Appendix: Considering RP-22

Last Updated: 10/20/2024

​​Quick Overview

The CEDIA/CTA-RP22 Immersive Audio Design Recommended Practice (1) is a document that recommends "best practices" to optimize immersive audio in home entertainment spaces. RP-22 describes how best to implement object-based formats like Atmos and DTS. It details performance criteria, including localization accuracy, envelopment, and dynamic range, to guide room and system design. Speaker positioning across base and height layers is emphasized to ensure spatial resolution and consistency across the seating area. For low-frequency optimization, subwoofer configurations are advised to minimize modal variance, and symmetrical multi-sub setups are discussed to smooth out low-frequency response.

A critical aspect of RP-22, threaded throughout the document, is defining four performance levels to guide a home theater project's scope. The specification uses these level definitions to describe balancing design compromises based on the room's starting characteristics, budget, and the user's desires. The requirements for each level are defined by 21 criteria divided into three categories: Spatial Resolution, Dynamics, and Timbre.

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• The document covers guidelines for optimizing the listening area to ensure uniform audio and to reduce acoustical issues such as room modes and excessive reflections.  

• RP-22 delves into applying acoustical treatments to control reverberation times and reflection decay time, helping to improve clarity. The document recommends how best to implement diffusion and absorption and the best materials.

• Recommendations for achieving optimal sound isolation include guidance on wall, ceiling, and floor construction techniques to manage sound transmission and prevent external noise intrusion, which is crucial for immersive environments.

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​Applying RP-22 to This Home Theater

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The summary states that RP-22 defines a checklist of design requirements correlated with several defined audio performance levels. This provides a common understanding of different categories of theater performance levels. For my curiosity, I took the RP-22 Appendix A performance table/checklist, which summarizes the performance criteria required for each level. I tried to correlate my theater to RP-22 Levels 1, 2, 3, or 4 to see what level my home theater achieves. This is shown in Tables 1-3. Unfortunately, some requirements cannot be estimated and measured, and as of this writing, I don't have the results. I added comments regarding the performance expectations in the right column of each table. In the spec column, I highlighted the expected performance (where I could estimate it) in a darker color.

The result of this exercise is that the room most likely should be considered a Level 1 theater, the lowest level, although some Level 2 parameters can be met.

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What key upgrades are needed to raise the room level from 1 to 2 or 3? The items I found are:

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• Increase the maximum loudness of the front three speakers by adding an amp or buying more efficient speakers.

• Lower the background noise in the theater by sealing the projector in a hush box. (or switch to a flat panel TV)

• Upgrade (or add to) the subwoofers to improve the room's low-frequency response.

• Enhancements to room treatments partly to improve RT60. (Debatable) 

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