WS-A550 Power Capacity
Power Capacity Rating
Like the WS-A500, the WS-A550 is rated in accordance
with EIA RS-426A, with a thermal power capacity of 400
watts.
WS-A550 systems
require
the signal processing of the
WS-SP2A for proper operation. They must also be operated
with
care and understanding of their limitations. Figure 7 plots
the thermal and displacement limits of safe operation for a
single WS-A550 when used with the WS-SP2A.
WS-A550 System with WS-SP2A
Thermal and Displacement-Limited
Power Capacities
1000
500
250
125
63
32
16
8
>
a.
118
Hll
b/
40
•;H
20
14
10
7.
h
H.h
Vh
I I I I I II
s
System
Thermal
Limits
>
r
0
m
m
A
•
C
,f
J
f
.
i
J
I
i
/
f
f—
)'
Displacement
Limits with
WS-SP2A
'
2 3 4 5 6 7 891
20 Hz
Frequency
(Fig.
7)
2
1
0.5
2
200 Hz
Human Hearing Criteria and Performance Exportations
From reading performance specifications, s single WS-A550
is capable of impressive output at subwoofer frequencies.
Human loudness perception comes into play, however, and the
results can fall short of expectations when these factors aren't
thoughtfully considered and understood. When this happens,
it Is very likely that the loudspeakers will also be operated
beyond their limits for safe operation.
Human hearing is least sensitive at very low
frequencies.
Figure
8 illustrates the upper range of Robinson-Dadson criteria for
equal loudness perception. The data shows a 30 Hz sound at
120
dB SPL to be perceived as equal in loudness to
10OdB
SPL
at
1
kHz. Because the acoustic output of a subwoofer system
is almost always balanced with the acoustic output of the
main loudspeakers by ear, these criteria provide an accurate
Indication
of typical performance expectations, and should be
used as a guide for planning of subwoofer systems.
70
10
00
90
80
70
60
50
1 III
LOUDNESS
120 LEVEL (PHON)
110
100
_90
J»
.70
60
50
2
3
4 5 6 7891
20 Hz
3
4 5 6 7 891
Frequency
2 3 4 5 6 7
891
2
2 kHz 20 kHz
(Fig.
8)
Use In Systems
Figure 9 shows the 1 meter maximum SPL vs. frequency
capabilities of a single WS-A550, considering mechanical
displacement limits alone. Everything to the right of the
displacement limit line is within the capabilities of the WS-A550,
while operation to the left is potentially hazardous. When we
consider human loudness perception criteria, the capabilities
of one WS-A550 appear far removed from expectations.
WS-A550
Maximum Displacement-Limited
SPL at 1 meter vs. Frequency
120
115
110.
E
•-
• 105.
_l
a
IS)
T3
100
95_
90
_
2 3 4 5 6 7 891 2
20 Hz 200 Hz
Frequency
(Fig.
9)
-5-
To Next Page
Loading...
