Dolby Atmos has been the Holy Grail of cinema surround sound since it was first revealed back in April 2012. Allowing filmmakers to turn individual sounds from a movie soundtrack into separate audio objects, it uses an overhead speaker array to put you in the middle of a dome-like soundscape, with trackable audio sources flying all around above you. It’s truly impressive, and is slowly being introduced to more and more multiplexes, and used increasingly by filmmakers.
Inevitably, anyone that hears an Atmos film wants to get something similar in their home, and earlier this summer Dolby announced it was partnering with a number of home cinema gear manufacturers to make that a reality. It also promised that in-ceiling speakers wouldn’t have to be a requirement, using separate up-firing speakers to emulate the effect by reflecting sounds off the ceiling.
Having heard the simulated reflected surround sound efforts of numerous soundbars, I was a little skeptical as to just how well the Dolby system would perform. It was with some trepidation then that I headed into Dolby’s London office for a demo of the home-bound Atmos kit, set to complement anything from a basic 5.1 set up to more lavish dedicated home cinema rooms. But not only does it work, it works bloody brilliantly.
Atmos supports 128 individual sound objects simultaneously within a mix. In a cinema, these can be sent to as many speakers as can be fitted into a multiplex screen, but in a home environment it’s rare for people to have anything more lavish than a 5.1 set-up. Atmos soundtracks headed to the home therefore are reworked using Dolby’s new Spatial Coding technology, which works within the Dolby Digital Plus and TrueHD formats to group sounds together and provide them with height and movement metadata fitting for more modest speaker arrays. This information is sent to the Dolby Atmos Home Theatre Renderer found in Atmos-compatible AVRs before being sent on to overhead or ceiling-facing Atmos-enabled speakers.
I was shown a number of Atmos demos, both in Dolby’s cinema-sized demo room and in a more intimate living room environment. The living room scenario held its own remarkably well -- I was surprised at how expertly it managed to retain the sense of scale and movement that the larger cinema environment boasted.
But what was most impressive was just how similar the installed overhead speakers and the ceiling-reflecting Atmos-enabled speakers sounded. For those that can’t afford (or get permission) to install overhead speakers in their home cinema room, a specially designed set of ceiling-facing speakers can be used with Atmos instead. These sit on top of (or as close as possible to) the front left and right and rear left and right channels.
Pitched at a particular angle, the Atmos Renderer in the AVR calculates exactly the micro-second delay at which to project sound towards the ceiling to make it reflect to your ear in a way that makes sound appear to come from a source physically above you. The specialised speakers will work just as well with 5.1 as 7.1 systems, and a number of leading home cinema speaker manufacturers are said to be waiting in the wings to announce their own Atmos compatible speakers and AVRs -- Onkyo being the first among them. Thankfully, there will be no need to get rid of your existing speaker set, should you have some.
Switching back and forth throughout a clip of Star Trek Into Darkness between the overhead and Atmos-enabled speakers, it was hard to hear the difference between each speaker set -- both convincingly gave the sensation of sound sources hovering overhead, and acted to heighten the sense of immersion in the scene. Spears thrown at Captain Kirk felt as though they travelled not just from the rear channel to the side around to the front, but overhead too, and it was easy to isolate individual objects seen on screen in the mix. Those worried that the reflected sounds would offer an inferior experience need not be concerned.
To achieve such a great performance from the reflected sounds, Dolby spent years researching how the ears and brain work in harmony to determine overhead, or “3D”, sounds. Taking into account the way overhead sounds hit the top of our heads before spreading down into our ears, Dolby’s reflected Atmos output features a “notch” taken out of the high end frequency range, making the sounds seem more natural as they hit the ear. That precise frequency range at present remains a closely-guarded “secret sauce” for Dolby (though a frequency range analyser and a white noise track would be able to identify it once the systems become commercially available).
There will of course be things unique to each room to consider when it comes to using the Atmos-enabled speaker set. The height and angle of your ceiling will affect the delivery of the sounds, as will the reflectivity of the surface. Though microphone-aided set-up systems will be able to make finding the optimum placement as hassle-free as possible, you may find yourself popping the speakers onto their own separate shelves slightly above or behind your standard speaker array to compensate for minute delays, should your audiophile standards not be met.
Your living room isn’t the only place Dolby has its sights set on for Atmos either. It’s working on mobile technology that will add a sensation of height to mobile videos (regardless of the headphones being used), and has also teased that soundbars using similar ceiling-directed speakers could be in the works. According to Dolby:
To test and optimise that technology for our partners, we have built our own home audio prototypes in a wide variety of form factors -- from high end set-ups involving ceiling speakers and Dolby Atmos-enabled speakers for the most sophisticated home theatre enthusiasts, to more streamlined Home-Theatres-In-A-Box and soundbars. We’ve shown these working prototypes to our consumer electronics, mobile device, and home audio partners, and have been pleased with their response.
It will not however, for the time being at least, be drawn on when or if we’ll ever see an Atmos-enabled soundbar in stores. As for content, Dolby points to Atmos-ready Blu-ray discs being available in time for Christmas, and is in talks to get the format supported by streaming services (something Dolby claims would have a minimal impact on bandwidth requirements). As for backwards compatibility, existing Blu-rays and DVDs will be able to harness the new overhead channels, but will be lacking the height metadata to make Atmos shine. It’ll be up to AVR manufacturers to introduce a post-processing option to simulate an Atmos mix on older titles.
If you haven’t already got a surround sound set-up, the added complexity of Atmos is unlikely to convince you to make the jump. More speakers + more cabling = more headaches during the initial installation, which is a hurdle all home cinema kit has to jump. But for members of the Home Cinema Master Race, with dedicated rooms already decked out with 7.1 speaker systems, La-Z-Boy armchairs and their own personal popcorn machines, Atmos will be a must-have upgrade.