Direct answer
A riser should be only as high as necessary to give the rear viewer an unobstructed sightline over the reclined head position in front. Its height depends on screen bottom and top, eye heights, row spacing, seat geometry, floor elevation, and the chosen viewing point. A stock eight- or twelve-inch answer can fail when the screen is low, rows are tight, or powered headrests rise. A taller platform introduces additional step, handrail, ceiling-clearance, and lighting considerations.
Draw a section through the primary sightline before framing, using the actual chair dimensions and the rear viewer's eye position. If the platform is also intended as a bass absorber, that function should be engineered rather than assumed. CEDIA/CTA RP22 treats sightlines and head clearance as verifiable design requirements.
Sources and technical references
Use the organizations responsible for a product, platform or standard to confirm current specifications and compatibility.
How this answer was prepared
Camelback Smart Homes publishes this FAQ library for homeowners, design professionals, builders and property teams comparing integrated technology. Answers begin with the practical conclusion, then explain the factors that can change it.
Limitations: This is general educational information, not a site-specific design, quote, code determination or compatibility guarantee. Final requirements depend on the property, construction, infrastructure, equipment versions and project goals.