Have you ever had the experience of removing all of the furnishings from a room in your house to either paint or when you were moving out and noticed how your voice sounded so much different than it did when the room had furnishings? If so, you now understand how much of a difference acoustics can make.
Live or Dead
Acoustics is both an art and a science. Experts in acoustics will refer to a space as “live” or “dead”. Ideally you want something in between. What you are trying to achieve is a balance between too much reflected sound (live) and not enough (dead). Reflected sounds are made up of the sounds that bounce off another surface before they arrive at your ears. This is compared to direct sound, which comes directly from the speaker to your ears. A room with no furniture in it would be a good example of a room with too much reflected sound (live). A room with all of the surfaces covered with sound absorbing material (an example would be an anechoic chamber used by speaker designers) would be a very “dead” room. The trick is to the right balance. Too much reflected sound and the dialog is almost impossible to understand. With too little reflected sound, you get no sense of space. (note, I think a drawing here would be good).
In addition to reflected sound, some amount of dispersed sound is also good. When sound waves hit a flat surface (such as sheetrock), then its considered reflected. When the sound hits an uneven surface and then bounces off in all directions, then it’s considered to be dispersed sound.
So how does all of this apply to your media room or home theater? In a media room you typically have to work with furnishings to get closer to ideal acoustics. Anything that has uneven surfaces is great. A bookcase full of books is ideal! Make sure from the main seating position that you can physically see all of the speakers. A speaker blocked by a piece of furniture is not ideal. If you can set yourself up to be equidistant from the left and right speakers do so. There are several ways to “treat” the acoustics of the room using common furnishings. Large leafy plants can make a big difference in the sound of a room. Adding a rug to a room with hard surfaces for the flooring will be an improvement as well. Tapestries and other wall hangings will help you get the right balance of reflected sound. Draperies and window treatments also help.
In a true home theater, the options for acoustic treatment are much better. Audio Advice can actually analyze your room and make suggestions on acoustic materials that can be placed on the walls. The best solution is to use a track for a decorative fabric, which hides the acoustic treatments behind the fabric. We will attach the various acoustic panel treatments to your walls, then fabric is stretched across the wall. This gives you the real theater look and is the best option. We’ll calculate where to put the absorptive panels, the reflective panels, the combination reflective/absorptive and the dispersive panels. If your room is rectangular, this becomes much more of a science and is very predictable.
What the heck is a mode or node?
The dimensions of every room effect how the sound waves bounce around in a room. These are called room modes. They will have dips and peaks at spots in your room where they build up (lots of modes) and where they cancel each other out (a node). The effect is most pronounced with low bass sounds. The dimensions of your room play the role of determining how big and at what frequency these problems occur. A cube would be the worst sounding room, filled with tons of acoustic problems. Take this into consideration if you can impact the dimensions of your future theater room. Even in a room with perfect dimensions, placing the main seating right in the middle of the room is not ideal. In the design process for your theater we will calculate the best place for your seating to be to minimize this effect and if we have the leeway, can help you get to the ideal dimensions, but as a general rule, try to have your main seating position about 1/3 away from the back or front wall. Room modes and nodes are typically less pronounced at these points.
What about noise?
When a home theater can put you on the edge of your seat without having to blast you with high volumes, the room probably has a very low noise floor. This means the inherent noises in the space are minimal so they do not mask out the subtle sounds of the film. Noise can come from many sources including equipment fans, the fan on your projector, a noisy appliance, or other external sources. If you have to turn the volume up louder to overcome these noises, your system will have less of a sense of dynamic range, and as a result be less satisfactory. Ideally you want to be able to literally be able to hear a pin drop in your room. We can work with you to be sure the design takes into account reducing noise.
It all adds up
Many people do not even consider acoustics when planning their theater space. It’s a real shame to spend lots of money on gear and not give it the right environment to perform to its best if you have the option available. If we help you nail the acoustics and construct a room with a very low noise floor, you would not believe how this can improve your experience. A $2500, professionally calibrated speaker package in a well engineered room will put most un-calibrated $10,000 speaker packages to shame that are placed a room with bad acoustic properties. Of course the better packages really shine in a well done room! I hope this article has helped you understand that the most important component of your home theater is the room itself!
