Hello!
I'm pretty inexperienced with Arduino, but I do have SOME experience under my belt. My goal is to connect a speaker that was harvested from a cheap bluetooth speaker to an Arduino.
Here's the specs:
4 Ohm
3 Watt
08T -- I don't know what this means
I want to hook this up, but I don't know what resistor to use, and I'd like to know how to go about determining that. Is it something with Ohm's law?
If someone could explain how to determine what type of current-limiting reistor to use, I'd hopefully be able to get through the coding part of it.
Thanks!!
Google Arduino + audio. There is no way to get even 1 watt of of an Arduino. Of course You can connect the speaker. Use 270 Ohm. That will keep the Arduino output transistor safe.
You could double the power by driving it differentially from two different output pins.
It is vital to use a series capacitor, not only does this stop DC getting in the speaker but prevents over current when the speaker is off, that is not receiving any sound. Use a 47uF capacitor with the positive end towards the Arduino. Then a 125R ( minimum ) series resistor and then the speaker with the other end to ground.
aarg:
You could double the power by driving it differentially from two different output pins.
That's a very bad idea 
A 4 Ohm speaker will already draw more than 1A at 5V, twice that current at 10Vss. At least 100 output pins in parallel are needed for 2A.
Either a speaker amplifier and power supply is required or a much more sensitive piezo speaker.