For some reason my speakers are only working on only the right channel. That is, only the right speaker and the subwoofer are making any noise. The left one just sits there. The thing is, I don't think it's my speakers problem, because I get the same problem when I plug in my headphones into my laptop. Any ideas on how i can fix this or how I can test that it is indeed the speaker jack?
This might sound stupid but is the plug all the way in , instead of just a little bit.

It happens to me sometimes.
If its a mac, go into your Sound Preferences in the System Preferences and make sure the output is centered. Mine does the same thing all the time, its an easy fix. If its a pc. just go to the sound preferences in the control panel and do the same thing.