I will explain. The lower the impedance the more the current draw. It takes power to make power. And the lower the impedance the lower the efficiency. The 40.1 is a high voltage amplifier. For example. You run it at 1 ohm on a 12volt system, when the bass hits, the voltage drops to 11.5 or eleven something, maybe even in the 10's. That means less power is being produced, it even may go into protections. If that occurs at one ohm imagine what will happen at 0.5 ohms. Now same impedance at 17 volts, drops in the 16's or high 15's, power is doubled. Just as much current draw, however the power is available for the amp to perform better. The 40.1 is a solid amp, however it is made for high current use, not low current use. Not saying it cant be used on a 12 volt system, you need to use it at 1 ohm or above. Unless you have like a 200 amp alternator and 2 group 3100 batts, then it might be okay. But over 16 volts, you can do almost any thing you want, and the 40.1 comes completely alive.Why would it be harder to run at low impedence on 12 volt rather than 17 volt? Seems like if it can handle the 17 volts, it should be able to handle the 12 better? Explain...