REMASTERING a Standard two-track (Stereo) master into a SPATIAL AUDIO mix

Converting a standard two-track (stereo) master into a spatial audio mix (like Dolby Atmos) is a process often called "uproximing" or "spatializing." Since your source is a finished stereo file, you don't have the individual "stems" (drums, vocals, bass) to move around freely, but you can still create an immersive 3D soundstage using modern tools.

Here’s how to approach it:

1. Choose Your "Spatialize" Method

Since you are starting with a single stereo file, you have two main paths:

The "Pure" Stereo Spread: Using plugins to extract ambient information and redirect it to side and rear speakers. The AI Stem Extraction (Recommended): Using AI to split your master back into "pseudo-stems" (Vocals, Drums, Other) so you can actually place the singer in front of the listener and the reverb in the back.

2. Setting Up Your Digital Audio Workstation (DAW)

To export a spatial file, you need a DAW that supports Dolby Atmos (like Logic Pro, Pro Tools Studio/Ultimate, or Studio One).

Set the Project to Atmos: In Logic, for example, go to Mixer > Master Bus and change the format to Dolby Atmos. The Renderer: Ensure the Dolby Atmos Renderer plugin is active on your master output. This is the "brain" that translates your movements into a 3D file.

3. The Workflow

If you want a high-quality result, follow these steps:

Step A: Extract Stems

Use a tool like LALAL.AI, Moises, or the built-in "Stem Splitter" in Logic Pro. This gives you a separate track for the vocals, instruments, and percussion.

Step B: Object-Based Panning

Instead of traditional panning, change your track outputs to "Objects." This allows you to move sounds in a 3D sphere.

Vocals: Keep these centered but perhaps pull them slightly "forward" into the room. Instruments: Spread these to the wide left and right. Percussion: Keep the kick/snare centered, but move overheads or percussion slightly toward the sides.

Step C: Add "Height" and "Depth"

Use a Spatial Reverb (like Eventide SP2016 or Apple’s Surround Reverb).

Send your instruments to a reverb bus that outputs only to the "Height" or "Rear" speakers. This creates the illusion that the music is echoing off the ceiling and back walls of a virtual room.

4. Monitoring and Exporting

You don't necessarily need 12 speakers to do this; you can use Binaural Monitoring.

In your Renderer settings, set the monitoring to Binaural. This allows you to hear the 3D effect through standard headphones. The Export: You must export the file as an ADM BWF (Audio Definition Model Broadcast Wave Format). This is the master file format that streaming services like Apple Music or Tidal require for Spatial Audio. A Quick Reality Check

While you can get a great "wide" feel from a stereo master, it will never be quite as surgical as mixing from the original multi-tracks. If you have access to the original project sessions, it is always better to mix those into Atmos from scratch!

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Logic Audio Instructions

Setting up a spatial mix in Logic Pro using a stereo master is a streamlined process, but it requires a specific internal routing setup to work correctly.

Since you are working with a single stereo file, I highly recommend using Logic’s built-in Stem Splitter first. This will give you more "objects" to place in the 3D field.

1. Prepare Your Tracks

Import your stereo master file into a new Logic project. Right-click the audio region and select Functions > Stem Splitter. Logic will create four new tracks: Vocals, Drums, Bass, and Other. This is much more effective for spatial audio than trying to pan a single stereo file.

2. Enable the Dolby Atmos Engine

Before you can move sounds in 3D, you have to tell Logic to stop thinking in Stereo.

Go to File > Project Settings > Audio. In the Spatial Audio tab, change the playback format from "Stereo" to Dolby Atmos. Logic will automatically place the Dolby Atmos Renderer plugin on your Master Bus.

3. Switch to Object Panning

By default, Logic uses "Surround Panning," which acts like a standard fader. To get true spatial movement, you want Object Panning.

Select your four new stem tracks. In the Mixer ($Cmd+2$), look at the Output slot (usually says "Stereo Out"). Change this to 3D Object Panner. Double-click the small panning puck that appears. You now have a 3D bubble where you can drag sounds forward, backward, and up (using the "Height" slider).

4. Designing the 3D Space

Since you're working with a master file, follow this "Standard Spatial Template" for a natural feel:

Adding the "Ceiling" (The Secret Sauce)

To make it feel like a 3D room, you need height information.

