By Brett Crockett, Senior Director of Sound Research
The news was covered all over the world and sparked lots of excited discussion among entertainment fans and audio enthusiasts. I wrote an overview of how Dolby Atmos will work in the living room, but I also saw that many home theater enthusiasts had more specific questions. They wanted to know more about how Dolby Atmos differs from current home theater technology and what they’d need to do to build a Dolby Atmos system of their own. I’ve tried to answer the main questions people have asked below.
How is Dolby Atmos different than typical channel-based home theater systems?
Dolby Atmos is the first home theater system that is based not on channels, but on audio objects. What is an audio object? Any sound heard in a movie scene—a child yelling, a helicopter taking off, a car horn blaring—is an audio object. Filmmakers using Dolby Atmos can decide exactly where those sounds should originate and precisely where they move as the scene develops.
Thinking about sound in this way eliminates many of the limitations of channel-based audio. In a channel-based system, filmmakers have to think about the speaker setup: Should this sound come from the left rear surrounds or the left side surrounds? With Dolby Atmos, filmmakers just have to think about the story: Where is that yelling child going to run? The Dolby Atmos system, whether in the cinema or a home theater, has the intelligence to determine what speakers to use to precisely recreate the child’s movement in the way the filmmakers intend.
Dolby Atmos is also far more flexible and adaptable than channel-based home theater. In a channel-based system with channel-based content, the number of speakers is fixed—a 7.1 system always consists of seven speakers and one subwoofer. With Dolby Atmos, in contrast, you have amazing flexibility: you can get the full experience with just seven speakers or get an even richer, more detailed sound by adding more speakers. As you add speakers, a Dolby Atmos enabled receiver will automatically determine how to use them to create fantastic, immersive audio.
If Dolby Atmos allows me to add more speakers, why do I see A/V receivers with just 11 channels?
Many hardware partners are building or planning to build Dolby Atmos enabled A/V receivers and speakers. Those partners decide what product configurations make the most sense for their customers. But the Dolby Atmos system itself is almost unlimited. If you have the space and budget, you can build a Dolby Atmos system with as many as 24 speakers on the floor and 10 overhead speakers. One of our hardware partners is planning to release an A/V receiver with 32 channels.
Do I have to install speakers in my ceiling?
In real life, sounds come from all around us, including overhead. Having the ability to recreate overhead sounds is a key element in making Dolby Atmos sound so realistic.
The obvious way to create overhead sounds is to install speakers in or on your ceiling. But that’s not the only way to get great overhead sound.
Through our knowledge of psychoacoustics and sound physics, we’ve developed speakers that can create overhead sound even though they’re only a few feet off the floor. These speakers fire sound upward, where it reflects off the ceiling to produce an incredibly lifelike recreation of overhead sound—you really have to hear them to believe them.
You will be able to buy integrated Dolby Atmos enabled speakers that include both traditional forward-firing speakers and upward-firing speakers in one speaker cabinet. (Those speakers have two sets of posts, one for the traditional speaker and one for the upward-firing speaker.)
But if you already have conventional speakers you like, you can simply buy Dolby Atmos enabled speaker modules. These include only the upward-firing speakers. You can put the modules on top of your current speakers or on another nearby surface.
Dolby Atmos enabled speakers can produce an incredibly accurate Dolby Atmos experience in many kinds of rooms. You’ll get the best sound if your ceiling is flat (not vaulted or angled) and made of an acoustically reflective material, such as standard drywall, plaster, concrete, or wood. While we designed the technology for rooms with ceiling heights of 8 to 9 feet (2.4 m to 2.7 m), our testing indicates that you can still hear incredible Dolby Atmos sound in rooms with ceilings as high as 14 feet (4.3 m), though the effect may become more diffuse in rooms with higher ceilings.
Recessed lighting fixtures, chandeliers, crown molding, and heating or air conditioning vents in your ceiling do not noticeably interfere with the Dolby Atmos experience.
How many overhead speakers do I need?
For the best Dolby Atmos experience, we recommend four overhead speakers for most homes. But you can get great sound with just two.
If this is not a channel-based system, why are there predefined speaker positions?
Because Dolby Atmos is new to home theater, we defined a few “reference” speaker configurations to ensure that early customers could have a great experience while having the option to keep most of the equipment they already have.
Among those reference setups are the 5.1.2 configuration, which involves adding two ceiling or Dolby Atmos enabled speakers to a traditional 5.1 system, and the 7.1.4 configuration, which starts with a traditional 7.1 system and adds four ceiling or Dolby Atmos enabled speakers.
But we believe this is just the beginning. Because the Dolby Atmos object-based audio system is so adaptable, you can use many other speaker configurations. No matter what system you build, the Dolby Atmos format and system will adapt itself to output the best audio experience possible.
How will I get Dolby Atmos movies?
We wanted to ensure that entertainment fans could get Dolby Atmos movies in the same ways they get movies now, on Blu-ray Disc™ or through streaming video services.
We invented new scalable algorithms and extensions to Dolby® TrueHD, our Blu-ray™ format, and Dolby Digital Plus™, which is used by leading streaming video providers. Both formats now support Dolby Atmos sound, meaning that you’ll be able to play Dolby Atmos movies from your Blu-ray player or through your favorite streaming service.
Will I have to replace my Blu-ray player or my HDMI cables?
Any Blu-ray player that fully conforms to the Blu-ray specification can play a Dolby Atmos movie without a firmware update. Just remember to set your player to audio bitsteam output mode.
There’s also no need to buy new HDMI® cables. The current HDMI spec fully supports Dolby Atmos audio.
What if I build a Dolby Atmos system but want to play content that isn’t in Dolby Atmos?
A Dolby Atmos home theater can play any stereo, 5.1, or 7.1 content. You can choose to have our technology automatically adapt that channel-based signal to use the full capabilities of your new system, including your overhead speakers, ensuring that you hear realistic and immersive sound.
I hope this post helps answer some of your top questions about Dolby Atmos for the home. We’ll be sharing more information as we get closer to the time when Dolby Atmos enabled equipment is available. Once it is, I urge you to get a demonstration of a Dolby Atmos enabled home theater at your local electronics or audio store. Seeing the system in action will answer your questions; hearing it will blow you away.
Editor’s Note: This blog post was published in June 2014. Please see http://www.dolby.com/us/en/technologies/dolby-atmos.html for the latest information about Dolby Atmos for home theater.
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