Convert 8 Ohm to 4 Ohm?

speakers or subs? what type of amp? but you dont have to do anything to the speaker or sub to run it at 8ohm on the amp that "specify" 4ohms it will just have effectively half the power.

Ketel22 is bang on. Just because your amp say it is stable at 4 ohms, read it as 4 ohms or greater. Do not read it as 4 ohms or less (bad things happen here). Here is an example for you on how ohms will relate to output. For examples sake let's say you have an amp that is rated at 50w rms x 2 @ 4ohms or 200w rms x 1 @ 4 ohms. Here is the possible outcomes. This will be for a basic 2 channel stereo amp only.

4 ohm stereo = 50 w x 2                     4 ohm mono = 200w x 1

8 ohm stereo = 25 w x 2                     8 ohm mono = 100w x 1

2 ohm stereo = 100w x 2                    2 ohm mono = not recommended with basic amp

2ohm stereo =  4ohm mono

1ohm stereo = 2ohm mono

Hope this helps.

I have a couple of surround Kenwood speakers  which I do not use and thinking of hooking up to my truck. And I have MTX amp which I think specify 4 ohm. Isn't car audio speakers usually 4 ohm and home speakers 8 ohm. What's the reason for this and I want to make sure that my MTX amp is not gonna burn for using 8 ohm speakers.