Let’s start by saying watts and ohms are all part of a series of mathematical formulas that put them together such that when one of them changes in value, the other often does too.
A brief explanation taken from Crutchfield:
“Amplifiers provide the electrical pressure in a circuit; ohms measure the resistance, or load, against that pressure; and watts measure how much power is released as work. So, using one of those math formulas, an amplifier that provides 100 watts of power through a 4-ohm speaker, will produce 200 watts through a 2-ohm speaker, because it’s easier to push that reduced load.”
What’s the difference between a 2 ohm subwoofer and 4 ohm subwoofer? Technically, they are different in only a few areas and that is:
- How much resistance one can get,
- How much power will pass through your subwoofers,
- How much dB (logarithmic unit to measure acoustics) they can produce.
What’s the difference between dual 2-ohm voice coils and dual 4-ohm voice coils?
It just gives you two options to choose from when you purchase the subwoofer, each one will be better/worse for a given type of amplifier. Each voice coil has a +/- terminal for wire to plug into, so you wire it sort of like it were two subwoofers .
The question is, do you run the power from the amp, through the first coil, then through the second coil, then back to the amp (wiring in series) or do you split the power wire and run it through both of the coils at the same time (wiring in parallel) . If you wire in series you add the ohms (impedence) of each voice coil to get your total ohms . If you wire in parallel its, often, half of the impedence of a single voice coil that becomes your total impedence .
Dual 2 ohm voice coil in series = 4 ohms .
Dual 2 ohm voice coil in parallel = 1 ohm .
Dual 4 ohm voice coil in series = 8 ohms .
Dual 4 ohm voice coil in parallel = 2 ohms .
Since they make two difference versions of the subwoofer, that gives you four options for hooking it up (with one speaker) . To pick which one is best for you, you just compare it to the amplifier that you have, or the one you intend to buy, for the speaker . If your amplifier puts out the most power at 2 ohms, you’ll want the Dual 4 Ohm subwoofer . If you amplifier puts out the most power at 1 ohm or 4 ohms, you’ll want the Dual 2 Ohm subwoofer .
That’s basically all it is, gives you options to make it easier to pick a matching amp .