Surround Speakers

What are surround speakers? They are the part of our home theater system and their purpose is to “surround” us with sound energy in the sides and rear of our video presentation. The left, right, and center speakers fill up the front of the room. The sunwoofer provides the “bang”

Surround sound speakers take the airplane that is flying over from the screen to the rear of the room and follows the video image with sound to produce the acoustical sound trail needed to fool our brains. As the plane flies overhead, the sides and rear channels are “handed” the signal from the front speaker system and move it from side to rear or even side to side as in a car crash. In order for this image to track correctly, the surround speakers must have their amount and rate of room reflections controlled though proper room treatment techniques.

A balance of sound diffusion and sound absorption techniques are needed to creat the correct ambient sound “image” at the viewing/listening position from the surround speakers. One must minimize room boundary reflections, so that the surround speakers can have a defined image across a wider surface area than is required from the front channel speaker system. Once we have used the correct amount of absorption and in some rooms over absorption, we add diffusion to spread that more defined signal out across a wider area along the sides and rear of our rooms without any more energy loss.

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Home Theater Design

Home theater design must take into consideration the electronics, which includes the video producing system, the amplification, and the speakers. The seating system and the room acoustics must be given more weight and concern than any other component when home theater design is considered.

The listening and viewing area serves two masters. First, it must be at the proper distance from the video monitor or screen in order to view the image correctly and without fatigue. Secondly, the listening and viewing position must be at the correct distance from all the speakers, so that all information is processed correctly by the ears and brain.

The video distances are easy to calculate in any home theater design. The size of the video screen will define the distance parameters used. The audio from multiple mono sources, the rear, sides, and front channels must be dealt with correctly in order for all sound sources to blend together and become balanced and un noticed as to their positions in the room. In the audio side, room distances, room boundary surfaces acoustical treatment, and subwoofer placement are critical and are often not given the consideration they deserve in most home theater designs.

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Listening Room

If you have a dedicated listening room, you are surely fortunate. A listening room is a portal through which one can enter many worlds.

In a dedicated listening room, all the energy of the room is controlled, so that it arrives at the listening position at the correct time. The sound at the listening position is a blend of the direct sound from our loudspeakers and the reflected energy from the room’s walls. Our acoustic goal is to achieve the correct blend and balance of both the direct and reflected energy. This balance, once achieved, provides for a sound stage that can allow someone to connect with the music. It can truly transport one to a different time and place.

With a proper soundstage, there is a height, width, and depth to the musical presentation that can bring an emotional connection to the music. It is this emotional connection we all strive so hard to achieve. One can “see” the vocals and instruments on the stage. There is a separation between the instruments and vocals and all sounds are heard clearly. One can even hear the breaths of air the singer takes. You are transported from the audience to the stage..

I love my listening room and could not imagine life without it. I hope I never have to. I wish the same for you.

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Home Theater Speakers

Home theater speakers come in many different flavors. First, we have the standard right and left channel speakers which we are all familiar with. Most of our musical information is present in the left and right channels. Movement on the screen, which goes from left to right, should begin at the left channel speaker and move to the right channel speaker in synch with the on screen presentation.

The center channel speaker is an integral part of any home theater speaker system. The center channel speaker is for dialogue. Most center channel speakers are positioned below or above the screen, so that the dialogue appears to be located on the screen. Some center channel speakers are positioned directly behind the screen. Obviously, the screen would have to have perforations in it to allow the sound energy from the center channel to pass through the screen.

Side and rear channel speakers are usually a blend of left and right channel information which is then spread out along the sides and rear of our home theater systems. This process is termed matrixed. Some source materials have discreet information recorded in them for the side and rear channels which means the engineer actually recorded separate tracks of data for the sides and rear channels instead of “borrowing” from the left and right channel data. The side and rear channels provide non – localized, ambient energy which if properly positioned and acoustically treated can add to the realism of the presentation.

The most important part of any home theater speaker package is the sub woofer. Its job is to provide the low frequency energy for explosions, car crashes, and the like. Most sources have a separate channel that contains this low frequency data. This is where the designation 5.1, 6.1, and even 7.1 comes from. The number to the right of the decimal point indicates that there is one channel for LFE or low frequency effects.

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Home Theater Receiver

A home theater receiver is an amplifier, preamp, video processor, and possibly a tuner to receive AM and FM signals. Another way to bring all of these functions into your home theater is to use separate components for all of these functions. Separates allow the end user to control the quality level of each component more accurately.

A home theater receiver manufacturer will design a receiver that will be sold for a particular price point in a certain market segment they are targeting. They will mix and try to match a video processor, amplifier, preamplifier etc. and make their quality and costs fit into a targeted pricing framework. This will create a product that has multiple functions, but will usually lack the individual quality level found in separates.

A home theater receiver has everything under one roof sort of speak, and thus they are all sharing a common circuit board, chassis, and cabinet. Separates will usually have all these components but will not have to share functions with other parts. For example, each component in a video processor will be designed to focus and create a video image full time without sharing any other functions of their design with a preamp or tuner. A manufacturer of separates can maximize the performance of his unit because he can focus solely on one function and maximize its potential.

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Home Theater System

A home theater system is composed of electronics, furniture, and a room. The electronics are the screen, projector, receiver, speakers, dvd player, and all the associated cable and control systems. The furniture can be a single chair or multiple rows of seats which can even have each row elevated above the row in front. The room in a home theater system is usually the last item to be considered.

