Wednesday 3 August 2016


An introduction to Object Based Audio

Or in other words, Dolby Atmos, DTS:X and Auro-3D.

What is OBA?

While regular home cinema systems comprise five, seven, nine or more speakers wrapped around a room to provide the surround sound experience, OBA takes this two stages further. Instead of the sound emanating from a horizontal circle of speakers, with the sounds panned around from speaker to speaker, OBA adds speakers above head height (and/or in the ceiling) which provide a third dimension to the sound experience, allowing the sound to come not just from the horizontal plane but the vertical as well.

This gives a much larger soundstage, with the addition of height and is very impressive in its own right, but where the technology really comes into its own is in the precision placement of the sounds. When the director and sound engineers are at the post production stage with their movie, they can position the sounds anywhere within a three dimensional space, so you feel like you’re right in the middle the action. In effect the sounds are freed up from the constraints of traditional channels (front, sides, rears etc.) and are now treated as individual audio objects (hence OBA) which can be placed anywhere in the room. The processing electronics then determine which combination of speakers in the room are required to position the sound exactly where the director wanted it.
Who makes OBA systems?
The first company to come to market with an OBA offering was, unsurprisingly, Dolby. As world leaders in cinema sound the company first introduced its Dolby Atmos system for use in commercial cinemas. With up to 64 independent speakers, the opportunities for creative sound design are immense. The Dolby Atmos sound objects (a total of 118) are used in conjunction with the traditional surround sound set up that features 9.1 beds of audio (nine conventional channels plus one sub-bass channel), to give a total of up to 128 independent audio tracks.

You can read more about the Dolby Atmos cinema system at this link:
Dolby then introduced a domestic version of Atmos, scaled down from the 64 speakers used in a cinema to a much more manageable number, typically seven, nine or 11 (although it is possible to use up to 34 speakers in a very large installation - 24 on the floor and 10 overhead).

The nomenclature for the domestic set ups follows the familiar 5.1, 7.1, 9.1 pattern established by conventional home cinema, but also indicates the number of ceiling/elevation speakers employed, e.g. 5.1.2 (five main speakers, one subwoofer and two ceiling speakers) or 7.1.4 (seven main speakers, one subwoofer and four ceiling speakers).

You can read more about the Dolby Atmos home system here:

Hot on the heels of Dolby was a system developed by Belgium based Auro Technologies called Auro-3D. Again taking the standard 5.1, 7.1 format, Auro-3D enhances this with both height and overhead channels. The height information recorded during production is mixed into a standard 5.1 surround PCM carrier and the Auro-3D decoder extracts the signals during playback to recreate the height channels via speakers placed around the room at 30 degrees above head height. This configuration is referred to as 9.1 (five ear-level surround speakers, four height speakers and one sub-bass speaker).

A single overhead speaker (sometimes called the Voice of God speaker) adds an extra dimension and forms a link between the height layer speakers around the room for ‘fly-over’ effects. The nomenclature for the simplest system featuring this VOG speaker is 10.1. Adding an extra height centre channel speaker makes it into an 11.1 system and two additional rear surround channels make it 13.1.

More information on the Auro-3D system can be found at this link:

An additional technology called AuroMax expands the basic Auro 11.1 and Auro 13.1  into "zones", allowing placement of sound at discrete points around the wall or ceiling and within the three dimensional space, making it similar to the other object based audio formats.

The third variant of OBA comes from DTS in the guise of its DTS:X system. This differs from the other two systems in that it isn’t tied to a particular speaker layout and will work (to a degree) with existing simple 5.1 speaker systems.

In the cinema environment, the speaker array used for DTS:X is a hybrid of the Dolby Atmos and Auro-3D set ups, with a standard eight channel base layer, a five channel height layer and three rows of speakers in the ceiling.

During the post production for the movie, the sound can be placed in three dimensional space using DTS:X’s Multi Dimensional Audio platform, just like the Dolby Atmos system. The DTS:X soundtrack from a Blu-ray is then decoded by the processor according to the number of speakers connected to it and their position in the room, giving the best possible results for that particular speaker set up. This makes it truly backwards compatible with existing surround sound systems, but for the best results the additional height/ceiling speakers are going to be needed.

More information about the DTS:X system can be found here:
What's required for OBA in the home?
Just like a traditional surround system you’ll need a Blu-ray plaver, processor and speakers.

Most of the major electronics brands are now incorporating OBA into their processors, particularly Dolby Atmos and DTS:X systems. Models such as the Yamaha RXA-660 feature both formats and are a very cost effective means of getting OBA into a customer’s house. As standard Blu-ray player can be used as all the processing is done within the AV Receiver.

The speakers for the main channels can be identical to the ones used for standard surround systems. For example ourCabasse Eole 3 sub/sat package is the perfect starting point for a compact OBA system. Or a more substantial installation could be done using dedicated cinema in-wall speakers such as the Atlantic Technology IW-155.

The requirement for height speakers presents the installer with two possible options:
  1. install dedicated in-ceiling speakers
  2. use specially designed up-firing speakers
The installation of ceiling speakers is the potentially tricky part of an OBA system. In a new build property or renovation, it’s not an issue of course, but upgrading an existing surround system or installing a whole new OBA system in a ‘finished’ house with the need to install ceiling speakers can be problematic.

For that reason, it is possible to specify dedicated up-firing speakers that beam the height channel information from the walls up to the ceiling, where it is reflected back to the listening position, creating a very effective illusion of sound coming from the ceiling. The Atlantic Technology 44-DAis such a speaker, designed to sit on top of floor-standing front/surround speakers or on a wall mounted shelf.

Where it is possible to install in-ceiling speakers, theCabasse Eole 3 system can be augmented with the matching dedicated Eole 3 in-ceiling version. Or for bigger systems the AtlanticTechnology IC6 OBAis a specially designed in-ceiling speaker for use with Dolby Atmos, DTS:X and Auro-3D systems. It features a frequency response and radiation pattern that has been specifically engineered to provide wide dispersion, eliminating hot spots that occur with standard in-ceiling speakers.
How do you set up the speakers for an OBA system?
Generally the setup is as per a standard 5.1, 7.1 or 9.1 system with the addition of the height channels. As DTS:X is not speaker position or number dependent, the two configurations that can be employed are specified by Dolby and Auro.

For a Dolby Atmos based system the additional two or four height channel speakers are installed in the ceiling or up-firing speakers can be used as per this set up guide:

Auro-3D is slightly different, in that the height speakers are installed on the wall directly above the positions of the main left, right, centre and surround channels at 30 degrees above the listening position. The VOG speaker is to be installed in the ceiling, directly above the main listening position.

Typical Auro-3D speaker set ups and an explanation of the three sound layers are accessible here:
What content is available?

The film companies were a little slow to respond to the opportunities of OBA and so content has been hard to come by. Fortunately this has changed now and the number of Blu-rays being offered with Dolby Atmos soundtracks is increasing all the time. For the latest catalogue of films see this link:

DTS:X movies on Blu-ray are listed here:

The limited number of Auro-3D Blu-rays can been seen at this link:

As more content is being released all the time it is worth bookmarking these links so you can check back regularly to see what new films have been released.

For owners of existing collections of discs, the AV Receivers will convert existing surround sound tracks into pseudo OBA, providing a very effective soundtrack upgrade for legacy movie collections.

1 comment:

  1. I have read your blog it is very helpful for me. I want to say thanks to you. I have bookmark your site for future updates.
    surround sound headsets