"Bill Never" wrote in message
om...
" Don't confuse watts with amps !!
The power rating of speakers is used as a sales point and usually bears
little resemblance to that actually developed, also of course in the
average
unit the power developed will vary with the frequency.
You could expect a lower output with a mismatch of the 4ohm speakers.

Okay, This is where I get confused. The car has a 12 volt battery.

1) Does the amp produce 40 amps?
2) Or is it powered by 40 watts?
3) Is the amp limited by the 12 volt battery?

I do not understand the difference between volts and watts/joules? Are
they not the same?

Where and how do volts become watts and vice versa?

Don't worry about the 12v supply, the amp has it's own internal switching
power supply to produce the required voltages, it likely has + and - 20v or
so rails with 40v between them. The wattage rating on the amp is worthless
marketing puke, just ignore it. You can get a reasonably accurate idea of
the power the amp can produce by measuring the voltage of the supply rails
and multiply it by .75 then calculate it into your speaker impedance with
ohms law but really who cares?