All About Atmos – a guide for MEs. Part 3

Seemingly out of nowhere, Atmos has become one of the most talked about formats. But if you haven’t worked in film audio, or have been burnt previously by investing in surround for audio, it can seem all a bit bewildering. 

In Part 2, we looked at what you, a ME could bring to Atmos. In this part, we’re looking at how to setup an Atmos room.


This is part 3. Click on the links to go straight to the other parts, or keep on reading 🙂

About Atmos -Part 1 : Atmos basics

  • What is it and how does it work?
  • Beds and objects
  • Atmos, 7.1, 5.1, Stereo and binaural
  • How do you master an Atmos mix?

About Atmos -Part 2 : What is the role of a ME in an Atmos mix?

  • Music or Video?
  • Stem mastering
  • ITB or Analogue chains
  • Back to school

About Atmos -Part 3 : Setting up an Atmos room

  • Rooms & Speakers
  • DAWs and other kit
  • Monitoring

About Atmos -Part 4 : Integrating a stereo room with Atmos

  • What to think about
  • Crookwood solutions

Part 3 : Setting up an Atmos room

OK, so you’ve decided to bite, and you want an Atmos setup.  Great!  So, what’s involved?

If you were going to build a new room and do audio, not music, it’s pretty straight forwards.  However, given that you already have a kick ass stereo room, it a bit more complicated.

Setup Basics

So, let’s cover the basics.  To make a room that can master Atmos, you’ll need as a minimum:

  • A reasonably sized treated room
  • A minimum of 9, preferable 11 speakers plus a LFE subwoofer
  • A good pair of headphones and a good headphone amp
  • A DAW capable of running Dolby Atmos production suite
  • Optionally another DAW which can run the Dolby Mastering suite program as a dedicated rendering PC
  • An audio interface with 12-16 outputs
  • A set of other Dolby Atmos plugins, and other surround plugins for processing, routing and metering the files
  • Something clever to link your stereo mastering chain to the Atmos system

Dolby have a lot of this information on their site, especially regarding rooms and speakers.  They also have preferred setups, which most of the film/post guys tend to stick to.

BTW, unless you intend to release material for film theatres, you don’t need (or really want) Dolby accreditation for your room/ setup.

Room

Dolby says:

DimensionMinimumRecommended
Height2.4M (8’)3M (10’)
Width3M (10’)5.5M (18’)
Length3.5M (11.5’)6,4M (21’)
Dolby recommended room sizes

Bear in mind, this is the finished inside space, not the room before treatment.  As you can see, these are not small edit room sizes.

Dolby also have a room curve they would like you to meet within ideally a 1dB variation at the engineer position.  You’ll require EQ on each main speaker channel to achieve this.  The Dolby Atmos Mastering suite has this EQ built in, as do a few multichannel interfaces.

Speakers

Ideally you’ll have a 7.1.4 setup :

  • 7 speakers on a horizontal plane (L,C, R, Ls, Rs, Lre, Rre)
  • A subwoofer (LFE)
  • 4 in the ceiling ( Ltf, Rtf, Ltr, Rtr)

BTW, if you want to do theatrical stuff, they’d like you to have a 9.1.6 setup.

In practice, you’ll want more than one sub to make the bass more linear, but these can be fed off the same LFE output, unless you need room EQ.

Speaker spec

  • The horizontal speakers should all be the same make and type
  • Be mounted at ear height (1.2M, 4’ off the floor). 
  • The ceiling speakers should be the same make, but you can use a smaller model.
  • Each speaker should be capable of outputting 40Hz to 18KHz
  • Have a flat response +/- 3dB
  • Produce about 105dB at the listening position
  • Smaller rooms can lose 3dB per speaker in max level, bigger rooms could do with an extra 3dB

Interestingly, the nominal level is 85dB SPL, and Dolby want there to be 20-23dB headroom available, per channel.  Bye bye super compression hey?

Headphones

Atmos puts the binaural headphone mix out on a separate set of channels, so you’ll need a good pair of cans plus a decent amp to drive them.  The Atmos renderer has controls to mute the mains while listening to the cans etc

DAW

You’ll need a DAW that can support the large number of channels needed, plus the final output files, and have enough power to run the renderer.  Or you can run the renderer on a separate PC.

The single PC solution requires you to run the DAW on a Mac. The second option requires you to purchase Dolby approved hardware, and a Mac Mini is the typical device chosen, connecting to the other PC which can be a Mac or Windows device via ethernet.  If I had my way, they would have forced the use of MADI (it was the original option), but I’m biased. Ethernet protocols – Dante, Ravenna, AES67 etc let you use a lot of affordable routing gear.  Especially as you’re running this all at 48KHz.

Ah yes, sample rates: Atmos will support 96KHz files for editing and monitoring.  But when you produce the final Atmos master, it needs 48kHz files.  This means all of your audio files will be automatically SRC’d (by Dolby) to 48KHz for encoding.  The original files will remain untouched.

If you are using 192KHz master files, you need to down-sample these to 96KHz to be able to work with the Atmos renderer,

Dolby software

Dolby makes two renderers – the production one and the master one.  The systems basically sit as a plug in on top of a normal mix session and renders the mix into a separate set of monitor and file outputs. 

They also make a panner plug in for certain DAWs, plus some converter and router tools.

The renderer has some basic room calibration and monitor tools inside it, namely:

  • Pink noise sources for calibration
  • Individual speaker delays
  • Individual speaker level trims
  • Individual speaker graphic EQ (mastering suite only)
  • Consumer bass manager simulation
  • Overall volume control
  • Dim (fixed level)
  • Mutes and solos
  • Different speaker layout presets – setup for a 5.1, 7.1, 2.0 etc, recalling EQ, levels etc

Audio Interface

Dolby has certain preferred setups usually involving a ProTools rig and a MTRX interface, and most film & video guys just use these approved preconfigured rigs.  However, there are a lot of rigs that don’t use these setups, and instead chose different hardware for cost or performance reasons.

As long as you can map the renderer outputs to an audio interface (Dolby helps here with their bridge product), you can use different interfaces.

Plugins

Here’s some ideas:

  • Inevitably, you’ll be doing something ITB on a surround bed.  For this reason, you’ll need some 7.1 EQs and tools.
  • For panning, you’ll need a Dolby panner or equivalent to place an object
  • You’ll also need to be aware of loudness levels, so an Atmos level meter is useful
  • Finally, you’ll need to create or inject some ambience, so multichannel reverb type plugins are also handy.

I suspect you’ll end up buying quite a few until you figure out what you really need. What fun you’ll have 😊

Something Clever

This is now where I can introduce the shameless plug for our own gear.

It’s hopefully become clear from the above that the focus from Atmos is on audio production, not music production.  Don’t get me wrong, they’ve done an excellent job, but it’s quite a different focus from an ME, who worries about converter, EQs, compressor, level, path and monitoring choices to a post engineer, where the focus is on matching the audio to the visuals, and the assumption is that the audio hardware is perfect.

We think we have some solutions for you.  In Part 4 – setting up an ME’s Atmos room.