Reference Home Theater

When we started to design our new reference home theater, we had one goal: to create a level of realism that did not exist anywhere in the Pacific Northwest, at any price, in any retail showroom. We literally wanted to redefine the term “home theater,” to mean being totally lost in the movie experience. And not just say it, but demonstrate it.

Just how does one go about doing that? Answer wasn’t in smell-o-vision, turning up the audio level until people wanted to run out of the room, or even
3-D video (even though our system presents the best home cinema 3-D possible). Instead, it was in “pure execution.” In other words, improving the audio/video fidelity so much that the equipment becomes invisible.

We knew at the start this meant partnering with the world-class acoustics and theater designer, Keith Yates. Keith has built an incredible reputation for building some of the highest performing and most beautiful theaters. His mastery of science of sound is second to none, backed by a level of design methodology not practiced by other acoustic designers.

But we are getting ahead of ourselves. First we need to explain why acoustics plays such an important role here. The problem we face is the pesky laws of physics. When we play low frequency tones (e.g. bass) in an enclosed room, the sound waves combine and subtract as they bounce around the walls, ceiling and floor and then overlap. Think of when you drop a ball in a pond and how the ripples reflect and interfere with each other, destroying the beautiful waves that started it all. Same thing happens with audio. You could have the best designed and most perfect speakers in the world but as soon as you put them in the room, the bass response radically changes. And you are no longer hearing the true nature of what is recorded in your source.

Worse yet, what is heard in one seat can be radically different than the seat next to it. While you may be enjoying good bass, the person next to you may not be hearing much, or going deaf.

In other words, not only is the low frequency response uneven, it also varies radically based on location in the room.

Acoustics design is the science (and art) of optimizing the room, and the equipment as to have the most even response, matching what was used to originally create the music or movie soundtrack. Think of how a car is made more aerodynamic as to make it have less air friction as it speeds. While the science is different, the approach of using engineering and design is not.

Advanced Mathematics to the Rescue

Computation Fluid Dynamics (CFD) Home Theater Design

The solution to this problem is the subject of a later white paper but for now, a quick teaser.

Keith uses fancy computer simulation software called Computational Fluid Dynamics (CFD). The entire room including its furnishings is then recreated using a 3-D model in the computer. Speakers are simulated using their physical characteristics and their sound waves allowed to “excite” the room. As the sound waves propagate there, we are able to see the precise frequency response at each location.

Using the above simulation then, we can run different trials, examining the various position and number of speakers as to both achieve a smooth low frequency response and least amount of seat to seat variations.

The above process is a far more sophisticated than the standard method used by acoustic designers. Instead of modeling the physical room and speakers, they make gross simplifications that allows them to use simple calculators to compute the bass anomalies.

Problem is that real world doesn't work that way. Drywall for example, flexes ever so slightly as the lower tone sound waves hit it and thereby absorbs some of the bass energy (a good thing). It is not a rigid boundary as the simplified acoustic modeling assumes. Chairs are soft and have an effect in the room. All of this adds up to a lot of inaccuracies.

Keith’s CFD modeling takes all of the above factors into account, creating surprisingly accurate results that come very close to actual measurements in the room (+- one decibel in technical talk). The drawback is the high cost of tools, the sophisticated expertise required to properly model the room, and good set of ears to know when the computer is wrong -- all the things Keith and his team excel at.

Pre-Visualization

The next step was the visualization of the overall look of the room and full set of engineering drawings. These were used by our General Contractor to construct the physical theater and by us to design and install the electronic system and its acoustic treatment.

The renderings created for us are a step down from the incredibly photo-realistic imagery that Keith usually creates. Not being a typical customer, we didn’t need the high-fidelity renderings. Still, looking at the picture below, you see how compelling the rendering is in conceptualizing what the theater would look like, enabling us to approve the overall design.

Back to design of the room, one of the often forgotten aspects of a good theater design is how quiet it is. Our ears have gotten used to very high level of ambient noise in our every day lives. It is not until such noise is removed that we realize what we are missing.

Just imagine the scene in the movie where there is a quiet rush of wind or the whisper quiet sound of distant wildlife. Unless your theater is far quieter than your everyday home, these sounds are either lost or barely heard, taking away from the true atmosphere the filmmaker wanted to create for you. And lost with it, is the illusion of really being there.

Special construction material and techniques can substantially lower the “noise floor” of the room, allowing these low level details to be heard. We used these methods as we constructed our theater.

