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Media Room and Home Theater Design and Construction

Your media room or home theater can be one of the most enjoyable rooms in your home.
The key to maximizing your enjoyment is careful design. Many disciplines comprise media
room design. It's part interior design, architecture, acoustics, electronic systems design,
electrical engineering, control systems design and video systems design. Recently
computer and network expertise has become increasingly necessary as well.

The more questions you ask and the more pertinent information you have to work with, the
more successful your project will be. You can't know too much about how the room will be
used or the personality and values of those who will be using it. Information is the key to
success in this area.

Questions that must be answered to ensure a successful media room or home
theater design include:

Facility Usage:
Is this a dedicated home theater or mixed use facility such as rec room or multi-media room?
Is it to be used for movie viewing only or will it accommodate mixed programming such as
TV programs or sports? If principally movies, what genre? Action, Horror, Drama, Comedy,
etc.
What is the number of seats required?
Will this facility be used principally by adults, children or both?

Physical and Construction:
What size and shape is the space?
Is altering either the size or shape an option if doing so would improve the end result?
What type of construction is the residence? Wood frame, steel studs, CMU blocks, etc.
Is there an ability to optimize construction for our purposes using techniques such as:
Double, staggered stud walls, R/C-mounted sheet rock, acoustic absorbing membrane, etc.
What is the exterior environment like? Noisy, hot, cold?
What type of HVAC system does the facility use? Hydronic, forced air, radiant?
What are the electrical requirements for the project. For new construction, these need to be
communicated to the electrical contractor. If an existing structure, can the required circuits
be installed?
What are the adjoining rooms used for?

Interior Design:
What type of seating is desired for the project? Theater chairs, Sofas? Recliners? Leather?
Cloth? Motorized? Sofas w/ Built-In recliners?
Is there a desired decor the home theater / media room should follow or is there already a
design theme in mind?
Does the project have an interior designer?
Is there a theme throughout the home the theater should retain?

Equipment / Speakers / Control:
Will there be ambient lighting control? If so, what type?
Will existing equipment be incorporated? If so, what components?
What sources are desired or available? Is What HDTV source(s) will you be using? Will
thins theater have Blu-Ray Disc, HD-DVD, or both?
How loud will the users want it to go?
Will the facility be used for gaming?
How comfortable are the system’s primary users with technology.
Is there specified for new construction, or already in use for an existing structure, a control
system of some type such as AMX, Crestron or a PC based system?

Once these questions have been answered, the theater design process can begin.

Obviously, knowing the intended use of the facility is paramount. A media room that is going
to be used primarily for a group of guys to watch sports on weekends is going to have some
very different requirements than a dedicated theater used chiefly for a couple to watch
movies. It is important to know as much about this as possible. Sometimes the client will
come out and tell you. Other times, you have to ask careful questions to get the best
picture of how the room will be used. If it is a personal theater design project, you obviously
have a much better idea. Keep in mind that once the room is complete, you may use it
differently than originally intended.

If the room will be used primarily for sports for example, the sound system and room
acoustics become less important. More of the budget can be shifted to video and control.
You may be able to get by with a good A/V receiver based audio system with good in-wall
speakers. Less of the budget needs to be allocated for interior room acoustic treatments
and sound isolation. This allows a greater percentage of the budget for large screen video
and the required control system. If the room is a single purpose facility, used only for
watching video, concealed components such as motorized video screens and projector lifts
become far less important, freeing resources for other areas.

A very popular configuration for sports rooms is having multiple HDTV feeds to a primary
display and several secondary displays. In this application, a large plasma or front
projection primary display would be complemented by several smaller LCD or plasma
displays. The secondary displays can be laid out either flanking or above the primary
display. Mounting them below usually doesn't’t give comparable results. It will cause the
primary display to be elevated above optimum sight lines.  If a motorized projection screen
is being used, secondary monitor placement will be limited to the sides of the primary
display.

This type of multi-display system needs much more sophisticated signal distribution and
switching than does a system with a single display. When using multiple displays, a touch
screen control interface is far easier to use. Touch screen controls tend to be far more
expensive for both the initial purchase and programming than a simple smart remote. This
cost is compensated for by the absolute simplicity it confers to the system’s operation.

