One of the costly elements of setting up a Dolby Atmos studio, other than a dozen or so speakers, is the need for a 7.1.4 monitor controller with all the features including speaker calibration. This would typically be achieved with an interface like the MTRX or a lower cost MTRX Studio. But what if one could use the DSP in an audio interface to create a much more cost-effective Eucon enabled monitor controller. Nathaniel Reichman and Mike Crehore sat down and worked out how to achieve a 7.1.4 monitor controller using the DSP in Metric Halo interfaces. Over to you Nathaniel…

Why Do I Need Dolby Atmos?

One of the most important things my mentors taught me early on was to look closely at the ROI (return on investment) of any equipment purchases. I’ve been fortunate to work with some very successful composers, producers, and engineers, and part of their success was the result of continuous education about the latest technology, but selective investment in only what was really needed to complete any given project. In 2017, producer John Bowen encouraged me to look and listen to Dolby Atmos and to think of it as a useful tool for more than just film. While our podcasting clients instantly fell in love with the binaural capabilities of Atmos, there wasn’t an overwhelming demand that year for the format with our television clients. So when an Atmos project did come in that required monitoring in a format higher than 5.1, I would prep the material in the Production Suite and then book another studio with the right gear to complete the project.

Now I Need Dolby Atmos At Home

Years passed, and COVID-19 hit right at a time when one of my best music clients had a slate of upcoming releases for which Dolby Atmos would be necessary.

I needed to mix in Atmos at home, but I also needed to be realistic about the ROI. COVID-19 had taken a bite out of the New York City post-production world. My existing home studio is in New York’s Hudson Valley, north of the city, in a medium-sized room with high ceilings and good acoustic treatment, based on an Avid S3/Dock, Pro Tools Ultimate (native), Mac Pro 6,1, MBox Pro, AJA T-Tap video, and JBL LSR4300 series 5.1 monitoring. The MBox Pro was about to turn into a doorstop with macOS Catalina, so at some point in the future I would need a new audio interface, but I also needed to preserve everything else in the studio that was working well. I also happened to have (6) Genelec 8040A loudspeakers sitting in the corner from a previous project.

High Cost Of Entry - Or Maybe Not?

The tradeshows and gear magazines would have you believe that the only way to start in immersive formats like Atmos requires tens of thousands of dollars of investment in high-end interfaces, external rendering units and brand-new loudspeakers. I’ve worked in rooms equipped with this gear, and they’re fabulous and flexible, but they’re overkill for the independent producer working in a project studio or at home. Because I do work in a variety of different rooms in New York City, I’ve always had a list of B-chain things to check in a room before doing any serious work or hosting any clients.

What Is The B-Chain?

Before we get to the list, I want to explain A-chain vs. B-chain. In film and TV, the A-chain is all the processing the re-recording mixer would do to edited-but-otherwise raw dialog, music and sound effects to make it sound right before re-recording the printmaster of the full mix, M+E, etc. Basically everything you do inside your mixer or DAW. The B-chain is the stuff installed in the room that lets you see and hear that mix in a proper, calibrated way. This includes amplifiers, speaker EQs and delays, bass management devices, etc. Here’s my “B-chain” checklist:

• Are the satellite speakers all calibrated to the same output level?

• Is the subwoofer’s output calibrated to match and is bass management needed?

• Can the monitor controller set the overall level of the room (stereo, 5.1, 7.1.4, etc.) and solo/mute individual speakers?

• Does the video interface support the codecs used in your project?

• Is the video screen sync offset right? (see Sync-One2)

If all this B-chain stuff is right, you can be confident that your mix will play properly in that room (and if it still sounds bad, it’s your fault and not the room!).

Can I Find A Cost Effective 7.1.4 Monitor Controller?

Looking at the economical Dolby Atmos monitor controller options, I read the specs on the JBL Intonato, Yamaha MMP-1, Xilica Neutrino and others. But they didn’t look like single-box solutions where you could combine the functions of an audio interface and monitor controller. Avid knew this was an issue and released the excellent MTRX Studio.

