Home Theater Viewing Angle

in Home Theater Design

So you’re getting ready to enjoy the awesomeness that is a big old projection screen in your home theater, which is excellent. There is nothing like the lights going down, and your show starting up on your screen. Of course, while you are designing your theater, there are many screen related questions like, What should the viewing distance be for my seats? What kind of screen should I get? And, what are viewing angles anyway? The shortest answer is this image below, the viewing angle is shown on this picture: On a high level, this is how ‘wide’ the image is to your eyes, when you are watching the screen. But, you want more than that, and you should. A properly designed home theater will take into account the viewing angle – and not just put the largest possible screen that can fit onto the wall. To explain this more, we need to discuss something called Field-of-view. Field-of-view is basically the visual area you can see, when your eyes are fixed on a point (meaning, you are not looking around at things, you are staring at one point). The more of your field-of-view that is taken up by your screen, the more immersive the image will be. While you can technically see nearly 180 degrees, from left to right, you can’t really see that large of an angle with any clarity or with any resolution. What you see on your far peripheral vision is very hard for your brain to concentrate on, so instead you focus on what is in front of you. You want your screen to be inside that comfortable field of view, and you want a viewing angle that will give you the amount of immersion that you desire. Now, even though that level of immersion is a personal preference, there are some standards to work with . The Society of Motion Picture and Television Engineers (SMPTE) define the ideal viewing angle at 30 degrees or more. THX defines the ideal viewing angle at 40 degrees or more. Now that 40 degree or more number, that THX recommends, is based on a 16×9 Screen Ratio. However, since more and more home theaters are using a 2.39:1 ratio for their screen, we really need to discuss that ratio more than the big screen TV ratio. The THX recommendation for a cinemascope (2.39:1) screen is that the farthest seat, in the center of the theater, has a viewing angle of 36 degrees. So in your theater, you are likely going to want to have a minimum viewing angle of 36 degrees. To add onto this discussion is the issue of image resolution. As the resolution of displays keeps increasing, the comfortable viewing angle will also increase. This means that with a higher resolution display, such as a 4K display, you can comfortably enjoy a larger viewing angle that you can with an old 480p display. With this increase in resolution, with the use of CinemaScope ratio screens, many theater owners are creating theaters with 60 to 70 degree viewing angles, or even higher. There is no perfect answer here, there is no ‘exact’ viewing angle that you should use in your theater. As a general rule though you will, most likely, end up with a viewing angle that is greater than 40 degrees. Ultimately, as is the case with most of the decisions you will make about your theater, it comes down to your own personal...