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Calibration
Why Calibrate
Calibration is important for both the video display device and the audio portion of the system. Audio Advice is a certified ISF (Image Science Foundation) calibrator for video displays. We have invested about $15,000 in the proper tools to calibrate your flat panel display or front projection system. Using our test gear, we can dial in the output performance of your display to be exactly (or as close as it will allow) to the standards set by SMPTE (Society of Motion Picture and Television Engineers). This will make your picture much more film like. Most video displays are preset at the factory to jump off the shelf when they are displayed at a mass merchant store under fluorescent lights. This does not lend itself for the best picture in a home environment. Using our test gear and the service menu of the set, we are able to bring the settings back to recommended levels for home viewing. Many of our customers are astounded at the difference a proper video calibration makes in the picture quality. Plus, without it being in “torch mode” (our industries term for how most sets come out of the box), you’ll actually reduce its operating costs by quite a bit!
Today’s home theater systems all include many different speakers. Your home theater receiver or processor has internal adjustments to allow a skilled technician or do it yourselfer to adjust the signal going out to each speaker to achieve a proper balance. There are typically adjustments for each speaker for distance and sound pressure level. Most systems give you the ability to adjust the crossover point as well. This is the frequency where you cut off sounds going to that particular speaker. An example of this would be a small speaker with a subwoofer, you would want to route the low bass sounds to the subwoofer since the small speaker could not handle this. When a system is properly calibrated, it can make a huge difference over the same one not calibrated.
The Steps of Audio Calibration
Audio Calibration, like acoustics, is part art and part science. A skilled calibrator will use both listening tests and sophisticated test equipment to dial in a system. On very high performance systems, this process can take up to two full days of a calibrators time, but the results are definitely worth it!
Speaker placement is the first step to calibration. If you have flexibility in your speaker positioning, try moving them around until you feel like the sound is more relaxed and less strained. This may sound strange at first, but just play a track you know well, push your speaker all the way against the back wall, listen, pull the speakers out about 3 feet from the wall and listen again. About 99% of the people will hear a big difference. Now, if you want to adjust more, you understand the concept.
If you are calibrating your media room, follow the recommended instructions in your manual for your receiver or processor. Many sets nowadays have an auto calibrate mode, but you should go back and check the settings and listen. Its best to play some material you are familiar with both before and after calibration. Once the auto part is done, try playing around with the levels on the center channel to make sure you can clearly understand the dialog over the special effects. You never want someone enjoying a movie with you to have to ask, “what did they say?”
For serious home theater calibration, Audio Advice has also invested in expensive test equipment. This allows us to actually measure where you have abnormalities in the room’s response. If your home theater processor has the right adjustments, we can, by using the test equipment and making changes to the processor, adjust out most of these issues. This service is offered for our high performance home theaters.
The Bottom Line
The learning from all of this is, you can spend as much as you want on the gear, but if it is not properly calibrated, you have not come anywhere close to getting what you paid for it!
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Viewing Distance, Viewing Height, and Screen Size
The first question we are usually asked is: just what size screen should I buy? The answer can take you down many paths. Tons and tons of research has been done on viewing angles by SMPTE (Society of Motion Picture and Television Engineers). Of course the distance you sit from your screen and its size will translate into your viewing angle.
When HDTV was being developed as a format, the final research indicated a 30 degree viewing angle was optimum for the 1080i standard of HDTV. The testing suggested viewers felt a pleasant level of presence and immersion when the viewing angle was 30 degrees or greater. To put this into perspective, a 52” diagonal HDTV set should be viewed at a maximum distance of about 7 feet.
For viewing movies, THX (Tom Holman and George Lucas’s company for movie standards) recommends a viewing angle of 36 degrees. SMPTE suggests the best viewing angles in a theater fall within the 35 to 55 degree range. Again, for some perspective, this puts the ideal distance from a 52” set at 5.8’ or less for viewing movies.
