Understanding Home Theater
(Download the PDF version here)

Basic Information for Audio/Video System Shoppers

When you begin looking for a new audio/video system for your home, there are two basic questions to ask yourself.

One, am I a music listener or a movie watcher? If you listen to more music, but like to watch an occasional movie, then you might want to consider building a high performance stereo system. If you have no real interest in the video aspect, then a surround sound system is probably not for you. (See our paper on “Understanding Hi-Fi” for more information on high performance stereo).

If you want a system for movies, then the second question to ask is what is the size of your room (listening space)? The size and layout of your room will determine the type and size of equipment that is best for you.

These basic criteria are things that any knowledgeable dealer should qualify before you begin your quest for knowledge of equipment. This paper assumes you are interested in building a home theater system with surround sound.

Surround Sound Introduction

Nothing enhances your enjoyment of movies and videos like a good sound system. Whereas a typical two channel stereo system provides a soundfield in front of the listener, surround sound produces a soundfield in front, on the sides and behind the viewer. This is accomplished by the typical five channel surround format: left front, center front, right front, and two surround (side) audio channels.

Movie sound is primarily music and voice. The musical score sets the tone and mood of the movie. The emotional involvement, suspense, tension and excitement of the movie are all a direct result of the movie’s sound track. When you audition audio/video systems, be sure to listen to various movie soundtracks and special effects. But, always use music to make your final evaluation of the systems. This is where real differences in equipment become obvious.

Surround Sound Formats:
- Dolby Pro Logic, Dolby Digital (AC-3), Dolby Digital Surround EX, DTS, THX, and THX Ultra

The first film produced with stereo sound was the 1941 release of Walt Disney’s “Fantasia”. With very few exceptions, not much more happened until the mid 1970’s when Dolby Laboratories created Dolby Surround (Dolby Stereo) for movie theaters.

Around the same time, home video recorders (VCR’s) became popular. People began viewing rented movies in their homes and the demand for better movie sound at home soon followed. In 1982 Dolby Surround was introduced to the video world. Original four channel surround tracks were transferred to two channel sound for storage on video tape and laser discs. When played back over two loudspeakers, these Surround encoded channels sounded like conventional stereo.

Dolby then created an enhanced version of Dolby Surround, called Dolby Pro Logic. Pro Logic added another channel to the mix, the center channel. This improved the localization of voices and effects between the front left and right channels giving a better sense of fill in across the front. Therefore, we now had left, center, and right front channels, along with left and right rear channels and separate connection for a subwoofer, which was tied into the left and right front channels.

The next step in cinema sound processing was THX. THX was developed by Lucasfilm to bring audiences the quality of sound experienced in post-production studios. Now there are also home theater versions. THX processors apply high frequency equalization to the channels and decorrelation to the rear channels.

Decorrelation splits the surround channels into two uncorrelated outputs to create a more ubiquitous, or defused soundfield. Also, THX uses timbre matching to maintain the timbre of the sounds moving from front to back.

After THX was introduced, Dolby Digital (AC-3) came into the theater and consumer market. Dolby Digital took the home theater experience to the next level over Pro Logic by storing the film soundtrack in digital format. Dolby Digital also stemmed from a desire to provide high quality multi-channel sound for High Definition Television (HDTV). Dolby Digital entered the consumer market in 1997 on DVD’s and laserdiscs, and soon the confusion between Pro Logic and Dolby Digital began.

In the same time frame that Dolby Digital hit the market, a new company emerged. Digital Theater Systems (DTS) began producing surround sound in movies, beginning with Jurassic Park in 1993, and the format war began. Approximately 55% of movies you see in theaters now are played in DTS surround sound, with most of the rest produced in Dolby Digital. The next time you attend a movie at the theater, look at the credits to see which format you will be listening to. Sony also has their own surround sound format called Sony Dynamic Digital Sound (SDDS). However, they do not produce consumer software, and it is only available in theaters.

