Alesis M1 ACTIVE - Surround Sound Setup

Suround
Sound
CHAPTER
3
SunnouruD
Souuo
About
surround
sound
Sunound
sound is
the
term used
for
several different
systems
which use multiple
channels
of ptayback
in the
listening
room to recreate
a
truly three-dimensional
sound experience.
The practice
of recording
music-only
in surround
sound is
a fairly
recent
innovation.
surround
sound for video,
howevet
has
been around for
over
ten
years.
With
modem
encoding
methods,
multichannel
audio
may be delivered
to
consurners
on standard
video
tape,
video discs,
and
even through
broadcast,
with
the
proper
encoders
(devices
whidr
take
multiple
charurels
of audio
and combine
them
into
two charurels)
and ilecoders (used
at the receiving
md to split
the signal
back into
rnultiple
charurels).
Systems are
in
use which
use
three
(eft,
right,
and
surround),
five
(left,
center,
right,
left surround,
right
surround,
often
supplemented
by a sixth
subwoofer
charureli
and
more
speakers.
The
original
Dolby
Sunound@
of the mid-eighties
was a
matrixed
threechannel-only
system.
It had
left, right
and a
mono
surround (rear)
track
^which
was usually
playid
through
two
su"rJund
speakers.
In 1982
D;by'pro
Logic@,
a
four-charmel
matrix
system,
was introduced.
Fro
Logic added
a
ded.icated
center
channel
to which
most
dialog
was assigned.
The rear
surround
channel
was
strll in mono.
h 1996,
Dolby
Digital@ (Ac-3)
and
DTS, f'lly
discrete
six-charurel
audiodelivery
plaffomrs
with
separate
left-rear
and
right-rear
channels
first
became
available
to
consumers
on laserdisc
and, more
recently,
on DVD (Digital
versatile
Disc).
With
so many
listeners
hearing
music
through
their
multimedia
systems,
it
is
important
for
mglneers
to
produce
music
on surround
systems, even
if
they,re not
working
for
film
or video
applications.
Powered
monitors
like
the Alesis
M1
Active
Biamplified
Reference
Monitor
have
proven
to be
a simple,
cost-effective
way
to add
five'channel
surround
to control
rooms.
Center
speakers
in rnusic
mixes
In
video applications,
with left,
center
and right
channels
all
set to deliver
equal
output,
the
ear tends
to hear
dialog
as coming
only from
the
center charurel.
(It's
a
psychoacoustic
effect
because
au right
and
all left
channel
signals
are fed
to the
cmter.)
In
Dolby Pro
Logic,
the center
charurel
information
is derived
from sum
and
difference
information
encoded
in the left
and
right
charurels. The
very attributes
that
make
this
matrix-type
system
viable
for video
application
make it lesjdesirable
for
music-only
reproduction.
In
practice,
there is
a hard
center
dialog channel
but
there
is
also a
sort of phantom
mono
channel
developed
betwem
the left and
center
channel
and
the right
and
center
channel.
This
between-channel
phantom
mono
image
exists
because
so much
of the information
contained
in
each channel
0eft anc
center or
right
and
center) is
identical.
Hence,
mono.
In the
few music-only
recordings
encoded
in Dolby
Pro
Logc
the derived
cmter channel
could
lead
to
some
drastic
changes
in
spatial perception.
Itr'
ACTT'E
REFERETCE
MAIIUAL
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