Room Layout and Component Placement – Screen SizeNow that you have established the basic design goals for your new home theater (location, room dimensions, display type, speaker configuration, etc.) the next steps in the planning process are to determine the screen size, seating locations, speaker placement and balancing the budget.
• Screen Size (Flat Panel TV)
• Screen Size (Front Projector)
• Seating Position
• Projector Location
• Speaker locations
Screen Size (Flat Panel TV)
TVs and projector screens are typically advertised using the diagonal screen dimension because it sounds bigger. However when we talk about determining the ideal screen size and seating positions for a given room size, the width of the screen is what we are really interested in.
(55″ x 0.872 = 48″)
Note: For a 16:9 display (1.78:1 AR)
Width = Diagonal x 0.872
Height = Diagonal x 0.49
If you plan to use a flat panel display device, your choice of screen size will most likely be heavily influenced by your budget; larger screens are generally more expensive. You might be happy with a 32″ ~ 46″ diagonal screen (16:9) display in a small room but the majority of users will most likely opt for a display device in the 50″ ~ 55″ range. This is where you will currently get the best bang for your dollar. For larger TVs, as the screen size increases beyond 60″, your buying options will decrease and the price will go up dramatically. If you really want a screen size larger than 60″ it might be worth re-evaluating your decision to go with a flat panel display. Maybe a projector and large screen is what you want after all. It is also possible that installing both a flat panel display and a projector would be more cost effective than purchasing a really large LCD or Plasma display.
Keep in mind that the main seating area distance from the display device will be significantly affected by your choice of screen size.
Screen Size (Front Projector)
Selecting the proper screen size becomes even more important when using a front projector. The size of the room, seating distance, projector light output and resolution should all be considered before deciding on the final screen size. It will also go hand-in-hand with selecting the optimum seating distance so you may have to go back and forth a few times to determine the ideal combination of screen size and seating distance.
Step 1: As a starting point, the size of the wall you plan to mount the screen on may limit your choices. And don’t forget to leave room for positioning speakers on either side as well as below (and/or above) the screen. Take measurements and make a sketch on graph paper of the front wall layout. Here are some things to consider:
• Research the screen you want and note both the viewable and installed dimensions (height and width)
• Decide on the aspect ratio (AR) of the screen you plan to use (1.78:1, 2.35:1, etc.)
• Will the screen be a pull-down, retractable style or a fixed-frame mounted to the wall?
• Center the screen horizontally on the front wall inline with the main seating area
• Position the screen vertically on the wall so a person seated in the front row will look straight into the bottom 1/3 of the screen. This also should leave room for positioning a center channel speaker below the screen
• Leave room on either side of the screen for the front-main speakers
You should now have a good idea of the approximate screen size (or a range of sizes: min/max) that can be used in the space you have available.
Standard 16:9 Screen Format (1.78:1 AR)
2.35:1 AR Screen for use with Anamorphic Lens
Step 2: Now compare the initial screen size you picked with the depth of the room and cross-check both the seating distance and projector mounting location (throw distance) to make sure all three work together (see below). Ideally you should arrive at a combination of screen size and seating distance that yields a 30 to 40 degree horizontal viewing angle. The Society of Motion Picture and Television Engineers (SMPTE) recommends a minimum viewing angle of 30° (THX recommends 36°). Once again, it would be a very good idea to make a sketch of the room layout with dimensions, which will allow you to measure the viewing angles at different seating locations.
Note: The following room layouts are for illustration and are not intended as building plans.
While the primary focus may be on the horizontal viewing angle it’s also important to consider the vertical viewing angle when selecting a screen size and seating distance. The screen should be positioned vertically on the wall so a person seated in the front row will look straight into the bottom 1/3 of the screen. Offsetting the screen towards the top of the front wall should also leave room for positioning a center channel speaker below the screen. You want at minimum of 2-1/2′ from the floor to the bottom of the screen and viewers in the back rows should ideally have a clear line of sight to the entire screen (risers may be required).
Step 3: Re-check that the screen size, seating distance, and projector location to insure all three are working together.
CAUTION: Bigger isn’t always better. Be realistic when deciding on the final screen size and don’t get carried away with a super-sized screen. If you wind up making the screen too big you may actually see pixilation and noise, especially if you like sitting up close to the screen. Another potential drawback to making the screen too big is that the image will become dimmer (less lumens per square foot) as the screen size increases (for a given projector), which can reduce image quality and wow factor.
Special Note for Anamorphic Lens Users: If you plan to incorporate an anamorphic lens and a fixed 2.35:1 screen AR in a CIH (Constant Image Height) system, you should use the equivalent 16:9 screen to determine your ideal screen size, seating distance and throw distance. For example, if you do the math and come up with a 96″ (diagonal) 16:9 screen; the 2.35:1 equivalent is a 120″ (diagonal) screen because they both have the same viewable image height (47″). (See the room layout drawing in the Projector Location section.)
(Anamorphic lenses from Isco and Prismasonic)
The main advantage of using an anamorphic lens is that it allows the projector imaging device to fully illuminate a 2.35:1 screen with all 1,920 x 1,080 pixels instead of wasting approximately 30% of the pixels on black bars. This will restore maximum resolution, increase brightness and eliminate the black bars from the top and bottom of the image. The major downside is the high cost of the outboard lens and a slight softening of the projected image.