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Get Surrounded: Home Theater Sound Modes Explained

September 16, 2013 | Comments

Without question, the A/V receiver is the most sophisticated component in a modern home theater system.

Think of it as command central, delivering power to five or more speakers, processing incoming audio signals and making it easy to switch between a Blu-ray player, game console, and cable or satellite box.

Many of today's receivers also serve as a gateway to the Internet, allowing you to enjoy movies and music from streaming services such as Netflix and Pandora. Some are equipped with wireless technologies like Bluetooth and AirPlay so you can stream movies and music from a smartphone or tablet to the receiver and listen over real speakers in glorious surround sound.

Not surprisingly, when it comes to surround sound, these do-everything components offer a dizzying array of playback modes, the most important of which make it possible to recreate the excitement of movie-theater sound at home. Let's take a closer look.

The Surround-Sound Standard

Dolby Digital(originally known as AC-3) was introduced in 1991 as a digital coding system for film soundtracks. Within a few years, it became the industry standard for delivering 5.1-channel surround sound in a variety of home entertainment applications, including DVDs, television, video games, and now Blu-ray Discs.

When you play a DVD movie, the Dolby Digital processor in your receiver decodes the soundtrack for playback through a 5.1-channel home theater setup with five speakers - three in the front of the room, two in the back - and a subwoofer that reproduces a bass-only ".1" channel (for those thunderous explosions we've come to expect from action/adventure flicks).

The technology uses "perceptual coding" to compress the audio signal by removing non-critical bits of data so a movie soundtrack will fit on a DVD and can be delivered efficiently (with lower data rates) over the Internet or broadcast TV.

Dolby Digital Plus is an enhanced version of Dolby Digital that's optimized for streaming and expands the surround-sound experience to 7.1 channels for systems that have four rear speakers instead of two.

DTS Digital Surround is a rival 5.1 format that, while conceptually the same as Dolby Digital, uses a compression algorithm that audiophiles consider more refined. Like Dolby Digital Plus, DTS-HD is a more efficient version of DTS Digital Surround that also supports 7.1-channel sound.

State-of-the-Art Surround Sound

Dolby TrueHD and DTS-HD Master Audio were introduced several years ago to bring state-of-the-art digital sound to high-definition Blu-ray Discs. The Holy Grail of home theater sound, these 7.1-channel formats deliver uncompressed sound that is identical to studio master recordings. In other words, with a high-quality A/V setup you will experience the same pristine sound Hollywood sound engineers hear when they mix movie soundtracks. How cool is that?

Stereo to Surround

Nestled among the sprawling list of sound modes found on today's receivers are advanced versions of the Dolby Pro Logic matrix technology that helped start the home theater revolution back in the 1980s.

  • Pro Logic II creates 5.1-channel surround sound from ordinary stereo content.
  • Pro Logic IIx expands stereo or 5.1 content to 6.1 or 7.1 surround sound.
  • Pro Logic IIz adds two front height channels to create an even more spacious 9.1-channel surround experience.

Taking things even further and providing incredible flexibility, DTS Neo:X creates 7.1-, 9.1- or 11.1-channel surround sound from stereo or multichannel sources. And you thought six speakers was a lot…

To learn more about home theater sound options, consult a CEDIA professional. Click here for a list of CEDIA-member home technology professional companies in your area.