But then I compared the specs of the MTRX Studio to a Metric Halo LIO-8. They’re very similar boxes, and for a lot of users, MTRX Studio is a solid choice. However, my JBL 4328s and 4312 subwoofer have AES/EBU digital inputs on every speaker, and there’s no AES/EBU I/O on the MTRX Studio. While I might be able to connect Pro Tools to the MTRX Studio via Dante, it was pretty clear that the main path to the unit was via Digilink. Not only was the MTRX Studio twice the price of an LIO-8, but I also mix 100% natively without HDX cards and really wanted a Thunderbolt or USB or ethernet interface. To use the MTRX Studio I would probably have to buy an old HD Native Thunderbolt box just to connect to it properly via Digilink, all of which I wanted to avoid if possible.

On the other hand, MTRX Studio is a very sophisticated device that has a lot of B-chain functions in the box, including:

• Individual speaker delays

• Individual speaker EQs

• Bass management across all speakers

• Monitor level control for all speakers

These were all functions I would need and so reluctantly I gave up on the LIO-8 and got in line for a MTRX Studio, thinking maybe Dante was the way to connect to it.

However, all was not lost, when record producer Rich Breen prompted me to look more closely at the DSP functions built into all of the Metric Halo interfaces. Metric Halo’s DSP section looks like it was designed to provide low-latency monitor functions in music sessions. But there were hundreds of freely configurable basic building blocks like EQs, summers, band-splitters, and all-pass filters.

Metric Halo Can Do It

I contacted Mike Crehore (co-founder of Dubway and a veteran of the NYC music scene), and he confirmed that the Metric Halo units could monitor in 7.1.4 and that you could set up monitor controllers in software, mixing and matching between the digital and analogue outputs of any number of units. I bought the LIO-8 (actually a LIO-8/4p with 4 mic pre’s) and in less than an hour I built a custom 11-channel bass management system in DSP:

Because this is happening after Pro Tools sends the audio to the LIO-8, it’s a B-chain function that has no impact on the mixes and stems I print in Pro Tools and/or the Atmos Renderer. Perfect. Being accustomed to an 80Hz crossover in my 5.1 system, I carried that over to my 7.1.4 system. Each ‘Band Split’ module in the block diagram above is set to 80Hz.

Metric Halo - Future-Proofing Their Interfaces

At this point, we turn to Mike Crehore, who was the guy that pointed out to me that the DSP in the Metric Halo interfaces could be configured in a B-chain, to take up the story and explain more, over to you Mike…

Today there is an interface for everybody in every price range, that will work on every kind of computer.  However, quality audio is still quality audio and for my “bang for the buck” mentality, there is no better company or hardware/software maker than Metric Halo.  Their mantra was “future proof” from the very beginning.  I have stuck with them for over 10 years and there are many out there still using an interface that they bought 18 years ago, now upgraded to the latest 3D version with a field installable card.  They stuck to their word and have a worldwide group of users who swear by their products.  The best part about the Metric Halo 3D system besides the stellar sound quality is the flexibility of the software and the I/O.  Each of their interfaces has an Edge Card slot that can accept a variety of different cards that range from stereo SPDIF/AES thru multi-channel ADAT (up to 32), 8 channels of AES to 3 different MADI configurations.  All in a price range that won’t break the bank.

All inputs and outputs can be accessed on any input channel or any monitor source.  So for multiple input source monitoring, it can all be set up any way that you like to work and all DSP can be accessed for any input or output point in the software.  So a standard LIO box will give you 8 channels of analogue and 8 channels of AES I/O simultaneously with no additional cards.  Add an Edge Card and you can configure the I/O as you like and the AD/DA is simply stunning.  Personally, I haven’t touched my industry-standard analogue hardware mic pre’s since I adopted the ULN8 and ULN2 interfaces I own.  They just sound that good.  Check out a great explanation of the new software environment as well as the Monitor Controller on the Metric Halo web site.

I was pleased to be able to steer Nathaniel toward them and the resulting home studio environment that he has built has my “do-it-yourselfer” persona all over it.  Because as we all know, ROI is the name of the game to survive and thrive in our industry.  I can’t wait to hear it in person!!

