User Guide

Sound System Design Reference Manual
The other approach is to use pre-existing
building blocks, such as the SP225-9 system.
Specifically, four of these systems can be arrayed
with sufficient space between them for good stereo
presentation and splayed to produce an included
coverage angle of 135°. Rigging is integral in the SP
Series, so that problem is solved. A center pair of
SP225-9 units should be located side by side and
splayed along their common back angle to give 120°
coverage. This channel is primarily for speech, but
may be used as well as a stereo center channel for
music. The remaining two SP225-9 units will be used
for left and right stereo presentation.
All units will have a nominal downward
elevation angle of about 60°, and the average throw
to the main floor is 10 meters. Level calculations are
as follows:
Level Power Distance
100 dB 1 W 1 meter
131 dB 1200 W 1 m
111 dB 1200 W 10 m
In this case, we are powering the two LF units
in each SP225-9 as a parallel (4 ohm) load to be
driven by one section of a MPX1200 amplifier.
7-11
Figure 7-9. Electrical diagram of delayed systems