Ohms are the measure of resistance to the flow of electricity in an electric circuit. Think of it like a freeway, the more cars congesting the freeway, the slower everyone will move due to traffic. Electricity, like the cars, can be slowed down in the circuit due to higher resistance. The higher the ohm value, the more difficult it is for current to flow through a circuit. Likewise, the lower the value, the easier it is for current to flow. Based on this, is there any other differences between the most common 2 and 4 ohm impedances?
Certain amplifiers are designed to power subwoofers at different impedances (ohms). For example, a 2 ohm rated amplifier will power a 2 ohm subwoofer, so long as the woofers “final impedance (ohms)” is 2. You can connect multiple subwoofers together and run them off an amplifier, so long as their final impedance is equal to the amplifiers impedance. We cover this in a different article. If you have 100 watts at 2 ohms, and 100 watts at 4 ohms, is there a difference? The answer is subjective, you will hear people say there is a sound difference, and some say there isn’t. It depends on how efficient the amplifier runs at the specified ohm level, as well as the speaker itself.
If you get technical, the different resistance values of a speaker will change the sound slightly, assuming wattage is the same. A lower impedance subwoofer has a voice coil with fewer windings, meaning less weight. A higher impedance subwoofer will have more coil windings, meaning more weight. It has more windings to counter act the resistance, so it’s like adding more lanes to the freeway to ease up traffic. This slight difference in weight will produce a slight sound quality difference. At 2 ohms you tend to have more projection of sound (louder), which causes poorer sound quality. At 4 ohms you will have less mid bass frequencies then at 2 ohms; however the sound quality is slightly improved.
If you’re not an audiophile, does this matter? Honestly, no it does not. Do not let this be a make or break when looking for sound system components. Two of the same subwoofers, just with different impedances, will produce almost the same sound if they are run at the same wattage. The difference in sound is so slight that it has little impact, especially when dealing with subwoofers, that you likely can’t tell the difference.