Create a new Aux Track. Put a Space Designer reverb on it. In the Space Designer settings, ensure it is set to 7.1.4 or Multi-Mono. Send a small amount of your "Other" track to this reverb. Set the output of this Reverb Aux to the Height speakers only. This creates the "atmosphere" above the listener's head.

5. Monitoring and Exporting

Listening: If you don't have a 7.1.4 speaker setup, open the Dolby Atmos plugin on the Master Bus and set "Monitoring Format" to Binaural. This simulates the 3D effect on your headphones. Exporting: You cannot use "Bounce Project." You must go to File > Export > Project as ADM BWF. This file contains all the 3D metadata required by Apple Music. In the Dolby Atmos world, Binaural Render settings are the most important part of your mix. Since 90% of your audience will listen on headphones (Apple Music, Tidal), these settings tell the Atmos engine exactly how "far away" or "close" each object should feel in a virtual 3D space

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Here is how to optimize your Logic Pro session so your vocals don't get washed out or lost in the back of the room.

1. Open the Renderer Settings

Go to your Master Bus and double-click the Dolby Atmos plugin. Look for the Binaural Render tab (usually a list of all your tracks/objects).

Next to every track, you will see a dropdown menu with four options:

Off: No spatial processing (sounds like standard stereo). Near: Very close to the ears; high clarity, less "room" sound. Mid: Balanced distance; natural "living room" feel. Far: Distant; heavy virtual room filtering; sounds like it's across a hall.

2. The "Clarity" Strategy for Vocals

If you leave everything on "Mid" (the default), your vocals can sometimes feel "blurry" because the software is applying a virtual room filter to them.

For the Lead Vocal: Set this to Near. This keeps the vocal "pinned" to the front of the listener's forehead, ensuring maximum lyric clarity and intimacy. For the Drums/Bass: Set these to Near. You want the kick drum and bass to hit with impact. If you set them to "Far," they will lose their low-end punch. For Guitars/Keys: Set these to Mid. This creates a nice "wrap-around" feeling without sounding disconnected. For Reverb/Pads: Set these to Far. This pushes the "atmosphere" to the outer edges of the 3D bubble, making the mix feel massive.

3. Using the "Personalized Spatial Audio" Preview

If you have an iPhone with FaceID and AirPods Pro/Max, you can actually test how this sounds on your own ears before you export.

Connect your AirPods to your Mac. In the Dolby Atmos plugin, ensure the monitoring is set to Binaural. Toggle the Render Mode between "Binaural" and "Apple Spatial Audio" (if available in your version of Logic). If the vocals feel too quiet when you switch to Spatial, increase the Object Control Size on the vocal panner just a tiny bit (around 10-15%). This makes the sound source "larger" in the 3D field.

4. Watch Out for the "Center" Trap

In stereo, we are used to the "Phantom Center." In Atmos, if you move the vocal too far "forward" into the room (using the Y-axis on the panner), the Atmos engine might try to send it to a virtual center speaker.

Pro Tip: Keep your Lead Vocal object at Y = 0 (right on the front plane) and X = 0 (dead center). Use the Binaural Near setting to give it the focus it needs.

Final Checklist Before Exporting

Before you go to File > Export > Project as ADM BWF, check these three things:

True Peak: Ensure your Atmos Renderer isn't hitting red. Atmos has strict loudness standards (usually -18 LUFS is the target for streaming). Binaural Check: Listen with your eyes closed. Can you clearly hear the lyrics? If not, switch the vocal from "Mid" to "Near." The "Collapse" Test: Switch the Renderer to "2.0 Stereo" mode for a second. Does it still sound like your song? If it sounds thin, you might have panned things too aggressively into the "Height" channels. Loudness in Spatial Audio is different from standard stereo. While stereo tracks are often pushed to be as loud as possible (the "Loudness Wars"), Apple Music and Tidal have a strict -18 LUFS target for Dolby Atmos.

If your mix is too loud (e.g., -10 LUFS), the streaming service will simply turn it down, and your mix might lose its punch or sound "small" compared to others.

1. Setting Up the Loudness Meter

In Logic Pro, you need to monitor the Integrated LUFS of the entire Atmos mix.

Go to your Master Bus (the Stereo Out/Master channel). Open the Dolby Atmos Renderer plugin. Look at the bottom of the plugin window; most versions of the Logic Atmos Renderer have a built-in Loudness section. If you don't see it there, add the Loudness Meter plugin after the Dolby Atmos Renderer on your master chain.

