Print, radio and television advertisements bombard us with the “Home Theater In A Box” pitch. It sounds pretty easy, as if there is not much to it. Anyone who has or plans to build a dedicated home theater knows it takes careful planning to create this special environment.

As a manufacturer of both the framing construction and interior acoustical treatments, we have seen many design attempts to provide the ultimate home theater.

There are typically three project stages that we become involved in –

First – The “After The Fact Stage”. The homeowner already has a completed room and realizes the room is too live and that to much sound transmits through the walls into the adjoining rooms. This is a real problem as adjoining rooms may be bedrooms, offices, living rooms, exercise rooms, kitchens etc.. The problem of sound transmitting through the wall is a double edge concern. While watching a favorite movie you don’t want to hear distracting sounds from out side the theater just as people outside the theater don’t want to be distracted by sounds from your favorite Action movie.

Second - The “Mid Stream Stage”. The homeowner is excited about the their new or existing home and the idea of having their very own home theater. They are overcome by the excitement and turn the builder or contractor loose on the construction of the dedicated theater. We get the call after the framing is complete and drywall is ready to be hung. Keep in mind, this is after all wires are pulled, HVAC ducting is in, and soffit’s are hung.

Third – The “Planning Stage”. Not always possible but the most preferred by all those involved. Involvement of an acoustical consultant if possible (experienced in home theater design), the architect if needed and most defiantly the builder and the audio video equipment dealer specializing in home theater sound and vibration isolation. This mix of talent makes for a well planned and trouble free installation.

This issue we’ll talk about the latter being the “Planning Stage”. The involvement of the above mentioned design talents generally means that the home owner is planning for the totally dedicated home theater room to be all it can be.

That being a “TOTAL ROOM WITHIN A ROOM” HOME THEATER or in simple terms, a room that is isolated from the surrounding structure for both sound and vibration.

How do we get started?

Assuming this is a new home in the design stage, convey the desire for such a space to your architect. Explain that you want the “TOTAL ROOM WITHIN A ROOM” HOME THEATER, which requires special considerations during the design stage. Such as a 2” recessed area in the concrete slab or sub floor and an extra course or two of a concrete block in the basement walls to maintain the desired finished ceiling height in the theater.

By this time you most likely have an Audio / Video dealer in mind. Today most dealers offer a sound and vibration isolation package along with all their electronic gear. You’re A/V dealer will provide information or sometimes put the architect or contractor directly in touch with the manufacturer of the sound and vibration isolation / interior acoustical treatment materials. The manufacturer can provide all specifications of products needed along with details to be included in the architect’s drawings if needed. Contractor installation drawings can also be provided.

Like any other project, consideration needs to be given to everything from the ground up starting with the floor.

The primary purpose of the floating floor is to provide a resilient building surface that de-couples the ROOM WITHIN A ROOM THEATER from the rest of the structure and to provide additional low frequency or bass absorption within the theater.

The floor is 1” in thickness which requires two layers of 1/2” thick five layer or five ply –plywood for a total height of 2”. Prior to the installation of the roll out floor system, it is preferable that a 2” recess area be formed in the concrete floor to match the perimeter shape of the dedicated theater room. This allows the isolated theater floor to be flush with the adjoining entrance. If this is not feasible for one reason or another, the floating floor material can be installed on top of the existing floor slab. Either way, prior to the installation of the floating floor material, a perimeter isolation material is installed around the entire room. This provides a horizontal resilient de-coupler from the floating floor to any perimeter walls.

The roll-out floor material that we produce has pre-positioned isolation pads provided in a 4’-0” wide roll of sound absorbing fiberglass. The load bearing isolation pads are coated with a waterproof flexible coating. After the rollout floor material is in position, additional pads are provided for high load areas such as under floating perimeter stud walls and theater seat risers.

Pad locations are called out on installation drawings by the factory. After the roll-out floor system is installed we position the first layer of 1/2” AC grade plywood, butting each sheet tight against the next and the perimeter isolation material.

After the first three rows are in position, we start the second layer perpendicular to the first applying rows of construction adhesive on the back-side of the top sheet, on 12” centers to eliminate potential squeaks. We also stagger the joints by a distance of 2’-0” and secure top sheet to bottom sheet with 1-1/4” drywall screws positioned on 12” centers.

Some installers choose to use 50# building felt between the two layers of plywood instead of adhesive however we prefer adhesive to maintain a clear visual of the sheet below during assembly.

After the entire floating floor is installed, it’s time to construct the walls.

Just as in every home construction project there are different design methods for wall construction. Some are 2x4 studs w/ 2x4 base and top plates with studs spaced on 16” or 24” centers. Some are 2x4 staggered studs w/ 2x6 base and top plates. The staggered stud approach is better acoustically if room size permits.

