanks, Jeff) I n ever would have guessed. (My
car radio was made in 1890.0


Both my original radio and the current one has modes for "driver only",
"front only" and "4 passenger". It's just a tweak to get the best sound
based on how many people are in the car.

Unlike other makes, GM radios used to, maybe still do, reverse left and
right for the back seat. I think that means wherever one is in the
car, he gets and equal dose of left and right, instead of having to sit
in the middle of the car (where no one sits.) It's a dilemma. When I
drove a stage coach, I was usually alone and I always sat in the middle,
so that I had the right balance of left and right.

Unless you have a radio that does the auto configuration, there is no point
having one of those mics.

You saved me some money.


-bruce