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.

By the end of class, you should be able to measure the complete mix, correct its level without changing the bed/object balance, and distinguish a playback render from an ADM master. We’ll demonstrate the workflow together using one prepared session.

Delivery levels

Use these course limits for both the music and film routes of Project 4 . They are adapted from music delivery practice, not universal specifications for all film or Atmos content:

-18 LUFS-IMaximum integrated loudnessMeasure the complete song or supplied film from the 5.1 loudness re-render according to ITU-R BS.1770. Quieter is acceptable.

-1 dBTPMaximum true peakMeasure true peak from the same 5.1 loudness re-render.

LUFS and LKFS are numerically equivalent. Integrated loudness measures the mix as a whole; true peak checks the highest reconstructed signal peak. A mix can pass one limit and fail the other.

Set up the surround master strip

Choose 5.1 as the Monitoring Format in the Dolby Atmos plug-in. On the surround master channel strip, use this order from top to bottom:

Dolby Atmos → Level Meter, set to True Peak → Loudness Meter

Add the meters from Audio FX > Metering. Use their multichannel versions so they measure the rendered bed and objects together. These readings apply to the 5.1 render, not the room’s 7.1 output or a binaural render.

Set the full mix’s start and end, including the final decay. Turn cycle off.
Reset the Level Meter peak values and the Loudness Meter. Enable the Loudness Meter’s Start/Pause analysis button.
Play the complete song or supplied film once without stopping. Read the Integrated value and the highest true-peak value across the channels.
Record both readings before starting another playback, which can reset the Level Meter’s peak holds.

Do not judge the integrated result from a short loop or from the momentary loudness display. We can use short excerpts for listening comparisons, but the delivery measurement covers the complete song or supplied film.

Correct the level in the source mix

If the mix measures -15 LUFS-I, reducing the complete mix by about 3 dB is a starting point. Remeasure the full mix and check true peak as well. Quieter than -18 LUFS-I is acceptable; do not raise a mix simply to hit the ceiling.

Adjust the bed and object source levels together while preserving their relative balance. VCA groups for bed tracks and object tracks can help; make sure returns and other contributing paths are accounted for without attenuating a signal twice.

Processing before the Dolby Atmos plug-in affects the bed, not the separate object signals. Processing after it affects the monitoring render and is not included in the ADM export. Lowering the surround output fader or adding a gain plug-in after the renderer is therefore not a fix for an over-level ADM master. Use that distinction in the demonstration: predict which changes will survive export.

Heavy limiting can reduce dynamics and alter the mix. First check source levels and isolated peaks instead of using a limiter to force the result.

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.

Native surround plug-ins

A native surround plug-in supports a multichannel format directly. Multi-mono processing instead uses separate plug-in instances for individual channels, with controls that can be linked or adjusted separately. Check the format available on the channel strip; not every plug-in supports every layout.

Useful examples in Logic include:

Plug-in	Use
Multichannel Gain	Adjust individual surround-channel levels
Surround Compressor	Control dynamics across a surround signal; supports up to 7.1
Space Designer	Create a surround reverberant space
Delay Designer	Create delay patterns across channels; supports up to 7.1
Level Meter and Loudness Meter	Inspect channel peaks and overall loudness

On the surround master, processing before Dolby Atmos affects the bed; it does not include the separate objects. Processing after Dolby Atmos affects the selected monitoring render, and is not part of the ADM master. Process an individual object on its own channel strip before it reaches the renderer.

For Friday, compare a short bed passage with and without surround processing. Open the plug-in’s channel controls and identify which channels it affects. Then solo an object and predict whether that bed processing will change it. Listen to test the prediction. What changes in the spatial balance, and is the processing helping?

See Apple’s native surround plug-in list and multi-mono controls .

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. Choose Project for the whole project or Selection for the complete song or supplied film if it occupies only part of the session. Check the range includes the final decay. In older versions, the command may be named Project as ADM BWF. The monitoring format selected in the Dolby Atmos plug-in does not affect this export.

After exporting, choose File > Import > Create Project from ADM BWF and listen through the resulting verification project. 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.

Metering checks the source mix’s levels. Reopening checks that the delivered file contains the intended mix and range. Mix and meter first, then export and verify the final file; you do not need to export after every level adjustment. An ADM is not a normal stereo listening file or an editable copy of your original Logic session, so keep the source project too.

For an Apple Music release, the Atmos master must match its stereo reference in length and sync. Use the same project version and start/end points for both. Project 4 requires the ADM master and QC record listed in its brief; it does not require a separate stereo master for release.

Check the renders

Our studio monitors a 7.1 render of the Atmos mix; it has no discrete height speakers. Listeners may hear other renders. 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. Compare Off, Near, Mid, and Far on one featured object, then choose settings that suit the mix. Off disables distance modeling; it does not mute the sound. The LFE channel is fixed at Off. A default setting is fine if it sounds appropriate.
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. Dolby’s binaural distance settings do not affect the Apple Renderer.
Check the 5.1 and stereo re-renders. Listen for missing elements, level changes, masking, phase problems, and an unstable center image.
Return to the room’s verified 7.1 monitoring layout after making changes for another render. A correction for one format should not damage the main mix.

Use the same short passage for each comparison. Predict what may change, listen, and name one audible difference. Headphone render comparisons need headphones; playing them through the room speakers does not demonstrate their intended spatial effect.

Check your understanding

Why do we measure the 5.1 render rather than the headphone render?
A gain plug-in after Dolby Atmos makes the meters pass. Has it corrected the exported master? Explain the signal path.
The source mix sounds right, but the ADM cuts off its final decay. What needs to change?

Apply this workflow as you finish Project 4 . Keep the final meter readings, screenshot, listening observation, and ADM verification result for the QC record described in the project brief.