In 1975 we bought a stereo system that came with two speakers, but could be upgraded for quadrophonic. The tuner is still serviceable–the original speakers, connecting wires, and turntable are long gone.
But I had bought four speakers, for reasons I prefer not to elaborate on. The whole shebang is hooked up now and works just fine. 
What I want to know is: Is it best to have all four speakers against the same wall or try to put two of them on opposite sides of the room?
The idea was to be a sort of surround sound, so you’d want the speakers around you - the regular left and right up front, and the other two in back.
Truthfully though, unless you’ve got some quad LPs, it doesn’t really matter. You’ll get some sense of “depth” on regular LPs or radio, but not to the extent real quad recordings would give.