If the room will be a single purpose, dedicated home theater, a different set of design
criteria enters the equation. The sound system, interior room acoustics and acoustic
isolation become much more critical. The primary purpose of a home theater is to create
what’s known in the motion picture industry as “suspension of disbelief”. To facilitate this,
the director crafts a sound track that elicits certain emotions and immerses the viewer in the
movie.

Many of the requisite sound track elements are very subtle. To experience these subtleties,
it is essential that the theater’s noise floor is very low. Lowering the ambient noise requires
acoustic isolation techniques to reduce sound transmission from the exterior environment. If
the noise floor is not suitably low, the volume of the small sounds must be increased to
compensate. If the sound system has good dynamic range, (the ability to reproduce very
quiet sounds and very, very loud sounds without distortion) increasing the volume of the
quiet sounds will render the louder portions of the sound track painfully loud. THX reference
level is 105db, which means the loudest sounds will be quite loud but the very subtle
sounds will be lost in a room with even a medium level of ambient noise.

Suspension of disbelief also requires the elimination of exterior sounds that will distract the
viewers. Nothing is worse than hearing the neighbor’s argument during a touching
emotional moment in the movie.

The other goal to strive for in reducing sound transmission is to keep the sound of your
theater from disturbing others. This especially true if you enjoy action/adventure movies
with really dynamic sound tracks. Bass from your cool, new subwoofers can penetrate walls
very effectively. Your neighbors and other family members may not appreciate this as you
enjoy the new Star Wars box set until 1am on a weeknight.

The best construction technique for eliminating sound transmission is thick, concrete walls,
underground, if possible. Failing this, there are other approaches that will reduce sound
transmission. Interior acoustic panels are not for reducing sound transmission. They are for
treating the room’s interior surfaces to improve internal room acoustics. This deals with the
behavior of sound inside the room and will be addressed shortly.

One of the easiest, and most common sound transmission reduction techniques is to mount
the drywall on resilient channel, also known as “c-channel”, “hat-channel” and “R/C
channel” or “R/C”. This is thin metal that is affixed to the wall studs and ceiling joists. The
drywall is then mounted to the resilient channel, effectively decoupling it from the room’s
structure. Sound is then not transmitted as effectively from the drywall to the room’s
structure or vice versa.

When locating electrical outlets, vacuum outlets, or any other wall penetration, be sure two
penetrations on opposite sides of the wall do not share a common stud bay. A penetration
on opposite sides of the wall, in a common bay, gives sound an unobstructed path from
your media room to the adjoining room or vice versa. A path around your sound isolation
technique is known as a flanking path. Any wall penetrations should also be sealed with an
acoustically effective foam sealer to prevent a flanking path from being created and voiding
the effectiveness of your construction techniques.

Staggered stud wall construction is an extremely effective technique to reduce sound
transmission as well. This technique keeps opposite walls from sharing studs. Dedicated
studs will reduce sound transfer from the media room’s drywall, into the wall studs and into
the adjoining room’s drywall. Drywall is a great sound radiator, and will re-radiate the sound
from the studs into an adjoining room with amazing effectiveness. When constructing the
wall, use top and bottom plates one size larger than your studs. For example, if you are
using 2x6 wall studs, use a 2x8 for the top & bottom plates. Use at least R-19 batt insulation
inside the wall. Lay it horizontally and weave it between the studs. (see picture)

Home Theater HVAC
An often overlooked area of ambient noise in home theaters is the noise contributed by the
HVAC system. This can be quite intrusive and seems to rear its ugly head at the most
inopportune times. Fortunately, there are simple, inexpensive techniques to reduce it. One
of the main causes of HVAC noise is created by rapidly moving air. Slowing down the HVAC
airflow into the theater, while maintaining the same volume of air is a key to reducing noise.
Increasing the number of or size of the registers is the best and simplest way to accomplish
this. Try to locate the theater as far away from the HVAC equipment as possible to minimize
noise transmitted directly from the equipment through the walls. This is often a more difficult
task. To minimize the mechanical sounds conveyed from the HVAC equipment through the
ducts, use lined ductwork with smooth radiused bends. Commercial HVAC contractors tend
to be more familiar with this type of insulated ductwork than those that do strictly residential
projects.

A very effective method for reducing the STC (sound transmission class) of the wall is to
use two layers of drywall. These should be of different thicknesses. A layer of 5/8” and a
layer of ½” works well. Using different thicknesses keeps the two layers from sharing a
common resonance frequency. If they do share a common resonance, that frequency will
have a greater propensity to travel through the wall.

