Why does this speaker have 3 pins?

I bought this speaker on Amazon. I can't find a datasheet for it. Any idea what the middle pin is for?

(deleted)

It's a buzzer, not a speaker.
So it can't be used for sound.
Leo..

Wawa:
It's a buzzer, not a speaker.
So it can't be used for sound.
Leo..

guess that depends on your definition of 'sound'
music?

I have to refrain from evaluation. being tone deaf, I have been asked by my 2 year old. 'daddy, you no sing'

A mechanical buzzer (with + and - stamped on the case) is different from a piezo speaker.
Only piezo speakers should be used for playing sound.
Sometimes hard to tell the difference.
Here is a piezo speaker (bare piezo element).
Leo..

FutureTense:
I bought this speaker on Amazon. I can't find a datasheet for it. Any idea what the middle pin is for?

Apparently nothing - is it actually connected to anything? If so, what? Just inspect it.

These (type of) modules are designed to connect to a "servo shield" using standard 3-wire servo cables, whether they actually require all three connections or not.

Wawa:
Here is a piezo speaker (bare piezo element).

Must be heavily gold plated for that price!

Paul__B:
Apparently nothing - is it actually connected to anything? If so, what? Just inspect it.

These (type of) modules are designed to connect to a "servo shield" using standard 3-wire servo cables, whether they actually require all three connections or not.
Must be heavily gold plated for that price!

the extra weight of all that gold would explain the high shipping price as well.

let's just assume that the OP's link in the first post is a duck.
it looks like a duck and if you connect it to the Arduino as if it were a piezo, you can certainly find out if it quacks like a duck

if he already bought it, I would recommend he at least try it out to see what it sounds like.

BTW, putting some cellophane tape over the opening will save your eardrums it you test it at the bench.