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Table of Contents
1. Introduction
1.1 What is a home theater?
1.2 Surround sound makes the difference
1.3 Dolby Digital: the sound of home
theater today
1.4 What is "5.1" surround sound?
1.5 Surround from VHS tapes and regular TV
2. Choosing your home
theater sound system
2.1 Your home theater: it's as easy as 1,
2, 3
2.2 The simplest solution: "home theater
in a box"
2.3 The A/V receiver route
2.4 The high end
2.5 About DVD-Audio
2.6 About home theater speakers
3. Speaker placement
3.1 Front speaker placement
3.2 Preferred surround speaker placement
3.3 Alternative surround speaker placement
alternatives
3.4 Surround placement for DVD-Audio
listening
4. Installation and
operation tips
4.1 The room
4.2 Speaker wiring
4.3 Speaker polarity
4.4 Analog audio/video connections
4.5 Digital audio connections
4.6 Bass management
4.7 Delay adjustments
4.8 Channel balance
4.9 Processing enhancements
4.10 Regular stereo programming
5. For more information
1. Introduction
1.1 What is a home theater?
A home theater is an audio/video playback
system that approximates in your home the experience of
seeing—and hearing—a film in a cinema. Setting up a home theater
can be as simple as adding a compact surround sound system to
the TV set in your family room, or as complex as building a
dedicated viewing room equipped with elaborate built-in
speakers, massive amplifiers, and a big-screen front-projection
TV system.
1.2 Surround sound makes the
difference
Surround sound, which is what turns
conventional TV viewing into home theater, originates from
program material such as DVDs that have multichannel
soundtracks. The multiple channels are reproduced by three
speakers across the front of the viewing area, and surround
speakers to either side (Figure 1). The result is sound
that transports you into the world of you're watching; you feel
less like a passive viewer and more like an active participant.
1.3 Dolby Digital: the sound
of home theater today
The leading surround sound technology today
is Dolby Digital. It is a method of compacting digital audio so
that high-quality multichannel soundtracks can be easily carried
via digital discs and broadcasts.
Soundtracks encoded in Dolby Digital come to
you via DVDs, digital television (DTV) broadcasts, and digital
satellite and cable transmissions. Dolby Digital decoding is
licensed by Dolby Laboratories to manufacturers of home playback
equipment. Programs with Dolby Digital soundtracks and playback
equipment with Dolby Digital decoding are usually identified
with the
logo.
1.4 What is "5.1" surround
sound?
Dolby Digital brings 5.1-channel surround
sound into your home. It provides five full-range audio
channels: three for speakers at the front and two for surround
speakers at the sides. A sixth, low-frequency effects (LFE)
channel carries those deep bass sound effects you feel more than
hear. Because it covers only about one-tenth of the audible
range, the LFE channel is called a ".1" channel. Its low bass
sounds can be channeled to the subwoofer in the home theater
system, if it has one, or to any other speakers in the system
that can reproduce low bass.
A newer variation of Dolby Digital, called
Surround EX, encodes Dolby Digital program material with a third
surround channel that can be decoded at the listener's option
for playback over additional surround speakers placed behind the
viewers (Figure 2). Surround EX program material is
fully compatible with regular Dolby Digital 5.1 playback (the
additional center rear information is split between the left and
right surround channels).
1.5 Surround from VHS tapes
and regular TV
Prior to the advent of digital audio, Dolby
Laboratories developed a way of delivering four-channel surround
sound from stereo VHS tapes, TV shows, video games, and other
analog sources. Called Dolby Surround, it encodes four channels
of information (left, right, center, and a single surround
channel) onto regular stereo soundtracks. The four original
channels can be reconstructed upon playback by means of a Dolby
Surround Pro Logic decoder, which is included in virtually all
home theater systems, including those that also have 5.1-channel
Dolby Digital decoding.
More recently, Dolby Laboratories introduced
an improved decoding process called Dolby Surround Pro Logic II.
It provides a listening experience more like Dolby Digital 5.1,
by deriving five channels, including two full-range surround
channels, not only from programs encoded in Dolby Surround, such
as movie videos, but also from regular stereo material, such as
music CDs. The result is improved spatiality and more accurate
localization of sounds on Dolby Surround material, and an
enveloping, lifelike soundfield on regular stereo recordings.