To really increase the effectiveness of this technique, sandwich a layer of sound deadening
barrier between the two layers of drywall.  This is a very heavy, acoustically dead material
that will effectively kill any resonance in the drywall. One type of material with a long track
record in this area is Homasote, a sound deadening material made of recycled newspaper.
It's been around since the early 1900's. A more modern solution is to use one of several
varieties of mass-loaded vinyl. This is a thin plastic sheet of enhanced mass, with
viscoelastic  properties. A new drywall is available with some of these sound damping
properties from Quiet Solution known as "QuietRock". This material can also be used
between the interior layer of drywall and the wall studs or, if used, resilient channel.

One of the main concerns, obviously, is the sound quality inside the room. It is very
important the room is designed to minimize problems due to the shape and size of the room
itself. This is so important because problems caused by the rooms shape or dimensions are
very difficult to solve. The main rule is to stay away from using the same length for two or
more of the room’s dimensions. The very worst shape is a perfect cube. Each dimension
(length, width, height) of the room causes specific audio frequencies to be reinforced and
others to be cancelled.

This reinforcement / cancellation is caused by the relationship between the wavelength of
the frequency in question and the room’s size in one or more dimensions. These are known
as room modes. If the wavelength, or an exact fraction of it, such as ½ or ¼, is the same as
the length of one of the room’s dimensions, that frequency will be reinforced by forming
what’s known as a standing wave.


The wavelength of a frequency is calculated by dividing the speed of sound over the
frequency in question. From this, you can see the lower frequencies are the most
problematic because their wavelengths tend to correspond to room dimensions in typical
sized rooms. The effects of standing waves are one of the most vexing problems
confronting theater room designers. They will cause certain locations in the room to be very
loud at certain frequencies while having virtually no sound at others. Careful selection of
room dimensions, seating and speaker, chiefly subwoofer, locations all help minimize the
problems caused by standing waves.

As mentioned previously, the first thing to look at is the dimensions of your room. The ratio
of any dimension should not be the same as, or an even multiple of, any other dimension.
You should not be able to multiply a dimension by an even number to get any other
dimension. Examples of poor ratios (height:width:length) are: [1:1:1], [1:2:4], [1 : 1.5 : 2], [1
: 1.4 : 2.8], etc. Some often used ratios proven to work are:[1 : 1.3 : 1.7], [1 : 1.7 : 1.9], [1 :
1.7 : 2.3]. As an example, using one of the better ratios would lead to a theater with a 10’
ceiling, 13’ wide and 17’ long. Rooms with non parallel sides can be very effective at
eliminating standing waves. These types of rooms tend to be much more complex to
calculate room modes. They are beyond the scope of most basic acoustic modeling
software.

Commercial grade modeling software works very well for this but can cost over $3,000. The
better commercial software is supported by most commercial speaker manufacturers, who
supply data about their speakers to include in the program’s database. This type of
software is rarely used in residential applications. Most custom installers simply do not have
it. Some do, however, or the acoustic modeling can be contracted to an outside acoustical
consulting firm if that level of sophistication is required.

Once dimensional and construction issues are taken care of, Seating, screen, and speaker
placement and interior acoustics are considered. These are no less important, they may
actually be more so, but they are also much easier to change, if necessary.

How Big Should My Home Theater Screen Be?
Screen size is usually derived from the seating distance. The number of seats, acoustic
concerns, and room size will determine the distance from the seats to the screen. The
distance to the  primary seating location, known in the industry as the "money seat", will
determine the optimum screen size.

The screen should occupy a viewing cone that extends 15 degrees to either side of center,
for a total of 30 deg. A basic rule of thumb dictates a screen width of 1/2 to 1/3 the distance
from the primary seat to the screen. For example a  distance of 14' (168") would support a
45" x 80" screen very well. Keep in mind this a general rule and there are many exceptions.
Too large a screen will lead to fatigue from constant eye movement.


This phenomenon is often unnoticed at first because it can be very subtle. Too small a
screen detracts from the theater experience by reducing the impact and amount of
information conveyed to the viewer. Most people tend to want the largest screen possible in
their theater. To that end, a 14' distance could easily support a 52" x 92" screen, but much
larger than that would be risking eye fatigue.
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