This major update to Fiedler’s immersive audio mastering suite could revolutionise your Atmos workflow.

My review of Fiedler Mastering Console version 1 was published as recently as SOS December 2024, and the fact that I’m already writing about a version 2 indicates both that Fiedler Audio seem able to move very quickly, and that this new version is a very significant advance. In fact, Fiedler describe it as an entirely new product — and I wouldn’t argue with that.

Fiedler Audio Mastering Console (or FMC, as I’ll refer to it from here) is a Dolby Atmos production tool that aims to provide an all‑in‑one fix for a workflow quirk that’s inherent in Atmos signal routing: within, say, a Pro Tools Atmos mix session, it’s not possible to apply global EQ, loudness adjustment, compression or limiting, or anything else, to an entire Atmos mix. This arises because an Atmos session typically comprises beds and objects. Beds are conventionally panned elements spread, typically, over a 7.1.2 channel width, and objects are discrete elements that are panned according to dynamic metadata that defines their intended position in space.

Notwithstanding that multi‑channel EQ, compressor or limiter plug‑ins that can be inserted on a 7.1.2 bus are somewhat niche, such a plug‑in wouldn’t ‘see’ the object channels, because they’re separately routed to the Dolby Atmos Renderer (there can also be up to 128 of them!). This isn’t simply an inconvenience, though; it’s a significant issue because, for example, it makes aiming for a specific mastered loudness level or an overall tonal balance decidedly tricky. It makes fade‑ins and fades‑outs complicated too because they potentially need to be applied to beds and each object individually. FMC aims to fix all this, and more.

Orientation

On launch, FMC 2 presents its Timeline window, which is where most of the fundamental mastering functions live. To begin a mastering session, the first step is to import an Atmos ADM (Audio Definition Model) file, a multi‑channel BWF WAV package that carries the Atmos metadata, and is the Atmos format output of the Dolby Atmos Rendererer that hangs off the end of the DAW Atmos mix session. Screen 1 shows six ADM files imported, because FMC 2 can master multiple files in one project. Despite the imported Atmos audio shown comprising a 7.1.2 bed with multiple objects, the display in the timeline shows ‘only’ a 5.1 channel width. While this may seem strange, it’s not remotely an issue in practice, and there’s sense in it: the convention is that loudness measurement of Atmos ADM files is determined on a 5.1 downmix.

Along with the Atmos ADM shown in Screen 1’s Timeline window, I’ve also imported six stereo files (shown in green) that were rendered and output by the Dolby Atmos renderer at the same time as the ADM files. Mastering for Atmos often means creating stereo companion files and FMC 2 can handle both. This makes sense, as it will help ensure consistency across mastered stereo and ADM exports.

There’s an option to consider here, though, because an alternative workflow is to import only the Atmos ADM and then, if stereo companion files are required, have FMC 2 render and export them. That was my preference initially, but I can see that the extra flexibility offered by importing separate stereo files, in particular the possibility of applying different processing (EQ, compression, loudness, limiting, etc) to stereo renders, is often likely to win the day. Still, importing separate ADM and stereo files, as in Screen 1, does enable me to illustrate the trim features and in/out fades that can be applied. The ADMs in the screenshot have been trimmed at both beginning and end, and had in/out fades applied (nonlinear fade curves are available), while the stereo files are untouched. Trims and fades are applied simply by grabbing the handles that appear automatically at the start and end of the timeline once a file has been imported.

While I’m writing about the Timeline window, I should mention the functions to which it provides access. Living at the top left are the session import and save functions, and access to a Settings page that I’ll cover below. Next are transport controls and a switch that toggles the playback output between the ADM and stereo files (if one has been imported). Alongside this is a stereo file playback level control. Below the transport controls is a toggle switch for Batch and Album modes, the latter then offering Ripple and Snap options. Some explanation is in order...

As I mentioned, FMC 2 is designed to enable multiple files to be imported, so that batches of tracks can be mastered in one project — so you can use FMC 2 to master an entire album, not just individual tracks. In Batch mode, each imported track is processed separately by FMC 2 with no regard to the track before or after it. In Album mode, however, FMC treats multiple tracks as if they’re an album, with silence, gapless transitions and/or crossfades instigated between them. In Album Ripple mode, a clip and all subsequent clips can be moved in the timeline together, with further options that offer Atmos or stereo only, and both. When Album Snap mode is on, files will snap to features such as file boundaries, fade starts or the playback pointer.

Spatial Awareness

Moving to the right in the Timeline window, you find Speakers and Phones (headphones) drop‑down menus to specify the speaker monitoring available or required, and the headphone format preferred. I wrote “available or required” because there’s a subtle distinction between the two. My Dynaudio BM5‑based Atmos monitoring is a 7.1.4 system, and I’d specify that channel format in the Speakers menu because that’s what is available. But if I want to hear what my mastered ADM will sound like downmixed to a lesser system, all the way down to stereo, I can select that from the drop‑down and FMC 2 will render the ADM appropriately. There are some similar options (Stereo, Binaural and Spatial Audio) in the Phones drop‑down. The first two probably don’t need any explanation, but the third, Spatial Audio, is Fiedler Audio’s implementation of the previously mysterious processing that Apple Music applies to Atmos ADMs to create the Apple Spatial format.

