Screen Size

One of the key decisions to be made when designing a home theater is what size screen you will use. This is a choice that has important consequences for the design of the theater, as well as your long-term enjoyment of it. Some of these consequences are obvious, and some are more subtle.

When the image is too small, it can make the action feel far away and un-engaging. This makes it tempting to just put in the biggest screen that will fit on the wall of your desired theater space. This is often not the best choice, however, because it’s also possible for an image to be too large for comfort. Above a certain size, it’s hard to follow the action, and many people will find that viewing an overly large image can be physically uncomfortable over the course of a feature film.

The best metric to start with when establishing your desired screen size is the apparent size of the image—how much of your visual field is occupied by the image. This is normally measured as an angle: if you were to draw lines from the left and right edges of the screen, meeting at your eyes, the angle that they form where they meet is the horizontal viewing angle.

There are industry-standard minimum and maximum recommended angles, but these are by nature averages across the population. Since you’re building your own theater, you can select the perfect angle for you.

One way to figure out your ideal angle is to spend some time at a commercial cinema. Most people know about where they like to sit in the theater—some will prefer to be closer to the screen, while others will feel more comfortable farther back. If you can establish your favorite row in the theater, you can then take a couple of quick measurements after the show, and easily find your preferred viewing angle.

For most people, this angle will fall somewhere in the range of 35° to 45°. Almost everyone will find anything above 50° to feel uncomfortably close to the screen. For reference, THX recommends a viewing angle of 40°, and a minimum viewing angle of 36°.

This Projector Calculator will help you determine your viewing angle.

To translate this angle into an actual physical screen size in feet and inches for your theater, you just need to know the distance between the screen and your seating location. This prompts a new question, though—where will you put your seat? See the section on seating layout for detailed thoughts on this subject, but in brief, if you will have more than one row of seats, then only one row will have your preferred/perfect horizontal viewing angle. This is the “prime” row. If there’s another row in front of the prime row, then obviously the screen will appear larger to viewers in that row, and viewers behind that row will perceive a smaller screen size.

Depending upon the size of your space and the number of seating rows you want to include, you may find that varying the screen size and seating location will allow you to find a configuration that hits your perfect angle in the “prime” row, while still providing acceptable and enjoyable image size in the other rows. Larger screen sizes will reduce the amount of row-to-row variation in angle, but there are practical limits for the screen size in any space, and most home installations will have a fair amount of variation in angle between the prime rows and the secondary rows.

Once you have an approximate screen size and seating location, there are some other factors to consider. For example: where will you put the speakers? An acoustically transparent (AT) projection screen is the most flexible solution in this regard—the three front speakers can all be behind the screen at whatever locations make sense acoustically, or you may end up with the left and right speakers concealed behind stretched fabric to either side of the screen, with just the center speaker behind it.

Non-AT screens (including flat-panel displays) have less flexibility for speaker placement. Typically, the center speaker is placed below the screen, and the left and right speakers are placed to the sides of the screen. This obviously requires that the screen is sized to leave adequate space on the sides and below the screen not just to fit the speakers, but also to ensure that they are far enough from the walls and floor to avoid unwanted acoustical interactions.

It may take several iterative adjustment cycles to arrive at a screen size that allows for proper speaker placement and satisfying viewing angles for all seating rows.