Dolby Atmos at Home: The Known Knowns and the Known Unknowns

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dolby-atmos_505_120312050748.jpgLast month, a number of hardware manufacturers officially lifted the lid off of the AV industry's worst-kept secret: Dolby Atmos was finally coming home. In some form or another, at least. New AV receivers and surround processors from Pioneer, Onkyo, Integra, Denon, Marantz, and Yamaha will support the object-based, multi-dimensional surround format, some sooner than later, via firmware updates scheduled to be released anywhere between September and "the end of the year."

In the days immediately following the announcements, two things became clear: one, a whole lot of home theater enthusiasts are excited about the prospect of adding Atmos to their systems; and two, the information initially provided by Dolby and its hardware partners raised more questions than it answered. How many objects can the home version of Atmos support, for example? How many channels will it theoretically support? How will Atmos be delivered at home? Do I need a new Blu-ray player? Are the ceiling channels matrixed?

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If those questions themselves don't make much sense to you, perhaps a bit of explanation is in order. The theatrical version of Dolby Atmos debuted back in 2012 with Pixar's Brave. The two features of Atmos that stood out for most moviegoers were that the format supported up to 64 channels of audio and added a distinctive overhead (or "Voice of God") element to the surround mix. In other words, rather than merely encircling you with audio, Atmos creates a dome of multi-dimensional sound over and around you.

dolby-atmos-speaker-placement-diagram-640x531.jpgPerhaps more interesting from a technical point of view is that, despite all the talk about how many channels it supports, Atmos isn't an entirely channel-based system. Instead, it's an object-based system. To understand what that means, think of it like this: in a traditional 5.1- or 7.1-channel surround mix, if the engineer wants a bumblebee to fly around the room clockwise from front left to back right, the sound of that bee is mixed into the front left speaker at a pretty high volume, which is faded down as its volume is quickly faded up in the center speaker, then down in the center as it's raised in the front right, and so on and so on. As soon as the final mix is completed in a purely channel-based system, that bumblebee is forever a part of those discrete channels, sharing space with soundtrack music, vocals, rain, wind, and whatever else might contribute to the aural landscape of the scene in question. In an object-based system like Dolby Atmos, though, that bumblebee is instead its own object (or element), which can be moved around in 3D space by the engineer. Combine that with what are called "beds," which correlate with the concept of channels in a traditional surround sound system, and you can see that Atmos is incredibly sophisticated under the hood.

The cinematic Atmos system supports up to 128 "bed plus object" combinations. If you have a 9.1-channel bed, the Atmos soundtrack can also handle up to 118 discrete objects whose exact distribution throughout the speaker system depends on how many speakers there are in the system and where they're placed. So, when enthusiasts ask how many objects Atmos at home supports, that's what they're asking about. It's probably safe to assume that the bed for Dolby at home will likely max out at 7.1 channels instead of the theatrical max of 9.1, but the simple truth is that we don't yet know exactly how the bed/object relationship will play out in the consumer space.

Click on over to Page 2 to find out where those 128 elements go and how to best confirgure your Atmos system . . .


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