What
You Need to Know for
Great Sights & Sound |
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The
ability to achieve a theater-quality picture in your home is determined by many factors,
but three of the most critical are accurate color reproduction, picture resolution
and sound quality. Additionally, your screen's Aspect
Ratio will impact how accurately you can re-create the theater experience
at home.
Color Accuracy The
average TV set is capable of decent color accuracy, but it sometimes needs a little help.
Adjusting the picture controls on your set can help the image be more pleasing. Using a
reference such as Color Bars & Test Patterns
can help in adjusting for color accuracy.
Color Temperature Many
TV sets now offer color-temperature settings, often labeled as Cool (brighter) or Warm
(more natural), with some options in between. Sets that offer this choice make a good
display for home theater systems and allow you to fine tune the display to your personal
taste.
Contrast & Brightness
Contrast settings can also be adjusted to suite your particular needs. First
thing you
should do is adjust the contrast setting to its midpoint. When Contrast is at its maximum,
the light output can distort the image and obscure detail. It can also damage the picture
tube and discolor the image. Once you've brought the contrast down, check the brightness.
If it is at its maximum or minimum, adjust it as well. Work with these two controls to
achieve an image that you like, but one that isn't distorting colors and detail.
Picture Clarity Clarity
is generally described in terms of resolution. Resolution is commonly measured in
horizontal lines - the more lines used to draw the picture, the higher the resolution. But
true resolution is not only a number on a TV spec sheet, it has to do with the format of
the image you want to display. For example, a VHS tape has a resolution of approximately
240 horizontal lines, which is half the resolution that any standard TV can display. The
DVD format offers approximately 500 lines of resolution, the maximum our television
system, NTSC, is capable of showing. HDTV and DTV (Digital Television) will offer display
signals ranging from 500 to nearly 1100 lines of resolution. These signals will require a
new digital-ready TV that is able to display them, or a converter box that can reformat
the signals for standard TV sets.
Comb Filter The comb
filter is one of the critical features of any TV set. Television signals commonly travel
as a single information signal, but to display the image the information needs to be
separated into its component parts: black & white information (brightness) and
luminance (color). How cleanly those signals are separated is the job of the comb filter.
When the images are displayed on the screen, the lines between colors should be sharp and
clean, not blurry as if drawn with a crayon, or jagged with blocky edges. Look for a set
that has a 3-D Comb Filter; if that's not offered, a 2-D or digital comb filter is
preferred. Notch filters are the crudest and are found on inexpensive, entry-level TV
sets.
Sharpness A Sharpness
control can often have the opposite effect. Check the setting on your TV - it's usually at
the midpoint. Adjust the control up and down. Watch the edges of lettering and lines. Turn
the Sharpness down until any white halos on lines or lettering are lessened or disappear.
If you watch DVD movies, your Sharpness setting should be low or at its minimum setting.
Direct View TV's Most
smaller-scale home theaters use direct-view televisions. This is the name applied to
conventional televisions, since the image viewed is created directly on the front of the
CRT (cathode-ray tube). The size of a TV used for a home theater is generally no less than
32 inches (measured diagonally), although you can create a home theater system around a
television as small as 25 inches for small rooms and bedrooms, with an appropriately
matched audio system.
Rear Projection Systems
are typically the favorite choice for those building a home theater. Rear projectors are
available with screens ranging from 40 to 200 inches, and the increased size brings a
sense of drama and involvement to films and sports events that a direct-view set can't
achieve.
As the name suggests, rear-projection televisions do not
project the image directly onto a picture tube. Instead, rear projectors basically install
front projectors into a box and, using mirrors, project the image onto the back of a
special screen.
Front Projection Systems
offer the best image quality and color accuracy, typically at the highest cost. One word
of caution: front projectors are the most vulnerable to ambient light because the picture
is literally projected across the room onto a screen, just as in a movie theater.
Therefore, front projectors require almost complete darkness for the image to reach the
screen. Front-projection systems are most appropriate for rooms that are dedicated theater
setups and can be darkened even during the day.
The sheer size of the image that a front projector can
produce elevates the movie experience to a new level. This is the point where you'd rather
watch a film at home than go to a theater.
What
is Great Sound
& How to
Obtain it. |
 |
Stereophonic sound uses two speakers to create a balance of sound
from the left and right. Surround sound (also known as multichannel sound) incorporates
multiple speakers to envelop the listener, providing sound in front, to the sides, and
behind. Movie theaters use surround sound to impact large audiences with the feeling of
being in the middle of the action, rather than distant observers. Likewise, surround sound
is an essential element in creating the home theater experience.
