Where do you start though? Well, if you are building a new house, then that makes it easy. The principles discussed here apply also to a renovation home theatre, but your freedom may be slightly more limited by the existing space or room that you have.
We will try and keep this as simple as possible. For more in depth explanations, contact us and we'll send you some links to some very helpful websites.
Start with the room
Room dimensions and materials have a real impact on how sound acts in the room, screen sizing, and layout options. When designing a home theatre in a new home, you have to think about your priorities too. How important is the performance of my home theater vs seating capacity, percentage of floor plan etc? If you are passionate about home theatre like we are, then do yourself a favour and make sound and picture your highest priority.
Working out room size
In the world of home theatre, there exist 'golden ratios' for correct sound performance and correct screen size and placement.
Room & Sound...
To work out your home theatre overall dimensions, we have to look at how sound acts. Sound waves coming from your speakers either get reflected (by reflective or hard materials on your walls or floor) or absorbed by materials (like carpet, fabrics, wall cavities, soft furniture etc.) in the room. The more randomly sound waves reflect off or absorb into surfaces, the more even the sound in the room will be and the less resonant or rebellious frequencies (over-prominent tones) will exist in the room. This gives every frequency that we can hear, an equal chance to fit into the sound performance evenly.
Home Theatre Room & Sound Rule #1:
Rectangular room. No dimension equal or double/divisable. Screen to the longest end.
Researcher L.W. Sepmeyer looked into room dimensions and their effect on sound waves. He came up with 3 'golden ratios' that equally distribute sound around a room:
Sepmeyer's Golden Ratios:
Room Type Ceiling Height Room Width Room Length
Room A C 1.14xC 1.39xC
Room B C 1.28xC 1.54xC
Room C C 1.60xC 2.33xC
You don't have to design your room to exactly these dimensions, as these ratios were discovered using just one speaker in the corner of the room and a listener at an exact location. Sound reacts differently when other objects or different seating positions are introduced. But these ratios give a very good starting point for your home theatre.
Some of the worst sound comes from square rooms, or rooms where two of the dimensions are divisible by each other. For instance, 2.7Hx4Wx8L. The width and length are divisible by each other, therefore creating big problems within the room due to 'standing sound waves.'
Home Theatre Room & Sound Rule #2:
Keep reflective surfaces to an absolute minimum. Use soft, absorbing materials like carpet, heavy fabrics. This tames problem frequencies. Especially low frequencies.
A room's acoustic performance is affected heavily by the materials used. You want as much sound as possible coming to your ears from the speakers. Not reflecting off the floor, walls or objects in your room. Reflecting sounds come at your ear at slightly different timings-making the sound lose it's clarity. Minimize reflective surfaces by using carpet for flooring, sound absorbing materials on your walls like acoustic panels or heavy curtains, (just like the movies) or other soft but dense materials.
Your furniture doesn't have to be soft though. The more complex the structure of the object, the more sound gets dissipated through an over-abundance of reflections. Bookshelves for instance offer many surfaces for the sound to reflect off and dissipate.
Home Theatre Room & Sound Rule #3:
Let nothing come between you and your sound.
Although this seems obvious, some of the worst sound will be experienced when something is placed in between you and a speaker. If you can't see your speaker via direct line of sight, you will get the worst sound in the room. The only exception to this is your subwoofer. Low frequencies are omni-directional, so subwoofers do not need to be seen to be heard.
The size of the movie screen in commercial theatres is determined by the audience's seating position. The closer you are, the larger the picture looks in your field of view. The further back you are, the smaller the screen looks in your field of view.
Home Theatre Screen Rule #1:
Stay between 30-40 degrees total horizontal viewing angle.
Screen size diagonally x 1.63 = approximately 30deg viewing angle.
So for a 50" (1.27m) screen [1.27x1.63 = 2.07m viewing distance].
Most movie theatres work on the assumption that the middle row in the room will have a 30 degree viewing angle. (Or 36deg at the back row as recommended by THX). Ideal for a full immersive experience without neck strain from twisting your head past it's comfortable extremities. This can be roughly worked out by multiplying your screen size diagonally (in meters) by 1.63. This will give you close to a 30 degree viewing angle just like the middle row in your local cinema.
If you are constrained by seating position, you can work out your optimum screen size (for a 40deg inclusive viewing angle) by measuring the viewing distance, and multiplying that by 0.6. That will give you the horizontal width of the ideal screen for that viewing distance) So if you have a viewing distance of 2 meters, multiply 2 by 0.6 and you get 1.2. This is roughly equivalent to a 55 inch screen (diagonally).
These screen sizes might seem huge. But remember we are trying to re-create the cinematic experience.
But what about the rows behind and in front you ask? Well, obviously these rows are not in an ideal location and their viewing angles will change. THX recommends a 36 degrees horizontal viewing angle at the back row of a cinema, or 40 degrees in a one row home theatre. Depending on the size and quality of your image, you may have to play with your seating position in order to determine the right position for the quality of your image. You should not be able to see any flicker or individual pixels in your screen.
Home Theatre Screen Rule #2:
Correct height of screen produces no more than 15 degrees (to the top or bottom of the image) of total vertical head tilt.
15 degrees is a comfortable head tilt for most people. This will also have a bearing on seat placement and even the correct seat design.
All rows of seating should have an unobstructed view of the screen from top to bottom. This usually means raising the seat row height the further back you go. Most cinemas work on a 1 foot or 27cm increase in height for each row behind the one in front. If you are limited for height, you can also stagger your seating so one seat is not directly behind the other.
We hope this has been a helpful look into designing a home theatre for your new home or existing home. Obviously we cannot cover everything in one blog post. Remember that if you have any further questions we are more than happy to help and can work with you to design a stylish and truly cinematic home theatre for you.