I am kind of in the dark with he whole ohm rating of subwoofers and of amps.I'm not a stranger to car stereo stuff but I fid myself confused when trying to figure out ohms of subs and amps.
A few years ago I bought a Rockford fosgate punch3 12 inh sub and a Rockford fosgate punch 5001bd amp. When I tookit home I wired up the dual voice coil on the p3 to amp, and wen I turned the stereo on the sub was hitting way harder and my car was accually surging because so much power was being drawn into the amp and my sub started smoking a little bit.
I shut it off and pulled the sub back out of the box to realize the guy at the stereo shop had sold me a 2ohm punch3 12.
I went back in and they traded me a 4 ohm p3 so that when I wired up the dual voice coil it would be running at 2 ohms. Was I running at 1 ohm having the 2ohm p3's dual voice coils wired up? This is where I get confused, I have read it is okay to run subs at 1ohm, but when I tried it the sub did not like it and got hot extremely fast. So when you are running a single sub to a fosgate 1bd amp do you want the sub to be 2ohm or 4ohm? And if you are going to run two 12s to a fosgate 1bd amp do you want them to be 2ohm or 4 ohm?
I'm sure this sounds like a stupid question, but I am thinking about getting a new system and I want to know this stuff so I can pick the right amp and subs to get some real good bass. Thanks

 

When you wire voice coils in parallel it halves the impedance (ohms). A sub with dual 4 ohm voice coils wired in parallel equals a 2 ohm load. If it was a dual 2 ohm sub that you had before, then it would be a 1 ohm load when wired in parallel, too low for the amp to run safely. The easiest way to remember how the series/wiring works is like this: to figure out the final load for parallel wiring you invert the two numbers, add them directly, then invert the answer. Example: dual 4 ohm coils= 1/4 + 1/4= 2/4 inverted equals 2. For series wiring they add directly. Dual 4 ohm coils in series equals 8 ohms. Some good info here: JL Audio » header » Support » Tutorials » Tutorial: Wiring Dual Voice Coil (DVC) Subwoofer Drivers

and also here: Basic Car Audio Electronics

Good luck.

 

Thanks for that link, that helps me understand quite a bit better. So if i bought a rockford fosgate t10001bd amp and two 12 inch subs would i want to get two 12's that are 2 ohm and wire the voice coils in series for a 2 ohm load? Or would it be better to get two 12's that are 4 ohm and wire each voice coil in parallel to get a 1 ohm load?

 

Glad to help. This amp?: Refurbished Rockford Fosgate T1001BD 1000 Watts Amplifier

If you are looking at dual voice coil subs then I believe you will want two dual 4 ohm subs. Wire the coil on each sub in parallel (2 ohm load per sub), then run the two subs in parallel to each other for a 1 ohm final load at the amp.

 

Whatever your amplifier is stable at is what you want your impedance to be. If your going to load the amp down be sure your wiring is sufficent and the electrical portion of the vehicle can handle it.

 

Theres a bit more to an amplifier. Its a 2 channel amp, that means 2 channels stereo. The left and right have different sounds. You can bridge them to make it 1 channel mono, which means its sums (combines) the sound from left and right channels, but that messes with your ohms too. If you hook a 4 ohm subwoofer to that bridged amplifier, it sees 2 ohms. So when you look at ratings it will give them in stereo and mono...

Looking at the specs on your amp, it looks like a mono amp, so that simplifies it a bit, but in case you ever get a 2 channel, thats how it works.