Now back to Nathaniel to continue his story…

Mike Crehore stepped in again because I found that the Metric Halo software “MIO,” doesn’t support 7.1.4 paths in the mixer (and neither does Pro Tools, but that’s another story). He showed me how to set up a monitor controller that bypassed the mixer, which enabled me to get all 12 channels with a mute control for each speaker:

I was very pleased to see that the MIO software is Eucon-ised, which meant that the Monitor knob on my Pro Tools Dock could control my monitor level and mute for the room. Admittedly, Eucon support in the MIO is not as deep as it is on the MTRX with DADman, but the basic functions I need are there. This also let me rack the LIO-8 away from my mix position and use only the Dock and the MIO software to control the B-chain in my LIO-8.

With bass-management figured out and Eucon working, I ordered a lot of cables and installed the additional 6 Genelecs for the sides and heights. Focussing on the bottom line, Mike Crehore and I found excellent, heavy-duty ceiling mounts from Cotytech that are less than a tenth the cost of a similar mount from a well-known loudspeaker manufacturer. I spent a weekend on a ladder with a stud finder putting lag bolts into the ceiling joists so I could be confident that the heavy Genelecs would stay put. For the side surrounds I used K&M mounts.

I followed the Dolby Atmos Home Entertainment Studio Certification Guide as closely as possible. My side surrounds and my rears are a touch high, but I pointed them down a bit more for additional vertical separation from the heights.

Once the system was installed, when it came to setting it up, the pink noise generator built into the Atmos renderer was very useful for calibrating the overall output level of my mixed set of JBL and Genelec loudspeakers.

What About The Differences Between The JBLs and Genelec Speakers?

I discovered that the analogue Genelecs were running low in comparison to the JBLs, and I was quite surprised to find that the monitor output trims in the MIO software are digitally controlled analogue circuits. This means they can go above zero. Adding 20dB of gain in the analogue domain was no problem.

I used the tone dip switches on the back of the Genelecs to match them as closely in overall character to the JBLs as possible. Not ideal, but not bad, and they were close enough that I didn’t immediately feel like I needed to insert EQs into the B-chain. But there was no doubt in my mind that the timing of the room was wrong.

To correct the timing, I added delay modules in the Monitor Output Graph and designed a loopback test by sending one-sample impulses through each speaker (first as objects and then as beds) and recording the output and measuring the delay in samples. The JBLs have their own room-calibration software, so they were pretty close in comparison to themselves, but the JBL/Genelec combo was way off. Here’s a picture of the updated graph:

With the delays in, the difference in the sound of the room was night and day. I saved my old Monitor Output setup. The MIO software loads new setups very quickly, making it very easy to A/B my speaker system with and without delays. It was a little bit of a shock, because some rough mixes I had done without delays that I thought were okay, really weren’t. The lack of proper delay compensation was adding a natural decorrelation to a lousy mix.

With the delays in, the speakers tightened up and revealed phase problems in my mix I wouldn’t have otherwise heard in my room. It reminded me of an Atmos mix that I completed in a well-known New York City studio in 2019. I had brought my favourite stereo reverbs and tried doubling them and placing them in the Atmos space, but the lack of decorrelation made them sound awkward and static.

In Conclusion, ROI Is King

To be clear, I’m doing single-system Dolby Atmos with the Production Suite, so there are features I don’t have that exist in the Dolby Atmos Mastering Suite, not to mention the load-balancing that occurs with two workstations instead of one.

But I want to circle back to ROI. With all the money I saved in hardware, I can spend some of that on things my clients will actually hear and appreciate when I send a mix for review. Things like good immersive reverb plugins, elegant noise reduction, really good microphones or room simulations, etc.

Finally, I am finding that mixing in Atmos takes more time, more expertise, and more gear. As an industry, we need to be fair, but we need to keep our rates up to protect the investments we’ve made in both technology and art.

Hit me up with any questions you may have in the comments section. And no, neither Mike nor I are Metric Halo salesmen, just happy customers.

Acknowledgements

Thanks to Mike Crehore for guiding me through setting up the B-chain using the DSP in my Metric Halo interfaces, when I thought all was lost and thanks also need to go to Metric Halo for their forethought in developing interfaces with DSP in them that you can configure to meet your needs.

Finally, special thanks must go to Marti D. Humphrey and Allison Ryan-Reichman for help writing this article.