Surround Sound is not limited to the large multi-channel system, but can also be applied to headphone listening. SRS Labs, Dolby Labs, and Yamaha all have incorporated surround sound technology with the headphone listening environment.
Normally, when listening to audio (either music or movies) using headphones, the sound seems to originate from within your head, which is unnatural. Dolby Headphone, SRS/DTS CS Headphone, DTS Headphone:X, Yamaha Silent Cinema and Smyth Research employ technologies that not only gives the listener an enveloping sound, but removes it from within listener's head and places the sound field in the front and side space around the head, which is more like listening to a regular speaker-based surround sound system.
The main benefit of the above-mentioned technologies is they will work with any set of headphones, no special headphones are required - all of the needed surround headphone audio processing is incorporated into the Home Theater Receiver, Preamp, or Surround Sound Processor that you would plug your headphones into. Also, these technologies can also work with wireless headphones.
Although any set of headphones can be used with the previous systems discussed above, they are dependent on the amplifier or receiver having the headphone surround sound technology built-in. In other words, check to see if your home theater receiver features Dolby Headphone, Yamaha Silent Cinema, SRS/DTS CS Headphone. However, with some headphones, you can still access a surround sound listening environment from any amplifier or receiver, such the Ultrasone S-Logic Headphones discussed next.
The Ultrasone S-Logic Headphone Surround System
Another type of approach to headphone surround sound is that taken by German Headphone maker, Ultrasone.
What makes the Ultrasone approach different is the incorporation of S-Logic. The key to S-Logic is the position of the headphone speaker driver. The driver not located in the center of the earpad, where it would send sound directly to your ear, but slightly off-center (see photo). For a comparison between the driver placement of the driver position used by ultrasone and more traditional headphones, check out how the driver is placed in the KOSS Pro4AAA Headphones.
By placing the driver in an off-center position, the sound is sent to the outer ear structure first, where it is then funneled into the middle and inner ear in a more natural fashion. In other words, the sound is heard as it would be in nature or when listening to speakers; the sound reaches the the outer ear first and is then sent into the middle and inner ear.
This approach can work very well. There is an increased expansiveness and directional perception of the soundstage. Instead of the sound just coming at your from left and right, the soundstage opened up to the beyond the earpad borders. Sound appears to originate from slightly above and slightly behind my ears as as well as slightly from the front. With music, voice and instrument placement was very precise and distinct. Of course, the degree of this effect also depends on the source material being played.
Although it is not the same experience listening to DVD and Blu-ray surround sound tracks with the Ultrasone S-Logic system as it is when listening to an actual 5.1 or 7.1 loudspeaker setup (rear sound effects are minimal), it is still a credible experience. One drawback is that the center channel is not placed at quite enough distance forward; it is more in the center of, and slightly above, your head. On the other hand, the left, right, and surround effects have enough spaciousness and direction.
Ultrasone has taken an innovative, yet simple, approach to headphone listening that is well suited for listening to either music CD or DVD/Blu-ray soundtrack material, and there is no additional equipment requirement other than the headphones. The effect is available with any amplifier or receiver with a headphone connection.
So, as you can see, I have outlined two practical ways to access surround sound in a headphone listening environment. One way is to make use of digital sound processing (DSP) technologies that can be used with any pair of headphones. The other way is to have special headphones that can create a surround sound listening environment with any amplifier or receiver with a headphone connection, regardless if the amplifier or receiver is equipped with dedicated DSP technology for surround sound headphone listening.
Both approaches are viable, it really boils down to what your own ear, and budget, favors.