I was an audio newbie a few months ago but I think I've learned enough about it through these boards and other boards that I can have an intelligent conversation about it now. But I still don't know what it means when it says when an amp or speaker is 2 or 4 ohms. And I don't understand how can you change the ohms? FOr example, an amps specs could say it is X Watts at 2 ohms and Y watts at 4 ohms. How do you change the ohms on an amp?