By Geoffrey Taylor, AIA

Design Considerations

The fundamental concerns of a home theater are the visual and audio performance of the experience. The placement of audio-visual equipment depends on the geometry of the theater space. Three modes of sound exist in the theater: axial, tangential, and oblique. Axial modes are the passage of sound between two parallel surfaces. Tangential modes move among four surfaces. Oblique modes involve all six surfaces of the space.

The quality of the sound in the theater can be maximized with good room proportions and the proper selection and location of acoustical treatments. Absorptive materials and reflective surfaces should be used to manipulate the movement of sound in the space. Some reflections are desired to create ambience and lifelike attributes.

An additional concern is the containment of noise within the theater, inhibiting its transmission through the perimeter barrier. Materials and methods of construction should preserve an acoustical boundary.

Projector locations vary depending on the technology selected and may feature descending lifts, floor-mounted units, or rear wall concealed units. If multiple rows of seating are desired, raised platforms will enhance sightlines to the screen.

Acoustical Performance

Doors
The entry door provides an easy path for sound to escape from the theater to adjacent spaces. The door should be of solid core construction and feature the highest possible sound transfer coefficient (STC). A good target performance rating is STC 45. If a vision panel is incorporated, it should consist of two panes of glazing with frames and seals to maintain the STC rating of the door assembly.

Doors represent an expansive, reflective surface; without interior surface-mounted acoustical panels, doors should not be place in the first half of the theater adjacent to the screen and the front channel speakers.

Acoustical seals should be used along the edges of the door, particularly at the threshold. The door leaf should feature a mortised, automatic door bottom seal. Gaskets should be closed cell neoprene or silicone rubber. Seals should be continuous along the hinge, lock, and head of the doorjamb and not conflict with installation of door hardware such as closures, exit devices, and panic bars.

Isolate the theater from adjacent spaces with double-wall construction with a continuous, uninterrupted air gap. Alternate assemblies include resilient channel over perimeter framing, or the use of composite framing members mechanically connected with resilient framing clips. With composite framing, the acoustical member shall be shorter than the structural member and not fastened to the sill and top plates. Ceiling construction should reduce low-frequency sound transmission by isolating the theater from adjacent spaces with double-framed construction or the use of mechanical hangers featuring neoprene pads.

Acoustical Panels
Materials applied to the interior surfaces of the space respond to the live/dead end properties of a rectangular room. Acoustical materials affixed to walls and the ceiling should feature a 6lb/cu ft density. The panels can be fabric wrapped if the covering does not interfere with the desired performance characteristics of the panel.

Acoustical Sealant
Applied to both sides of the perimeter wall construction, at both the sill and the top plates, the sealant should be applied in continuous beads. If necessary, backer rods should fill large voids before the sealant is applied.

Floors
Isolating the movement of the floor from the perimeter boundary inhibits the transmission of sound from the theater. A floating floor should be executed with a closed cell foam acoustical floor mat or high-density molded fiberglass isolator pads. Isolation of the theater from adjacent construction can be accomplished by turning up the acoustical floor mat along the perimeter or by using an isolation board. The isolation board should be rigid glass fiber or neoprene sponge rubber (10 lb/cu ft). The floating floor should be finished with carpet to provide the best acoustical performance for tangential and oblique modes.

Batt Insulation
Wall cavities should be completely filled with 3-1/2 in. batt insulation with a sound transfer coefficient performance of at least STC 14. Fiberglass materials should have a minimum density of 3 lb/cu ft.

Mechanical Pipe Insulation
Pipe conduit penetrations of stud drywall construction should be wrapped with 1/2 in. thick pipe insulation extended 2 in. beyond both faces of construction with drywall installed tight to sheet insulation and sealed with acoustical sealant. If multiple ducts, pipes, or conduits penetrate the exterior envelope, each element should be separated by a minimum of 4 in. in all directions.

Dutwork Insulation
To minimize the transmission of sound, the duct should be lined with 1-2 in. of fiberglass insulation with a minimum 1.5 lb/cu ft density. The noise reduction coefficient (NRC) rating for 1 in. duct lining should be 0.45 and 0.72 for 2 in. duct lining.

Ductwork Penetrations
Provide 4 in. sheet insulation around any perimeter wall penetrations. Extend insulation 2 in. beyond the width of perimeter partition to each side.

HVAC
Linear diffusers should be used to minimize the airflow noise within the theater. Supply airflow rates should be limited to 600 ft/min. in the main duct and 425 ft/min. in branch ducts. Diffuser neck velocities should be limited to 325 ft/min.

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