When I was 12 or so (might have been older)? I had convinced my parents to buy me a lantern battery (6v) and lots of wire. I connected all in series - two speak

When I was 12 or so (might have been older)? I had convinced my parents to buy me a lantern battery (6v) and lots of wire. I connected all in series - two speakers and the battery connecting my room to my brother's room. Unfortunately only I could control which speaker was acting as a microphone (I had to swap the battery terminals the wires were connected.) I guess that was my "tin can".