Home Theater Viewing Distance

in Home Theater Design

Once you have decided to have a home theater, nothing will stop you! During your journey of creating your home theater, there are lots of decisions you have to make (which is a common theme of the home theater process). This includes lots about your screen – learning about viewing angles, screen choices, and how far away should your seats be from your screen. In a prior post, we talked about viewing angles, and here we’ll get into where your seats go, and how you can figure out the correct viewing distances for your theater. There are some formulas to figure out the recommended viewing angle limitations, but keep in mind that your own personal preference matters as well. Don’t focus solely on the math of these basic formulas, at the expense of ignoring what you personally like. In other words, do you like to sit closer to a screen, and have that ‘bigger’ feel, or do you like to sit farther away from the screen? That matters as well, it isn’t just about the math. But, It Is Easy Math! OK, so onto the basic math here. Don’t worry, it isn’t going to be hard! We’ll go through the main two formulas, starting with the SMPTE recommendation and then the THX recommendation. The Society of Motion Picture and Television Engineers (SMPTE) define the farthest viewing angle at 30 degrees. To use this formula, and to create your viewing distance, you take the Screen Diagonal (in inches) divided by 0.6. The answer (also in inches) to that is your viewing distance, at a 30 degree viewing angle. Let’s work through a common example, using a screen diagonal of 120 inches. 120 divided by 0.6 equals 200. 200 inches, divided by 12 is 16 feet, 8 inches. This means that, when following the SMPTE recommendation, your eyes should be 16 feet 8 inches away from a screen that is 120 inches diagonal, at the farthest seating position. Now the THX recommendation ends up with you closer to the screen, and provides a more immersive experience. This originates from THX being for the commercial movie theater market, where the bigger screen experience is preferred. The basic formula is the same, you start with your Screen Diagonal (in inches) size and you divide it. However, with the THX recommendation, you divide by 0.84, and your answer (in inches) is your viewing distance. Let’s work through the same common example, a screen diagonal of 120 inches. 120 divided by 0.84 equals 143 (excluding the fractional remainder).  143 inches, divided by 12 is 11 feet, 11 inches, so just under 12 feet, and this would be the farthest recommended seating location. You can see that with the SMPTE viewing angle, the seating is 16′ 8″ from the screen, and with the THX viewing angle, the seating is 11′ 11″ from the screen, that is already a pretty large range of where you should put your seats, so clearly there is room for flexibility here. In interviews with THX, the discussion of an ‘ideal viewing angle’ comes up, and it is right around 50 degrees, on a scope screen, so if you are looking for a good starting point, you can begin there. Forget Angles, Let’s Just Go With Height The other way of calculating your viewing distance is using the height of the screen as your starting point. The general consensus on the closest would be two times the screen height and the farthest being 4 times the screen height. So back to our example screen. Let’s say you have a 2.39:1 ratio screen, that has a diagonal of 120 inches. That screen is 111 inches wide and 47 inches high. That means that the closest you would want to sit, if using a 2 times image height, would be 7′ 10″ from the screen, and the farthest, if using a 4 times image height, would be 15′ 8″. With THX recommending 50 degrees as the ideal viewing location, that is 2.4 times the image height. If we stick with our 120 inch scope screen then, at 50 degrees, you would have your primary seating spot be 9′ 5″. To illustrate all this, let’s look at a visual example. This is a large home theater, with a twenty foot width on the front wall, and a screen that is twelve feet wide. The screen dimensions are 144″ wide and 60″ high.   If we take a look at this theater and three rows of seats, at 2x height, 3x height and 4x height, you can see that the seats are 10′, 15′, and 20′ from the screen, all based on the height of the screen. Do What You Like Here is a trick that I recommend to everyone who is trying to figure out the right seating distance for themselves, because even though we have formulas and specifications, at the end of the day it is your theater and you need it to be right for you…. Go buy a ticket to your favorite commercial movie theater. Get there early enough to pick any seat you desire. On the ceiling will be tiles, and those tiles will be 2 feet x 4 feet (or if square they are 2×2). Find your favorite seat and then look up. Count the number of tiles from right over your head to the screen. That tells you how...

Home Theater Subwoofer Placement

in Home Theater Audio, Home Theater Design

When it comes to home theater, most owners really want to bring the bass, they want powerful, clean, and strong bass. This requires subwoofers, there is no way around it. You can have excellent main speakers, but if you really want the boom, you need a subwoofer, and – if possible – more than one. The subwoofer is a critical element of your home theater. Interestingly, there isn’t nearly as much audio coming out of this speaker as you might think; if you were to mute all your speakers except for your subwoofer you might be surprised at how little comes out of that speaker, compared to all the others. However, what does come from your subwoofer is so extremely important to your overall sound and enjoyment of your home theater. Without a great subwoofer, you can miss entire sections of the soundtrack, and even lose out on important parts of the movie’s story. Subwoofer placement is a little bit more of an art than the rest of your speaker placement. While there are guidelines that we will discuss, there aren’t quite the same set-in-stone angles and recommendations as there are with the rest of your speakers. One of the main reasons for this is because subwoofer frequencies are not directional, meaning you shouldn’t be able to detect where the bass is coming from in the room, the low frequencies should ‘seem’ to be everywhere. Another reason that there is no single recommendation to use is that the performance of the subwoofer is tied to the size of the room (meaning the actual dimensions and air volume of the room), the room impacts the sound of the subwoofer dramatically. In other words, the exact same subwoofer will perform quite differently in a room that is 10′ wide x 12′ long x 8′ tall compared to a room that is 16′ wide x 22′ long x 10′ high. To add to this issue, where you are in a room also impacts what you hear from the subwoofer, this means that as you move around the room, the audible level of the subwoofer will seem to change, even if there has been no change in volume at the source. At the most basic level, if you just want the most bass, go ahead and stick the subwoofer in the corner of your room. Putting the subwoofer there will ‘enhance’ the apparent sound level coming from the subwoofer, to some of the seating location in your room. The downside here is that other seats will have far less bass – the performance of the subwoofer will not seem even throughout your room. This is why corners are not the most ideal location for a subwoofer in your theater. Yes, you can create what sounds like an increase in bass level, but the performance is so uneven throughout your theater that the bass level from one row to another (and from the left seat to the right seat) can be drastically different. When you take it out of the corner, that ‘enhancement’ will seem to diminish and the sound level will also seem to diminish. However, you will have a more even performance throughout your room. So what you should do is put on some music, or a movie scene, that you know and love really well. Let that section repeat, and while it does, move the subwoofer away from the corner. Move it towards the center of the room a foot, move it towards the seating position a foot, and so on. There is no exact answer to this, again due to the fact that the room dimensions have such an impact on performance. At each position, sit in your seats and listen. Close your eyes and just listen. You should be able to hear an obvious audio difference as you move the subwoofer around in your room. If you are open to trying it, there is a fun method called the Subwoofer Crawl. The Subwoofer Crawl is pretty simple in concept, and is actually an effective method, for the average person in their home theater, for finding the best subwoofer location. To perform a Subwoofer Crawl, what you do is place the subwoofer in your seating location, so you might have to move your seat to do this. The sub is temporarily placed in that seat’s place. After the sub is in your seating location, go ahead and play your music or movie scene. The, drop down onto your knees and crawl around the walls, the entire perimeter, of your theater. While you are crawling, listen to the bass level. You will hear that some parts of your crawl have strong bass, some have weak bass, and some have even bass. When you are at a location that has even bass, that is a location where you would put your subwoofer. If you add another subwoofer, you then are dealing with placement of multiple subwoofers, which is a separate (although related) project in your theater. Adding that second subwoofer will not remove any of your room’s standing waves, the nulls, or the peaks (those are based on the math of the room). However, adding a second subwoofer can create a more even level of bass throughout the room, which means more of your theater’s seats will experience the exact same level of bass performance. So if you can, go ahead and...

