By Robin Shore
Last month Dolby announced that its groundbreaking Atmos surround sound format will soon be available outside of commercial cinemas. By sometime early next year consumer’s will be able to buy special Atmos-enabled A/V receivers and speakers for their home theater systems.
I recently had the chance to demo a prototype of an Atmos home system at an event hosted at Dolby’s New York offices.
A brief overview for those who might not be totally familiar with this technology: Atmos is Dolby’s latest surround sound format. It includes overhead speakers which allow sounds to be panned above the audience. Rather than using a traditional track-based paradigm, Atmos mixes are object-oriented. An Atmos mix contains up to 128 audio objects, each with embedded metadata that controls the precise panning location of that particular sound. A hardware unit, referred to as a renderer, interprets this metadata during playback and creates a custom mix tailored to a room’s particular speaker configuration.
While an Atmos-equipped cinema can have up to 64 discrete channels, the home systems will be a little bit smaller. The system on display at Dolby contained only 12 speaker channels in a 7.1.4 configuration, (a standard 7.1 setup with an additional 4 height channels) and those with cash to burn and space to spare can max out their home systems with an impressive 24.2.10 system (24 normal speakers, two subwoofers and 10 height speakers).
For the height channels, Dolby has come up with an innovative solution to simulate the effect of a ceiling mounted speaker without actually having to put anything up there. Soon to be available, Atmos-enabled speakers feature an upward facing driver that bounces sound off the ceiling, tricking the listener into thinking the sound is coming from above. The illusion is enhanced even further with a special filter in the speaker that simulates the psycho acoustic properties of an overhead sound.
Truly ambitious home-theater enthusiasts can still opt to actually mount speakers into their ceiling, but for most people it seems this really won’t be necessary or even advantageous. After listening to the Atmos-enabled speakers I am happy to say that the illusion really does work. The folks at Dolby even showed us an A/B comparison between a set of Atmos-enabled speakers and some real ceiling mounted speakers, and surprisingly nearly everyone in the room agreed that the Atmos-enabled speakers felt more like they were coming from above than the actual in-ceiling ones
The implications of all of this for those working in audio post production seem pretty interesting. Until now, Atmos has been limited to cinema-bound feature films, and only a select number of high-end facilities are currently capable of producing Atmos mixes. The introduction of consumer Atmos systems opens the possibility of Atmos being used in a much wider variety of media (Dolby reps already confirmed that they are actively working to bring Atmos mixes to TV), and with small systems being developed for the home it does not seem out of the question that we may soon see the possibility of Atmos being installed in small- and medium-sized post rooms.
Audio engineer Robin Shore is a founding member and co-owner of Silver Sound, an audio post production house in New York City.