Hey There, I'm trying to build a speaker with a subwoofer of 8ohm impedance and 15watt threshold and 2x 4ohm 5w tweeters. I want to power the setup using a battery but dont know what battery to use as I dont know how to find the power consumption of the speakers. Plz Help!!
You aren't using the battery to power the speakers you are using it to power the amplifier that will do so.
The amp will have a voltage that it will require to work. The more current the battery or batteries can supply the longer the speakers will play.
How long that will be will depend on the efficiency of the amp and how loud you play the speakers.