Circa 1989, I had a three-channel system that was made up of a small amplifier unit along with three speakers. I think it had just a single audio input, but there could have been more.
For the speakers it came with, one was rectangular that you were supposed to center along the front of the room, and the two others you put in the back (corners). The back ones were triangle-shaped when you looked at them from their sides (see drawing).
I didn't have this item for too long as I soon moved to a Pioneer receiver with Dolby Surround at which point I hooked up four speakers.
I don't think Pioneer made this unit. Maybe Kenwood? So far my searching has come up empty.
Other notes: I think the rear two speakers were about a foot or so wide. Depth maybe about 8 inches. The third rectangular speaker wasn't much bigger.
