Home Theater Blog
By Ric Warner
Behind the Numbers
Long, long ago in a land all too familiar, manufacturers decided they would baffle the general public with numbers. Most people are faced with a decision. Either take the time to study video numerology or, take a salesperson’s word for it. I will attempt to simplify and clarify this tedious subject. The 2 sets of numbers that are put in our face the most are aspect ratio & resolution.
Aspect Ratio
Aspect ratio compares a video displays width to its height. Most current TVs are 16:9 ratio. That tells us if the screen is 16” wide then it will be 9” tall. Please do not apply the aspect ratio to television size. TVs are measured diagonally. A 55” TV is not 55” wide. There are many aspect ratios out there but, here are the 3 most common.
4:3 actually started with Thomas Edison. This is the ratio Edison & Kodak used for their early films. The Academy of Motion Picture Arts and Sciences later set 4:3 as its standard for shooting and displaying movies in the early 20th century. The TV we all grew up watching was 4:3. This ratio is still widely used with older CRT TVs.
16:9 was the result of a study done to determine how wide versus tall manufacturers could make CRT picture tubes before TV sets would become unmanageablely large. During this period flat panel displays were replacing CRTs but, the 16:9 ratio stuck. That is why most displays today are 16:9.
2.35:1 was made popular in the 1950s by Hollywood. They found the public loved the wider screen. This resolution uses the same film. In the past an anamorphic lens is attached to the camera and to the projector to achieve this ratio. A few of the newer projectors will allow this much wider screen to be a reality in your home, with no anamorphic lens required. In the next decade you will notice this ratio used more and more.
Resolution
In order to keep confusion to a minimum we will only discuss how this affects modern displays. Video resolution is simply the number of pixels horizontally compared to the number of pixels vertically.The best description of a pixel is a piece of a picture. The more pieces the clearer the picture. See the chart below:
Common Consumer Resolutions
720P (1280 pixels by 720 pixels) 921,600 total pixels
1080p (1920 pixels by 1080 pixels) 2,073,600 total pixels
2K (2048 pixels by 1566 pixels) 3,207,168 total pixels
4K (4096 pixels by 2160 pixels) 8,847,360 total pixels
The total number of pixels is a good starting point to define quality but, many other characteristics are factors. The number of LCD particles in each pixel, pixel grid construction, light engine, and video processor are the most important factors. Unfortunately there are no readily available numbers to compare these display attributes.
2K and 4K may be new to you. That will not be the case for long. 4K is starting to gain a lot of traction. Sony has introduced the first native 4K consumer projector. Yes this projector has a exceptionally clear picture but, that is just the beginning. 4k accomodates all the common aspect ratios and resolutions without video processors or additional lens.
4K makes all the numbers we have discussed irrelavent. You will have the ultimate picture, with the ultimate flexability. All displays will migrate to 4K. This will take a little time but, the future is very bright.
Going into the Third Dimension
3D is a huge topic when picking a TV or Projector. Like any new technology it has taken a little time for the media industry to offer enough subject matter to justify purchasing the equipment. Most high profile new films have a 3D version. Avatar is stunning. Many sporting events are available in 3D. To my surprise , watching a game in 3D is fantastic. There are several 3D channels available. Even the gaming industry is taking advantage of 3D. The video games are incredible. You can even make home movies and pictures with the new camcorders and cameras. It is not a fad. Electronics manufacturers and Hollywood studios are very invested in 3D. It is time to enjoy the new depth and realism 3D provides.
The picture above demonstrates how images seem to pop out of your display at you. Personally I enjoy the depth. You really feel like it is possible to reach your hand inside the TV. If the equipment is set up properly and the media is made in 3D it is a great experience.
From 50’s -80’s anaglyph 3D (Blue & Red Lens) was very popular. It was very distracting and, it actually reduced the quality of the image. The new 3D technologies are far superior.
There are 2 main technologies for 3D today. The first is active shutter glasses. By using high-frame rate LCDs with a “frame sequential display”, it is possible to watch Full HD 3D quality video on 3D compatible LCD TVs. This technology involves alternately transmitting images for the left eye and right eye to the screen. When viewed through the “active shutter glasses”, the two separate images on the shutter glasses are synchronized with the onscreen image with their Full HD quality intact and precisely transmitted to the viewer’s eyes.
An alternate 3D display technology for TVs is Line-by-Line method, which uses polarizing filters to alter the direction of alternate lines of pixels on the TV, so that alternate lines of the image are displayed for the left eye and right eye respectively. The TV is to be viewed with 3D glasses in which the polarization of the lenses is oriented for the different directions transmitted, so that the image information for each eye is only recognized by the respective eye. However, this technology reduces the native resolution of the display by half, because only half of the display information is available for each eye. As a result, it is difficult to reproduce precise clear images.
