I guess the easiest way to understand it is, you want to wire the subs and or sub to where they have the least amount of ohms that your amp will handle. In other words, if you have a mono amp that is stable at 2 ohms, you could bridge two 4 ohm subs to equal 2 ohms which would give you the most power from your amp. And/or, if you only had one sub with two voice coils, you would want to wire it to 2 ohms. If you had two 8 ohm subs, you would not get all the power from your amp and it would not sound as good(loud). You would have to look at the woofer wiring wizard at www.rockfordfosgate.com to understand the wiring of woofers. That's why it's importat to get the right ohm sub or subs that you plan on using for your amp/amps.