Home Theater Speaker Placement

in Home Theater Audio, Home Theater Design

You want a great home theater? Then you have to have your room right, and you need to have your speakers in the right location. If you buy some awesome speakers, but you put them in the wrong places in your room, those awesome speakers won’t sound nearly as awesome as they could. In this article, we’ll go through the best practices in setting up your home theater speakers. As an important note, please keep in mind that loudspeaker manufacturers will have specific guidelines for their products, so always follow what the manufacturer specifies. One other note, all the discussions you read tend to be about the single seated position. I’ll be using the same concept here, but realize that the farther away from that ideal seated position, the more out of ‘alignment’ your audio will be. That is where audio calibration comes into play, your audio performance does not stop with where you position your speakers. OK, so let’s get started… Center Channel Placement Your center channel is the workhorse of your home theater speakers, and the placement of this speaker is critical. This speaker is where the vast majority of dialogue is located, and the true ‘center’ of the audio you hear while you are listening to your system. Ideally, the tweeter(s) of your center channel should be horizontally aligned with the tweeters of your front left and right speakers. If you cannot place the tweeters on the exact same height, then you should have the tweeter(s) of the center channel within 12 inches of the tweeters on the left and right speakers. In terms of where to put the speaker, you should have your center channel positioned directly in the middle of your display. Doing so, gives you three options, one is to place this speaker above your screen, the second is to place the speaker below your screen, and the third option is to place the speaker centered directly behind your screen. There are pros and cons to both above and below the screen. When the speaker is below the screen, the tweeter is more likely within that 12 inch range of your left and right speakers, however if you have multiple rows in your theater, then the viewers in the front row are likely going to block the audio from reaching the subsequent rows. When you place your center channel above the screen, a downside is that there is a large difference between the tweeter height of your left and right speakers with your center channel. You can angle it down towards the audience, however you might still pickup that the speaker is well above your left and right speakers. So your best option is to place your center channel speaker directly behind the screen, with the tweeters aligned in a straight line. Of course, if you make the choice to have your center channel directly behind your screen, you will have to be using an Acoustically Transparent screen surface, so that your audio can come right through from the center of the screen. Regardless of your vertical position choice, the center channel speaker is considered 0 degrees from the listening position, meaning it is exactly centered on that seat. Front Left and Right Speakers While your center channel is the workhorse, the other two speakers that make up your front sound stage are your front left and right speakers. These two speakers are, obviously, placed on the left and the right of your center channel. There really isn’t an exact distance apart for these two speakers, rather the distance between them is based on where your seating is positioned. You should try to have the tweeter of this speaker in line with the ear height of your listening position, and (as mentioned) your center channel should have the same tweet height. This keeps the audio that is moving from left to right, smooth and on the same plane. These two speakers should be in a range that is anywhere between 22 degrees and 30 degrees from the listening position. With an acoustically transparent screen, this can often place the front left and right speakers behind the screen, so keep that in mind when you are planning your room.   Side Surround Speakers Your center channel, your front left, and your front right speaker all make up a single soundstage, with audio moving smoothly from one speaker to the other, and with you able to easily follow that movement. When it comes to your surround speakers, your placement is designed so that the entire surround sound audio blends into an envelope around the side, and rear, of the listening position. While the audio engineer might create sounds that are coming from specific speakers, in general, your surround sound is diffused, and you shouldn’t be able to easily pick out what sound is coming from what speaker. These speakers are placed anywhere between 90 degrees and 110 degrees from the listening position. And, where you want your front soundstage speakers to have the tweeter at ear height, with your surrounds you do not. Your surround sound speakers should be above ear height, if your room allows it they should be two to three feet higher than the ear height of the listening position. Remember the idea here is to create an immersive sound field, not point the speakers directly at the ears of the listeners....

