Watching a film in a cinema is all about the atmosphere. Plush seats, vivid imagery and expansive audio envelop you into a truly immersive entertainment experience. The movie theatre experience evokes a feeling of verisimilitude, engrossing you totally in the reality presented on screen.
While home cinema is hardly a new concept, a relatively recent innovation has changed the game when it comes to recreating the theatrical effect experienced by movie-goers in the residence. Standards such as Dolby Atmos, Auro 3D and DTS:X have raised the bar when it comes to delivering three-dimensional audio that puts you right in the centre of the action.
So what exactly is 3D audio?
A simple way to understand 3D sound delivery is to compare it to a 3D film: for video, you expand the image out towards the viewer; when it comes to audio you raise it up overhead. An evolution on previous surround sound systems, 3D audio adds a ‘voice of god’ layer or height speakers to add a vertical element to the aural experience.
By delivering sound from all angles – except from below – 3D audio creates a listening experience that hews more closely to how we intercept sounds in real life. Each of the major 3D audio platforms does this in its own unique way, delivering slightly different aural experiences.
Dolby, Auro or DTS?
Dolby Atmos and DTS:X both employ an object-based method for delivering audio. In essence, these systems determine a physical location from which each sound will emanate and then determine in real-time how much sound needs to be channelled through each speaker to create the most accurate directional sound.
This on-the-fly processing relies on certain metadata parameters set by the codec. In Dolby’s case, these set the overall playback level, audio signal compression and level of down-mixing required to create the optimum sound delivery for the number of speakers. As the audio processor knows the precise location of each speaker, it can accurately specify the volume and positioning of each sound within the room, on up to 128 independent audio objects.
Dolby Atmos can support a maximum speaker configuration of up to 24.1.10 (these designate speaker types and should be read as surround:subwoofer:height). Although DTS claims its technology can support ‘any speaker configuration within a hemispherical layout’, it currently only supports up to 7.1.4 or 7.2.4 speaker set-ups. This staggered release strategy from DTS means it lags behind the others in terms of flexibility, despite its promises of greater flexibility over its rivals.
Auro 3D, with its channel-based delivery, comes with the most stringent requirements. For this system to provide the best effect possible, speaker placement must be built strictly in line with the company’s optimum speaker configurations, which run to a maximum of 13.1. Like the other codecs, a vertical audio channel is incorporated into the ceiling to deliver that all important helicopter flying overhead.
Despite the differences between them, the choice of most suitable codec will undoubtedly come down to content. Much as in the Blu-ray/HD DVD format war, various movie studios have pledged support for different 3D audio platforms; although Dolby, with its reputation as a benchmark in quality, is well ahead in this regard.
In order to maximise the amount of content available for your home cinema, an ideal set-up will support more than one of these systems. Ideal layouts have been devised for multi-codec support with the least amount of compromise between the various platforms; a connected home expert will be best placed to advise on this, as this varies significantly depending on the construction and layout of the room.
“As with any audio set-up, correct speaker placement can greatly improve the aural experience. With the more forgiving object-based codecs, the installer is given a bit of flexibility; however, it still requires careful calculation. A codec won’t be able to make up for poor quality speakers or amplifiers or bad room acoustics (although some products can certainly help), nor will it perform acceptably unless calibrated using the right source material. Room design and layout is therefore a crucial part of creating a successful home cinema environment, and the acoustics of the room itself are the single most important aspect.”
— Ryan Ovens, projects director at Andrew Lucas London
The height and finish of the ceiling will have a significant effect of audio quality, as will the material used for the walls and flooring. Ceiling tiles and fabric will reflect sound differently from plaster, potentially muffling or causing the sound to become slightly unaligned. This is a particular problem when specifying upward-firing speakers, which are additional units that sit on top of the surround sound unit and emit sound that rebounds off the ceiling to reach the listener. In-ceiling speakers can deliver the ‘voice of god’ channel in a more accurate way and will offer much better audio quality in rooms where the acoustics are less than perfect.
A new high point for home entertainment
In the same way that 4K has become well established as benchmark for visual quality, so too is 3D audio quickly becoming the new standard for high-end cinematic audio. For the three companies behind the dominant codecs, the end goal is surely to have utter flexibility regarding speaker positions – this means no channel assignments at all; instead, everything will be handled by the processor. For now, 3D audio takes careful planning and implementation in order to get it right – but the results are absolutely worth it.