Acoustics of a Dolby ATMOS Studio: Creating the Perfect Sound Environment
Jun 27, 2024Dolby ATMOS has been the new rage here in Nashville and in many parts of the world. I see a lot of people designing ATMOS systems, but I don't see a lot of conversations around the acoustics of how to make them sound good in your room. This article will go over the fundamental acoustic requirements of an ATMOS set up.
1) Understanding Dolby Atmos
Dolby Atmos is an object-based audio format that allows sound designers to place and move audio objects anywhere within a 3D space. Unlike traditional surround sound, which assigns sounds to specific channels, Dolby Atmos frees sounds from channels, providing a more dynamic and immersive listening experience. This technology necessitates a sophisticated acoustic environment to ensure accurate sound reproduction.
2) Room Geometry and Symmetry
Symmetry: One of the fundamental principles in designing a Dolby Atmos studio is maintaining symmetry. Symmetrical room geometry helps in achieving a balanced sound field, preventing any distortions that might arise from asymmetrical reflections. This also leads to a cleaner phantom image, meaning when you place a sound in ATMOS 3D it actually emanates from where you placed it.
Room Shape: Ideally, the room should be rectangular, as this shape is easier to control acoustically. Non-parallel walls can help reduce flutter echo, but must be used carefully to avoid other acoustic issues. Plus you lose a lot of space angling walls. If you want to angle any walls it should be an acoustic wall that is breathable to absorb high, mid and low frequencies.
Room Ratios:
Starting with room ratios that reduce the modal issues in your room is always be a good starting point, although much more is accomplished with acoustic treatment rather than the room ratio alone. Nonetheless, watching my video on Room Modes and using a calculator like AMROC will get you closer to a good starting point if you have that luxury.
3) Acoustic Treatment
When looking at the acoustics of a Dolby ATMOS setup we should borrow many design ideas from stereo mixing rooms (control rooms). The two main design concepts are the LIve End Dead End room and the Non-Environment room.
LIve End Dead End:
In an LEDE room, the front half (the "dead end") where the speakers and listening position are located is heavily treated with sound-absorbing materials to minimize early reflections and reverberations, providing a clear and precise sound image. The back half (the "live end") of the room is treated with diffusive materials to maintain some natural reverberation and prevent the space from sounding too dead or unnatural. This combination helps in achieving an acoustically neutral space where sound can be accurately monitored and mixed, ensuring that the audio translates well across different playback systems.
Non- Environment:
The Non-Environment (NE) room design is an acoustic treatment approach aimed at creating an extremely controlled and neutral listening environment, primarily for critical audio mixing and mastering. In an NE room, the entire space is treated with extensive sound-absorbing materials to eliminate all reflections and reverberations, resulting in a completely "dead" acoustic environment. This design ensures that the sound heard at the listening position is solely from the speakers, free from any coloration caused by the room itself. The goal is to provide the most accurate and unaltered sound reproduction possible, allowing audio engineers to make precise mixing and mastering decisions that will translate reliably across various playback systems.
Before I continue I have to mention that surround sound inherently will have less fidelity and accuracy than stereo sound. As Philip Newell states in his book, Recording Studio Design, "To compromise high quality stereo for amore enveloping sound is to trade quality for quantity..." (Philip Richard Newell, 575).
My recommendation for an ATMOS room would be to shoot for the Non-Environment approach. With so many speakers the amount of reflection off the walls or diffusion panels would create a phase nightmare. These means what you hear will be colored, distorted and inaccurate.
For this reason, I would lean on absorption over diffusion and I would shoot for covering the left, right, back and ceiling with as much absorption as possible.
Leave the front and floor uncovered to bring enough life in the room so it doesn't become anechoic. Once you have finished with absorption included bass traps in the four corners and where the walls and ceiling meet then you can test the room with the ATMOS system and decide if it is accurate using ATMOS reference tracks. Remember, testing and adjusting will be key to dial in your system. This includes finding a spot in the room where your subwoofer is not in a modal peak or null.
Conclusion
Designing the acoustics of a Dolby Atmos studio is a meticulous process that requires a deep understanding of acoustics, precise planning, and careful implementation. By focusing on room geometry, acoustic treatment, speaker placement, and continuous calibration, you can create a studio environment that fully harnesses the power of Dolby Atmos. This will enable you to produce immersive, high-quality audio experiences that captivate listeners. If you need help designing your ATMOS room sign up for a Soundproof Clarity Call to learn more about how I can help you.
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Works Cited:
Philip Richard Newell. Recording Studio Design. New York ; London, Routledge, Taylor & Francis Group, 2017.
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