Apple Spatial is generally a binaural render of an ADM, but for the first few years following its introduction to Apple Music streaming, Apple released scant details of what it actually did to an Atmos ADM; it just sounded very obviously different to the binaural render built into the Dolby Atmos Renderer. This resulted in some unhappy Atmos mix engineers who, on hearing their work streamed as Apple Spatial, found it bore only an approximate relation to what they expected. Apple have since provided developers with details of the Apple Spatial render process, and this is what FMC 2 uses.

It is an incredibly useful feature to be able to hear what an Atmos mix will sound like when rendered to Apple Spatial — because that’s how much Atmos music is consumed.

Switching between Binaural and Spatial Audio output from the FMC 2 is fascinating. Not only does Spatial Audio sound very different to Binaural in spatial terms, its tonal balance is significantly different also. It is an incredibly useful feature to be able to hear what an Atmos mix will sound like when rendered to Apple Spatial — because that’s how much Atmos music is consumed. Beneath the Speaker and Phones drop‑downs are settings to engage head tracking on compatible headphones. Apple‑ and Supperware‑equipped headphones fall into the compatible category, but having neither available I wasn’t able to evaluate the head‑tracking feature.

Moving along, top right in the Timeline window is a pretty self‑explanatory set of speaker and headphone level indicators (with mute and solo buttons). Above them is the Additional Render Headroom button, and Fiedler explain that a limiter is built into the Dolby Atmos Renderer output that emulates the limiting applied during its own ADM export process. The FMC 2 Additional Render Headroom function provides a method to avoid triggering this limiter within FMC, by attenuating the input by 60dB and subsequently recovering 60dB at the output. This is of benefit, Fiedler say, because the output limiter can change the sound of the rendered Dolby Atmos mix if its level is above the usual loudness norms. The Additional Render Headroom ensures the renderer behaves linearly, so that loudness adjustment within FMC 2 is valid. Finally along the top line of Timeline window functions is a bunch of buttons and sliders that provide gain and dim functions, mute (entire mix, beds or objects), and both horizontal and vertical timeline display zoom.

Chain Gang

Bottom left of the Timeline window is one of FMC 2’s most significant features: this is where mastering chain plug‑ins can be instigated and applied on a file/track basis. Fiedler have developed an ADM‑compatible plug‑in format called OBAM (Object Based Audio Module) and their first OBAM plug‑in is the Gravitas multi‑channel mastering compressor. I wrote about Gravitas back in my original review of FMC, so I won’t regurgitate that here, except to repeat that Gravitas is a fully featured mastering compressor with everything we’ve come to expect of such a beast. Gravitas is Fiedler Audio’s only current OBAM plug‑in, but mastering EQ is available via the OBAM Equalizer Pro from Toneboosters, and in Screen 1 you’ll notice that I’ve instantiated this along with Gravitas. (This isn’t a review of Equalizer Pro, but it’s an extremely well‑equipped EQ plug‑in that does everything required and quite a bit more!)

Alongside the FMC 2 plug‑in slot is a master gain slider and then further along the lower portion of the Timeline window there’s limiting and loudness functionality. Loudness measurements can be made on 5.1 or stereo data and clicking on the Measure button opens the window shown in Screen 2, where the offline measurements are instigated and reported.

Finally on the Timeline window of Screen 1 are matrix and 3D displays showing active bed and object channels. Clicking on the ‘expand’ icon of the 3D display opens the 3D window (see Screen 3) that provides an expanded view along with options to selectively hide channels and/or objects. In Screen 4 I’ve illustrated the Editor window, where alternative binaural perspective settings can be applied to bed and object channels, and where parameters that define how ADM data is rendered to lower‑channel‑count playback systems can be modified.

Once trims and fades have been applied, loudness targets have been hit and things are sounding as required, it’s time to export files from FMC 2 so that masters can be set free to become worldwide hits, disappear into obscurity or, most likely, do something between the two. Screen 5 shows the FMC 2 export window, where each file in the timeline (or a complete album) can be simultaneously exported. Export formats on offer comprise ‘native’ ADM, alternative X.X.X channel widths, or stereo, binaural and Spatial Audio renders.

Impressed?

I’ve written over 2000 words on FMC 2, and it’s time to draw this review to a close. But while I hope I’ve given you a sense of what this software makes possible, I still don’t really feel that I’ve fully done it justice! FMC 2 seems to me to be hugely significant in the Atmos music mix business, because it offers a superbly capable fix to one of the major Atmos workflow bottlenecks. It deserves to become very popular.