Dolby Digital and DTS processors consist of six separate digital to analog (d/a) converters, associated power supplies, and analog sections. In other words, they are like a complicated CD player. The difference in sound quality is like listening to inexpensive CD players versus high quality CD players. If we haven’t done CD player comparisons for you, ask for one. You will be very surprised. The bottom line: Pro Logic, Dolby Digital, DTS and THX systems will coexist for several years. There will be multiple styles of digital formats still to come. The good news is that speakers, amps, cables, and subwoofers support all these formats and will support future formats as well. Note that with separate components you will have more flexibility for adapting to changes in the future (not to mention better sound).

The newest format that has been produced is Dolby Digital Surround EX (6.1). When does it end? It doesn’t! 6.1 made its debut in Star Wars: Episode 1 – The Phantom Menace. This format was co-developed by Dolby Laboratories and Lucasfilm THX. Basically, it adds an extra set of rear channels. The rear channels in typical 5.1 digital surround become side surrounds in the 6.1 format. Then either a single or pair of speakers is added in the back.

For your system to support this format, you will need to add more amplification, wire and speakers. Not to mention, more money for added processing and power supplies.

Lucasfilm also set up a program with electronic manufacturers whereas equipment can be “THX Certified” if it meets certain technical specs qualified by Lucasfilm. Manufacturers pay a royalty to Lucasfilm for every THX certified unit sold, so some choose to not participate in the program.

The best processors are all THX certified. THX also has THX-ULTRA, which is basically higher standards for equipment. The market has receivers from $1,600 to thousands of dollars for processors and amplifiers with the ULTRA rating.

When it comes to speakers, amplifiers, subwoofers, and cables, THX certification is best considered a starting point, or minimum standard if you will. You will find that all of our speakers, amps, subs and cables go beyond what THX calls for. Because of this, we can provide you with better sound than you will find in theaters and standard home THX certified electronics.

Assembling a Home Theater System

A surround sound system can be fit into any given space, but how it is implemented is the key to quality sound. In assembling an A/V system it is still important to follow the basic rules of hi-fi:

1) All the links in the chain are equally important.
2) Audio and video reproduction are damage control jobs.

In any audio system the signal is passed down a chain. Sound travels from the source components (DVD or CD player, VCR, satellite, etc.), to the control components (preamp or surround processing preamp), to the amplifiers and then to the speakers. The base rule is the signal can never be improved within the chain once it is started. It can only be maintained or degraded.

Thus, audio (and video) reproduction is a damage control job. If we don’t get quality information from the source, the preamp, amps and speakers cannot improve the signal. The preamp and amps just make a bigger copy of the signal, which the speakers reproduce. No equipment can improve the signal given to it. What is generated from the source component will be reproduced, but not improved, in the chain. Thus, the goal is to change the signal as little as possible.

However, even the very best amplifier is not perfect and changes the sound a little. A poor amplifier changes the sound a lot. Accordingly, the best sounding equipment is often the simplest in design, with no unneeded features. Since tone controls are not needed and don’t improve anything, the best equipment does away with them.

This rule also means you cannot fix an amp problem with a speaker. Only a better amp can fix the problems caused by a poor amp.

One way we can help is by determining what combination of components will give you the best results within your budget. Or, if you are upgrading one component at a time, we can help determine what to replace first.

Most people pursuing a surround sound or home theater system break these two basic rules. They end up paying for a lot of effects, or “bells and whistles”. They end up with a system that has a lot of “effects” for the money, but at the same time does a poor job of reproducing the true signal. Because music is important, we design systems that will do an excellent job of playing music. If a system does a convincing job of recreating a man or woman singing and playing a guitar, then it will easily reproduce the sound of glass breaking, doors slamming, telephones ringing, etc. Music is more complex and difficult to reproduce, so we use music as a baseline for performance.

The Home Theater Room

The goal of the surround sound system is to integrate the movie sound with the picture. To do this, the positioning of the speakers is critical. This is best accomplished in a dedicated room that is arranged like a theater. Room construction and furnishings can make a difference too, but room layout is paramount.

