For those of you that haven’t checked out MDA’s VSTs yet, there are many cool stuff, and among other things the Round panner, that simulates panning 180 degrees left and/or right with an option to automatically keep panning (adding movement). Round panner is part of the bundle, so just download all VSTs from the link.
The effect is not spectacularly awesome, but with a bit of imagination, you can almost hear it pan behind your head. Of course, an actual visual would help get that feeling, as well as movement from other sounds in the mix.
I’ve read a bit on 3D sound in general, and the point seems to be that there’s no such thing as 3D sound coming out of 2 speakers. If you hear it, you’ve got a vivid imagination and/or a visual that suggests 3D. Anway, for rather weird panning effect, this VST will do just fine.
You can get a reasonable approximation of front/back sound placement; play any modern FPS with headphones on and you can definitely get a sense that sounds are coming from behind or in front of you – even if it doesn’t physically give you the sense of depth it does provide sufficient cues that your brain somehow knows where it’s meant to come from.
(Re: MDA plugins, I’ve found the OS X versions to be somewhat unstable, in particular the DX10 and vocoder…)
Actually, you can get a reasonable representation of 3D with two speakers if they are directly to each side of your head instead of in front of you. This isn’t a very practical setup however, so it’s not used a lot.