How Big Should the Theater Be?

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You might answer that question a number of ways: “As big as it can be”, “As small as it can be”, or “Big enough to accommodate twelve seats”, or maybe “the exact size of the existing room I plan to convert”. However, many considerations are to be made before you answer too quickly. There is a lot of science involved in the design of a high performance theater, even in just determining its size. There are also budgetary constraints and physical limitations that come into play. Each theater has its own equation that must be understood and calculated based on these factors and the customer’s personal direction. It is the intent of this series of articles, titled “Home Theater Planning, Design, Calibration & Enjoyment,” to help you make educated decisions during the process. There are always pros and cons that must be weighed, and as a consultant, it is my job to make sure that my clients can make an intelligent decision. Customers may end up dissatisfied with the results if they didn’t know there was a choice to be made, or didn’t fully understand what the consequences were going to be. There are some things we cannot control, but we can influence almost every factor that determines our eventual success. It becomes a question of prioritizing. I cannot make these decisions for you because they are personal, but I’ll guide you through to a happy ending.

So what are some of the decisions to be made in regard to theater size? Probably the most important driver will be, “how many seats do you want?” After we include some other factors, you may pose this question differently and ask how many do you need, rather than want. Seats can take up a lot of real estate, especially if they are the reclining type. You don’t want to squeeze people in, and seating them next to a wall or speaker is not a sound idea. Proximity is very important to fidelity, to both sound and picture. As the listener/viewer numbers increase, the room must expand proportionally (like a balloon) in order to accommodate. If not, as rows increase, you’ll have viewers too close for comfort and they will see the elements that make up the picture. They will also have a poor sound stage, meaning that they will experience too much sound from the front channels and not enough from the surrounds. Those too far away will miss impact and details in the picture, too little sound from the front channels and too much from the rears. As the rows grow wider, those to the outside will experience loss of light, color and geometry distortions in the picture, and tonal and spatial distortions in the audio. Compromises can be made; cut down on the number of total seats, only allow one row of recliners, decide that kids won’t care, bring in bean bags for kids to use wherever, whenever.

Another factor might be noise isolation for the theater. You don’t want noise to enter the theater, as this would be annoying. Noise might be a hum from an equipment room, outside traffic, the game room, etc. These can be distractions, smother small audio details and limit dynamics. You may also not want noise to exit the theater. This might be a problem for neighbors or someone who is trying to study or sleep. Controlling sound, especially low frequencies, requires some real estate too. Wall, ceiling and floor systems must be designed to handle the task at hand. The lower and the louder the frequencies, the thicker these systems must be. The sound must be blocked, isolated, absorbed and/or broken. Well-designed systems combine these strategies in order to save space, weight, money, time and/or costs. Don’t let yourself be fooled into thinking that your theater will be sound proof. Low frequencies are very long in length (50 Hz. wave is 22.5’ long) and can pass through weak barriers. They can also vibrate to the far end of the house through the interconnected structure. A room alone cannot be very sound proof, but a room within a room can be. This takes more real estate, but might be what you need in order to have what you want.

Room modes are low frequency standing waves, physically dictated by the length, width and height of the room. They cannot be avoided, but they can certainly be controlled in a manner that is pleasing to the ear. If not, they become annoying, resulting in some bass notes being comparatively loud and others soft. How the length, width and height modes are distributed is key. If good room dimensions can be designed within the constraints, smooth bass response can be enjoyed. We’ll look further into room modes next in the series.

Speakers, like listeners, should also be located away from boundaries and room modes. Speakers on the wall will not sound as good as speakers away from them. Tonality and spatial imaging suffer. The same is true for speakers in the wall, with the added cost of less noise control.

Available space, noise control, costs and performance, all must be prioritized. These are most of the serious decisions to be made in order to determine the best room size for your home theater. Hopefully this has given you some insight into how to weigh those determiners, so that you can fully enjoy your home theater.

Norman Varney is the owner of A/V Room Service Ltd.

Room Acoustics, #1 Component