I'm not sure if I can help with this problem without sounding sarcastic, but I'll try. One solution should be to get your friends and yourself to turn off the speakers and use a pair of headphones. Problem should be solved after that. Otherwise, you and your friends will have to adjust your speaker volume and positioning relative to your mic and hope for the best. Maybe check your sound settings to see if there's some echo cancellation available that might also reduce it.
Oh, silly, if that were the problem we'd have tried that. We are not in the same room, let alone the same house. The echoed voices are definitively coming from my machine. None of us are using microphones to communicate. We use text based communication.