welshmousepk :
by 'real' he means multi-driver headsets.
by having more than one driver (speaker) in each ear cup, it can genuinely replicate surround sound. but in such a close space the sound can be a little hard to discern, while the movement of an audio stream from one speaker to another can be very noticeable and break immersion.
virtual surround uses only two speakers, but internal deflectors and very clever software to create directional audio without speaker separation. many people say that virtual surround sound is not 'real' surround sound, but in my opinion (and just about every other gamer i know who has used both) its a much more accurate and believable form of surround sound for headphones.
Agreed. Personally, I've tried numerous "real" 5.1 headphones and they all pretty much suck. Trying to physical cram 5+ drivers into a set of headphones usually results in tiny drivers with crappy sound quality. I'd strongly recommend a set of GOOD stereo headphones paired with either CMSS-3D Headphone or Dolby Headphone.
I most recently switched from a Tritton AX 720 (simulated 5.1 via an optical Dolby Digital connection) to a pair of Audio Technica ATH-A900s and I have to say the A900s with CMSS-3D Headphone sound WAY better. I think really it comes down to sound quality of the headphones, which a "real" surround headphone will probably always lack IMHO.