There are three primary formats for home theater:
Dolby™ Surround Sound, Dolby Digital™ (AC-3), and DTS™ Digital Surround.
Surround Sound
The concept of surround sound for motion pictures was introduced by the Disney Studios in
the early 1940s and first used for Fantasia. Known as "Fantasound," this
system used three channels behind the movie screen, with various speakers placed to the
sides of and behind the audience. The cost of the transition for movie theaters was high
and the concept did not truly catch on until the late 1950s, when such "epic"
films as Ben Hur and The Ten Commandments made it to the screen, demanding
sound that was large and full enough to match the visual experience.
Movie-theater surround sound became truly popular with the
creation of Dolby™ Stereo, first introduced to movie going audiences in 1977 with Star
Wars. Within just a few years, Dolby™ Stereo had become the common audio format
for movie theaters across America.
Types of Surround-Sound Decoding
Dolby™ Surround, which evolved from Dolby™ Stereo used in theaters, was
an early form of home-theater sound. It is a three-channel process designed to create the
sense of ambience experienced in a theater. The Dolby™ stereo track is decoded into
normal left and right channels, and the surround speakers are fed a mono signal that has
been mixed from the stereo audio tracks.
Dolby Pro Logic™ Dolby Pro Logic is an advanced
version of Dolby™ Surround. Although the term "Dolby™ Surround" is
used for both Surround and Pro Logic decoding, Pro Logic was the next step in bringing
theater sound into the home. Dolby™ Pro Logic is a four-channel system that began the
process of directing information to certain speakers. The front left and right channels
were fed a full stereo signal, but now there was also a center-channel signal to reproduce
dialogue, music, and effects. The surround channels were fed a limited mono signal to
create a sense of space and ambience. The separation from the two-channel signal was
accomplished with steering logic in the decoding. This process had some leakage of
information between speakers.
Dolby™ Digital (also known as AC-3) is a
multichannel format introduced in 1996 that used advances in digital sound technology to
bring the home theater experience even closer to the cinema experience. Dolby™
Digital uses 5.1 (six) discrete audio channels. "Discrete" here means that
information can be assigned to exact speakers - the center channel or the right surround
channel, etc. - with no leakage of information into another speaker. Sounds can be
precisely controlled to realistically create any effect imaginable. Dolby™ Digital is
known as a 5.1-channel process because five of the six channels carry the entire bandwidth
of sound, from 20Hz (a very low bass sound) to 20,000Hz (the highest sound audible by the
average human ear).
The sixth channel (.1) is known as the LFE (Low-Frequency
Effects) Channel. This channel allows for additional low-bass sounds, maximizing
action-adventure sequences with fuller explosions and booms. In your home theater, sounds
from the LFE Channel are played back via the subwoofer. You can still hear bass from your
left and right front speakers even without a subwoofer, but you won't experience the full
impact of the LFE Channel as you would with a subwoofer.
Dolby™ Digital works only on program material encoded
in Dolby™ Digital processing. It is part of the DVD-audio standard, so it is included
on most releases where it is appropriate. Some laserdiscs offer the 5.1-channel
process as well. It is not compatible with standard VHS tapes. Dolby™ Digital is also
the audio standard that will be used with HDTV (High Definition Television).
DTS™ Digital Surround has its own multichannel
digital surround format that competes with Dolby™ Digital for movie-theater sound
systems as well as for home theater movie and music software releases. The format, known
as DTS™ Digital Surround (or just DTS), also features 5.1-channel audio that, like
Dolby™ Digital, can be placed with pinpoint accuracy in any of five full-range
speakers channels as well as in the sixth (.1) LFE (low-frequency effects) channel. The
basic difference between these two formats is the method of compression - how the large
audio data files are manipulated to fit in less space. DTS™ specs their system to use
about one-fourth the compression that Dolby™ Digital uses for the same audio signal.
In theory, that should translate into more overall information available on the
soundtrack.
These two formats are not compatible, and require their own
branded decoding chips on audio receivers and processors, as well as separate digital
outputs on DVD players. Some listeners can hear distinct differences between the two, and
some cannot. But Dolby™ Digital is part of the DVD movie standard and the HDTV
standard, so it will be an integral part of any multichannel audio system
DTS™ and Dolby™ Digital will continue to co-exist
in the marketplace. Both should be included in a system if at all possible, because
both formats will have the exclusive rights to certain movie and music releases.
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