well, from the battery when the car is off, or the alternator when the motor is running, yes. at 2 Ohms, the amp will draw about twice the current as a 4 Ohm load. The amp will also put out about twice the power.
loud and low
this will depend on if you are using more power than you were at 4 ohms. for example if you had an amp that pushed 500 watts at 4 ohms and were pushing all 500 to the sub and you switched to 2 ohms then the amp might do 1000 at 2 ohms. but if you still used only 500 watts then your power would be cut in half. i think. im really not sure about that when im thinkin about it now but it seem to make sence that an amp would draw the same amount of current at its max 4 ohm and its max 2 ohm. lets see if glasswolf comments on this but i think that correct.
simple Ohm's Law here. when the impedance is doubled, and voltage is fixed, the current draw is halved.
when impedance is halved, and voltage is fixed, current doubles.
loud and low
strange my computer showed that no one had answered yet sorry about that apparently im wrong. so glass say i wire my amp (us amps 2000)at 4 ohms and it puts out 1000 watts and then i wire it at 2 ohms and it puts out 2000 watts. i will be drawing twice the current at the 2 ohm load? which would mean that the amp draw rating is based off of the lowest possible ohm's the amp can handle. so since i have a "factory modifided" version that is claimed to go down to 1 ohm briged that my amp draw rating will be much higher. also if your familiar with the us amps company can you tell me if i should really trust that lower ohm rating not to damage my amp i don't know much about electronics but i would think that it would be a far more compicated change to make an amp run so much lower than the normal stats than what every they did.
you got it. take the rated RMS power output, divide that by 12, and for a class-D amplifier, then add about 10% to that figure, and you have an approximate current draw for the amp.
4Kwatts @ 1 Ohm / 12 (volts) = 333.3 amperes 333.3 = 10% (33.3) = ~367 Amperes of current draw for that amplifier.
that's one big alternator to handle that thing.
to get 2 ohm load, u have to wire 2 subwoofer in parallel so if I had 4 subwoofer and wired in to 200w at 2 ohm amp that has 2 channel (2 subs for each channel), then amp would be drawing 800W from my alternator right??