Thanks for your help.

I didn't receive a receiver with my speakers. I'll be patient.

I myself wasn't thinking about an electronical way, but about other kinds of slutions: I know you can attach things to your wall - I don't know the right English translation, we call it 'egg boxes' - which would make sure the sound isn't heard outside of a room, so i was thinking about putting something to my right wall that would kind of amplify the sound or something like that.