Another bonus of an ultra-quiet room is that when there is a sudden loud sound, its impact is far more dramatic. That is because there is a larger difference between the room’s basic noise level and the maximum loudness of that sound. Imagine how loud a person screaming is in a quiet room as opposed to the middle of a freeway.

Making a room quiet works both ways in the way it keeps the sound in the theater, inside it. This means what goes on in your theater, stays in your theater! Sorry, we could not resist borrowing this line from the Las Vegas commercials :).

Electronics

Another ground-breaking approach we wanted to use in this theater was to showcase two independent audio systems, from speakers to amplifiers and processing. The idea was to let the customer for the first time, instantly compare how different approaches to sound work in an identical situation. Tastes in audio differ amongst people and we wanted our customers to make an informed choice.

Actually, the original designed allowed for a third, music-only system. You can see that in Keith's rendering with the two tower speakers. We currently use that configuration on request, bringing our Revel Salon 2 speakers in for special auditioning. Otherwise, there are no visible speakers in the theater.

Our theater has a JBL Synthesis system which is the de-facto standard in live music and movie reproduction. And another, the Wisdom Audio Planar Magnetics, which work by moving air using large sheets of DuPont polyamide film, instead of the traditional speaker cones. You can see an early configuration of these in the above rendering.

Theater Front Wall

To the right is a picture of the front wall where the screen would go while the theater was being constructed.

Visible there are the three front JBL Synthesis speaker pairs, comprised of traditional woofers in a dual-configuration with a “compression driver” behind the horn, mounted vertically.

The Wisdom system is the taller arrays. The shiny parts are the planar speakers playing from mid-bass to high frequencies. The lower notes are played by the array of smaller speakers. The separation indicates individual components driven by their own dedicated amplifiers.

With each channel being 500 watts, the center channel alone has whopping 3,000 watts of power driving it! As it should. Most of the content in a movie is in the center channel. You do not want that channel starving for power and distorting. Despite this factor, many times you find theater installers and retailers selling you small and underperforming speakers and amplifiers for the center channel.

Flanking the front stage are two tall cylinders. These are acoustic products we call "bass traps." As the name indicates, they absorb destructive low frequencies as to make the response smoother in the room. More so, the entire front wall is one giant bass-trap. This is implemented using those rectangular boxes which are designed using circular holes (which you can barely see through the fabric) to absorb certain bass frequencies.

There are mind boggling numbers of subwoofers in the theater delivering the lower frequencies. To find places for them, they are put on almost every surface but the floor! There are subs on the front, side, and rear walls and even on the ceiling. Yes, you will be showered with bass frequencies. Luckily, our ears cannot locate the source of low frequencies so the fact that they are not in the usual locations is not a concern.

Importantly, using more than one subwoofer not only increases the impact of sound effects and low frequencies in general, but they also help smooth the frequency response in the room. The reason for this is a subject of a future article. For now, if your theater only has one subwoofer, you have a less than optimal configuration.

All the speakers are then covered by either the projection screen in the front or beautifully stretched and installed fabric on all other surfaces. In order to be able to demonstrate what went into the design of the theater, we have installed lighting behind our fabric which lights up all the components behind them. Here is a neat comparison shot with the lights on and off:

Side-by-Side View of speakers and acoustics in theater

Side-by-Side View of speakers and acoustics in theater

Who needs to go to Disneyland with a light show like this? :)

Visible above are two pairs of JBL sub-woofers on the side wall and myriads of specially designed acoustic panels to manage the sound reflections. You can also see a glimmer of the projection window above the door. More on this later.

Advantages of Bi-amplification

Each system has roughly 20 channels of audio. Alas, our sources on even high-definition Blu-ray are limited to eight (8) channels. So where do the rest of the channels come from? Well, each primary channel is divided into three regions:

Extremely low frequencies. This is directed to a set of subwoofers.
Lower frequencies. These have their own amplifier driving the low frequency drivers in the speakers (woofers in the JBL and small traditional drivers in Wisdom).
Middle to high frequencies. These again have their own amplifiers to drive the high frequency elements of the speakers.

By using separate amplifiers and speakers, cross-talk is removed between the low and high frequencies. If the amplifier becomes distorted in a traditional speaker, the distortion that is created adds harshness which manifests itself as high-frequency tones that are then played by the tweeter. In the bi-amplified scenario, the amplifier driving the bass frequencies does just that: bass frequencies. It if gets distorted, its distortion remains there and cannot get routed to the high-frequency drivers since it has no connection to them anymore. Since our ears tolerate a lot more distortion in low frequencies than high, then any distortion created is likely much less audible. And at any rate, less annoying.

