when an amp say 2Channel:
4 ohm: 200
2 ohm: 400


what is the difference in the ohms, will they sound the same, and how do you change the ohms...can i do it with a switch or is it done through the way of the installation?
what is the best way to go?

 

ohms are the load that the amp see's
they are changed by the setup you have
i'm not exactly sure on which setup does what right now

 

Ohms is the unit of electrical resistance, determined by the load or in car audio, the speaker. The lower the ohm, the less resistance therefore the more current can pass through. The lower the resistance, the higher the current (flow of power) and the more power in watts it can put out. Resistance is a DC measurement, while Impedance is an AC measurement... basically the same thing.

In your case, your amp will put out 200 watts under a 4 ohm load and 400 watts under a 2 ohm load. You'll be putting out twice the amount of power into a 2 ohm load than a 4 ohm load, but you will also be drawing twice the amount of current. The lower the ohms, more current is used and more heat is generated and the harder the amp works. Sometimes the amp doesn't like this and it will shut off because it is being overloaded.

The ohms is determined by the speaker's voice coil windings and it cannot be changed. However, if you have two different voicecoils, such as in the case if you have a pair of speakers, you can change the overall ohms or resistance seen by the amp. If you have a 2 4 ohms speakers, you can wire them in parallel for a 2 ohm load (+ to +, - to -) or you can wire them in series for an 8 ohm load (+ to -, + to -).

Sometimes amps have a switch that will let you optimize the amp depending on what you are running.

I hope I am making sense. It's pretty hot right now and my brain is fried. What are you trying to connect?

 

actually im looking to buy a new ppi and a new jl subfor a friend. so what your saying is it all depends what ohm sub i going to buy correct?..the sub i have in my car now is a 4 ohm sub...is that the most common ohm?

 

well that depends on if its a dvc sub. there really are no "common" subs cause the good ones usually have a 2 or 4 available. and with the dvc subs you can have 1 or 4 setup, or a 2 or 8 ohm setup. oh and if you wire them up differently it changes it too