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I have a car audio system I am building and installing my self, and I have one specific question. I am planning on having a 60 watt (RMS), 2 ohm speaker powered by a 90 watt (RMS @ 2 ohms) amplifier, and I would like to eliminate the extra 30 watts of power, so that I don't blow the speaker. Through my college physics class, I know that P=E*I, P=I^2*R, and P=E^2/R. Through my math, operating under the assumption that E is approx 13.6V, I find that I need a 6.2ohm resistor.

HOWEVER, there are several other assumptions I am operating under that I want to check if I am right or not.

1. The change in power I am looking for can be solved using the P=E^2/R equation.

2. The resistance of the speaker doesn't need to be taken into account, since it is all ready accounted for in the RMS Power rating of the speaker.

Can anyone clarify this for me/tell me where I'm wrong/etc??? I would appreciate it very much if it were explained to me so that I can calculate this stuff on my own! Thanks in advance for the help!