Home Theater Room Dimensions

in Home Theater Construction, Home Theater Design

If you want to build a great home theater, the place you’ll be starting is the actual room itself. The size of the room, and the shape of the room, both will have a significant impact on the performance of your home theater. The room really is the key “component” to the entire project. The room is the most important part of your entire system, which is the core philosophy of this entire site and all the resources available here. You can take incredible equipment and place it in a horrible room, and it will sound way below average – while on the flipside you can take average equipment and place it in an excellent room, and it will sound way above average. In other words, your room is the critical element during the entire process of making your home theater dream come to life. Of course, unless you are building a room addition, you do not have unlimited space to work with, and will have to deal with the constraints and limitations of the space you have available to you. And for most home theaters, the shape will be a rectangle, which is the easiest to work with, so that is a good thing. The Bad Ratios When we start getting into room dimensions, where we are talking about Length x Width x Height, there are some clear ratios that you should avoid, if at all possible. If your only option is to work with a space that is exactly like one of these ratios, don’t let that stop you from building and enjoying your home theater, just do so with the knowledge that you will have to really work on the acoustics inside the space, once it is built. So the worst room ratio, meaning the worst shape, would be a simple cube. For example, if you had a room that was ten feet long, ten feet wide, and ten feet high. That would be bad, very bad. If you have a room where one dimension is an exact multiple of another dimension, that also would be bad (not as bad as a cube though). For example, if you had a room that was 16 feet long, 16 feet wide, and eight feet high, that would not be a good set of dimensions. Related to the above, you should also avoid ratios that are all simple multiples of one another. For example, if you had a room that was 24 feet long, 16 feet wide, and 8 feet high, that wouldn’t be an ideal set of dimensions, because you have exact multiples of 8 in each dimension. Modes, Waves, Peaks, and Valleys The reason for not wanting a theater with these exact multiples is related to how sound actually moves around and resonates inside a room. That will be discussed in depth in another library article, but at the high level, room dimensions can make certain frequencies seem louder, and others softer, which is not something you want to have happening too much in your theater. The Golden Ratio OK, so this part of the discussion can quickly bring out some strong opinions. There is a school of thought that you can build a room with a “golden ratio”, which means the ideal and perfect ratio of length to width to height and your room will be wonderful. The reality however, is that there is no perfect ratio. All rooms will have modes, all rooms will have acoustic issues to deal with, and all rooms have challenges. Since you cannot build a room without these, the issue then is to work with a ratio that is known to give you the least amount of trouble. In Alton Everest’s Master Handbook of Acoustics (which is the best reference on these subjects) lists the ratios of four industry experts. Here are the four ratios: Sepmeyer: 1.0 : 1.28 : 1.54 Louden: 1.0 : 1.4 : 1.9 Volkmann 1.0 : 1.5 : 2.5 Boner: 1.0 : 1.26 : 1.59 You’ll notice that even with these four experts, there is no one single Golden Ratio that everyone agrees on. In almost all home theaters, the limiting dimension is height, we simply don’t have unlimited vertical space to work with. So when you are calculating your room, using one of these ratios, the 1.0 ratio will be your height, and you work out the other dimensions from there. An eight foot ceiling height is average for many home theaters, so below are the dimensions using the ratio of height : width : length, and using eight feet as the ceiling height. Sepmeyer: 8.0 : 10.24 : 12.32 Louden: 8.0 : 11.2 : 15.2 Volkmann 8.0 : 12.0 : 20.0 Boner: 8.0 : 10.08 : 12.72 Using this example and the Volkmann ratio, you would have a room that is 8 feet tall, 12 feet wide, and 20 feet deep. What This Means At the end of the day, though the theory is nice, you have to work with the space you have available to you. If you have a large open space, or if you are adding on a new space, you can create a room that is using one of these more preferred ratios, dimensions without multiples of one another. If you are working with a room that is already defined in dimension, then that is what you work with –...