Friend just gave me a Power Acoustik PS4-300 but for the life of me I cannot figure out how to connect the speaker wire. It's driving me nuts because I can't find anything on the internet about it. It just has this connection on the side that says "HI INPUT AND SPEAKER OUTPUT" and it looks like something needs to be plugged into it. Can anyone help? Every other amp I've worked with has simple speaker outputs that u just screw the wire in.