Abstract: The basics of treating a room for a better home theater

Abstract: The basics of treating a room for a better home theater
Home Theater Room Treatment
Abstract:
The basics of treating a room for a better home
theater experience include room dimensions,
placement, absorbers, diffusers, and bass traps.
Placement of Speakers:
For a standard 7.1 channel surround sound
system, the placement of the speakers is as
follows:
Introduction:
The ideal home theater sound system needs to
produce the exact sound that the producer (the
person who made the audio) intended their
audience to hear. The most common mistake
when setting up a home theater sound system is
not treating the room it is in. The room is the most
important part of setting up a home theater
system because sound waves interact with the
room before hitting the listener’s ear. These
interactions with the room change the sound away
from the ideal.
Room Dimensions:
The first thing to consider is the room dimensions.
The goal is to avoid dimensions that allow
common frequencies to become stationary.
Figure 1: Diagram of a standing wave.
Standing waves will occur at any frequency
proportional to twice the length of the room. So to
avoid having one frequency get amplified, one
must chose a room that does not have a length,
width, and height that are multiples of each other.
Some golden ratios for room dimensions
calculated by experts include:
Sepmeyer: 1.0 : 1.28 : 1.54
Louden:
1.0 : 1.4 : 1.9
Volkmann: 1.0 : 1.5 : 2.5
Boner:
1.0 : 1.26 : 1.59
Bass Traps:
Low frequencies require a special type of
absorbing panel called Bass Traps. Bass traps
are typically placed in the corners of the room
because low frequency waves become stationary
in the corners.
Figure 4: Bass Trap panel. Notice how it looks like the absorbing panel but has a corner shape.
Treatment Placement:
Below is an example layout of a room with
treatment.
Figure 2: Layout of a standard 7.1 channel surround sound system. The angle values are as
follows: Angle 1 = 22° to 30° , Angle 2 = 90° to 110° , Angle 3 = 135° to 150°.
A common technique to placing the subwoofer is
called the subwoofer crawl where the listener
places the subwoofer in the listening position
and crawls around until they hear the best
sound. That spot is where the subwoofer should
be placed for the best bass.
Treating Reflections:
Sound will reflect off of surfaces in the room,
some more than others. These reflected sound
waves take an extra amount of time to hit the
listeners ears than normal, thus creating a slight
echo. This delay may not be desirable and so to
alter how the sound interacts with the wall, the
listener can place sound absorbers or diffusers.
Figure 5: Example of room treatment in a home theater system. The white panels on the right and
left of the room are sound absorbing panels. The wooden panels with slits in them are also sound
absorbers. There are also sound absorbers on the ceiling. There are four bass traps, two per corner.
There are no definitive rules for placing room
treatment because in the end it comes down to
what sound the listener thinks sounds best.
However, generally, absorbing panels should be
placed at least on the reflection points on the left
and right walls. Bass traps should also be used in
all corners. Diffusers are commonly used on the
back wall and back ceiling to simulate a surround
effect for systems that do not have surround
speakers.
Figure 3: Example of a sound absorbing panel (Left) and a sound diffusing panel (Right).
Absorbing and diffusing panels have many variations on how they look. These are just examples.
Author: Ethan Harte
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