You can't get a 1 Ohm load with 1 dual voice-coil woofer unless its a dual 2 Ohm voice-coil. But its very easy to get a 2 Ohm load with a single dual voice-coil woofer. JL Audio and Rockford Fosgate both have great woofer wiring tutorials on their web sites.

Here are some wiring diagrams that should help and give you a few options.

Your Dual 4ohm subwoofer can be wired 2 different ways (normally). You can achieve your desired 2ohm load by putting a jumper wire between your two positive terminals and another between your two negative terminals. This will connect both coils together in "parallel" to make one big 2ohm coil. To get that load to your amplifier, you simply need to connect your amplifier positive wire to one of the speaker positive terminals and your amplifier negative wire to one of the speaker negative terminals.

Another way to wire it would be in "series" to make a single 8ohm coil. To do this, you take a single jumper wire and put it between one coil positive terminal and the other coil negative terminal. The two remaining terminals that are not connected to are the ones you run to your amplifier (one + and one -). There are basically NO amplifiers made today for car audio that are designed to run a single 8ohm load.

Wiring 2 of these subs is another step altogether. If any more q's; please ask.