User Guide

Sound System Design Reference Manual
Entering values and rearranging:
10 log Efficiency = 92 -109 - 5 = -22
The efficiency is then 10
-22/10
= 10
-2.2
= .63%
The total contribution to the reverberant field
will be from all 18 loudspeakers working at once. We
can then calculate the radiated acoustical power as:
18 x 10 x 0.0063 = 1.134 acoustical watts. Here, 18
is the number of individual loudspeakers, 10 W is the
electrical power applied to each of them, and 0.0063
is the efficiency.
For the next step in the analysis we need to
determine the resulting reverberant level in the room.
L
rev
= 126 + 10 log W
A
- 10 log R
In relatively live spaces, Sα and R are virtually
identical; therefore,
L
rev
= 126 - 0.6 - 29 = 96 dB SPL.
We have now reached a point in our analysis
where we can estimate the overall system
performance regarding speech intelligibility. We know
the following:
7-14
Figure 7-12. Electrical diagram of delay zoning system