Specifications

3 Installation
19
Fig. 14
Ideal horizontal loudspeaker placement.
level to compensate for the increased distance to
the listeners.
The Center Loudspeaker
The center loudspeaker should be equidistant from
the left and right loudspeakers. Whenever possible,
it should also lie on a plane formed by the listener
and the left and right loudspeakers. That is, it
should be horizontally aligned from the listener
∗
s
viewpoint, as shown in
Figure 14
.
In many cases, whether due to the stage, a video
screen, or architectural requirements, the center
loudspeaker needs to be higher than the left and
right loudspeakers. This is OK to some extent, and
can even be helpful for more even level distribution
across the audience. However if it is extreme, the
soundstage may be quite noticeably distorted. Still,
the result in most cases is effective and very
pleasing.
It is usually best to set the center loudspeaker back
somewhat, as shown in
Figures 10
and
11
. A good
rule of thumb is to place all three loudspeakers
equidistant from a point near the rear-center of the
listening area, creating a loudspeaker "arc".
To some extent, the signal drive level of the center
loudspeaker can compensate for imperfect depth or
distance. For example, in
Figure 13
, the center
loudspeaker may have its level reduced somewhat.
The correct relative level is determined by listening,
which is part of the setup procedure. This way, the
effect of placement on audible level will be perfectly
compensated.
It is generally beneficial for the center loudspeaker
to provide wide dispersion. This helps eliminate any
on-axis hot spot, while providing uniform coverage
for the entire listening area.
Using an Unmatched Center Loudspeaker
In certain installations, it will be desirable or
practical for the center loudspeaker to be different
from the side loudspeakers. In typical auditorium
situations, the center loudspeaker needs to have a
wider dispersion angle in order to cover the entire
audience area. Architectural considerations often
dictate a different type of center loudspeaker. While
the theoretical principles of stereo imaging are
based upon matched sound sources, good imaging
still can be achieved with an unmatched center
loudspeaker.
If an unmatched center loudspeaker is used, special
consideration of its equalization and gain can
improve the imaging capability.
Using a separate equalizer for the center
loudspeaker, adjust the equalization so that the
overall response and sound quality matches the
side loudspeakers. Appropriate test equipment can
be helpful for this purpose, but the final evaluation
should be done by listening carefully during the
setup procedure and then to the results during
normal operation.
The center amplifier will very likely need to have a
different gain setting from the left and right
amplifiers. The setup procedure covers this. For a
non-matching center loudspeaker, the
bridged-center amplifier connection is not
recommended.
Surround Loudspeakers
Surround loudspeakers should be positioned behind
and/or to the sides of the listening area, as shown in
Figure 6
. Especially in larger venues, multiple
loudspeakers may be used to provide more even
coverage. If desired, they can be connected in
series, parallel, or series-parallel, to maintain
appropriate amplifier loading. They can also be
delayed to maintain optimum timing with the main
front loudspeakers. In some applications such as
small rooms, it can be advantageous to point each
surround loudspeaker toward a wall or corner so
that the
reflected
sound emanates toward the
listening area. The emphasis of reflected sound will
be inherent if dipole loudspeakers are used. Unlike
the front loudspeakers, a more diffuse sound field is
often desirable from the surround loudspeakers.
Multiple Multisonic Imaging
There are many ways to further improve sound
staging using multiple Multisonic arrays of
loudspeakers. In live surround-sound applications it
may be desirable to use a separate Multisonic
Imaging array for a rear sound stage. In this case a
four-channel mix could be created based on stereo
front and stereo rear pairs of channels. This allows
specific directionality in the rear system as well as
the front. The rear of the listening area is set up with