2 Ohms vs 4 Ohms vs 8 Ohms

What is the difference between 2 ohms, 4 ohms, and 8 ohms when it comes to an amplifier/sub.  For example, if you run a 500W RMS sub from an amp pushing 500W RMS amp 2 ohms, 4 ohms, or 8 ohms, what will the difference be.  Why would you choose one over the other?   I have seen amps that do something like : 400 x1 @ 4 ohms or 700x1 @ 2 ohms.  I know if you do the 700 at 2 ohms, you are pushing more power, but if you do 400 at 4 ohms, there are more ohms.  Im a bit confused how all of this works, and would much appriciate an explination.  Thanks to everyone who helps!

Ohms is basically the resistance that a speaker places on your amplifier.  The less the resistance the more the amp will push.

You have many options with this situation.  You can opt to use a seperate mono amp for each sub running them at  2 ohms depending on the amp this option would optimize the output of the amp.

You can wire the sub the subs up indiviually up to 8 ohms and than parallel them to achieve a 4 ohm mono load, this set-up can be powered by most amp today.

Those are just two options there are many more... 

Hope that this helped a little

In my opinion it's better to run both subs off of one amp because then you know that both subs are getting the same amount of power, and if the amp uses a mono input signal, both subs would technically be playing the same sound.

Very good choice for subs...I love the Perfects.  Glad to see you're getting the DVC version as well.

Since this sub has two 4-ohm voice coils, they can either be wired together in series, for an 8-ohm load, or parallel, for a 2-ohm load.  Then when you put two of them together, you'd wire them up to the amplifier in series (4-ohm total load) or parallel (1-ohm total load).

Most two-channel amps can be bridged to have a single 4-ohm load that maximizes the power output of the amp.  Ideally you would want to find one that puts out 800 watts RMS x 1 channel bridged @ 4 ohms; because each sub is rated for 400 watts continuous power handling.  You don't have to match that exactly, especially if you aren't going to push the subs as hard as they will go.  Nevertheless, there are so many 2-channel amps out there that it's really hard to know which one to select; also I don't know what your budget is or how much you're willing to spend on the amp itself.

If you can find the JBL BP600.1 amp somewhere on ebay, it'll only set you back around $200 or $250, and these are sweet sub amps.  They're 1-ohm stable and their power output is 600 watts RMS x 1 channel @ 1 or 2 ohms.  So each sub would be getting 300 watts.  That is probably plenty power for you unless you're looking to put together a competition system or something like that.  One reason I really love these amps is that they are 1-ohm stable, which really opens the door to a lot of different wiring configurations that most other amps couldn't handle.

If you want to send more power to them, think about the JBL BP1200.1.  It's basically the same as the BP600.1, but double the power output.  Although it would send 600 watts to each sub, I think as long as you use common sense and keep an eye on the gains, the subs will be able to handle that amp just fine. Now whether or not you're going to ever be using the extra power is another story, and it will depend on how hard you push them.  Keep in mind though that 300 watts per sub is still a lot of power, and certainly enough to make you deaf real quick! 

Most likely the people who told you it's better to run a sub off of a separate amp, were thinking of the SVC subs.  Each one by itself presents a single 4-ohm load to an amplifier which as I said before is the ideal hookup for a typical 2-channel amp.  But if you were to try and hook up two SVC subs to a single amp, the single 2-ohm load would not be supported by nearly all 2-channel amps out there.

Thanks everyone, you really helped me out!  Between this thread, and some othes i have been reading on this site, i really have a much better understanding of how the whole thing works now.

I have been considering the JBL 1200.1, but id like some input on some others i have thought about.

What are your opinions on the Rockford Fosgate  Power 1501bd - 750x1 @ 4 ohms   and     Power 851S - 850x1 @ 4ohms.

Those arent quite as much overkill as the JBL 1200.1, and are closer to matching the peak RMS of my subs.

Thanks again for all the help!

Basically all the really good amps cost a lot because of the name which came about because they make really good stuff. Just about any brand new RF, Infinity, or JL amp i've ever tested rated at higher than listed on the box.  A lot of times the best way to get a deal is to buy from up and coming companies that have been around long enough to ask others what they think about them but not so long that they're overcharging because of the name....such as audiobahn or cadence.