As an example, it is a safe bet that you have never been to a theater with a fireplace in the middle of the wall and the video screen in the corner, problems often associated with home theater. Such obstacles can make it difficult to get the speakers far enough apart and the seating symmetrical to the screen. If this can be avoided in your home, then system set up and placement is much easier. Corners of rooms also impact results, but we can build a very nice system that is centered in a corner. Approximately 40% of all systems place the TV or video screen in a corner, so we are use to the challenge.

System Components - Separates

The components that make up a surround sound system are very similar to that of a regular stereo system. As stated earlier, the same rules apply. We are passing the signal, or information, down the chain of components to the speakers. The various components of a surround sound system are:

Source Components:
The source components are devices that input the audio and video information into the system. Source components can be DVD players, VCRs, satellite receivers, AM/FM tuners, tape decks, etc. Source components are where the information signal is originated. Remember, if the source component does a poor job of originating the information, we place a bad signal into the chain. Unfortunately, this is an area where most dealers place the least emphasis. However, we emphasize this area the most. The better the DVD player, the better the sound and picture will be. Differences in quality can be demonstrated to you.

Processing Preamp:
Audio and video signals are sent to the preamp, which selects the input source (picking which source you want to listen to or watch), controls the volume, processes the sound and controls the amount of power the amps give to the speakers. (Also referred to as a control amplifier or controller). The surround processor that is built into the preamp takes the audio signals from the source components (DVD, VCR, satellite), and directs them to the appropriate amplifiers. Any small error by the preamp, such as noise, distortion or harshness, will be multiplied when the amplifier makes a bigger copy and sends it to the speakers. Preamps are the heart of the system.

Amplification:
The amplifier(s) receives the signal that is sent to it, makes a larger copy and sends it to the speakers where it is reproduced as sound. Simply, the amps control the speakers. There is no magic power number or spec to look for. This is an area where specs are blown out of proportion and misleading. If you want to compare amps, listen to them. We can demonstrate the differences to you and make recommendations for your system. Bigger is not always better. Quality is what is important. Often, the less power you see for more money, the better the amp is.

THX specifications here are not important, nor an indication of quality. Once again, it is a minimum standard. For example, an amp can be built with loosely regulated power supplies and achieve high dynamic headroom and meet THX specs. In that case, big power and headroom numbers are achieved at the expense of clarity, detail, smoothness and control over the speakers. We don’t care if an amp has a THX badge, we want the best amp for the money!

Speakers:
The speakers are the window to the system and will reflect the quality (or lack of) of equipment in front of them. The speakers must be capable of reproducing what is sent to them without adding their own colorations or distortions. They must be capable of great clarity and dynamic range.

Surround sound most often consists of five speakers plus a subwoofer (covered later). The five speakers consist of three front speakers (center, left and right) and two rear (surround) speakers. Symmetry must be maintained across the front three channels. 50% of the sound in a movie will be sent to the center speaker, so this is the most critical speaker for a video system.

In the THX/Pro Logic surround systems, diffusion in the rear channels was the key so that sounds were not localized. This is where speakers for rear channels were termed as dipole or bipolar. Think of a dipole speaker playing sound in a figure 8 shape, with sound emitted front and back. A bipolar speaker plays in a 360-degree formation. It emits sound all the way around.

THX recommends bipolar speakers. But that does not mean that it is the best thing for you. When a speaker plays, the signal comes off the tweeter, midrange and woofer at 180-degrees. So you can use a point source, or front firing only speaker just as well for this application, if it positioned properly into the room. 60% of the systems we install use flush mounted speakers in the ceiling or in the rear wall for rear sound. With Dolby Digital and DTS, the rear channel information is now as dynamic as what comes out of the front channels. Rears are now starting to get bigger to handle the more dynamic information. In the scheme of the system, these speakers handle 10% of the overall information.

