Hey. Your speakers have two sets of speaker wire inputs on the back. That's to allow you to either bi-wire or bi-amp, if you choose. The result is that, if you connect a single speaker wire to them and plug them into the top (for the tweeter) or the bottom (for the woofer) without the gold shorting straps, then you'll only hear sound from the one cone that is connected.
So, here's how you fix it - leave the gold shorting straps connected. If that doesn't sound familiar, you can look on page 31 of your owners manual (you can download a copy from Energy's website
here - just do a search for "C-200" and click on the link).
You mentioned a "2.1" system. Do you have a sub that also needs to get connected? That's generally what the ".1" stands for. Just asking to see if you need help with another connection.
Please let us know if that helps out, or if you need anything else.
Adam