3D imaging

I I started thinking about this yesterday. What makes speakers produce a 3D image? I figured the first thing is the recording itself. I'm guessing mic placement has a lot to do with this. Next I would imagine is room,and speaker placement. Downstream gear certainly has to have some effect on this. Does the crossover have something to do with providing this "illusion " for lack of a better term? 
     Now please understand,I don't have anywhere near the technical knowledge a lot of you folks have,so as you explain this phenomenon,please dumb it down for me! 
    Thanks in advance,
        Ray