Dolby Atmos - 3D Sound in Home Theater

Everyone is talking about Dolby Atmos, the first AV receivers for it will soon be available, and the first Blu-rays with the new sound format are also expected to appear shortly. But is this all just a ploy to sell more speakers, or is there really something behind it? An overview. Since 2012, not only have images in the cinema been three-dimensional, but so has the sound. Dolby Atmos is the technology behind this effect, first experienced in the Dolby Theatre in Hollywood. Some major cinemas in Germany, Austria, and Switzerland are now equipped with Dolby Atmos, creating a spectacularly realistic movie experience in combination with 4K projection. Now, this new technology is slowly but surely making its way into home theaters. But how exactly does Dolby Atmos differ from “classic” surround sound?

Atmos: More tracks, more speakers, more 3D

Dolby Atmos allows for more precise sound placement in the room than surround systems like 5.1 or 7.1 can offer. This is achieved by giving each of the maximum 64 usable speakers an individual signal. The use of ceiling speakers is crucial, as they create an additional layer besides the front, back, left, and right sound. This is not the case with previous surround sets. Not only is the sound from above missing, but often the same audio signal is sent to several speakers at once. With Dolby Atmos, in theory, there can be an unlimited number of audio tracks, but the first generation supports up to 64 individual tracks.

Dolby Atmos: What’s new

But the new sound format is actually more than just an upgraded Dolby TrueHD with extra tracks. For the first time, it promises realistic three-dimensional movement of sound objects in the room. In previous formats, the surround atmosphere and sound movements are encoded into different tracks during mixing. At home, the home theater system tries to reproduce this studio-defined spatiality as well as possible. And even with the advances in calibration and room correction in recent years, this reproduction can sometimes work better, sometimes worse. The further the room and speaker setup deviate from a standardized cinema situation, the less likely it is that the acoustic presentation will be correct. With Atmos, Dolby takes a different approach: initially, they start with the usual 5.1 or 7.1 fixed audio tracks, produced and mixed as before. Thus, Dolby Atmos is logically also compatible with older AV receivers. All additional tracks are assigned to up to 128 audio objects. These can be synthetic effects or the sounds of real objects moving through the room. Metadata is also stored for each audio object, containing information about the spatial position and size of each object at any given time. During playback, this metadata is also available to the AV receiver, so it is not only dependent on fixed audio signals. In fact, the receiver recalculates the acoustic movements of all audio objects in real time, so they can be reproduced optimally under the given conditions. The result is a realistic three-dimensional acoustic image, which was not possible with previous means and should be much less dependent on room conditions.

'Smart' Surround

It becomes especially spectacular when, for example, a helicopter moves from the front left to the back right over the audience. The speakers along the simulated path of the helicopter are then powered with the appropriate signal one after another. Ambient sounds are also placed much more precisely and don’t just blend into a one-dimensional background. As a result, viewers can perceive many more details and assign them spatially, so they can immerse themselves even more in what's happening on screen. The advantage of object-based audio mixing is that it should also work with smaller setups and you don’t have to install dozens of speakers. In a large cinema hall, it makes perfect sense to make use of the space—but what about the home theater fan in their more limited movie room at home? First, they need a Dolby Atmos-capable AV receiver. Onkyo, Denon, and Marantz already added suitable devices to their portfolios in June. At least you won’t need a new Blu-ray player, as the Dolby Atmos audio tracks are processed by the appropriate AV receiver.

What you need for Dolby Atmos

Theoretically, Dolby Atmos should be able to improve spatiality even with a conventional 7.1 system. However, to achieve a true 3D effect, in addition to the new AV receiver, ceiling speakers are also required. At least two should be present, but Dolby recommends four for a home theater setup. They can be added to an existing surround system, turning it into, for example, a 5.1.2 (five main speakers plus subwoofer plus two ceiling speakers) or 7.1.4 system. Since it's clear not all home theater enthusiasts want or are able to mount speakers on the ceiling, Dolby has looked for other solutions from the beginning. They believe they've found these in special speakers with an additional Atmos unit built in, which emits the relevant signals upward. Reflections from the ceiling are supposed to create an effect comparable to permanently installed ceiling speakers. Whether this actually works in reality remains to be seen. Still, the idea is exciting, especially since there are even special Atmos add-ons available that can upgrade existing speaker systems. Either way, you won’t get around at least one new purchase if you want to upgrade to Dolby Atmos. At least if you’re already planning to buy a new AV receiver, the additional investment is quite manageable. However, Dolby Atmos faces the same initial challenges as all other new technologies: so far, aside from a few demo discs, there are no sources with the new format. The first films on Blu-ray with Dolby Atmos are expected to be available in the last quarter of 2014.

Outlook

At least it seems that things are moving much faster with Atmos than was the case with 4K resolution, for example. Just in time for the season, practically all relevant AV receiver manufacturers have announced their first Atmos-enabled products, and the first ones should actually be available right about now. With Steinway & Sons, even the first recognized high-end manufacturer has announced an appropriate processor. And the first Atmos speakers and speaker add-ons are also coming soon.