The Ins and Outs of Dolby Atmos

Dolby Atmos (or Atmos) is currently the dominant immersive audio format. While often thought of as an evolutionary step from 5.1 and 7.1 surround sound, it differs significantly from previous speaker-based surround, stereo and quad formats.

Atmos and immersive audio are object-based rather than “channel-based,” where an audio track is assigned to a speaker. Being object-based allows immersive mixes to scale to both larger and smaller speaker setups, ranging from large-scale theaters down to stereo, 5.1, and even binaural headphone listening.

The minimum speaker configuration for mixing in Dolby Atmos is 7.1.4, which equates to seven surround speakers, one low-frequency extension speaker (a subwoofer, but not acting as a boom-boom box (see Will Kennedy’s “Know Your Lows,” June 2024), and four height speakers. 9.1.4 and 9.1.6 are also common standard Atmos mixing configurations.

This equates to a minimum of 12 speakers required for a basic Atmos setup.

I chose an immersive bundle of 11 matched IK Multimedia iLoud MTM MKII monitors and added a JBL\LSR310S subwoofer. This decision was based not only on this model’s excellent, physics-defying sound, but just as crucially, the model’s compact size.

When it came to choosing an Atmos interface, I quickly learned there were many factors to consider.

The Inputs and Outputs of a Dolby Atmos Interface

To accommodate a 7.1.4 configuration, one needs an interface with 12 outputs. Since most audio interfaces typically come in configurations of 2, 4, 8 or 16 channels, with an equal number of inputs and outputs, the most obvious starting point is a 16×16 channel option.

From a functional standpoint, any 16-channel interface should work, right? The assumed answer is yes. The practical answer is sort of.

Regarding Atmos, you also need to consider factors such as volume control, corrective room EQ and time delay (essentially to ensure the sound of the speakers around you arrives at your ears simultaneously and phase aligned).

Channel Count Practicalities

First, some questions: Are you planning to mix strictly in Atmos, or will you also be mixing in stereo? Will you be using the left (L) and right (R) Atmos speakers for both tasks, or do you have a different dedicated set of stereo monitors? Are you focused only on mixing music, or are you also recording?

Suppose the answer to all of the above is yes. In that case, a 16-channel interface will cover your bases nicely—plenty for tracking, plenty for immersive mixing and even four remaining outputs for an extra pair or two of stereo monitors.

If you only plan on mixing, then on a practical level, a 16×16 channel interface is a waste of input channels.

A modular and expandable option could be to start with a four or eight-channel interface equipped with an ADAT optical output, and add an ADAT expansion box. Three that come instantly to mind are the Ferrofish Pulse8 AE 8×8 AD/DA converter, the Solid State Logic Alpha 8 and the Arturia AudioFuse X8 OUT. Each unit can add eight extra outputs to a modest 4×4 audio interface, providing the exact channel count required for a base Atmos setup.

Of course, with Ferrofish and SSL, you still get a full complement of eight inputs and eight outputs, while the eight-output-only Arturia unit could be a perfect fit for those in a mix-only Atmos scenario.

Another practical consideration is that you need to be aware of what kind of outputs an interface offers. Most audio interfaces provide ¹/₄” balanced outputs, or in the case of many 8- and 16-channel models, the outputs are on D-Sub (DB25) connectors. It’s uncommon to find XLR-based outputs beyond an occasional stereo pair.

Most studio monitors use either XLR,  ¹/₄” TRS, or sometimes both. It will be up to you to select the appropriate cabling to go from your interface to your monitors. Refer back to part three, where I delve into greater depth on the subject of outputs, cable considerations and your speakers.

Turn It Up, Turn It Down

Now, just because an audio interface offers the correct number of outputs needed for Atmos, a simple, yet vital question is, “How am I going to change the volume level simultaneously for 12 speakers?” Some interfaces can, and many cannot.

In the stereo realm, many studios often employ an external monitor control for both speaker and source selection, as well as the simple task of volume control.

This has also long been true for most traditional surround setups. Companies such as Dangerous Music, SPL, Crane Song, Grace Designs, Audient, DAD and Trinnov manufacture external monitor controllers for 5.1 and even some 7.1 setups. In the world of immersive audio, the options get narrower.

Today, the primary immersive monitor controller options include the Trinnov MC Processor, SPL MC16, Grace Design m908 and multiple offerings from DAD.