Of course you do need specialized equipment. Your TV or Projector, HDMI cabling, Bluray Player, and A/V Receiver all have to be 3D compliant. The proper projection screen makes for an increase in quality as well. You may have been in a big box store and watched the 3D demo and you were not impressed. Maybe your neighbor got a new 3D setup and you thought that is not for me. Please do not let this affect your opinion. Like most things in life, the product is a direct result of the effort used in production. The proper setup & equipment, along with quality media is the only way to truly experience 3D.
Things that make you go Boom!
Speakers are a huge part of everyone’s life. Your phone, TV, computer, radio, Ipod, and so much more all utilize speakers. Most people have no idea how they work or the physics behind them. I will give a general overview of a speaker and surround sound system. Then I will break down the different types of theater speakers used in a dedicated home theater.
A speaker pushes air. Which makes sound waves (changes in air pressure). Our ears differentiate the pressure levels produced by the speaker. Our brains perceive this information as sound.
A magnet, coil, and a cone are the 3 basic parts of a speaker. The magnet is in a fixed position. The coil is attached to the cone. When a current is applied to the coil a magnetic field is produced. This current can be in a positive state or a negative state. The coil will interact with the magnet at this point. The cone will either be pushed or pulled depending on the state of the current. Just like the magnets we played with when we were children. Positive to positive repels. While positive to negative attracts.
Low, Mid, and High frequencies usually have a separate speaker dedicated to each of them. To direct the various frequencies to the desired speakers we use crossovers. Crossovers can be as simple as a capacitor or an inductor. Quality speakers will have a crossover circuit board. This allows the frequencies to be divided very accurately.
Like most things in life, this is a simple process but, the devil is in the details. The engineering design, materials, and quality of manufacturing have a huge affect on the performance and longevity of a speaker.
Surround sound is several speakers, amplifiers, and a processor working in unison to provide a specific experience. The picture and sound in the studio are perfect by definition. The experience is defined by the director in the studio when the film was mixed and edited. Our goal is to experience the film exactly as the director intended.
There are several different versions of surround sound. 2.1, 3.1, 5.1, 6.1, 7.1, 10.2, 22.2 are all common versions of surround sound. The numerical value pertains to the number of discrete channels the audio is divided into. It is a common misconception that the numerical value pertains to the amount of speakers. For instance in a 7.1 surround sound system you have 8 channels but, we can use the surround right and left channels for 4 speakers instead of 2. This would give you a total of 10 speakers not 8. The size, shape, and materials used to build the room will dictate which surround sound system should be selected. The placement of the speakers will also be dictated by the room.
The following list includes the different types of speakers used in a typical dedicated theater:
Center Channel- Up to 90% of a movies sound comes from this speaker. The majority of the dialogue comes from here. It is the most important speaker in the theater.
Front High Channels- These channels handle the sounds above the screen.
Left and Right Channels – These speakers handle the front right and left channels. Any sound that should come from the far right or left of the screen.
Surround Channels- These speakers handle the sounds for the middle of the room.
Rear Surround Channels- These speakers handle the sounds for the rear of the room.
Subwoofer- This speaker/speakers handles all of the low frequency effects.
Speaker placement is often taken for granted. You can find general guidelines for speaker placement just about anywhere. To avoid wave cancellation, room modes, echos, and reverberations speaker placement is critical. Unfortunately without a audio meter and signal generator proper speaker placement is extremely difficult. After installation each speaker should be tuned to its location in the room.
The version of surround sound selected, the type of speaker used for each location, the amplifier, the processor, and speaker placement all play a critical role in the surround sound system. Each theater we install has its unique set of challenges. Constant education for the ever evolving equipment and years of experience are the only way to ensure you get the most from your dedicated theater.
PROJECTION SCREENS
In our last article we discussed projectors. Naturally , our next topic should be projection screens. The projection screen should maintain the image projected. It should not alter the image in any way. At first glance this seems like a very attainable goal. Just aim the projector at a flat, white wall and presto your done. Although you can see the image if you do this. Much of the clarity, contrast, and color accuracy of the image will be lost. A good screen will maintain the contrast and color accuracy of the image projected. As well as direct the light towards the audience. There are several factors considered in choosing the proper screen for any project. Below are the main factors to consider.