What does this mean for the consumer? On first take, it means most people are sitting way too far away from their sets for an immersive experience! We think that is totally true. If you really want the true home theater experience, you need a big front projection screen, period. However, lets not forget that a 52” HDTV set is still a lot more fun to watch than an old 36” tube non-HD TV!! We suggest you buy the biggest (and best, because big and not good is unpleasant) picture you can get. Don’t go over the recommended ratios, but try to stay as close as your room and budget allow.
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Screen Diagonal 16:9 size
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SMPTE Recommended Distance for HDTV
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THX Recommended Distance for Cinema
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26″
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3.5′
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2.9′
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32″
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4.4′
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3.6′
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40″
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5.4′
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4.5′
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46″
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6.3′
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5.2′
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52″
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7.1′
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5.8′
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55″
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7.5′
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6.2′
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60″
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8.2′
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6.7′
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65″
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8.8′
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7.3′
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84″
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11.4′
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9.4′
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92″
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12.5′
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10.3′
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108″
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14.7′
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12.1′
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114″
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15.5′
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12.8′
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The good news is, for the typical room used as a home theater, you can achieve real SMPTE standards and have that immersive effect!
And what about how high you put the screen? THX states in their manual for designing movie theaters, the maximum vertical angle should be 35 degrees. This means if you were looking straight ahead from your seat and looked up, you should not have to look up more than 35 degrees to see the top of your picture. We feel this is actually pushing the limit as this spec pertains to the front row of seats in a theater. For most people an angle of 15-25 degrees works out about perfectly. In the world of home theater, this can get a bit tricky to achieve with multiple rows of seating and sight line issues. This is when hiring a home theater company skilled in theater design can make or break your home theater project.
Once again, this means many people with flat panel TV’s above their fireplace have them mounted up too high to meet the spec. However, remember, if you slouch back or have a reclining chair, the angles all shift!
One great way to figure out both screen size and viewing angle is to simply get some painters tape and mask off the proposed image size on your wall, or for smaller screens, just cut out a piece of cardboard. Sit back and see if it seems right from both a size and height perspective, then at least you will know you did a little analysis before you made your decision. Of course, for a true home theater, our experts will lay out all of this for you to help design the optimum experience for your room!. And, don’t forget to ask about the newest technology for film viewing in the home, the 2:35 anamorphic experience. This really puts you in the cinema for the best immersive experience we have ever seen!
Also, if you want to learn more about the future of the viewing experience, check out this article on the SMPTE website: http://www.smpte.org/journal/wp-content/uploads/2008/03/2008-04-uhdtv.pdf
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Matt Lyons of LyonSound Home Theater Solutions visited us this week for a great presentation about and training in his company’s services. Matt will work with us to see that your room acoustics are correctly engineered, that your theater has a level of noise isolation that’s right for its location in your home, and that your system is optimized for the very best possible sound.
Matt has a phenomenal level of experience. He has degrees in music performance and audio engineering from the Peabody Institute of the Johns Hopkins University, and for the last twelve years has been an adjunct professor there, teaching masters level courses in audio engineering and acoustics. He has also worked for loudspeaker and electronics manufacturers, bringing experience at designing components at every stage of the sound reproduction chain.
We’re excited about the possibilities from the services that LyonSound allows Audio Advice to offer you. Your home theater room is an investment you want to be sure to receive the maximum amount of value from, and this is a level of expertise you can’t get at any other integrator in the area.
We can bring Matt into the design process and insure that when your theater room is complete, your movie experience is the very best possible. Get in touch now and find out more about what can be done for you to get the greatest amount of pleasure from your home theater investment.
If you are already working with one of our consultants, you may contact him directly about LyonSound theater solutions. If you are new to Audio Advice, you may call us at (919) 881-2005, or e-mail us at mailto:info@audioadvice.com for more information.
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