Make Your Point: Strategies for Home Theater Sound Reflection
Sound control strategies for home theaters can be complicated if the individual methods themselves are not fully understood. Along with absorptive material and corner panel placement comes the need to appreciate the effect of reflection points for top quality sound control in home theater systems.
Sound absorption in home theaters often follows common sound absorption strategies. Many times home theater owners choose to focus their sound absorption attention on strategies that include basically involved the lower half of the wall. Perhaps a chair rail is installed to divide the upper and lower halves of the wall, limiting sound absorption to the lower half, restricting sound absorption to ear level and below. The ideal location for installing sound absorbers is on reflection points. Imagine a little gnome sitting on top of your speaker with a hand full of rubber balls. The spot on the left side at which you have to bounce that ball to hit you in the left ear is the perfect place to put an absorber. Although above the chair rail level, the panel will control early reflections. The same principle is true of the first reflection points of the ceiling, the right wall, and perhaps even behind the primary seating area. The best places for panel placement are corners in a diagonal mounting to control low frequency and the first reflection points off your side walls and ceiling.
To find your first reflection points, there is a way to figure them out using a mirror. While remaining seated in the primary listening/viewing area, have someone hold a mirror flat to the wall and move it around. The reflection point is established when the speaker is visible in the mirror. However, as most people who ever played pool, or billiards, already know, reflection points are easily discernable with the naked eye. For example, if you are sitting in your home theater and you want to bounce a red rubber ball off the left wall and hit your speaker, determine where you would throw the ball to determine the reflection point. Yet another concern of home theater owners is whether or not to add sound absorption to front speakers. By adding absorption to front speakers, the sound that is heard when facing the front of the room will be from the speakers and not from any reflections off the front wall, making the speakers sound more precise.
For additional early reflections points, a panel should be installed behind each speaker with a third hung in the middle. The closer the listener is to the wall, the closer the first reflection point is to your speaker. For sound absorption directly behind the primary seating area, the closer the listener is to a wall the more the home theater space will benefit from rear-hung panels. The secret is to not overtreat the room. Remove the least amount of objects necessary for a clear, precise sound and leave all other surfaces bare for some echo and reverberation. Finally, when sound treating smaller rooms, it is recommended to use the thickest panel possible. If there is simply not enough room for the thickest panel on the market, a thinner panel is the most practical. Aside from the acoustics, the overall goal is to furnish the available space to be comfortable and aesthetically pleasing.
Home theater acoustic rules are made to be broken. Although thicker panels are naturally better because of better low frequency absorption, they may not always be the most reasonable for the available space. When possible, it is recommended for home theater owners to use thicker sound-absorbing panels. There is a perceivable benefit for the listener and the overall cost is negligible.
Put Your Panel Where Your Sound Is: Home Theater Corner Panel Placement
When planning the best possible output from a home theater system, sound is obviously a priority. As part of home theater sound control, the proper placement of sound absorbing panels is paramount to maximizing the home theater experience. Using some simple sound control methods, strategic panel placement can make the most of any home theater system.
The placement of sound control panels is as important as the sound output components. Wherever a panel is mounted – hung from the ceiling, hung from the corner, hung on the wall – having some gap behind it will produce some modest benefit in additional low frequency absorptions. But hanging panels in the corner is a special case. There is an enormous benefit of corner mounting panels. There is a large boost in absorption that occurs at about 100Hz and on a 4-inch thick mineral fiber panel, made out of semi-rigid fiberglass, twice the absorption is possible as would be if the panel is simply hung on a wall. The corner mounting is for the purpose of low frequency absorption.
The corner mounting of sound panels does have specifics that should be understood before proceeding to the actual placement of the panels. Although there is a benefit of an air gap in the corner, there is not necessarily a benefit from an air gap within the panel itself. The corner mounting is more than just an air gap. There is a resonance in the panel that arises from the way that it is mounted. The corner-mounted panel traps a large triangular cross-section of air behind it and works almost like a semi-Helmholtz bottle, similar to the frequency captured by blowing across the mouth of a bottle. The corner mounting of panels is a special case in comparison to hanging panels from the ceiling walls. At around 80Hz every panel that is hung in the corner is worth two or three panels hung somewhere else.
Bass trapping, or low frequency, is the most important thing to do in the home theater. For easy and efficient placement, vertical corners where two walls meet are usually out of the way and available. But when they are not, there is also a corner formed where the floor and the walls meet. Often times, two or three 4-foot long panels are positioned leaning against the wall or underneath the screen in the front of the room, which is a corner. Also, where the ceiling and wall meet is a corner and a location for the hanging of panels. And as far as low frequency sound is concerned, the location of the corner is irrelevant. They are all good. Sound does not distinguish between up and own. The real trick is to get sufficient corner mounting treatment in the room; and it is the easiest, least expensive, and most reliable way to introduce low frequency absorption.
The placement of sound absorbing panels is an integral part of maximizing the home theater experience. Awareness of how corner placement of panels can improve your home theater sound in comparison to alternative panel mounting can make a measurable difference in how low frequency sounds are projected by the available sound absorbing materials.
