Filter
Top Products
2-12
Using the polar information of the speaker, in combination with the distance between the speaker
and the listener, you can determine the area that a speaker can cover. The “Coverage Area” is
defined as the plane where the SPL at the edge of the plane drops 6 dB below the on-axis SPL,
as illustrated below:
93dB
93dB
Floor
Listener level
10' high ceiling
99dB @5' 1W
Simplex 4902-9721
Ceiling Mount Speaker
Polar Plot - 2kHz 0º
6dB/division
7
5
º
o
f
f
a
x
i
s
51º
of
f ax
i
s
97dB
93dB
97dB
93dB
Coverage Diameter
Distance off axis
D2
D2
5.0'
10.0'
Dispersion Angle
Critical Polar Angle
12.8' 6dB variation
Figure 2-5. Speaker Coverage
Coverage area is determined by a combination of speaker polar loss and the inverse square loss
off-axis. To illustrate, consider a speaker with no polar loss, i.e. the speaker’s SPL is the same
over all angles. As the listener moves away from the center of the speaker, the distance to the
speaker increases resulting in a lower SPL. From the Inverse Square Law, the off-axis SPL is 6
dB lower than the on-axis SPL when the distance from the speaker to the listener has doubled.
From simple geometry, it can be determined that the maximum useable coverage angle is 120
degrees:
60°
Listener
Height
Ceiling
Height
2
x
C
e
i
l
i
n
g
H
e
i
g
h
t
-
L
i
s
t
e
n
e
r
H
e
i
g
h
t
-6dB edge of
coverage area
Figure 2-6. Maximum Theoretical Coverage Angle
Continued on next page
Speaker Basics, Continued
Speaker Coverage