Everyone knows what a 3D movie is, but what about 3D sound? A traditional sound system creates realistic effects by radiating sound from all sides of the viewer. 3D sound does this and more: Effective use of sound from above as well as the skillful placement of moving sound objects in the room effectively fill all gaps in the soundstage produced by a traditional surround sound system. The result is a truly immersive — and highly realistic — experience.
For those of you who have never heard of Dolby Atmos, that doesn’t mean you haven’t actually heard it. Many movie theaters have been using this technology for a few years now, so in all likelihood, you have. What’s new is the extension of this 3D sound technology into home cinemas. Surround sound systems with Dolby Atmos speakers along with corresponding Blu-ray discs with soundtracks mixed for Dolby Atmos are available now from a range of manufacturers.
How does Dolby Atmos work?
Unlike traditional surround sound systems, the moving audio component in Dolby Atmos is not channel-based, but rather works with so-called sound objects. In a 5.1 or 7.1 channel-based system, the sound is mixed in a way that allows it to be allocated to the 6 or 8 available channels. To enhance the effect of an explosion on the left side of the screen, the sound would simply be sent to the speakers on the left side.
This system works well, but it limits the way sound can be mixed as well as the number and arrangement of the hardware components employed to play it back. It’s the reason surround sound systems almost always come as 5.1 or 7.1 speaker configurations. Dolby Atmos, on the other hand, is a scalable and adaptable system. A soundtrack mixed for Dolby Atmos can work with 8 speakers in a 5.1.2. arrangement in a home cinema or with up to 64 individual speakers in a large movie theater. For home cinema use, however, a 5.1.2, 5.1.4, 7.1.2 or 7.1.4 are the most common arrangements. The numbers are broken down as follows: First the surround speakers, then the number of subwoofers (usually 1) followed by the ceiling-mounted or upfiring speakers.
The Dolby Atmos speakers in movie theaters are inevitably mounted to the ceiling and this is also an option with home cinemas. Discrete ceiling-mounted speakers, however, involve a good bit of installation work. Luckily, there are other options such as upfiring speakers that can be placed on top of existing front or rear speakers. Upfiring speakers use the ceiling as an acoustic mirror to reflect sound waves. This is why they are sometimes referred to as Atmos reflection speakers. The sound that reflects off the ceiling effectively places the sounds above the viewer/listener, a system that not only saves time and nerves, but which works very well acoustically.
Sound objects: Assigning a sound to a space, not a speaker
The use of sound objects instead of channels gives the Dolby Atmos system an incredible amount of flexibility. The sound object is an aural element that has been liberated from a fixed point of playback. Instead of radiating from a front right or center speaker, a sound object is defined as a movement through space, or directional data. A special renderer in Dolby Atmos A/V receivers uses the Atmos algorithm to correctly allocate sound objects to the various available speakers in a system, allowing the object to move freely through the soundstage.
This is very different from a fixed channel system., Dolby Atmos sound objects are not preassigned to discreet channels in the recording studio. With Dolby Atmos, the example we used before of an explosion on the left side of the screen is simply defined as a sound object coming from a certain leftwards position. It doesn’t matter how many loudspeakers are available on the left side: Dolby Atmos technology will activate the speakers available to it as needed to produce the given effect. Note that basic surround sound is still produced by the traditional 5.1/7.1 channel-based setup. This system has not been replaced, it has merely been supplemented by the addition of more dynamic sound effects.
The hardware: What do you need to make it work?
Let’s start with receivers. It’s a pretty safe bet that all A/V receivers on the market today are equipped with Dolby Atmos. There’s even a good chance that slightly older versions have already incorporated new firmware than allows for Dolby Atmos playback, e.g. the A/V receivers from Onkyo launched at the beginning of 2014 (TX-NR636, TX-NR737 and TX-NR838). Yamaha has also recently announced that it will be making its 2014 range of devices compatible with Dolby Atmos via a firmware update. This is only possible, however, because Yamaha had the foresight to pre-install Dolby Atmos processors in these systems. Models that predate 2014, however, will most likely not be able to support this standard, which means a new A/V receiver is required. You’ll find a list of A/V receivers with Dolby Atmos technology available for purchase here.
The good news for all those who are already happy with their current speaker system but wouldn’t mind migrating over to the new technology is that Dolby Atmos receivers can be used with standard surround sound systems. The system can then be supplemented with add-on modules such as additional ceiling or upfiring Dolby Atmos speakers. For those who are looking to get a new home cinema system, it’s worth considering a Dolby Atmos surround sound set.
Just as an existing system can be upgraded for Dolby Atmos, a Dolby Atmos system is also backward compatible and can also be used to play back standard home cinema signals. This, however, should become increasingly unnecessary as more and more movies are being released on Blu-ray with Dolby Atmos soundtracks. The first ever movie released on Blu-ray encoded for Dolby Atmos was Transformers 4, launched on September 30, 2014. Since then, the number of movies available in this format has grown to be quite large and includes Mad Max: Fury Road, American Sniper and Pixels. You’ll find a list of movies with Dolby Atmos soundtracks here. Many streaming services also offer films with Dolby Atmos soundtracks.
The range of surround sound loudspeaker systems equipped for Dolby Atmos is also increasing. At the present time, just about every manufacturer of home cinema systems is working on the construction of Dolby Atmos speakers. Teufel Audio, a pioneer with its early and broad adoption of THX standards, was quick to respond to this latest surround sound innovation as well, presenting its first Dolby Atmos prototype at IFA 2014. At IFA 2015, Teufel unveiled the LT 5 licensed by Dolby Atmos, this time not as a prototype, but as a finished product available now in the Teufel Audio webshop.
Coda: A revolutionary way to experience home cinema
At the present time, Dolby Atmos looks set to become the new standard for home cinema sound. One reason for the current wide adoption of the standard is the successful development of upfiring speakers capable of creating targeted moving audio from above. These easily implemented speakers can be used instead of discrete ceiling-mounted units, components that all but die-hard home cinema fans would be loath to install. One exciting aspect of the increased deployment of Dolby Atmos is the scope for creativity it opens to sound designers. Instead of allotting sounds to 6 or 8 strictly defined channels, effects can be more freely distributed for soundtracks that live up to the best picture quality in terms of dynamics, clarity and hyper-realism.