Car Stereos: 1ohm vs. 4ohm load, power supply voltage, ohm load

Question
Brian,
Its me again!! Lol, I wanted to ask you what the benefits are of running a 1 ohm load vs. a 4ohm load. If there is better sound quality with the 1 ohm load then I will go purchase an amp that will support it, but if the difference is not really noticeable then I will save my money. Again thank you for you expertise and time answering my  questions. I will be voting for you to be the volunteer of the month for sure!

Thanks again,
Bryan

Answer
Hi Bryan,

The load impedance determines how much the subwoofer system resists the power that's being generated by the amplifier.  In most cases, an amplifier can produce more power when it's being used with a 1-ohm load than it can when it's used with a 4-ohm load. In simple terms, lower resistance results in higher current.  Power, by definition, is the product of voltage and current; so higher current means higher power.

Most amplifiers come with more than one power rating:  you'll see different ratings for 4 ohms, 2 ohms, and 1 ohm.  For example, Rockford Fosgate makes an amplifier that's rated for 250 watts into 4 ohms, 500 watts into 2 ohms, and 1000 watts into a 1-ohm load.  This is a pretty expensive amplifier; most amps can't double their power when cutting the impedance in half, and most aren't stable with a 1-ohm load.

The trouble with a lower impedance is that higher current means more heat.  An amp designed for 1-ohm use must be engineered to handle the extra heat that's generated, and it needs larger storage capacitors to maintain an adequate power supply voltage under a high current draw. That's why most mono amps require a load impedance of 2 ohms or higher.

In terms of sound quality, you wouldn't normally notice a difference, but an amplifier will "clip" more easily with a 1-ohm load than a 4-ohm load.  The real disadvantage to using a 4-ohm load over a lower impedance is that you're not getting all the power that the amp is capable of producing.  However, as long as you've got enough power to make the sub as loud as you wish, then it's not a problem; and a 4-ohm load will let the amp run cooler, which might let you keep it longer.

Thanks for the feedback!

Brian