Handbook for Sound Engineers

Surround Sound 1597

next decade, home theater was the fastest growing cate-
gory of consumer electronics products, and today is
enjoyed by many millions of consumers worldwide.
The appetite for Dolby Surround encoded program-
ming increased accordingly, not only for videos of
Dolby encoded movies, but also regular TV series,
specials, and sports events. Content providers rose to
the occasion by mixing more and more program mate-
rial in Dolby Surround, confident that the material
would play properly on any system, mono, stereo, or
surround. And the Dolby Surround format soon
extended to include the soundtracks of video and PC
games, Fig. 45-6.
The purpose of a home theater system is to provide a
convincing facsimile of what is heard in the cinema. In
order to do that, the speakers should be placed as shown
in Fig. 45-6, with three speakers across the front of the
viewing area at about ear level, with the left and right
speakers subtending a 45–60 degrees angle with the
center seating position. A surround speaker goes to
either side of the prime seating area well above ear
level. Their relatively high placement helps to provide a
diffuse surround soundfield, like that in a cinema, that
does not call attention to itself.
When home theater was in its infancy, some pundits
were skeptical that home listeners would put up with five
loudspeakers in their living rooms (just as their ances-
tors had predicted failure for home stereo because two
speakers were required). However, enough enthusiasts
invested in the original, bulky home theater equipment to
prompt loudspeaker manufacturers to develop sleek
satellite/subwoofer systems that both eliminated most of
the objections and lowered costs. While many devotees
still assemble home theater systems from elaborate tower
loudspeakers and other models, the majority of home
listeners today opt for single-brand sub/sat systems.

Satellite/subwoofer systems take advantage of the

fact that the lowest bass frequencies are nondirectional,

that is, the ear cannot readily detect where bass sounds

are coming from. As a result, these systems channel the

low bass to a dedicated bass loudspeaker called a

subwoofer. The subwoofer can usually be tucked out of

the way, because its placement is not critical to repro-

ducing the directionality of the original sound.

Because they are not required to reproduce low bass,

the satellite loudspeakers 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 loudspeakers

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, and

somewhat different units (usually with respect to their

radiating characteristic) for the surrounds. The surround

loudspeakers should still be timbre-matched to the front

loudspeakers.

45.6 Digital 5.1 in the Home

Much like Dolby’s original analog film sound formats

migrated into the home as Dolby Surround, Dolby Digi-

tal in the cinema provided a springboard for consumer

formats with 5.1-channel digital surround. Beginning

with laser discs in 1995, Dolby Digital 5.1 soon made

its way to DVD, cable TV, DBS systems, digital TV

broadcasting, and multimedia applications including

video and PC games, Fig.45-7. DTS also entered the

home market, although program material with DTS

encoded soundtracks is found on relatively few DVD

titles, and is unavailable via digital broadcast formats.

Figure 45-6. A four-channel home theater system equipped with Pro Logic decoding is configured much like a four-channel
cinema system. Surprisingly, the need for at least five loudspeakers did not prove to be a deterrent, particularly as loud-
speaker manufacturers developed compact and cost-effective satellite subwoofer systems

Home theater system

with Dolby Surround

Pro Logic decoding

Dolby Surround encode

2 channel program

Broadcast radio

Satellite TV

Video game

NTSC laser disc

Video cassette Audio cassette

CD,

DVD

Cable

Broadcast TV

Surround

Left Center Right

Surround