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What is Surround Sound?: Stereo, Surround and ATMOS Demystified

June, 2019

Surround sound is something that we hear about all the time when discussing technology. “Would you like to purchase a surround-sound package?” “You would benefit from the extra speakers.” The comments are endless. But what IS surround sound? What does it actually do? These are questions that aren’t always answered in stores. As your audio experts, we want to make sure those questions are never part of the equation. Therefore, we have put together a list of different surround sound systems and explain what they actually do. We also raise the question- do you really need it? 

 

Stereo

The current standard for televisions throughout the world is stereo sound.  This means a discrete left and right speaker, each able to produce its own signal.  Picture a car whooshing by in a car chase scene. As the car enters the left side of the screen, the engine sound is heard in the left speaker.  As the car crosses the screen from left to right the sound follows the vehicle: first in the left speaker, then evenly between both, and finally just played back from the right speaker before fading away.  This stereo system allows sound engineers to “move” the sound with the picture by adjusting the level of sounds between the 2 speakers.

 

Surround (5.1 & 7.1)

Surround sound builds on the existing 2 speaker stereo format by adding 3 additional speakers and a subwoofer (also referred to as a Low Frequency Emitter or LFE).  A Center speaker is added to the Stereo Left and Right. 2 additional rear speakers, Left Rear and Right Rear, are added to “surround” the listener. “5.1” represents a system using 5 speakers with 1 subwoofer.

 

7.1 surround sound adds 2 additional speakers directly to the left and right of the listener.  This format is less common than the traditional 5.1.

 

ATMOS

Dolby’s ATMOS format adds vertical information by including overhead speakers in its surround sound design.  The clever part of ATMOS is its ability to scale the audio to the number of speakers in the system. An ATMOS system, with a corresponding ATMOS mix, can scale up to as many as 88 speakers or down to smaller home-sized systems.  These systems are typically 5.1.2 or 7.1.4 (adding 2 or 4 height speakers to the existing 5.1 or 7.1 format). More recently available are home theater systems and soundbars which include upwards firing speakers. These speakers are designed to “bounce” the sound off the ceiling, in an attempt to replicate the performance of actual ceiling mounted speakers.

 

Challenges with ATMOS and Surround

ATMOS requires an ATMOS mix as well as an ATMOS-compatible system.  ATMOS mixes can be found on some premium streaming services, but aren’t typically available via standard cable boxes.  Multi-speaker surround sound systems can also be complex to set-up and install, usually requiring in-wall wiring for the cleanest appearance.  While some soundbars can now offer a limited ATMOS or surround experience, these devices can be expensive (starting ~$500 for ATMOS support) and aren’t realistic to put on multiple TVs throughout the home.

 

Getting the best sound from stereo TV

Outside of adding on complex or expensive sound systems, how do you get the best audio performance from your stereo TV?  Televisions that use dbx-tv audio enhancement (like the Hisense H9 series), use sophisticated algorithms to improve sound.  First, the frequency response is enhanced which allows the TV’s speakers to reproduce the rumbling lows typically sent to a subwoofer.  dbx-tv also offer Total Surround, which uses psycho-acoustic algorithms to create the perception of a wide surround sound field, using just the 2 speakers in the TV.

 

Sound too good to be true?  Check out some of our video demos here.