I believe that the Pioneer ES2000 (1973-1976) was a complete stereo system with receiver, turntable and speakers. The speaker wires that came with it had proprietary terminals that were kinda like mini-banana plugs, very similar to the plugs in a computer power harness.

If you have any skill with soldering you could find a speaker output block and attach it to the back and solder the speaker leads from inside to the terminal block.