I checked the user manual of my HK AVR 635, it does DH1/DH2/DH3. Quoted from the user manual:
Dolby Headphone Dolby Headphone enables ordinary stereo headphones to portray the sound of a five-speaker surround-playback system.
- The DH1 mode creates headphone presentation that resembles a small, well-damped room and is appropriate for use with both movies and music-only recordings.
- The DH2 mode creates a more acoustically live room particularly suited to music listening.
- The DH3 mode creates a larger room, more like a concert hall or movie theater.
I just played with the default mode (which I assume is DH1). I liked it better compared to my -expensive- 5.1 SS setup: front, center, back speakers KEF KHT 5005, and the 10" Velodyne sub. Wearing the headphones just emerges you so much better.
By the way, until yesterday I played games on my 480p TV (which sits upstairs), yesterday -when testing the DH- I played on my 720p plasma in the living room... OH MY GOD, what a difference. NO way I am going back to 480p gaming...