Another advantage is the fact that we now have double the power (or more in the case of Wisdoms) being applied since each segment of the speaker has its own dedicated channel. The power is not shared amongst the various components of the speaker. Further, since there is no crossover in the speaker separating the low and high frequency components, there is no power loss or shift in operating parameters.

Advanced Audio Processing

No matter how much goes into the design of the room (within reason), there still remains some frequency variations. Speakers themselves don’t have flat response in the room and some amount of optimization is always necessary.

The star of the show in our theater and the solution to above problem is the JBL Synthesis SDEC-4500. This is a powerful audio processor originally built for professional audio processing in live sound reproduction. By addition of special measurement and optimization software, the processor is now used in home theater applications to flatten and or customize the audio response with incredible resolution (24 bits, 96 KHz sampling and processing).

Our SDEC processor is transforming the audio for both audio systems, handling whopping 40 channels of audio at the same time! If that is not manly enough for the guys reading this article, we are not sure what is! :)

Here is the picture of the 4500 with its companion expansion device, the SDC-4500X:

JBL Synthesis SDEC-4500

A specialized measurement kit with another processor similar to SDEC-4000, utilizing 8 different microphones measures how the room responds at the desired seating positions, making sure that the optimizations applied do not make the sound better at one seat but worse at another (a common problem).

You may have heard of room optimization logic that exists in traditional mass market products. Alas, while they can improve the audio at times, their capability is highly limited due to cost restrictions. Blind testing done by Harman, the parent company of JBL, shows that some of these systems are actually worse than doing nothing at all!
”Room

The results are plotted to the right.

The left two columns are the scores for the JBL system (one optimized for just one seat, the other for all eight). The rightmost bar is for the most common and widely available equalization system which ships as part of most mass market home theater receivers. The “no EQ” is the reference where nothing was in the audio path.

As you can tell, the JBL system not only outperformed its competitors, but also improved fidelity significantly over doing nothing. On the other hand, the mass market solution actually made the room response worse, not better.

Alas, as good as any automatic audio optimization software can be, nothing yet replaces the ear of a skilled acoustician. So post automatic optimization phase, we used the sophisticated software that programs the SDEC processor (running on a PC) to fine-tuned the overall sound.

Above is another important area of differentiation from mass market products which have an all or nothing setting. With the JBL Synthesis, we can customize the sound and create different profiles for any taste or content type. For example, you may prefer one setting for music, and another for movies. Or even multiples of each.

Switching and Audio/Video Processing

Upstream of the JBL SDEC processor is the Mark Levinson No 502 “Media Processor.” This incredible tour-de-force of video processors handles the audio/video switching, allowing us to play different content from movies and music to video games. Its on-board high-definition LCD allows one to see what is playing. It also handles synthesis of 7.1 channels from the most common 5.1 available on most movie soundtracks, recreating the two rear channels of audio using Harman’s legendary process. Also available is a JBL processor if a less feature-laden unit is desired.

Movies and Music on Demand

We finally get to the heart of the matter: our beloved movies and music. The component powering this is a Kaleidescape server. It lives in our audio/video rack and stores all the movies we feed it. New discs are loaded into it and after a few minutes are available for instant access in any room in the house, or in our case, different areas of our showroom. The system is extremely easy to use. If you can play a DVD, you can choose and find any of your content in this system.

The Kaleidescape can instantly play the movies which were originally stored on DVDs and Blu-rays. If you have ever sat through what seems to be an infinity, waiting for a Blu-ray movie to actually start and get past all the trailers, you will really appreciate this feature. Find your movie, click play and it starts. Of course, if desired, the system can also play the whole disc.

The server is easily expandable allowing the system to grow with your needs. Modular storage units mean that we can do this without replacing the entire server.

Kaleidescape System

Players can be full function like the one in our rack with an optical slot. Or the smaller unit to be hidden behind a flat panel or in a cabinet. You can see all three pieces in the picture on the right.

If you have never played with such a system, you owe it to yourself to try it. No words can describe the smile it puts on your face the first time you start a movie you like without hunting for the disc or waiting for it to start per above. And oh, you can also store your music library in it as we have done, and use a single interface for both.

