El Platform Details; High-Frequency Horn Aiming - JBL 4671 Instruction Manual

EL Platform Details

Frame dimensions
slightly larger than
bottom of enclosure.
Frame and legs, 2 x 4
lumber
Braces 1 x 4 lumber.
All JBL theater systems must be oriented as shown
in Figure 1 A. In particular, the models 4670B and 4675A
should NOT be assembled with the low-frequency enclo-
sure lying on its side.
The loudspeaker should be placed on a dense foam
rubber pad or section of carpet so that it cannot possibly
rattle when driven at high levels. When the loudspeaker
is placed on an elevated support, it is advisable to
anchor the loudspeaker with four or more angle irons so
that it cannot possibly shift position.
The back wall behind the screen should be covered
with a sound absorptive material.

1. High-frequency Horn Aiming:

Figure 3 shows details of mounting the components
in the various systems. Note that the high-frequency
horns are aimed straight out into the theater. JBL has
found that this mounting will be best for most installa-
tions for the reasons shown in Figure 4A. Since the off-
axis response of our new horns is quite uniform out to 12
kHz, we can trade off the inverse square losses in the
room with the off-axis horn losses to provide more even
front-to-back coverage in the seating area.
Top covered
V 2 " thick plywood.
Bracing required on
four sides.
FIGURE 3- INSTALLING TRANSDUCERS
AND COMPONENTS IN SYSTEMS
A N G L E IRON
A.
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