XP400 - Dolby Digital 5.1/7.1 Surround Sound

What is surround sound?

Please check out this instructional video from our YouTube channel, which contains both an explanation and audio demos that you can hear yourself, if you are wearing headphones:

When most people hear the words "Surround Sound", they think of big multi-speaker surround sound systems.  In that case, how can Turtle Beach make a "surround sound headset"?

You don't actually need 6 or 8 speakers, such as you would use for 5.1 or 7.1 surround sound systems, to re-produce a surround sound experience.  When you're wearing headphones, you only need one speaker for each of your ears.

Most of the time, when using headphones, you hear stereo audio.  This means that there is a left channel and right channel of audio.  When using headphones, the audio source will sound like it's coming from your left, from your right, or inside of your head, depending on how the audio is balanced.

In a traditional 5.1 surround sound system, you have 5 speakers and a subwoofer.  There will be one speaker front and center, which is used for the audio that is front and center on your TV.  This is most commonly used as the dialogue channel.  The subwoofer is used for bass effects and producing other deep, rumbling audio.

The remaining speakers are front left, front right, rear left, and rear right.  By adjusting how much audio comes through each of these speakers, you can make it seem like the source of audio is moving all around you.  For example, if only the rear right speaker plays audio, it will sound like the audio is coming from behind and to your right.

Based on the way the audio arrives to each of your ears, your brain can pinpoint where the source of the audio is.  Even with just two ears, you can identify the source of audio in three dimensions based on how the audio goes around your head and how the sound reverberates in your environment.

How do you create surround sound in a headset?

With normal surround sound speakers, both of your ears pick up the audio from each speaker.  In headphones, each ear only hears its own speaker.  By employing some algorithms and processing, we can create a sound environment in your ears that matches what they would hear up from a surround sound speaker system in a room.


5.1/7.1 Dolby Digital

Dolby 7.1 is the exact same thing as Dolby 5.1, except that 7.1 has two additional channels that are derived using a process similar to Dolby Pro Logic. In other words, the additional two channels are not two discrete, separate channels, but rather are derived "effects" channels.

The Dolby capable Headsets decode both Dolby 5.1 and 7.1 channel surround sound, also known as Dolby Digital EX. The Dolby Digital EX 7.1 channel option is available on many movie DVDs, such as the Star Wars trilogy and a number of other DVDs. Most XBOX games use 5.1 channels, but newer Xbox games are being specially optimized for 7.1 channel playback.

Although the SPDIF signal from the XBOX to the Headset can only send up to 5.1 discrete audio channels, the extra two channels for 7.1 are encoded in the L and R surround channels as matrix encoded channels. The PLIIx decoder in the Dolby Headsets extracts these in the decoding process to reproduce all 7.1 channels. So, if you have a game or a movie with a Dolby Digital EX 7.1 channel setting, the extra two channels for 7.1 are encoded into the rear left and right channels, transmitted via SPDIF as 5.1 channels, then decoded by the Dolby Headset's DSP into extra channels for full 7.1 channel surround sound. The extra rear channel speakers are placed behind your head so positioning of sounds from the side, rear and behind are more precise than with 5.1 channels. The result makes you feel like you're even more in the center of the action.

The Dolby Headsets also use Dolby Pro Logic IIx technology to deliver a simulated 7.1-channel listening experience to XBOX games by creating the effect of 7.1 playback from stereo and 5.1 content to enhance spatial depth and improve the directionality of sound cues in the game.


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