Atmos Delivery: Loudness, the ADM Master, and Binaural QC
Atmos uses the same loudness measurement system you learned in DAD 322, but the target and master format are different. You also need to check how the mix translates to several playback formats before you submit it.
Delivery levels
Use these targets for the music project:
These numbers apply to the 5.1 loudness re-render, not the 7.1.4 speaker output or a binaural render. In Logic, choose 5.1 as the monitoring format in the Dolby Atmos plug-in. Place a multichannel loudness meter after the plug-in, reset the meter, and play the entire song without interruption.
If the mix measures -15 LKFS, lower the overall level. Heavy limiting may raise loudness while reducing the dynamics and space that Atmos is meant to preserve. It also provides no delivery advantage: a service may turn down a master that exceeds its loudness limit.
Keep the LFE channel for low-frequency effects rather than using it as a bass-management channel. Apple also prohibits Atmos masters made by upmixing, de-mixing, or adding spatial effects to a finished stereo master. Build the Atmos mix from the multitracks or from stems created from those multitracks.
The ADM BWF master
Deliver the Atmos mix as an ADM BWF. This single multichannel WAV file stores the bed and object audio along with position, binaural, and downmix metadata. Compatible Atmos tools and streaming services use that information to render the mix for different playback systems.
In current versions of Logic, choose
File > Export > Project as Spatial Audio, then select
Dolby Atmos ADM BWF. The monitoring format selected in the Dolby Atmos
plug-in does not affect this export.
After exporting, create a project from the ADM BWF and listen through it. Confirm the beginning and end, object movement, automation, and overall balance. If you find a problem, correct it in the source project and export a new master.
Apple requires the Atmos master to match its stereo reference in length and sync. Export both from the same version of the project and use the same start and end points.
Check the renders
Listeners will not all hear the 7.1.4 mix you hear in the studio. The Atmos master may be rendered for headphones, stereo speakers, surround systems, or a device with speaker virtualization. Check those versions as part of the mixing process.
- Listen to the Dolby Renderer over headphones. Set each bed channel and
object to
Off,Near,Mid, orFardeliberately rather than leaving the binaural render mode at its default. - Listen with Logic’s Apple Renderer in Music mode. This previews the headphone virtualization used by Apple Music. The Apple Renderer controls affect monitoring only; they are not written to the ADM BWF.
- Check the 5.1 and stereo re-renders. Listen for missing elements, level changes, masking, phase problems, and an unstable center image.
- Return to 7.1.4 after making changes to a re-render. A correction for one format should not damage the main mix.
The goal is one mix that translates across all of these formats, meets the delivery levels, and survives export and re-import without surprises.
Lab: make Project 4 submission-ready
Bring your Atmos mix in progress.
- Choose the 5.1 monitoring format and measure integrated loudness and true peak over the full song. Record both values.
- Adjust the overall level until the mix is at or below -18 LKFS integrated and -1 dBTP. Do not use heavy limiting simply to reach -18 LKFS.
- Monitor through the Dolby Renderer over headphones. Review the binaural render mode for every bed channel and object.
- Monitor through the Apple Renderer in Music mode, then check the stereo re-render. Write down anything that disappears, shifts, or becomes masked.
- Export an ADM BWF, create a new project from it, and compare it with the source project.