Program material encoded in Dolby Surround
is usually identified with a
or
logo. Playback equipment with Dolby Surround Pro Logic or Pro
Logic II decoding is identified with a
or
logo respectively.
2. Choosing your home
theater sound system
This Guide assumes you are putting together
a new home theater sound system from scratch. If you are
converting an existing analog Dolby Surround system to Dolby
Digital, you will find helpful information in Frequently Asked
Questions about Dolby Digital in the Home, located under Home
Theater.
While we can help you get the most out of
your home theater system, Dolby Laboratories cannot make
specific equipment recommendations. However, you can rest
assured that all products licensed to incorporate Dolby Digital
decoding meet Dolby Laboratories' high performance standards.
For specific product recommendations,
consult the various publications that test home theater
products, and/or home entertainment equipment retailers.
2.1 Your home theater: it's as
easy as 1, 2, 3
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To play Dolby Digital programming, you need one or more
program sources equipped with a Dolby Digital output, such
as a DVD player, digital television (DTV) receiver, digital
satellite set-top box, and/or a digital cable set-top box.
To play Dolby Surround programming, all you need are regular
analog stereo sources, such as a conventional TV receiver,
VHS deck, satellite receiver, or cable box.
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To decode surround sound programming, you need an A/V
receiver or other playback electronics that incorporates a
5.1-channel Dolby Digital decoder for programming with Dolby
Digital soundtracks, and a Dolby Surround Pro Logic or Pro
Logic II decoder for analog Dolby Surround soundtracks.
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To hear Dolby Digital and Dolby Surround soundtracks,
you need five speakers (six, if you use a subwoofer), and
the same number of amplifier channels in the playback
electronics.
Put these basic elements together with your
television set and you have a home theater, like the one shown
in Figure 3.
2.2 The simplest solution:
"home theater in a box"
Many audio manufacturers offer complete,
integrated home theater sound systems. Because the equipment is
often compact enough to fit into a single shipping carton, this
kind of system is sometimes referred to as a "home theater in a
box."
These uncomplicated, cost-effective systems
supply the necessary playback electronics, including Dolby
Digital decoding, along with a multichannel speaker system
typically consisting of five small satellite units and a compact
subwoofer.
The electronics may be contained in a simple
A/V receiver to which you connect your program sources and the
speakers, or built right into one of the speakers (usually the
subwoofer). There are also systems that combine a DVD player and
the system electronics in one compact unit, to which you connect
the speakers.
Regardless of configuration, a "home theater
in a box" can be a practical, good-sounding solution,
particularly if you're on a limited budget or short on space.
2.3 The A/V receiver route
If you're looking for higher-quality sound,
and/or prefer to choose among components from different
manufacturers, consider a system similar to the one illustrated
above in Figure 3. This consists of one or more Dolby
Digital and Dolby Surround program sources; an A/V receiver that
integrates all electronics-control circuitry, Dolby Digital 5.1
and Dolby Surround Pro Logic decoding, multiple amplifiers, and
a radio tuner-in one convenient unit; and a home theater speaker
system consisting of five satellite units plus a subwoofer.
2.4 The high end
Specialty audio manufacturers offer a wide
range of high-performance home theater products, including
elaborate, software-based sound processor units; ultra-powerful
amplifiers; and sophisticated speaker systems. If you are
contemplating a high-end system, we suggest you consult a
specialist retailer/installer, such as one affiliated with the
Custom Electronics Design and Installation Association (CEDIA),
which is active in the US, Europe, Australia, and South America,
among other areas (www.cedia.org).
2.5 About DVD-Audio
DVD-Audio is a variation of the DVD format
that provides superb high-resolution music recordings going well
beyond the limits of CDs. DVD-Audio music programs can be
recorded with up to six discrete channels of surround sound,
making them ideal for playback over a home theater system.
To play multichannel high-resolution
DVD-Audio programs, you need a DVD-Audio player, most of which
also play DVD-Video discs. In addition, your receiver or other
audio controller unit must have a six-channel analog input. This
is because DVD-Audio players internally decode the
high-resolution programs on DVD-Audio discs to as many as six
analog output channels.
