Headphone Surround Sound - The Basics

Watching TV With Headphones
Watching TV With Headphones. Getty Images 106748964 - Schedivy Pictures Inc. - DigitalVision

How We Hear Sound

When hearing sound in normal conditions, or listening to speakers, the sound elements arrive at your ears at different times due to distance, wall reflections, bouncing off other objects in the listening environment, even off your shoulders and parts of your head. In fact, even sound that is coming from one direction (say from the left), even though is heard by the left ear first, is still heard in a lessened manner by the right ear as the sound passes through your environment.

All these factors provide information regarding the distance of the sound sources from your ears. How sound interacts with your head and ears is referred to as the HRTF (Head Related Transfer Function).

In addition to HRTF, the characteristics of sounds coming at you change as you move in your environment, as well as moving objects emitting sound change their distance from you (resulting in the The Doppler Effect).

Sound In Your Head

Unlike hearing sound in the natural world or via speakers, when listening to audio (either music or movies) using wired headphones or headphones connected wirelessly to your television, the sound seems to originate from within your head, which is unnatural.

The reason for this is that when wearing headphones, all sounds arrive at your ears at the same time, which means there are no distance cues and no natural sound reflections, thus negating the HRTF effect. As a result, everything sounds like is it coming from inside your head.

Even sounds entering your ears from left or right in a headphone environment sound like they are inside the left or right side of your head, instead of a distance from it.

To compensate for this, there are various techniques that can be employed for headphone listening that deliver sound with more natural depth that can more closely approximate the characteristics of sound arriving at your ears as it might with your ears exposed to the natural environment.

Even the use of open or closed headphones can impact the sonic signature.

Expanding The Sound Field

With stereo, expanding the sound field a matter of placing center channel sound elements (such as vocals) in front of you, while the left and right channels are placed farther from the left and right of your head.

With surround sound, the task is more complex, but it is possible to place left, center, right, left surround, right surround, or more channel (surround sound) cues accurately in the "space" beyond the borders of your head, rather than inside it.

There are several (but similar) technologies that have been developed to accomplish this task, such as:

  • Dolby Headphone - Can use any pair of headphones, but home theater receiver, laptop, or mobile device needs to have feature built-in.
  • DTS Headphone:X - Can use any pair of headphones, but home theater receiver, laptop, or mobile device needs to have feature built-in. DTS Headphone:X not only provides a horizontal surround environment, but can also provide overhead sound cues with compatible content.
  • Yamaha Silent Cinema - Can use any pair of headphones connected to any Yamaha Home Theater Receiver, HTIB (Home Theater-in-a-Box), or sound bar that provides Silent Cinema audio processing.
  • Auro 3D Audio (for headphones) - Can use any pair of headphones, but requires home theater receiver, or mobile device to feature Auro 3D Audio for headphones processing. Provides immersive sound environment with with both horizontal and overhead sound depending on content.
  • Dirac VR - For music one can use any pair of headphones, but requires home theater receiver, or mobile device that features Dirac Surround Sound processing for headphones. For audio/video VR application, you need compatible VR headgear system and content. Dirac VR processing includes head-tracking capability. In other words, if you turn your head, the sounds still come from the proper direction, just like when you are listening to room speakers or natural sound.
  • Smyth Research - Can use any pair of headphones, but requires purchase of a special audio decoder/processor that provides inputs for sources, such as CD/DVD/Blu-ray Disc players, and USB flash drives. Includes similar head-tracking capability as the Dirac system.

These technologies employ algorithms that create a virtual surround environment 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 that, as mentioned, will work with any set of headphones, no special headphones are required - all of the needed surround headphone audio processing for each method is incorporated into the Home Theater Receiver, Preamp, Surround Sound Processor, or other compatible device, that you would plug your headphones into. Also, these technologies can also work with wireless headphones (Bluetooth is limited to Stereo).

For home theater, check to see if your home theater receiver (or one that you may be considering) features Dolby Headphone, Yamaha Silent Cinema, or other headphone surround sound processing system that allows the use of any set of headphones.

However, even if your home theater receiver, or other device that provides headphone listening doesn't come with built-in surround sound headphone processing, with some headphones, you can still access a surround sound listening environment. One example is with 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 reference 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 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/Ultra HD Blu-ray soundtrack material, and there is no additional equipment or special sound processing requirement other than the headphones. The effect is available with any amplifier or receiver with a headphone connection.

The Bottom Line

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 virtual or digital sound processing 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 the appropriate dedicated virtual or DSP technology for surround sound headphone listening.

Both approaches are viable, it really boils down to what your own ear, and budget, favors.