Subwoofers:
The addition of a good subwoofer, or in some cases a pair of subs, will add a foundation of bass and solidity to the program. Movies have substantially more bass than most music, so there is a tremendous need for subs regardless of how big your front speakers are. Good subs will cleanly play low bass without boominess or muddying up the midrange. The high amounts of distortion in poor quality subs add a muddy boom that distorts the sound coming from the rest of the speakers. The great subs blend with big speakers so that when you switch from movies to music, it doesn’t sound disjointed.

Subs need to have a very solid and well built cabinet and good quality amplification to run it. All good subs will have a built in or companion amp to power it. Remember, in a subwoofer you are buying an amp, a crossover, a woofer and cabinet, so don’t expect a lot if it is much under $700. Again, quality is more important than size or specs. We can easily demonstrate the difference between subs for you.

All - In - One Surround Receivers:

A less expensive alternative to the processor and separate amps is the surround receiver. A receiver performs the same functions as a controller/processor, but also serves as its own amplifier. There are a variety of surround receivers on the market, however they are all limited by the use of one power supply. That one power supply must power the am/fm tuner, the preamp section and amplification for all five channels. The classic case of trying to do too much in one box.

If you must go this route to save money, then you want three things: 1) good solid power supplies, 2) discrete output amplifier sections, and 3) ease of operation. If you can’t walk up to it and work basic functions without reading the manual, don’t buy it. A word of caution: if you already have a $500 stereo receiver, a $500 surround receiver will likely sound worse. Because of the added amplifiers and surround circuitry, a surround receiver of the same quality is simply going to be more expensive.

Cables:
This is the forgotten component! Cables hook everything together, and it is where the most noise, distortion, and signal loss occurs. Unfortunately, it is typically the weakest link in most systems. It is an area where a little more money goes a long way. When you see and hear the difference cables can make, you will be amazed! Be weary of stores that give away cables, as they can severely limit the performance of the whole system. People often ask where to spend a bit more money and receive the greatest benefit. Cables are the answer. We love to loan them out so you can try them in your system.

Choosing the Right Store:
We are not cabinetmakers, appliance salesmen, or interior decorators. We are specialists in assembling, installing, and servicing audio and video systems. We choose our equipment based on performance and reliability, not on how much we can make. This is our passion!

As a company, we have a minimum standard of performance for everything we sell. Because of this, our least expensive equipment often outperforms more expensive products found elsewhere. Very often, you don’t have to pay more, you just need to buy the right products.

Getting good service and advice, great products and a fair price are what we consider to be a real value. These are things you cannot get from the Internet. That is the great thing about dealing with an actual store. You always have a place to go if there is a problem. Call us at 913-341-2222 if you have questions.

Bibliography:

Dolby Technical Papers, “AC-3: Flexible Perceptual Coding for Audio Transmission and Storage,” Craig C. Todd, Grant A. Davidson, Mark F Davis, Louis D. Fielder, Brian D. Link, Steve Vernon, pg.2, Dolby publication No. S95/10152/10492, Reprint Feb.26, 1994 – March 1, 1994.

Widescreen Review, Perry Sun, “Dolby Digital Surround EX The Third Dimension in Surround Sound 5.1+1m,” Volume 8, Number 3, Issue 32 pp.18-22.

Cabinet Requirements:

Very often, when we go to someone’s home to do an installation, the design of the cabinet makes the job much tougher than it should be. Here are some very basic tips for your cabinetmaker:

1) We want adjustable shelves if possible

2) We want a hole or slot in the back of the shelf. The hole or slot should be large enough to get two hands in the opening. In other words, make it big! 8 x 4 inches or larger

3) The inside dimensions of the cabinet should be larger than the equipment. 22 wide by 22 deep will accommodate most equipment.

4) If the cabinet is built in, remember that we need electricity. At least a fourplex outlet.

5) We need ventilation for the amplifiers. It can be openings in the cabinet, or a small fan, or both.

As obvious as these things are, most cabinets are made with a couple of these things wrong. If there is a question, have your cabinetmaker give us a call. We’ll be glad to talk to him.