Unfortunately, there is no one size fits all for a Home Theater Room. The biggest suggestion is to avoid cube-shaped rooms where the height, width, and depth of the room are equal or very similar. Instead, use a generally accepted ratio of H (Height) x 1.28H (Width) x 1.54H (Length/Depth).
Ideally, the room should also be large enough to accommodate a projector screen/television, seating, enough space for speakers, and sometimes the equipment. The topic of home theater room dimensions has been debated for many years. I will do my best to explain some of the common or recommended ideals for the sizing of a room, as well as, other things to consider when choosing a home theater room.
There have been countless studies done on ratios for the best acoustics in a room. There are so many different ones out there that deciding on which one is "right" can be extremely difficult. I am going to recommend three "golden room" ratios developed and researched by L.W. Sepmeyer. Note that these ratios are based on the height of the room!
These ratios were developed by studying the wavelength of low-frequency sound and how it reacts inside of different sized rooms. A room within one of these ratios is much more likely to carry low-end frequencies better with less acoustical problems.
I will explain more about this below, but first, here are some examples of room sizes using the above "golden ratios".
Example 1: Height of 8ft = 8 x 9.12 x 11.12 with a cubic volume of 811.32ft³
Example 2: Height of 10ft = 10 x 11.4 x 13.9 with a cubic volume of 1584.6ft³
Example 1: Height of 8ft = 8 x 10.24 x 12.32 with a cubic volume of 1009.25ft³
Example 2: Height of 10ft = 10 x 12.8 x 15.4 with a cubic volume of 1971.2ft³
Example 1: Height of 8ft = 8 x 12.8 x 18.64 with a cubic volume of 1908.74ft³
Example 2: Height of 10ft = 10 x 16 x 23.3 with a cubic volume of 3728ft³
The shape of a home theater room is pretty important with regard to acoustics. Just because a room is large enough to fit all of the components to a home theater, doesn't mean it is ideal for how it will sound! However, do keep in mind, a room that doesn't match one of these "golden ratios" is still perfectly acceptable to use as a home theater room.
There are some things you can do to control the acoustics in the room if you are unable to change the actual size of the room.
As I mentioned at the beginning of this post, you want to avoid using a cube-shaped room as a home theater room. The issue with a cube-shaped room is how the acoustics will travel. Sound waves will travel from the speakers and bounce off of just about any flat surface in a room. The ceiling, walls, floor, etc.
Contained within a cube room, it is more likely for standing waves to occur. A standing wave is a low-frequency resonance (reinforcement of sound by reflection) caused by a source wave colliding with a reflected wave of the same or similar frequency.
You should try to mitigate standing waves in your home theater room because they can cause three different acoustical issues.
All of these acoustical issues disrupt the integrity of the low-end frequencies inside the room. You should know that standing waves usually only extend to around 300 Hz. Resulting from standing waves, bass sound can resonate and play for longer than originally intended in certain areas. There can also be pockets or holes of bass.
This means that there are areas of low pressure in the room, usually caused by sound waves colliding with each other. It can be a little difficult to imagine what a standing wave is, so here is a visual example: Making Standing Waves Video
You can utilize acoustic panels to minimize standing waves and help contain the sound within the room. I wrote a very in-depth article all about acoustic panels and how they can help a home theater room.
The shape of a home theater room is pretty important when it comes to acoustics, but you can do some things to help with that. There are other characteristics that should be considered when choosing a location for your home theater.
If you are fortunate enough to design the room size and layout, then you should be able to eliminate some of these issues before the room is constructed. But most people do not have much say in the construction of a home theater room. You will usually have to make do with what is available, plus perform some simple modifications to the room.
Obviously, the room should be large enough to fit the projector screen/television, seating, speakers, and other equipment. A room that is 8 feet tall x 10 feet wide x 12 feet deep actually fits one of Sepmeyer's golden ratios pretty closely. But do you think that will be an ample amount of space for everything to fit comfortably? Well, probably not, unless you want the max capacity to be just 3-4 people.
You could probably fit more than 4 people in this small of a room, but they may be sitting pretty close to the screen, which can become disorienting with a large display. Again, as mentioned earlier, a cube-shaped room is not the ideal shape. You want to try and stick close to one of the golden ratios provided. These typically have the least amount of issues when it comes to acoustics inside the room.
Considering the size of a room, it may be difficult to position a projector in a location that isn't directly overhead. Projectors tend to produce a lot of heat, as well as, a lot of noise due to their fans. Check out this article on short throw projectors and their benefits to home theaters.
Note that the room should have as few doors and windows as possible. Doors and windows will affect how sound is reflected and bounced around the room. Windows will reflect sound more different than a normal wall will. Doors will allow sound to escape the room, affecting both the volume within the room and allow more sound to be heard outside of the room.
If you have a lot of control over the room structure, then the walls should be constructed closer together in the front (where the display will be located) and further apart near the back of the room. This will help tremendously with the acoustics of the room.
Sound waves typically bounce more when they meet a 90-degree corner of a room. A home theater room with a narrow front and wider back allows for the sound waves to dissipate more and to not cause as many standing waves.
However, this is usually not ideal for how homes are built nowadays because most rooms are built as normal rectangles. A room shaped like this causes other construction issues for remaining areas.
The lighting for a home theater room is extremely important! A room with many windows is not ideal because the excess light will drown out the projector or television's image.
If there are some windows in the preferred room, then you can simply install blackout window shades. Our home theater is actually located in our living room, so if we were to watch something in the middle of the day, then the image is very difficult to see. However, we installed some blackout window shades and some curtains, and it completely blocks out the sunlight when needed.
You will also want to install dimmable lighting in the room. Dimmable lighting will allow you to not smash your pinky toe into the corner of a wall. Plus it allows you to control the brightness of the lights in the room. Also, ensure you use high-quality dimmable lights. Cheap dimmable lights will sometimes flicker when dimmed to a low level.
The basement is often a great location for a home theater room. A home with an unfinished basement allows you to build a home theater room to your own specifications if you choose to do so. It is often easy to control the ambient light, run cables, and is usually a level or 2 below bedrooms.
Basement home theaters generally cause fewer vibrations in the house as well. Concrete foundations tend to not vibrate very much. If you choose to locate the home theater close to other bedrooms, make sure you are courteous when using it late at night. It will likely vibrate the surrounding rooms slightly. To combat this, read the next section of this article about sound isolation.
A home theater room full of loudspeakers will likely cause vibrations throughout the home. And depending on where the room is located; the vibrations could travel to multiple stories of the home.
Windows are not great sound insulators. They tend to leak a lot of sounds and could possibly be heard at a neighbors house if the room is poorly insulated enough. Avoid windows as best as possible.
As mentioned earlier, 90-degree corners cause sound waves to bounce all over the place. You can add acoustic foam bass traps (on Amazon) to different corners of the room to help dampen and reduce the bouncing of sound waves within the home theater room. A room isolated from the rest of the house will require less sound dampening material. A home theater room close to bedrooms may require much more sound dampening material.
After reading this article, you may be thinking that maybe your house doesn't have an ideal room for a home theater. I urge you to stop thinking that way right now. You can implement a home theater room into your house even with the most non-ideal circumstances, I simply wanted to provide you with some of the issues you may encounter.
It's good to know these things ahead of time before it is too late! Now if your home truly doesn't have a room capable of housing a home theater, then consider using your living room! Check out my article on using a projector in a living room. You will run into some sound issues with a living room home theater, but they will be minimal as the sound has more area to escape. I hope you found this article useful!