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What is Dolby Atmos and Do You Need It?

  • 5 min read

There are dozens of surround sound formats available for use in home theater setups, along with traditional stereo. One format getting a lot of attention is Dolby Atmos.

Let’s find out: 

  • How Dolby Atmos Works
  • How to use Dolby Atmos 
  • Where to find Dolby Atmos content
  • Dolby Atmos pros and cons
  • Is Dolby Atmos right for you?

How Dolby Atmos Works

Dolby Atmos is one of a long line of surround sound formats developed by Dolby Labs. What makes it different is that it uses a special type of spatial coding so that the surround sound experience is more immersive than previous formats. 

Instead of assigning sound elements to specific channels or speakers, each sound element (as decided by a movie sound mixer) is assigned to a spot in 3D-dimensional space (this is where the spatial coding process comes in). This means that Dolby Atmos is an object-based surround sound format, rather than strictly a channel-based format. Of course, to hear the results, you still need speakers. 

After assigning sound object placement, the information is placed into metadata that, in turn, is delivered through a bitstream encoded on a Blu-ray Disc or in a streaming movie or program. The bitstream is then decoded by a special chip in a home theater receiver or AV processor. The receiver/processor then assigns the decoded spatial elements based on the channel/speaker setup used. 

The commercial version of Dolby Atmos provides up to 64-channels to work with. Front, side, rear, back, and overhead speakers are combined with an audio algorithm designed to immerse the listener within a 3D bubble of sound. 

Examples of Dolby Atmos use include effects such as wind, thunder/lightning, rain, planes, helicopters, and other sounds that actually come from overhead with more accurate distance cues than can be achieved with traditional surround sound layouts. It results in the smooth flow of sounds as they move through a movie theater auditorium. It also provides more pinpoint location accuracy for stationary sounds. 

Although having started out for use in commercial movie theaters, Dolby Atmos has been scaled down to provide a similar experience for home users. 

Using Dolby Atmos in a Home Theater

For the home environment, the number of speakers required to support a 64-channel theatrical version isn't practical, so Dolby has provided a way for Dolby Atmos soundtracks to be scaled down to fit the number of channels and speakers that may be available in a variety of home theater setups.

With Dolby Atmos surround sound channel/speaker placement is described differently than what you may be accustomed to. Instead of the 3.1, 5.1, 7.1, 9.1 designations, you will see descriptions such as 3.1.2, 5.1.2, 5.1.4, 7.1.2, 7.1.4, etc…The more channels and speakers that can be used, the more precise the spatial positioning.

 Here is how to translate this number system:

  • Horizontally placed speakers (left/right/center front and surrounds) are the first number (3, 5,7,9, etc....)
  • The second number (.1 or .2) designates the number of subwoofers.
  • The last number (usually .2 or .4) designates the number of ceiling-mounted or up-vertically-firing speakers required to hear overhead effects accurately. 

To start, Dolby Atmos can be found in some soundbars and TVs, but obviously there would be limitations in recreating spatial sound coming from a slim bar sitting below your TV. A Dolby Atmos capable sound bar or TV would be reliant on speaker drivers pointing towards your ceilings and walls to bounce sounds to create the perception of surround sound. 

While this can work in an ideal symmetrical room environment with flat walls and ceilings, every living room is different which leads to an inconsistent experience depending on your configuration. 

Also, if you are passing Dolby TrueHD encoded Atmos signals through a TV to an external audio system, the TV and the audio system need to be equipped with eARC to handle the additional bandwidth. However, some recent model TVs capable of decoding Dolby Atmos can pass the Dolby Digital Plus encoded Atmos signal to an audio system via ARC.

For a more traditional wired setup, look for a Dolby Atmos ready AV receiver paired with separate speakers. To get the maximum benefit of Dolby Atmos height effects, it's best to use ceiling-mounted speakers for the height channels.

Dolby Atmos

A more convenient, but less effective option is to employ vertically firing floor standing or bookshelf speakers in your setup. This allows Dolby Atmos information to be directed to and bounced off the ceiling, then back down to the listening position. The ceiling needs to be flat. The speakers also need to be able to project sound the required distance to reach the ceiling with enough force to reflect back down. 

NOTE: If a speaker cabinet houses both horizontally and vertically firing speakers, the vertically firing speakers require separate speaker connections. 

Dolby surround sound

Where to Find Dolby Atmos Content

Dolby Atmos-encoded content is available on a growing number of Blu-ray and Ultra HD Blu-ray Discs, as well as select streaming content from Netflix, Amazon Prime, iTunes, Vudu, and other services, provided your smart TV or streaming device supports it.

If a specific Blu-ray/UHD Blu-ray disc or streaming content is Dolby Atmos coded, but your receiver or system isn't Dolby Atmos-compatible, it just ignores that information and defaults to another compatible surround sound format that is included in the content, such as Dolby Digital or Dolby Digital Plus.

Dolby Atmos In a Nutshell

Dolby Atmos Pros

Dolby Atmos Cons

Expands surround sound to include overhead effects.

Overhead sound cues need to be encoded in the content. 

More precise placement of sound objects around the room. 

Not all content benefits from overhead sound effects. 

Content available on Blu-ray/Ultra HD Blu-ray and select streaming movies/programs.

Requires compatible receiver/processor to decode Dolby Atmos information.

Almost all existing Blu-ray Disc players and HDMI cables are compatible. 

Not all smart TVs or media streaming devices can pass-through Dolby Atmos coding.

Also available on some soundbars and smart TVs. 

Requires a more complicated setup with additional speakers and a flat ceiling for the best results. 

Dolby Atmos Isn’t Right for Everyone

If you have the budget to meet the added costs and a room with a flat ceiling, Dolby Atmos can enhance your home theater experience, but keep in mind that the optimal setup is more complex than a basic 5.1 channel system. In addition to compatible equipment, you need more speakers and more speaker wire. 

A traditional 5.1 channel system with left/right front, center, left/right surround speakers and subwoofer, is the most widely used home theater setup and provides a satisfying surround sound experience, especially with smaller rooms. 

Surround Sound Setup

Another thing to take into consideration is that the majority of available DVD, Blu-ray Disc, and streaming content has been and continues to be mixed in Dolby or DTS 5.1 surround sound.

However, just with any surround sound layout, a 5.1 channel setup in most cases uses wired speakers, and many consumers end up going with a soundbar and diminished surround sound performance to avoid that extra hassle.

A good solution to consider is a system that provides wireless speakers, such as the WiSA Certified Enclave Audio CineHome II or THX-Certified CineHome Pro. These are both 5.1 channel systems with Dolby Digital Plus, Dolby Digital, DTS Digital Surround, 2 and 5.1 channel uncompressed PCM that connects easily to a TV via an HDMI-ARC (Audio Return Channel) connection.

The Enclave Audio systems also provide additional Dolby ProLogic II, Whole Room Stereo, and Dolby Dynamic Mode audio processing which adds further listening flexibility.

NOTE:WiSA announced in March 2020 that it's adding support for Dolby Atmos, but its product licensees, including Enclave Audio, have not adopted its use.

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