The room in a home theater system can make all the sound difference when it comes to accurately portraying all the capabilities of the purchased electronics. If the dimensions of the room are not taken into consideration, the finest sounding speakers in the world will not be able to produce the sound quality the original designer intended. Room modes can eliminate and exaggerate certain frequency ranges or groupings and sounds in those areas may not be heard at all or magnified to the point of appearing unreal.

Low frequencies produced by the sub woofer or sub woofers, will smother the middle frequencies and dialogue will be blurred or smeared. Multiple speakers from the sides and rear channels will interfere with the left, right, and center channels in our home theater systems, so that image quality and presentation will be blurred. Wall reflections from the right and left channels will create sonic distortions at the listening positions in our home theater systems.

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Home Theater Set Up

Home Theater set up includes all the electronics to produce the sound, furniture to sit in and view the screen, and room acoustic treatments. Unfortunately, many individuals purchase the equipment and furniture for the room and expect it to sound good without treating the acoustical issues present in all rooms.

Home theater set up must include some type of room acoustic treatment because of all the energy produced by the home theater speakers in the room. First, we have the three front channels which produce energy into the room. Next, we have the side and rear channels which add their own energy into the presentation. Finally, the biggest energy producer is the sub woofer or sub woofers which produce the low frequency energy for numerous on screen special effects.

A proper home theater set up will allow for a strong and focused center image from the center channel speaker for dialogue. The left and right channel speakers allow for placement and movement of sound that goes from left to right and right to left on the screen. With proper room acoustic treatment, the vocals will be centered on the screen and if a car or airplane moves from left to right across the screen the audio will track with the video so they are in synch at the viewing positions.

The sub woofer or sub woofers produce the low frequency energy that creates our explosions, car crashes, and any other low frequency effects. Sub woofers must first be positioned in the room correctly to avoid all the acoustical issues that low frequency energy generates. The room must be treated with low frequency absorption to “sponge up” excess energy so that this excess energy does not interfere with the front, side, and rear channel presentations at the viewing positions.

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Diffusor

Sound can be absorbed, reflected, or diffused. To absorb sound, we need to change the electromechanical energy of our sound systems to heat energy. Through this exchange process, using sound absorption techniques and materials, sound energy is converted to heat. This conversion process results in lost sound energy and thus sound absorption occurs.

Sound diffusion does not require any energy conversion. Sound diffusion takes the existing energy and through the use of a diffusor, spreads that energy out in different planes or fields. A quadratic sound diffusor with a vertical array of wells or troughs, spreads sound out in a horizontal plane or field. A sound diffusor with horizontally positioned wells or troughs, spreads the sound energy that enters into it out in a vertical array or field. Both vertical and horizontally positioned quadratic sound diffusors create a two dimensional sound field.

Quadratic sound difusors consists of a series of wells or troughs at different depths but same well widths. Each well or trough depth in the quadratic sound diffusor accounts for a particular frequency group. Each well depth conforms to one quarter wavelength theory. Well widths in a quadratic theory diffusor conform to one half wave length theory.

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Acoustical

The dictionary defines acoustical as ” of or relating to sound, the sense of hearing, or the science of sound.” Lets look at each one of these phrases.

Defining acoustical as “of or relating to sound” starts the process. We try to design our environments that we live and work in with our relationship to sound in mind. Sometimes our sound “relatives” are hard to relate to and we have to absorb some of their excesses with sound absorption technology. Sometimes, we have to diffuse their energy by seperating and spreading their energy out many directions, so there is less energy to deal with in certain room areas. This technique can also work with human relatives.

Defining acoustical as “the sense of sound”, hopefully, refers to our actual human sense of hearing. Binaural hearing is our chosen methodology for capturing sound energy and processing it into our brains. Our brains then apply localization and pressure filters to help our brain understand the sound energy and where it is coming from. The sound localization filter is also attached to the eyes. Hearing and seeing are tied together, probably for survival purposes.

Defining acoustical as “the science of sound” is probably the most accurate of all the dictionary definitions. The science of acoustics explains why sound acts the way it does, and how our brains interpret it. Defining how sound acts the way it does is one thing; explaining how the brain interprets the data is very complicated and has its own diciplinary name. It is called the science of psychoacoustics.

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Acoustic Panels

Acoustic panels can take many forms. Acoustic panels can be made from sound absorptive or sound diffusion type materials that are arranged in a certain way to create sound diffusion that operates in both a horizontal and vertical plane.

Acoustic panels that are sound absorptive in nature can be made of foam, insulation type material, or as it is called in the building trades fiberglass insulation. Different materials can have different rates and levels of absorption. One must know the frequencies that absorptive materials work at in order to pick the appropriate acoustic panel for the particular application one is using.

Sound diffusor type acoustic panels must have materials arranged in a certain length and height to allow for sound frequencies to be diffused back into the room. Sound diffusors reduce the unwanted room boundary reflections by sending the energy from the reflection back into the room spread out in a fan like array. Acoustic panels that have vertical arrays, diffuse sound out into the room in a horizontal direction. Acoustic panels that arrange diffusion elements in a horizontal array, diffuse sound in a vertical direction. One can create a two dimensional sound field by installing both vertical and horizontal diffusors.

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