If you are unsure about committing to the
new DVD-Audio format, we recommend that you choose a receiver or
controller that has a six-channel input, which allows you to
easily add a DVD-Audio player at a later time. In the meantime,
almost all DVD-Audio discs include a Dolby Digital 5.1-channel
version of the program in addition to the high-resolution
version. This means you can play these discs on a DVD-Video
player with standard-resolution surround sound, and purchase a
DVD-Audio player later to "unlock" their high-resolution
programs.
2.6 About home theater
speakers
Most speaker manufacturers offer complete
home theater systems, usually based on a satellite/subwoofer
configuration (see Figure 4). These integrated systems
make choosing and installing a home theater system much easier
than it used to be, and often provide higher performance for the
dollar than a random assembly of individual component speakers.
Satellite/subwoofer systems take advantage
of the fact that the lowest bass frequencies are
non-directional, which means the ear cannot readily detect where
bass sounds are coming from. As a result, these systems channel
the low bass to a dedicated bass speaker called a subwoofer. The
subwoofer can usually be tucked out of the way, because its
placement is not critical to reproducing the directionality of
the original sound.
Because they are not required to reproduce
low bass, the satellite speakers can be compact, making them
less intrusive and easier to place. Many systems use identical
satellites for the left, center, right, and surround channels.
This means that all speakers have the same timbre, or tonal
characteristic, which is desirable in a home theater system.
Other systems provide identical satellites for left, center, and
right, but the surround units may be somewhat different, usually
with respect to their radiating characteristic. Nevertheless,
the surround speakers should still be timbre-matched to the
front speakers.
Of course, there are excellent alternatives
to satellite systems. For example, you can create a home theater
system using larger, full-range tower speakers for the front
left and right channels, or for both the front and the surround
channels. Their manufacturers usually provide well-matched
center and surround speaker options. Some of today's tower
speakers have built-in powered subwoofers, making them
particularly suitable for a home theater.
If you do assemble a home theater speaker
system from individual speaker units, as opposed to a satellite
system, it is best to use models from the same manufacturer for
the sake of timbre-matching, and to follow the manufacturer's
advice for mixing and matching their models. Also, be sure that
all front speakers are magnetically shielded to prevent
interference with the television's picture (in general, speakers
designated specifically for the front channels of a home theater
are shielded).
3. Speaker placement
3.1 Front speaker placement
The front speakers should be arrayed across
the front of the viewing area, as shown in Figure 5. If
you plan mostly solo viewing, arrange the speakers as shown so
that your seating position is equidistant from the left, center,
and right speakers (A). If your system is used
mostly for group viewing, arrange the speakers in a straight
line (B). In any case, avoid placing the center
speaker closer to the viewers than the left and right speakers (C).
The left and right speakers should include
an angle of from 45 to 60 degrees with the center-most viewer,
as shown in Figure 6. An angle nearer to 45 degrees is
preferred if you use your system mostly to watch movies, as it
approximates the circumstances under which film soundtracks are
mixed and monitored. A wider angle, with the left and right
speakers further apart, is recommended if you use your system
for music listening more often than watching movies.
Finally, the three front speakers should be
as close as possible to the same height, at or near ear level (Figure
7). Because it is often easiest to place the center speaker
on top of the TV set at a fixed height, consider mounting the
left and right speakers on adjustable stands so that you can
match their height to that of the center speaker.
3.2 Preferred surround speaker
placement
The surround speakers should be placed
alongside and slightly to the rear of (but not behind) the prime
seating position (Figure 8); well above ear level, to
help minimize localization effects (Figure 9); and
aimed directly across the listening area, not down at the
listeners (Figure 10). This arrangement creates a
diffuse, enveloping surround soundfield throughout the listening
area, like that in cinemas and in the dubbing theaters where
soundtracks are mixed. If the speakers are too far forward, you
won't get sufficient rearward effect, and if the speakers are
too far back, there will be a loss of envelopment and
integration of the surround information with the whole
soundfield.
3.3 Alternative surround
speaker placement alternatives
Of course, not every home theater
installation has sidewalls in just the right place to mount
surround speakers. If this is your situation, consider the
following alternatives.
