Published On: July 28, 2014

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

Published On: July 28, 2014
Last Updated on: October 31, 2020
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Dolby Atmos at Home: The Known Knowns and the Known Unknowns

Last 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,...

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

By Author: Dennis Burger

Dennis Burger is a native Alabamian whose passion for AV began sometime before the age of seven, when he dismantled his parents' brand new 25-inch solid-state Zenith console TV and exclaimed--to the amusement of no one except the delivery guy--that it was missing all of its vacuum tubes. He has since contributed to Home Theater Magazine, Wirecutter, Cineluxe, Electronic House, and more. His specialties include high-end audio, home theater receivers, advanced home automation, and video codecs.

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 . . .

atmos.jpgAs I said above, cinematic Atmos is capable of delivering those 128 elements to as many as 64 speakers (62 independent full-range channels, plus two LFE channels). I don't think anyone expected Atmos at home to support nearly that many, but our early peeks at the receivers and preamp-processors announced thus far painted a pretty limiting picture of what was possible and led to some confusion as to exactly where the overhead channels would be placed in an Atmos home theater system. Pioneer's SC-89 9.2-Channel Networked Class D3 AV Receiver, for example, features eleven sets of speaker binding posts in all, with the extra channels (beyond 7.1) labeled "Front Wide" and "Top Middle." Others, like Onkyo's upcoming TX-NR3030 11.2-Channel Dolby Atmos Ready Network A/V Receiver, label the extra channels as simply "Top 1" and "Top 2."

I got in touch with Katherine Harbeston of Pioneer to ask why the extra channels are labeled this way, and she told me, "The speaker outputs are not locked. The owner's manual shows how different configurations can be wired. There's just no easy way to label the rear panel for all situations." And she's right. There isn't. Most Atmos-capable receivers and preamps come in either 9.2 or 11.2 varieties for now (with a few mid-priced models, like Onkyo's existing TX-NR636, which is getting an Atmos update in the coming months, limited to 7.2). But even the 11.2-channel models support a number of different setup configurations. To explain them, we need to add another decimal place beyond the traditional "point one" or "point two" to accommodate how many overhead speakers you use.

With 11 amplified channels at your disposal, you could opt for a 7.1-channel system on the floor and four speakers overhead (7.1.4); 5.1 plus front width speakers on the floor with four speakers overhead (also 7.1.4); 5.1 on the floor plus front-height channels, with four speakers overhead (also also called 7.1.4); a 7.1 system plus front width channels on the floor with two overhead speakers (9.1.2); or a 7.1 system on the floor with front heights plus two overhead speakers (also called 9.1.2).

For now, that looks to be the limit to the amount of channels that receiver manufacturers are willing to cram into one chassis, but it's not the theoretical limit of Atmos' home capabilities. In a new blog post, Dolby Director of Sound Research Brett Crockett reveals that the home version of Atmos is capable of handling up to 24 speakers on the floor and 10 overhead, and that one of Dolby's hardware partners is indeed planning to release a 32-channel AV receiver at some point. (It's unclear if Crockett is referring to the Trinnov Audio Altitude 32 AV processor slated to debut in September, or if an actual integrated receiver is also in the works.) He also clarified that, since Atmos at home is being delivered as an extension of Dolby TrueHD and Dolby Digital Plus, you won't need a new Blu-ray player or media streamer (or new HDMI cables) to deliver the format to compatible receivers and pre/pros. You'll merely need to ensure that your player's output is set to bitstream instead of PCM.

Another question that consumers have been curious about is whether or not future Blu-ray discs (once existing titles are re-released with Atmos) will come in the form of separate Atmos and non-Atmos versions. I spoke with Chris Walker, Director of Product Planning and Marketing for Pioneer Electronics, last week, and he cleared up that question for me. As it turns out, Dolby will be delivering Atmos and non-Atmos audio within the same stream. So, if you play an Atmos-equipped disc on a non-Atmos-equipped receiver or surround processor, it will recognize that fact and "degrade" to standard 7.1- or 5.1-channel TrueHD. In fact, the audio stream will include within it lossless Atmos, lossless 7.1 TrueHD, lossy Dolby Digital Plus Atmos, and DD Plus surround sound, as well as plain vanilla Dolby Digital.

Of course, you have to ask yourself, "Self, do I really have room for five pairs of in-ceiling speakers? Or any in-ceiling speakers, for that matter?" After all, some home theater enthusiasts rent or lease or live in homes in which in-ceiling speakers aren't a possibility for structural reasons. In such cases, you'll have to opt for something like Pioneer's new Andrew Jones-designed Dolby Atmos-enabled Elite speaker system, which includes, in addition to a pretty conventional subwoofer and center speaker, both floorstanding tower speakers and bookshelf speakers that feature an additional set of binding posts for upward-firing concentric drivers that bounce the "Voice of God" sound channels off the ceiling. Crockett also revealed in his initial blog post on Atmos at home that Atmos-enabled speaker modules will be available that serve the same purpose but sit on top of the speaker system you already own and love.

futureworks-dolby-atmos-mixing-studio.jpgWhether you opt for in-ceiling speakers (Dolby's preferred solution) or upward-aiming modules or drivers, Atmos will work best if you have a flat ceiling, rather than a vaulted or angled one. With the Atmos-enabled floor speakers, it's also worth noting that they were designed for eight- or nine-foot ceilings, but that they will work (to a diminished degree) with ceilings as high as 14 feet, as long as the ceiling is flat and fairly reflective.

As yet, though, we (and by "we," I mean both consumers and Dolby's hardware partners) don't really have a definitive guide on optimal placement for all of the additional speakers that Atmos brings to the living room, beyond the fact that the currently announced slate of Atmos-enabled receivers label the positioning of the ceiling speakers alternately as Top Front Left and Right, Top Rear Left and Right, and Top Middle Left and Right, with the first two presumably being used for x.x.4 systems (four top speakers) and the latter being used for x.x.2 systems (two top speakers).

It stands to reason that Dolby will release a white paper at some point before September giving more details about optimal speaker placement, but until then I wouldn't go cutting extra holes in your ceilings just yet.

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