Home Theater Diffusion and Reflection: Pairing Up Plates and Panels for Superb Sound
Creating the perfect sound in any home theater is a challenge to say the least. Many homeowners are searching for the panacea that will alleviate any and all reflection and absorption problems. By combining treatment options, sounds at all frequencies may be successfully managed, generating a professional sound at an amateur price.
• Frame it up. Commercially marketed bass trap frames and plates can be a tricky proposition for those who are limited in both expense and knowledge. To reduce confusion, home theater owners should be aware of the existence of steel-framed bass traps and corresponding plates for maximizing diffusion. The advantages of the available steel-framed bass traps and plates include:
o With steel frames, the home theater owner is able to either purchase corresponding fabric bags or create fashion bags using fabrics that complement the room’s décor.
o The steel frame provides a ridged means to hang panels from the ceiling or the walls
o Newly available bass trap include those made of a fire rated plastic material that is heavy enough that it does not resonate. The plates are also equipped with tabs and grooves, enabling them to be snapped directly into acoustic frames.
Frames and plates, when properly paired, create rigid units that do not resonate, regardless of the sound field, resulting in the desired diffusive reflection.
• Property values. One concern some home theater owners may have is the inhibition of bass trap properties. The diffusion is able to achieve the following without compromising bass trap function:
o Reflection improved at higher frequencies.
o Absorption reduced at higher frequencies.
o Effort retained at lower frequencies.
Diffusion of waves below about 300-400 hertz would be negligible. Below 350 hertz, the diffusion plate would more likely be considered an absorber.
• Flying high again. There is a common problem with sound treatments that involve the complete elimination of high end reverberations. Contents of a dedicated theater space include carpeting and drapes that absorptive on higher frequencies but not low frequencies. In order to have a sound balance, try the following:
- Control the lows. Broadband absorptive materials help to control the low frequencies not addressed by other treatments, e.g. corner panels and 4-inch panels on the walls and ceiling.
- Reflect the highs. Bass trap plates improve reflection of the higher frequencies in a diffusive way. Now when the sound hits it the sound gets spread over a wide 120 degree arc.
By adding plates to bass traps, high frequency reverberation is returned to the room as it diminishes the amount of absorption taking place.
Battling reflection, absorption, and diffusion challenges can be mentally taxing and can send some home theater owners digging in their wallets for a high-end solution for a low-end problem. Although sound is a priority in home theaters, solutions are available that not only create the desired result but also let the homeowner keep a little in his wallet for the next big home theater discovery.
Home Theater Sound Design: Making the Grade with Diffusion Gradings
No matter how dedicated a home theater owner may be to great sound production, a good diffuser is not the most economical sound treatment currently on the market. Most of the products available are based on number theories that promise to generate reflections that are phase coherent and steered all around the room based on series of wells and slots of varying depths in specially designed boxes. Rather than running the numbers, there are some simpler steps to improving home theater sound.
• Get bent. Many sound experts do not put a great deal of stock into complicated systems of grade diffusers that require extensive mathematical intervention. The central problems with most high-end diffusers are:
o Frequency inconsistence. In relation to acoustic wavelengths, only series of frequency bands are properly diffused.
o Frequency incoherence. Frequencies in between bands are returned as frequency incoherent.
o Frequency bounce. Unbent frequencies result in a chaotic bounce off the wall.
• Back to the future. To address not only the cost of new-on-the-market diffusers but also the often unreliable performance, many home theater experts recommend poly-cylindrical built-in panels. Although dating back before diffraction gradings became popular, the poly panels function well by putting the beams under compressive force and producing the same result as is found from the bending of panels.
• Buckle up. For those home theater owners who have the ingenuity and initiative, an alternative to commercial diffusion is a self-made panel. These steps will produce the desired results without the added expense:
o Materials. Measure and cut a frame for the desired space. Insert a slightly oversized piece of plywood in the frame
o Function. The bending of the plywood makes a smooth curve out of the constructed panel, allowing for a buckled beam.
o Location. For those designing and building a home theater with a larger back wall, it is possible to put the panels into the walls for a special touch.
The diffraction grading style diffusers available on the market can be expensive. However, there are some companies making corrugated surface grading types out of molded plastic. The only downside to the molded plastic versions is the possibility of rattling due to their light weight, but they are considerably more affordable. Quite possibly the best route is to construct a frame and bend the corresponding panel rather than purchasing a commercial product.
