Home Theater Acoustics

Go to any movie theater and you will notice acoustic treatment covering a large percentage of the walls. Chairs are soft and well padded. The sound system is nothing short of impressive. The whole room has been carefully crafted to work as a single system and when properly put together, the combined experience of a powerful visual presentation, good acting and great sound becomes and emotional ride that can take you away, make you laugh or keep you riveted on the edge of your seat.

In a movie theater, the room acoustics play a critical role in making sure that everyone can clearly hear the dialogue, no matter where they are seated. By eliminating near-wall reflections, those seated at the periphery are not fighting to discern the sound from the speakers versus the sound reflecting off the walls. The padded seats have been carefully designed to be comfortable, and when not in use, they help control bass. When a theater is properly treated, it improves our ability to comprehend what is being said. This is known as ‘intelligibility’.

This image shows a vector as the direct sound from the loudspeaker arrives at the listening position. A few milliseconds later, the reflected sound arrives. Depending on distance and frequency, if left untreated these sounds interact and either amplify or cancel each other out, reducing intelligibility.

Your home theater is no different, only smaller. This means that you do not need as much treatment and with a little forethought on panel positioning, you can dramatically improve the sound of your room, add excitement to every event and make it look terrific too!

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Understanding the problem

In a typical 5.1 system, the center channel is the most important as this is where the dialogue is primarily generated. Our primary goal is to ensure that the message or dialogue is clearly understood by all that are in the room.

The direct sound (green) is the sound we want to hear. But just as in the movie theater, if the walls are left untreated, sound will echo off the nearby surfaces and will interfere with the direct sound.

Primary or first order reflections (red) are the most powerful and are generally the first we will want to control. Then, the trailing reverberant field (blue) or flutter echo should be addressed.

Applying the solution

Mount acoustic panels to the wall surfaces.

Sound in the voice range tends to be directional. As such, we can draw vectors on a floor plan to strategically position the acoustic panels where they will be most effective. The more panels we use, the ‘darker sounding’ the room will be.

Most find that 25% to 30% wall coverage provides plenty of absorption without over deadening the room.

Managing the acoustics in different rooms

Although dedicated home theaters tend to be large rectangular spaces, most home theaters are in fact multi-purpose rooms that combine a traditional living room with a home theater set up. Generally speaking, we want to control primary reflections and reduce flutter echo while creating a balanced audio environment. The following images are some examples of acoustic treatment using the Primacoustic London 10 room kit as it would be applied to various room layouts.

The direct sound (1) from the center speaker carries the dialogue. We can predict a powerful first order reflection off the wall at top (2). Because the distance to the other wall at bottom is greater, we can leave this wall uncovered. Flutter echo (3) will be taken care of by the absorption on the wall at top and behind the primary listening position.

Dialogue (1) will typically come from the center channel. Ideally, we will treat the side walls to reduce first order reflections (2) and then mount a series of acoustic panels behind the listening position (3) to absorb front to back echo and flutter.

In open room concepts, the center channel (1) will compete with powerful first order reflections (2) off nearby walls. Treatment usually begins with side walls and then behind the listening position. The side wall treatment also helps reduce flutter echo (3).

Absorption Coverage

The most common question we get is: ‘How much treatment should I use in my room?’ Although there are no hard rules when it comes to acoustic treatment, most dedicated home theaters tend to have more acoustic coverage while multi-purpose family rooms have less. This has more to do with available wall space than anything else.

To make the process as simple as possible, we have created a series of tables. To use them, estimate the floor size of your home theater or living room and the average height of your ceiling.

So for instance, say you have a home theater that is 14 feet wide and 16 feet deep with an 8ft ceiling. Multiply 14 x 16 to get the square footage which, in this case would be 224 sq-ft. You would go to the table for 8 foot ceilings and then consider your options.

If your home theater also serves as a family room, then you may be limited as far as available wall space and opt for 48 square-feet of absorption. This could be done using the London 10 room kit or maybe 12 of the Control Columns (4sq-ft each), or even a mix of panels including Cumulus tri-corner traps or some great looking Primacoustic Accent panels. These will help reduce powerful primary reflections and make movie watching better.

Room Calculation Tables in Feet

Room Calculation Tables in Meters

If on the other hand you really like to crank up the volume and want the same effect as a full on movie theater, you can use a greater amount of absorption by heavily treating the side and rear walls. If you are not sure, always start with less. You can always add more treatment after you listen to your room.

Determining Coverage

To determine the coverage, we have created a series of easy-to-use tables that enable you to choose between various degrees of treatment depending on your budget and the desired outcome. Most facilities find that a ‘light’ level of treatment provides sufficient sound abatement while keeping the budget in check. If budgets are tight, start with minimal treatment and then add more panels as funds become available.