Initial Home Theater Space Planning
This page outlines the preliminary steps undertaken (or that should have been undertaken) for this example home theater design. The design presumes a projector-based setup to achieve the desired screen size. The first step describes some initial considerations for determining the room's dimensions.
Some Room Size Tradeoffs
Last Updated: 12/10/2024
The layout of the basement home theater was primarily determined by its relationship to neighboring spaces, such as the kitchen/bar, workroom, and exercise room. Acoustic optimization, large projector screen integration, and two rows of seating were considered to further refine the room's dimensions. This section explores the factors that influenced the theater's floor plan optimization. A significant assumption was that to fit two rows of seats, the screen would need to be placed on the short wall.
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Room Dimensions for Seating and Walkways​
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First, the room length was reviewed. To support two rows of seating, it was estimated that a row composed of a typical recliner requires ~5-7 feet of space. An additional 2-3 feet behind the last row is needed for access and 4-6 feet of clearance from the front row to the screen. Summing up, the initial estimate added up to 19-21 feet, but by using a couch for the front row and moving the front row a little too close to the screen, I was able to fit everything and still meet other basement floorplan restrictions, which limited the maximum length to ~17 feet.
Next, I checked the room's width to ensure I could fit the desired seating. I wanted to fit three seats per row, each 36 inches wide, and allow for about 36 inches of space between the row's end and the wall. This resulted in an estimated minimum width of 12 feet. The final measurement was 13 feet, which fits, but a tradeoff was that one seat needed to be placed close to a sidewall.​​​​
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Door Placement
Another consideration if one has the flexibility is where to place the room door relative to the screen and seating. In this design, the door ended up at the back near the center of the room, primarily due to limitations in the basement floor plan. At the back of the room was acceptable because placing a row off the back wall and two-thirds from the screen is good acoustically and leaves room for an aisleway behind the back row. However, this left less room to install two rows of seating, and as previously mentioned, the front row was a little closer to the screen than ideal.
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Figure 1. Chosen Room Size for our Home Theater
Room Dimension Acoustical Considerations
​​Room acoustics are significantly influenced by size and shape, particularly in low-frequency response. This is due to the room dimensions aligning with the wavelengths of sound frequencies, which can cause room modes. Ideally, according to several sources, room dimensions should be set to distribute these resonances evenly across the lower frequency spectrum.
​​Extensive resources and web-based calculators exist for estimating and analyzing room modes; some are listed at the end of this section.
A common guideline derived from these resources is that specific ratios of a rectangular room's dimensions can minimize the detrimental effects of room modes by evenly distributing them across the lower frequency spectrum. One frequently mentioned guideline is referred to as the "golden ratio" of room dimensions, which is 2.6 (length):1.6 (width): 1 (height). Again, this is believed to yield favorable acoustics by evenly distributing the lower-frequency room modes.
In this theater, compromises to the room dimensions were mainly based on other practical architectural considerations. ​Acoustics did not significantly impact the final room size, but this was reviewed. The room dimension ratio is 2.25:1.7:1. This was reasonably good acoustically, as shown in Figure 2.
Figure 2. Room Modes for the Room in Figure 1.
Figure 3. Room Modes for the Golden Room Dimensions
Summary
​To summarize, there were a couple of tradeoffs made that would be nice to address and improve. They are/were:
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The room length ideally should be 2-3 ft. longer.
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Placing door location on a corner or side wall to optimize space.
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The room mode analysis indicates that the room dimensions should achieve good audio results despite other constraints. Next, we will work on seat placement details.
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​​References:
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amcoutics.com—A room mode calculator with very informational graphics that identifies room modes based on room dimensions.
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calicoacoustics.com—This site has a page with another room mode calculator.
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roommodes.com—Detailed explanations of room modes.
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R. H. Bolt, "Note on The Normal Frequency Statistics in Rectangular Rooms," J. Acoustics. Soc. Am., vol. 18, pp. 130-133 (1946).
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Golden Ratio in Acoustics—auralexchange.com, optimum room dimensions.
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