I want to control a speaker via GPIO to play a square wave of varying frequencies. The first speaker I found laying around my house had 4Ω 10W printed on the back. I know for a fact this is not an ideal speaker for this purpose, but I want to make sure my reasoning below is correct, even if I end up using a different speaker.
First, would hooking the speaker up to, for example, GPIO12(pin 32) and GROUND(pin 30) fry my pi? I don't think it will, but I just want to be safe.
Second, since the GPIO only outputs 3.3V, and the speaker resistance is 4Ω, what is the maximum wattage I should be able to get? Using W=(V^2)/Ω, I calculated a wattage of 2.7225W.
Third, assuming I am correct about the maximum wattage being much lower than 10W, would the speaker just be really quiet? Or would it not work at all?