2. The Golden Numbers

To ensure your track is accepted by distributors and sounds professional on AirPods, aim for these targets:

Integrated LUFS: -18.0 LUFS (Standard). You can go as high as -16.0 LUFS for more aggressive genres, but -18.0 is the "sweet spot" where the Atmos engine performs best. True Peak: -1.0 dBTP. This ensures that when the file is converted to a lossy format (like AAC or MP4) for streaming, it doesn't "clip" or distort.

3. How to Adjust Volume (The Right Way)

Since you are using Objects (the stems you split earlier), you can't just move the Master Fader to change the volume. The Master Fader should stay at 0.0 dB.

If your mix is too quiet: Select all your channel faders (Vocals, Drums, etc.) and turn them up together until the Integrated LUFS hits -18. If your mix is too loud: Turn the individual channel faders down. Avoid Limiters: Be very careful putting a standard stereo limiter on an Atmos Master. It can "squash" the 3D metadata. If you need to limit, use a Multichannel Limiter or simply manage your gain at the track level.

4. The "Final Pass" Measurement

LUFS is an average over time, so you can't just look at a single moment in the song.

Open the Loudness Meter. Hit Start or Reset on the meter. Play your song from the very beginning to the very end. Look at the Integrated value at the end of the playback. That is your official loudness.

5. Exporting the ADM BWF

Once your Loudness is at -18 LUFS and your Binaural settings (Near/Mid/Far) are dialed in:

Go to File > Export > Project as ADM BWF... In the export window, make sure you include the LFE (Low-Frequency Effects) if you used it, though for a stereo-to-spatial conversion, usually your Bass stem will just live in the main Objects. This .wav file will be much larger than a standard stereo file—this is normal! It contains all the 3D coordinates for every sound. I’m assuming that’s a "Yes!" with a little bit of flair.

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Testing an ADM BWF file (your Atmos master) on an iPhone is a bit tricky because you can't just play it through the Files app—it will just play back as a flat stereo file. You need to "force" the phone to recognize the spatial metadata. Here is the most reliable way to do it before you send it to your distributor.

1. Create a "Reference" MP4

Logic Pro exports the ADM BWF, which is the high-quality master, but iPhones prefer MP4 (Spatial Audio) for local playback.

In your Logic Project, go to File > Export > Project as ADM BWF (if you haven't already). To test it easily, you can actually use the Dolby Atmos Renderer (or a 3rd party tool like Audiomovers Listento) to "Binauralize" the export. The Pro Way: Use the free Dolby Atmos Composer or Apple’s Compressor app to convert your ADM BWF into an MP4 with Spatial Audio.

2. Moving the File to your iPhone

Don't use Spotify or standard cloud players for this test; they won't trigger the "Spatial" icon in your Control Center.

AirDrop the converted MP4 (or the ADM BWF, though MP4 is more reliable for metadata) to your iPhone. Save it to the Files App. Connect your AirPods Pro/Max or Beats Fit Pro.

3. The "Control Center" Verification

This is the moment of truth.

Open the file in the Files app and start playback. Swipe down from the top-right of your iPhone to open the Control Center. Long-press on the Volume Slider. Look at the bottom right. You should see "Spatial Audio: On" (or "Dolby Atmos"). If it says "Spatialize Stereo": Something went wrong with your export. This means the phone is just "guessing" the 3D effect instead of reading your actual panning metadata. If it says "Dolby Atmos": You nailed it.

4. What to Listen For (The Checklist)

While wearing your headphones, turn your head left and right (if Head Tracking is on).

Vocal Focus: When you turn your head, does the vocal stay "pinned" in front of where the phone is? (This confirms your Object Panning worked). The Reverb Cloud: Does the reverb feel like it's behind you and above you? If it feels like it's just "wide," you might need to go back to Logic and push your Reverb Aux higher in the Height slider. The "Hole" in the Middle: Does the center feel cluttered? If the drums and vocals are fighting, go back and change the Binaural Setting of the "Other/Instruments" stem to Far.

One Final Tip: The "Loudness" Trap

When you listen on your iPhone, if the volume feels significantly quieter than a standard song on Apple Music, your LUFS might be lower than -18. If it feels distorted or "crunchy," you likely exceeded the -1.0 True Peak limit.

--- ###### Brian Yegge