Eiii seemed so dazed & confused (and somewhat sad), that I the urge of a terrapin to leave my shell.
"3d" happens because of us receiving information from two identical receivers with a physical separation, our eyes and ears are both examples. A processor, or our brains, then take the two discrete signals and compare the similarities and differences. The differences allow for the 3rd dimension; in the case of our eyes, depth. We as humans have incredibly poor vertical from the fact that there is hypothetically no vertically difference of our ears relative to the brain, unless you are Sloth from Goons. No physical difference in height means we dont pick up any of the intricacies of that sound throughout its vertical spectrum.
Stereo contains all the information for 3d sound, the important thing to remember is that traditionally it is always "mastered" (final process for the people recording) to present a fairly tight stage (image) filling the space between and behind the speakers. What you might interpet when listening is sound placement on the horizontal plane, from favoring loudness of in one speaker, and depth, from altering volume of combined speakers relative to another sound in the recording.
The best analogy to consider for classical audio stereo is that of the loudspeaker pair projecting a holographic image in between themselves and behind. It is still 3 dimensional in everyway, but more like looking at "3d" picture with special glasses or looking at a stereoscopic image that pops out at you when you cross your eyes just right. Surround would then be the same 3d stereo recording but with the listener moved into the heart of the soundfield. You are now in the midst of what you were sitting in front of with stereo, so with different mastering and places the sounds differently you are able to hear sound from the rear as well as all sounds have an extreme degree of directionality. this was not supposed to be this long, idk what happened. im a ramblin gamblin and this is overcooked.
mewa