Home Theater Acoustics

Have you ever had the experience of removing all of the furnishings from a room in your house to either paint or when you were moving out and noticed how your voice sounded so much different than it did when the room had furnishings?  If so, you now understand how much of a difference acoustics can make.

Live or Dead

Acoustics is both an art and a science.  Experts in acoustics will refer to a space as “live” or “dead”.  Ideally you want something in between.  What you are trying to achieve is a balance between too much reflected sound (live) and not enough (dead).  Reflected sounds are made up of the sounds that bounce off another surface before they arrive at your ears. This is compared to direct sound, which comes directly from the speaker to your ears.  A room with no furniture in it would be a good example of a room with too much reflected sound (live). A room with all of the surfaces covered with sound absorbing material (an example would be an anechoic chamber used by speaker designers) would be a very “dead” room.  The trick is to the right balance.  Too much reflected sound and the dialog is almost impossible to understand.  With too little reflected sound, you get no sense of space.  

In addition to reflected sound, some amount of dispersed sound is also good.  When sound waves hit a flat surface (such as sheetrock), then its considered reflected.  When the sound hits an uneven surface and then bounces off in all directions, then it’s considered to be dispersed sound. 

So how does all of this apply to your media room or home theater?  In a media room you typically have to work with furnishings to get closer to ideal acoustics.  Anything that has uneven surfaces is great.  A bookcase full of books is ideal!  Make sure from the main seating position that you can physically see all of the speakers.  A speaker blocked by a piece of furniture is not ideal.  If you can set yourself up to be equidistant from the left and right speakers do so. There are several ways to “treat” the acoustics of the room using common furnishings.  Large leafy plants can make a big difference in the sound of a room.  Adding a rug to a room with hard surfaces for the flooring will be an improvement as well.  Tapestries and other wall hangings will help you get the right balance of reflected sound.  Draperies and window treatments also help.

In a true home theater, the options for acoustic treatment are much better.  Audio Video Design can actually analyze your room and make suggestions on acoustic materials that can be placed on the walls.  The best solution is to use a track for a decorative fabric, which hides the acoustic treatments behind the fabric.  We will attach the various acoustic panel treatments to your walls, then fabric is stretched across the wall. This gives you the real theater look and is the best option.  We’ll calculate where to put the absorptive panels, the reflective panels, the combination reflective/absorptive and the dispersive panels.  If your room is rectangular, this becomes much more of a science and is very predictable.

What the Heck is a Mode or Node?

The dimensions of every room effect how the sound waves bounce around in a room.  These are called room modes.  They will have dips and peaks at spots in your room where they build up (lots of modes) and where they cancel each other out (a node).  The effect is most pronounced with low bass sounds.  The dimensions of your room play the role of determining how big and at what frequency these problems occur.  A cube would be the worst sounding room, filled with tons of acoustic problems. Take this into consideration if you can impact the dimensions of your future theater room.  Even in a room with perfect dimensions, placing the main seating right in the middle of the room is not ideal.  In the design process for your theater we will calculate the best place for your seating to be to minimize this effect and if we have the leeway, can help you get to the ideal dimensions, but as a general rule, try to have your main seating position about 1/3 away from the back or front wall.  Room modes and nodes are typically less pronounced at these points.

What About Noise

When a home theater can put you on the edge of your seat without having to blast you with high volumes, the room probably has a very low noise floor.  This means the inherent noises in the space are minimal so they do not mask out the subtle sounds of the film.  Noise can come from many sources including equipment fans, the fan on your projector, a noisy appliance, or other external sources.  If you have to turn the volume up louder to overcome these noises, your system will have less of a sense of dynamic range, and as a result be less satisfactory.  Ideally you want to be able to literally be able to hear a pin drop in your room.  We can work with you to be sure the design takes into account reducing noise.

It All Adds Up

Many people do not even consider acoustics when planning their theater space.  It’s a real shame to spend lots of money on gear and not give it the right environment to perform to its best if you have the option available. If we help you nail the acoustics and construct a room with a very low noise floor, you would not believe how this can improve your experience.  A $2500, professionaly calibrated speaker package in a well engineered room will put most un-calibrated $10,000 speaker packages to shame that are placed a room with bad acoustic properties.  Of course the better packages really shine in a well done room.  I hope this article has helped you understand that the most important component of your home theater is the room itself.

© Audio Video Design 2013