The stud wall is assembled on the floor and built 2” shorter then the distance from the top of the floating floor to the bottom of the floor joist above. This allows spacing for the resilient wall isolation sway braces.

Prior to standing the wall up, we install a 1 psf sound barrier material that is screwed to the outside of the stud cavity (outside of stud cavity now facing up). The barrier material is over-lapped and taped along the vertical edges and cut off even at top and bottom of stud plates with razor knife.

We then raise the wall assembly and tap into final position. Remember the wall falls 2” short of the above floor joist bottom. At this time we install the isolation sway braces connecting the floating stud wall to the bottom of the joist. This is done typically on 24” centers.

The bottom stud plate is then screwed to the floating floor deck.

Each remaining wall is constructed and erected in the same manor.

After all walls are installed and secured at the top with resilient sway braces, it’s time to install the isolated ceiling.

Again, the factory or acoustical consultant will provide the recommended ceiling hanger locations. The isolation hangers are designed for standard dimensional wood joist construction, wood “I” joist or microlam beams.

After ceiling hangers are installed typically on 4’-0” centers, an off the shelf cold-roll steel or black iron channel is installed through the bottom of the hangers stopping 1-1/2” short of the stud wall. The black iron channel runs are parallel to each other as called out on reflected ceiling plan. Off the shelf hat channel is inverted and screwed to the bottom of the black iron channel in a perpendicular direction on 2’ centers also stopping 1-1/2” short of the wall. Self-tapping screws are used for this connection.

Now it is time for other trades to become involved. Starting with the mechanical contractor, the HVAC register boxes are installed for both supply and return air.

The dedicated “ROOM WITHIN A ROOM” home theater is well under way. At this stage one very important factor is commonly overlooked. It is equally important to control the mid range and low frequency sound from transmitting to the outside of the theater as it is to control the outside noise from entering into the theater. Both supply (inbound fan noise) and return air ducts (outbound theater noise) act as a channel of sound in both directions. We use a silencer designed to fit up in the floor joist cavity above. It is important to position both supply and return silencer as close to the registers as possible. Some consultants also recommend the use of in-line flex duct connectors that are installed on the far end of each silencer away from the theater.

After HVAC air ducting is in position, all AC power lines, speaker runs and any other low voltage requirements are routed, it is time to think about surround speakers. If surround speakers are the in-wall or in-ceiling type, we install a pre-formed speaker well lined with barrier material that contains speaker bleed from entering into the stud or joist cavity. This is very important if any speaker penetrations are to be cut through drywall. Not required if surrounds are surface mounted.

Prior to the installation of drywall, we scan the area directly overhead and in close proximity of the theater for water lines and soil pipe drain lines. Any water lines that are strapped tight against the floor joist above are released from the clamps and suspended with small isolation hangers. Usually we see this recommended for a distance starting 8’ to 10’ before reaching the theater area and continuing 8’ to 10’ past the opposite side. Secondly wrap the copper pipe with a barrier material to reduce water flow noise. This is also done for the same distance. Soil pipes are also wrapped with barrier material for the same reason.

After all HVAC and electrical work is complete in the theater, it’s time to insulate.

Use a non-backed fiberglass acoustical insulation batting.

It is important to fill all stud wall cavity’s (in this case a nominal 6” deep) and all exposed ceiling joist cavity’s (full joist height) prior to the installation of drywall.

Now it’s time for drywall. Normally the acoustical consultant specifies a minimum of two layers of 5/8” drywall on both ceiling and walls. Some prefer a combination of two different thicknesses. The progression of the “ROOM WITHIN A ROOM” home theater project requires the wall surface drywall to be installed first, followed by the ceiling.

Typically the first layer is installed running horizontally, trimming drywall flush at top of stud wall. Use drywall screws not nails.

Tape and spackle all joints but don’t bother to sand. Install the second layer of 5/8” drywall in the vertical direction offsetting parallel joints by 2’-0”. Again trim second layer off even with top of wall. Tape and spackle all joints for desired finish. For the ceiling, install the first layer of 5/8” drywall with drywall screws into the inverted hat channel, running drywall tight against the walls. Install and spackle the ceiling just like the walls.

At this point your theater room is totally free and floating. The outside of the floating theater room is now ready for drywall. Stop the external drywall about 1/4” short of the floor and 1/4” short of the bottom of the floor joist above. The factory can provide details for finish recommendations based on actual conditions.

To totally button up the room a selection of acoustical doors and seals must be made. At minimum a solid core door would be installed or a higher performance acoustical composite door. Along with a top of the line door seal your “ROOM WITHIN A ROOM” home theater is ready for interior acoustical treatments.

Larry Holben is the VP of Retail Sales for Kinetics Noise Control located in Dublin, Ohio. KNC is a 46 year old company specializing in the control of noise and vibration for commercial and residential projects. www.kineticshometheater.com