Generally, placing surround speakers on the
wall directly behind the listeners is not preferred. But when
there's no alternative, there are several mounting techniques
you can try, as shown in Figure 11. Mount them well
above ear level, and try aiming them at each other (A),
towards the front (B), or to reflect off the
sidewalls (C and D).
Experiment with placing and aiming the speakers until the
surround soundfield seems to envelop you, rather than coming
from behind.
Alternatives to wall placement are shown in
Figure 12. Mounting the surround speakers on stands
above ear level (A) to either side gives much
the same effect as sidewall mounting. You can also try placing
them to the sides or rear aimed upwards, either right on the
floor, or, preferably, raised a couple of feet off the floor (B).
3.4 Surround placement for
DVD-Audio listening
The multichannel music programs on DVD-Audio
discs are mixed under different circumstances from movie
soundtracks. Films are mixed in large rooms called dubbing
theaters that are sized and configured like actual cinemas,
while DVD-Audio music programs are typically mixed in much
smaller recording studios.
As shown in Figure 13, dubbing
theaters (and cinemas) use multiple surround speakers arranged
along the sides and rear, mounted high to create a diffuse,
enveloping surround soundfield. The advice we've given so far
for placing surround speakers is aimed at duplicating this
effect at home. In most DVD-Audio mixing facilities, however,
there are five identical speakers arranged at ear level in a
circle around the mixer.
Chances are that you will be pleased by the
sound of multichannel DVD-Audio programs with your surround
speakers optimally placed for movie playback. However, if you
wish to more closely replicate what mixers hear when preparing
music for DVD-Audio releases, you have two choices. One is to
effect a compromise by lowering your surround speakers to a
height of four or five feet from the floor to split the
difference between the diffuseness desired for film sound and
the more direct radiation preferred for surround sound music.
The other alternative is to install and
switch between two pairs of surround speakers, one optimized for
film playback, and the other, identical to the front speakers,
placed at ear level for optimum DVD-Audio playback. This purist
(and potentially costly) approach is facilitated on some A/V
receiver models by the inclusion of connections and switching
for two pairs of surround speakers. However, while this approach
may optimize the effect for a listener in the center "sweet
spot," those seated off-center may hear too much of one surround
speaker or the other.
4. Installation and
operation tips
4.1 The room
The sound of your home theater system is
critically affected by your room's acoustics. These tips are
designed to help you achieve more satisfying performance.
However, if you have severe acoustical problems, consider
consulting a professional home theater installer for customized
assistance.
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Too many bare surfaces can cause reflections that add
harshness to the sound or muddy the dialogue; try adding
carpeting and/or drapes to keep them in check.
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If you have a choice of rooms, avoid those that are
perfectly square, or that have one dimension exactly twice
another; they can aggravate resonances that color the sound.
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If possible, center the seating area between the
sidewalls on which you mount the surround speakers.
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The closer a speaker is placed to intersecting room
surfaces-corner, wall and ceiling, wall and floor-the
stronger its bass output (possibly too strong in some
cases).
4.2 Speaker wiring
Prepare speaker wires by stripping their
ends (A), then twisting the bared strands
tightly together (B) to prevent shorts across
terminals (C). Or, if speaker and
amplifier/receiver terminals permit, use banana plugs to ensure
solid connections (D).
4.3 Speaker polarity
As shown in Figure 15, connect the
"+" and "-" terminals (usually red and black, respectively) on
each amplifier channel to the corresponding terminals on each
speaker. To make this easier, speaker cable is coded with a bead
or stripe down one lead's insulation, and/or with different
color wires. Connected identically, all speakers will operate
"in phase," with their cones moving back and forth together.
"Out of phase" connections, while doing no electrical harm,
muddy spatial effects and weaken bass.
4.4 Analog audio/video
connections
Use good-quality shielded cables, and be
sure plugs are fully inserted into jacks. Follow the color code
used on most connectors and cables to prevent confusion.
4.5 Digital audio connections
Most products capable of playing or
receiving programs with Dolby Digital soundtracks, such as
DVD-Video players, have a stereo analog output, plus at least
one digital output. Some units let you choose between two types
of digital output, coaxial or optical, as shown in Figure 17.
