Topics covered in this article:
- Creative use of Dolby Atmos
- Creative practices for mixing music in Dolby Atmos
- Tips for mixing in Dolby Atmos
- Mastering, exports, and conversion
What follows are some suggestions and tips for working on Dolby Atmos Music content. This is not meant to be prescriptive. Every project is different, and every facility and mixer has or will develop techniques and methods best suited to them.
If working with pre-recorded content, gather audio assets for the final mix that will allow the mixer the highest level of flexibility for panning and mixing. If possible, request music stems in sets of stereo and mono files. Dolby Atmos relies on mono or stereo elements that can be dynamically panned and moved, and in this sense is no different in concept to layered editing and mixing in Stereo, 5.1, and 7.1. If only 5.1 stems are received, the output will likely be a static, mostly 5.1 mix, as it is more challenging to separate individual, movable Objects once a premix has been flattened to 5.1.
Multichannel microphones are not always practical, but they can be invaluable for post-production of recorded live concerts. Soundfield/Ambisonics microphones (such as those from Sennheiser (Ambeo) SoundField, CoreSound, Røde, Schoeps (ORTF-3D) et al.) are becoming increasingly popular for immersive capture. The multichannel output of these systems can be decoded to Dolby Atmos to reproduce the height plane. Placement of these microphones is more convenient than hanging mics over the sound stage, but the result can be more diffuse than using multiple directional microphones. You are also ‘baking in’ the directionality of sound sources within a scene, meaning you are unable to actively place those elements within the recording.
Music Production Practices
There are several best practices that can make Dolby Atmos Music production workflows more streamlined and predictable. Planning helps in finding an approach that works best for a given mix and can be maintained across multiple mixes if working on an album.
Closely follow delivery specifications and plan on the best way to achieve creation of all the deliverables required.
There are four possible settings for binaural: near, mid, far and off, the last of which lets the mixer turn binaural processing on an object off completely. The “mid” setting is the default and simulates the approximate distance between the sound source and the listener if they were listening on loudspeakers 1.5 meters away. If mixing on headphones the mixer can add some depth to the mix by choosing to set objects to “near,” and bring them closer, or to “far,” and push them further away.
From a creative standpoint this allows specific sounds to be more intimate and allow more space in others and is applicable to both music production and audio post production.
It is good practice to distribute objects equally between near, mid and far, and ultimately the settings the mixer chooses may be dependent on an Object’s timbre. This includes placing rhythmic sounds like drums in near or mid mode to give them more impact, and putting things that might already have some reverb on them like guitars and synths in far mode. These are by no means rules, and can vary a lot from mix to mix.
If a mixer wants to make an object sound very close to the listeners head but wants to avoid bringing an object “off the wall” or into the room, which may make the object sound more diffuse on loudspeakers, using the “near” setting can be a great way to achieve that effect on headphones without having to make any sacrifices for loudspeaker playback. Because of this difference in rendering between loudspeakers and headphone, its generally preferable to pan objects near the edge of the Atmos cube.
Creative Practices for Mixing Music in Dolby Atmos
- Percussion elements work particularly well in the front wide and front overheads.
- Try to receive the drum stems broken down into smaller groups rather than one stereo or 5.1 drum stem.
- Steady rhythmic elements, such as shakers, are meant to be locked in time and are best kept in the front half of the mix soundstage to assure cohesion with similar elements in L/R. This will help maintain tight rhythmic phase with the front rhythmic elements.
- Look at using upmixers on stems or finished sub-mixes to create overhead space. These can turn stereo, 5.1, or 7.1 mixes and stems into 7.1.2 Beds. Some are built with algorithms that can retain centered vocals and downmixes in a stereo deliverable. Use the channel balance to control how much overhead sound is extracted.
- The Size parameter can spread tracks to fill out larger areas of the sound stage and make the room sound bigger.
- There are a number of excellent 7.1.2 (and higher) reverbs on the market. Use the FMP feature (Follow Main Pan) in Pro Tools when sending an Object to a surround reverb to maintain natural panning in the reverb return.
Tips for Mixing in Dolby Atmos
Beds vs. Objects:
- Typical uses for a 7.1.2 bed:
- Individual drums tracks i.e. Kick, Snare, etc.
- Main Vocal tracks
- Reverb returns
- Musical elements meant to envelop the listener
- Typical uses for Objects are sounds that require more precise and dynamic placement:
- FX and Ambience
- Individual musical elements
There is no right or wrong approach, and the Bus/Object toggle can be utilized as needed.
- Approach a mix from the top down – Dolby Atmos (7.1.2) to 5.1 to stereo. Approaching Dolby Atmos as “mix 5.1 or 7.1 first and adding supplemental elements” does not lead to optimal results.
- Building contrasting elements in the overheads and sides can increase the feeling of immersion.
- Sounds that are intentionally diffuse in the overheads, like reverb, are best placed in the overhead Bed channels, which cover the whole ceiling. Using Objects, especially without size metadata, may be too focused to be as effective.
- In the Dolby Atmos Panner, use the wedge shape automatic height panning mode when mostly staying left/right; use sphere for pans that go over and across the mix.
- Pay close attention to how many speakers are being used as you pan to the interior. Panning too far into the middle of the room can decrease the stereo image and quickly become mono.
- Size can be a handy way to grow a sound to fill more speakers (with no phase issues), but be aware that as it is basically a 3D cube, it can quickly become room-filling mono.
- Humans have more acuity to localize things as being above us if they are higher in the frequency spectrum. If you want a sound to be accentuated in the overheads, it’s best to use tracks that have some frequency content above 2K.
- Dolby Atmos allows for the full frequency range in all speakers. However, it is important to be aware of where bass-heavy Objects are panned. Not only do humans perceive the verticality of higher frequencies better than bass frequencies, but most consumer playback systems route much of the bass to the sub, so directionality will be less noticeable than intended. Excessive low-end in a Dolby Atmos mix may take up too much headroom and weight in the stereo re-render if this is a target deliverable. (This doesn't pertain to the LFE channel, as LFE is not included in LtRt or LoRo re-renders. As such, it is not recommended to route content solely to the LFE channel.)
- Monitor a mix with Spatial Coding Emulation turned on. You can simulate the final presentation in Dolby Digital Plus at data rates used by leading streaming services by selecting 16 elements in Preferences or Settings.
- In Pro Tools, VCAs can be used to control and hit loudness target levels as measured by the Renderer or plug-ins (via the loudness re-render).
- In Pro Tools, you can use groups to gang only plug-in parameters in a given slot. Use this to your advantage to control compressors, limiters, filters, and EQ on multiple Objects.
- Use care when using track groups and master busses with Objects, especially if you are toggling between Objects and Beds, as your Bed master busses may have additional processing, such as limiters.
- Use the Groups in the Renderer to their full advantage; plan routing to make multiple deliverables much easier.
- Use the Description field of the Renderer input page. This description shows up in Pro Tools in the "Mapping to Renderer" field in the bus routing. This helps organize complex routing between the two applications.
Mastering, Exports, and Conversion
- Use both the realtime loudness metering and offline Loudness Analysis in the Renderer to comply with loudness requirements.
- Alternatively, use the loudness-specific re-render with other loudness measurement plug-ins and applications.
- Check the mix using different monitor layout to verify how channel-based re-renders will sound.