Not to take any one side of this issue, Here is my 2 cents. I work professionally in the sound reinforcement industry, and the things that can be done with today's technology is amazing. Yes, as humans, we have only two ears, but that is not where it ends fortunately. The brain, although very complex and powerful, CAN be fooled. Simple example is a movie theater (go see an action flick to experience this) The other would be a concert hall, or house of worship, etc. The trend today is to have wide, and fairly shallow venues (think twice as wide as it would be front to rear).
In these cases, to get true stereo (or surround) seperation is a battle. If you sit on the exterme right or left of the auditorium you are closer to one speaker than the other. To combat this the new designs are a LCR setup (Left-Center-Right) with the center cluster having speakers that point left, center, and right. All of the speakers fire off at different times. A basic example is that you, as the listener, are on the far right, you would normally hear sound from the right speaker first because it is closer. With the DSP technology today, that sound from the right can be delayed (measured in milliseconds even) as the center cluster fires off it the left ear so that the listener's brain is fooled into thinking that both sides arrive at the same time (most newer home theatre systems now have this delay option to make up "perfect" mounting). Also if the room is fairly deep front to rear you may notice another cluster (or two) hanging from the ceiling towards the rear of the room (i.e. in front of the listeners in ther balcony) these are also typically delayed or synched with the other speakers in the room. This is so you see and hear the action at the same time because you are farther from stage than the rest of the audience. e.g. a drummer hits the snare drum and you hear the sound at the same he/she puts the stick on the drum head unlike seeing a flash of lightening, then hearing the thunder.
In "surround headphones" there are five (or six) different speakers angled at you ear canal in different ways. Keeping this in mind the DSP software can fire off different speakers at different times. Although there is no true distance/time = speed arithmetic involved, your brain "perceives" space, dimension and distance. As far as bass/sub-bass freqs. are concerned, they are non-directional and that is the reason for them being on the outside of the phones' most of the time. So if you have an ugly sub at home, stick it behind the couch, or better yet, in the corner(facing it) and you will notice no difference.
I apologize for being so verbose, but this is the simplest way I can describe it, without getting into doppler effect, and how the Digital Signal Processers actually work, and so on.
Quick add-on: If the signal going to your phones, stereo, etc is not a 5.1 (or other ype of signal i.e. Aces HIgh2), then you will not get TRUE channel seperation as you would with a proper signal. This is not to say that they will not work, or even somewhat sound like 5.1, but that it will not be TRUE surround sound.
Thanks for (ahem) listening.
