Circle Surround: What You Need to Know

If you own an older soundbar, HDTV, or home theater receiver, you may notice a setting on the audio setting menu labeled "Circle Surround." What is it exactly?

The Life Cycle of Circle Surround

Long before the Dolby Atmos and DTS:X surround sound formats, a company known as SRS Labs was working on ways to create a surround sound format that was more immersive than the Dolby and DTS formats available at that time.

At the time of its development, Circle Surround (and later its successor Circle Surround II) approached surround sound in a unique way. While Dolby Digital/Dolby TrueHD and DTS Digital Surround/DTS-HD Master Audio approach surround sound from a precise directional standpoint (specific sounds emanating from specific speakers), Circle Surround emphasized sound immersion.

In 2012, DTS bought SRS Labs. DTS took elements of Circle Surround and Circle Surround II technology and incorporated them into DTS Studio Sound, a premium audio enhancement suite.

How Circle Surround Worked

To accomplish sound immersion, Circle Surround encoded a normal 5.1 audio source down to two channels and then re-encoded it back into 5.1 channels and distributed it to five speakers (front left, center, front right, left surround, right surround) plus the subwoofer in such a way as to create a more immersive sound without losing the directionality of the original 5.1 channel source material. Circle Surround also expanded two-channel source material into a full 5.1 channel surround sound listening experience.

Circle Surround Applications

Music and movie sound engineers could encode content in the Circle Surround format. If the playback device (TV, soundbar, or home theater receiver) had a Circle Surround decoder, a listener could experience a somewhat immersive surround sound effect different from what was experienced from straight Dolby Digital or DTS-based formats.

For example, a number of audio CDs were encoded in Circle Surround. These CDs could be played on any CD player, with the Circle Surround-encoded source passing through the player's analog stereo outputs and then decoded by a home theater receiver with a built-in Circle Surround decoder. If the home theater receiver didn't have the proper decoder, the listener heard the standard stereo CD sound.

Circle Surround II expanded the original Circle Surround listening environment from five to six channels (front left, center, front right, left surround, center back, right surround, plus the subwoofer), and added the following:

• Improved dialog clarity and localization.
• Bass enhancement.
• Full frequency range for all channels.
• Improved channel separation.

More Information

Examples of past products that included either Circle Surround or Circle Surround II processing include:

• Marantz SR7300ose AV Receiver (2003)
• Vizio S4251w-B4 5.1 Channel Sound Bar Home Theater System (2013)
• Circle Surround-encoded CDs

Related Surround Sound technologies initially developed by SRS and transferred to DTS include TruSurround and TruSurround XT. These audio processing formats can receive multi-channel surround sound sources, such as Dolby Digital 5.1, and recreate a surround sound listening experience using two speakers.

About DTS Studio Sound and Studio Sound II

DTS Studio Sound premium audio enhancement suite features include volume leveling for smoother transitions between sources and when changing channels, bass enhancement, which improves bass from smaller speakers, speaker EQ for more precise speaker level control, and dialog enhancement.

DTS Studio Sound II expands virtual surround sound flexibility further with improved directional accuracy and more precise bass enhancement. Studio Sound II also incorporates a multi-channel version of DTS TruVolume (formerly SRS TruVolume) that provides better control of volume fluctuations both within the content and between sources.

DTS Studio Sound II can be integrated into TVs, soundbars, PCs, laptops, and mobile devices.