Video Projection System

Nothing screams movie realism like a large screen that lets you get lost in it. There is a reason IMAX has the appeal that it has. If your screen is too small, your eye wanders past the edges and as soon as it does, your brain is reminded that it is watching a movie, and not a real-life experience. A sufficiently large screen fills your field of view, keeping you in the experience all the time.

For the size theater we had, we decided on an image that is 17 feet wide, or nearly 20 feet diagonally (this is how displays are typically measured). That is a whopping 15 times more screen real estate than a 60 inch flat panel TV!

Law of big numbers can be one’s friend or enemy. The dark side of having a large screen, pun intended, is that the light level also drops proportional to the *area* of the screen. Double the screen and you lose four times the brightness you had. Put inversely, you need a projector that is four times brighter to achieve the same light level and picture brightness.

Another major consideration was the fidelity of projector. Units made to support large screen tend to have three imaging elements (DLP in our case). While this approach provides the best fidelity in theory, in practice many projectors have alignment issues which cause the three colors to not converge on the same point. This reduces picture sharpness and creates color bleeding.

After searching for nearly two years, we found the ideal projector in the form of Italian designed Sim2 Lumis 3-D Solo. Yes, the name is kind of long but it is worth pronouncing given the superb quality of this projector.

As the name implies, it is a single unit 3-D projector that uses active shutter glasses to present a 3-D image. Our large screen is a perfect match for it, putting in the middle of the story unlike the poor experience created by small flat panel displays and projectors. The Solo sports “triple flash” which succinctly means it replicates the technology used in theaters to avoid flicker and eye strain. This is an exclusive feature to Sim2, putting it ahead of pack compared to any other consumer projector.

3-D requires more light due to light loss in the polarized glasses. The triple flash in Sim2 Solo helps keep the brightness level up and automatic color correction compensates for color shifts causes by the glasses.

From an aesthetics point of view, the choice of acoustically transparent screen was an obvious one. This is a type of screen that hides the objects behind it but reflects the image from the projection screen while at the same time passing through the sound waves. Traditionally, these screens have been problematic in that they could introduce moiré patterns (interference).

The screen we use by Screen Research uses a woven fabric. The complex weave does not create the above distortion. It does however cause some light loss as some of it goes through the screen and gets lost behind it. For this reason, it is important to have a projector with sufficient light output as we have.

The other negative with these screens is that they can cause slight reduction in the volume of higher frequency tones. Fortunately with our Synthesis processor and measurement system, this can be completely nullified, giving us neutral response.

Constant Height Presentation

Our screen also has “powered masking.” What this means is that the black sides of the screen can expand and contract, in essence enlarging and shrinking the width of the screen respectively. Why is that necessary? It is because the video and movie content we play can come in different “aspect ratios.” Some can be narrow and wide, others taller and less wide.

A good example is TV content which has the tallest aspect ratio (called 16:9). If you set up your screen for that content, then when you play a typical movie, with aspect ratio of 2.35:1, you will have dark areas above and below your image. This can take away from the cinematic experience.

Our projector sports an “anamorphic” lens which means it automatically stretches the image to match the aspect ratio of the screen, eliminating annoying black bars on top and bottom of the screen.

Add the Kaleidescape server telling our control system what aspect ratio is to be used for each piece of content stored in it, and the change becomes completely automatic! Point the system to what you like to watch and the screen and projector automatically adjust to the right size without you doing anything.

The Experience

At the risk of stating the obvious, words cannot describe the cinematic experience we have created. But we must because you are reading this instead of being there.

It all starts when you walk in and we close the door. Without playing anything, something is different. You can’t quite put your finger on it, but it is. It is how quiet the room is! It is a sensation that you probably have never felt. The absence of noise is an experience by itself.

Next you sit there and we open up with a clip from the movie, Book of Eli. Not a especially good movie although worth a watch. The clip starts quiet. You can hear every little detail. When the movie is quiet, it is quiet. You can talk to the person next to you in normal voice. It is so relaxing and comfortable.

Then Bam! Shooting starts. The shots have dynamic power like you have not heard before. You not only feel them in your seat but also in your pant legs as they move in response to ultra-low frequency notes. It is as if the wind is blowing past you! But nothing is really “loud” or obnoxious. As soon as the impact goes away, you can again speak in normal volume. Try this at any other home theater.

Now let’s talk about video. Like the movie Stargate you are literally pulled into the image. The sound and wide field of view completely fool your brain, making you forget that you are sitting in a theater. The only thing missing is the pay you might get if you played that role in the movie you are watching!

To be continued....

Further Reading: Keith Yates Design Group