1. Size- The room size has an impact on the screen size however audience size and placement is the determining factor. How many rows and how many seats in a row? Is the most important question in a typical theater layout. Most residential theater seats are roughly 3’ wide. If you have more than 1 row you will need a walk way of at least 2.5’. (Example: 16’ wide x 20’ deep room will accommodate 2 rows of seats. A row of 5 and a row of 4.) Now determine the closest seat to the screen. Have someone of normal height sit in the closest seat. Once their seated ,measure the distance from the screen to the eyes of the person in the seat. Take that measurement in inches and divide it by 1.1. This will give you the maximum diagonal screen size. The next question you must answer is ceiling height. You ideally want the bottom of your screen to be 30” to 36” from the floor. Above the screen you will need at least 10” of space to allow for crown molding and spacing. A good rule of thumb is ceiling height in inches multiplied by 1.1. That will give you a maximum diagonal screen size for that ceiling height. Now that you have made the calculations for minimum seating distance and ceiling height all you have to do is pick the lesser of the 2. That is your maximum screen size . Other factors may apply.
2. Screen Type – There are several types of screens for different applications. Manual Pull or Motorized Screen- Typically used in a multipurpose setting. The screen will roll up into the ceiling when not in use. Rear Projection- Used in a area with a large amount of ambient light. Requires complex angular mirror system and a large area behind the wall the screen is on.
Fixed Screen- Used in a dedicated room(typical home theater).
Curved Screen- Used with large 2.35:1 & 2.4:1 ratios.
3. Screen Material- There are several types of screen materials as well. There are different methods used to manufacture these screens. The methods vary in quality and difficulty. Usually the method of manufacturing is reflected in the price. Higher priced screens normally produce a better picture. You must decide the point at which your budget meets your expectations. Listed below are the most common screen materials. Acoustically Transparent- Used when mounting speakers behind the screen. Matte white- The highest gain screen. Used in well lit areas with high powered projectors(classrooms, conference rooms). HD Grey Screen- Improves image contrast. Used in areas where the light is controlled. (Most common home theater screen) Light Rejecting Screen- Rejects off axis ambient light. Used in rooms with strategically placed lighting. (game room/theater combination)
4. Ambient Light- Should be measured when the image is projected. This will allow the proper material selection. Your screen can only be as dark as the area in which it resides.
5. Image Ratio- Below the 3 main screen ratios are listed.
4:3- Old format, commonly associated with black bars on the sides of the image. (antiquated)
16:9- Most common, the format used with HD flat panel TVs. Most images are made for this ratio and will be in the foreseeable future. (recommended)
2.35:1/2.4:1- Produces a much wider image through special lens and a image scaler. Although this ratio does offer a better viewing experience. The complexity and higher price is usually a deterent.
These factors are very important if you desire the optimum picture quality. The projector is another factor I chose to leave out. Please read my article titled Projectors for the Uninitiated for details on projectors . Once you have weighed the factors and made the proper decisions you will have a lifetime of enjoyment from your Home Theater.
CHOOSING THE RIGHT PROJECTOR
- Quality- Several companies produce projectors with good statistics. There is a lot of heat produced in most projectors. If a projector is made with quality components the heat will not be an issue. On the other hand if the projector is made with cheap components the heat will effect the projector over time. This will cause a multitude of problems. Quality projectors are very reasonable now. The projector is the main component in your theater.
- Contrast- Is the difference between the brightest white and the darkest black a unit can produce. There is no standard process for measuring contrast. Each manufacturer may measure contrast using different methods. This makes the contrast ratio a poor way to compare brands but, very effective when comparing models of the same brand.
- Brightness- Is measured in ANSI lumens. ANSI lumens is a measuring method of the American National Standards Institute IT7.228. Since there is no uniform method of measuring brightness, specifications will vary among manufactures. If your room is completely dark 800 ANSI lumens will be more than enough. If you have light in the area. You will need a brighter projector. There are several screens on the market that help combat light as well. The right combination of screen and projector is crucial for the best experience possible. Remember a projector that is to bright will hurt your eyes over time. An experienced professional should be consulted.
- Processor- This is the most important component in the projector. Unfortunately there is no good specification to compare model to model. If you have the opportunity to compare recently calibrated projectors in an equal environment with the same content take it. That is the only way to truly compare the processors. Ghosting, Digitization, Blurring, and many other factors are directly affected by the processor.
- Lens System- A quality lens system is very important and often overlooked. Image distortion, such as, Warping, Sizing,and Blurring are directly affected by the lens system. Again ,there is no specification to help you compare models.
An experienced proffessional should be consulted when choosing a projector. Without comparing projectors in an equal environment with identical media you are taking a big gamble. Your new theater will be everyones favorite room. You will get years and years of enjoyment from your theater. It all starts with the proper planning.