The analog outputs are for connection to a
conventional stereo or analog home theater system. For
5.1-channel Dolby Digital playback, you need to connect the
unit's digital output to an appropriate digital input of your
5.1-channel playback system. The digital output passes through
Dolby Digital 5.1 soundtracks for decoding by your playback
system's 5.1-channel Dolby Digital decoder.
If your system components allow you to
choose between two types of digital connector, note that both
have identical audio performance. Under some circumstances,
however, very long coaxial cables can be more susceptible to
radio frequency (RF) interference than optical cables. Because
optical cables are more expensive, try coaxial cables first and
switch to optical only if you encounter problems.
4.6 Bass management
Receivers and other units that incorporate
Dolby Digital 5.1-channel decoding provide a feature called Bass
Management, which allows you to distribute low bass just to
those speakers in your system that can handle it. By keeping low
bass out of the other speakers, such as small satellites, the
system will be able to play louder with less distortion.
If you have a typical home theater speaker
system with a subwoofer and five small satellites, select the
mode that sends all bass-from the main channels as well
as from the low-frequency effects (".1") channel-to the
subwoofer. If you have some other speaker configuration, check
your receiver's owner's manual for the Bass Management option
suited to your particular system.
4.7 Delay adjustments
Because the surround speakers in a home
theater system are usually closer to viewers than the front
speakers, both Dolby Digital and Dolby Surround Pro Logic
decoders provide a split-second electronic delay of the surround
channels.
In the case of Dolby Digital, the delay
ensures that the sound from the surround and front speakers
arrive simultaneously. For Dolby Surround Pro Logic, which has
less inherent channel separation than Dolby Digital, a slightly
longer delay ensures that sound from the surrounds arrives just
after sound from the front speakers. This delay makes
it difficult to detect any leakage of sounds that should come
only from the front, such as dialogue, into the surround
speakers.
While your system may provide the option of
adjusting these delays, and in some cases a delay for the center
speaker as well, the default settings provide proper performance
in most cases. If you wish to optimize the settings, many
receivers and processors allow you to do so through an onscreen
menu, which asks you to enter the distance from your listening
position to each speaker, and then automatically calculates the
proper delays for you.
If your system allows you to adjust delays
arbitrarily, without an onscreen menu requiring you to enter
distances to the speakers, you will find information on making
the adjustments properly in Frequently Asked Questions about
Dolby Digital in the Home, located under Home Theater. Improper
delay settings can have an adverse effect on the sound of your
system.
4.8 Channel balance
Systems with Dolby Digital and Dolby Pro
Logic decoding feature a test signal generator for balancing the
channels. As the signal moves from channel to channel, you
adjust the balance controls until each channel plays at the same
volume. You can do this by ear if you wish, but it's better to
use a sound pressure level meter, such as the relatively
inexpensive Radio Shack 33-2050.
Even though you should adjust the surround
channels to be as loud as the others on the test signal, you'll
find that on actual program material the surround level is much
lower than the front much of the time. Film sound mixers in
particular use surround mostly for subtle atmospherics and
ambience, and only rarely for special effects. A good surround
mix doesn't call attention to itself; if it did, it would soon
become tiresome.
4.9 Processing enhancements
In addition to Dolby Digital and Dolby
Surround Pro Logic decoding, some systems offer the option of
switching on additional processing enhancements. Some, such as
THX-licensed processes, are intended to make your home theater
sound more like a movie theater or the dubbing theaters in which
movie soundtracks are mixed. Others are intended to provide
special acoustic effects on stereo music (for example, "Hall,"
"Jazz Club," and other venue modes). In general, critical
listeners find that some of these enhancements work well, while
others sound artificial.
4.10 Regular stereo
programming
Many stereo recordings and TV broadcast
soundtracks contain natural ambience that a Dolby Surround Pro
Logic or Pro Logic II decoder treats much like surround sound.
We suggest that you try leaving the decoder on when listening to
stereo material.
On some material, particularly
dialogue-intensive TV shows, original Pro Logic can provide a
pleasant, more cinematic effect. On music-only recordings,
however, it may reduce the stereo width across the front more
than you like. Pro Logic II, on the other hand, can provide a
wide, astonishingly life-like soundstage with accurate
localization on all kinds of material, since it was specifically
designed to extract five-channel sound from both surround
encoded and conventional stereo recordings.
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