Excuse me if I'm in the wrong forum for this question, as I'm new here. I'm building a set of speakers for my motorcycle and do not know how to correctly choose a volume control. The bike is 12V; the speakers are 4 Ohm; the amp is 150W max; an MP3 player will be the music source. Can anyone help me understand the correct qualities or rating of an appropriate volume control (potentiometer/rheostat). I see some with an Ohm rating or a watt rating, but I do not know how to correlate that to my parts. It seems to be a very large potentiometer for a 150 Watts, so that seems not to be the correct quality to be used as the appropriate criteria. Is Ohms or voltage how to choose the correct volume control part, and if it is either one, am I to look for a potentiometer rated greater than or equal to 4 Ohms (the speaker's criteria), or 12 volts (the bikes electrical system)? Or am I all dazed and confused !? Thanks for any help.