The benefit of this solution is that you can choose to use the interface or a high-end D-to-A converter of your choice. The potential downside is cost, as this is a decidedly “upper-end” solution.

There are also a few multi-channel audio interfaces capable of immersive monitoring and level control when paired with a dedicated remote control.

In this category, you will find options such as the Antelope Audio MRC (Multichannel Remote Controller) connected to one of the company’s current Galaxy
or Orion Synergy Core units. Any Atmos-capable RME interface can be adjusted with the company’s RME ARC USB remote, and Apogee offers a similar solution with the Apogee\Control hardware remote.

It’s also worth noting that some companies, such as Avid, allow their interfaces to be remotely controlled by the popular DAD MOM.

For those fluent in the Dante Protocol, there is the Focusrite Red 16Line interface paired with the Focusrite RedNet R1 desktop remote controller. In these scenarios, you have an audio interface, paired with a dedicated, proprietary remote control box.

Some companies, such as Merging Technologies, allow you to use a smaller desktop-style interface, in this case, the Merging Anibus interface in monitor control mode, to control the I/O on the multi-channel Merging Hapi audio interface. Universal Audio (UA) also offers a similar solution, by pairing an Apollo x4 or Apollo Twin X as a controller paired with an Apollo x16.

In a variation on this theme, Genelec fans can choose any of the company’s Smart Active Monitoring (SAM) equipped speakers, controlled by the Genelec 9320A SAM Reference Controller. The company also manufactures the 9301B AES/EBU multichannel interface and the 9401A, a multichannel audio-over-IP solution.

Atmos Onboard

Reigning this back into the world of audio interfaces capable of Atmos monitoring/level control, current popular options include the HDX-based Avid MTRX Studio. In addition to its new Symphony Studio line, which we will discuss shortly, the flagship Symphony I/O MKII from Apogee was made fully Atmos monitoring-capable last year via a firmware update.

Similarly, Lynx Studio Technology also released a firmware update for its Aurora (n) series, offering full Atmos capability. RME was one of the first to offer Atmos speaker management and control for its DSP-equipped UFX III, UFX II, UCX II and 802 FS interfaces.

UA added Atmos speaker control when it released the Apollo x16 Gen 2\interface. Notably, UA has made this option backward compatible with the first-generation Apollo x16. Finally, Arturia has included immersive audio support in its flagship AudioFuse 16Rig.

As mentioned, Antelope Audio and Merging Technologies both offer Atmos-capable interfaces. This also includes the Neumann MT48, which is a sister unit to the Merging Anubis.

One caveat with some offerings from RME, Neumann and Merging is that although these interfaces are fully Atmos-capable, not all natively provide 12 to 16 physical outputs. They require an expansion unit via ADAT or networked audio, which each company offers. Note that Merging and Neumann are sister companies under the Sennheiser umbrella, and similarly, RME and Ferrofish are both part of the Synthax family.

There may be a company or interface I have not mentioned, but the takeaway here is that, despite this impressive collection of Atmos-capable interfaces, it remains a relatively small and specialized club compared to the dozens of “regular” interface options on the market. Also note that most of the interfaces (and even controllers like the Grace, DAD, and Trinnov) also offer immersive EQ and delay-based room correction options. However, there are still some, like the Focusrite Red and Arturia AudioFuse 16Rig, for instance, that only offer monitor control as of this writing.

Room Correction

Speaker management is an integral component of an Atmos system—which in this case refers to the ability to EQ and time-correct each speaker individually within the system, most often via that unit’s internal DSP mixing software.

The next consideration is whether you need to make your measurements with a program such as Room EQ Wizard (REW) or via an automated room correction process like the widely popular Sound ID Reference from Sonarworks.

Then, can you load those directly into the interface, or must you enter them manually— parameter by parameter, speaker by speaker?

As of now, UA, AVID, Audient, RME, Lynx and Merging all offer direct SoundID integration.

Trinnov utilizes its own cutting-edge room correction microphone and process in conjunction with its interfaces and controllers.

Genelec and IK Multimedia both offer speaker-based correction stored in each monitor via a proprietary process. Genelec utilizes SAM and a GLM kit; IK Multimedia employs its ARC system.

Similarly, some monitor manufacturers, such as Wayne Jones Audio, ADAM Audio and Fluid Audio, each offer speaker-by-speaker Sonarworks SoundID integration. Please note that DAD and Grace Design controllers also offer SoundID integration, and, of course, Sonarworks can run independently on your computer for multichannel correction.

For Your Studio