S15 Two-Way Stage Speaker System
S15 Two-Way Stage Speaker System
ensure that the S15 speaker system is ide-
ally suited to a long and reliable life on the
road.
Frequency Response
The combination of a 15-inch woofer, wide-
bandwidth high-frequency driver and an
equalized crossover results in the wide and
smooth overall response shown in Figure 1.
This response was measured at 3.05 meters
(10 feet), using a 4-volt swept sine-wave in-
put in an anechoic chamber. No external
equalization was used. Figure 1 has been
averaged and corrected for 1 watt at 1 meter.
Connections
The S15 is equipped with two parallel
1/4-inch phone jacks. (The S15-E has two
parallel Neutrik Speakon
®
NL4MP connec-
tors.) Another system can be connected in
parallel by using the other connector. Care
must be taken not to abuse the amplifier by
connecting impedances which are too low.
Constant-Directivity Speaker System
The crossover frequency and speaker com-
ponent geometries have been selected so that
the directional characteristics of the woofer
and constant-directivity horn match at the
crossover frequency to create a special sys-
tem type — the constant-directivity system.
At higher frequencies the horizontal cover-
age pattern remains constant and the verti-
cal pattern smoothly transitions to a 40° angle
above 5,000 Hz. Response within the 60°x 40°
rated coverage angle is uniform, which
means dependable audience coverage with-
out “hot spots” or dead zones at certain fre-
quencies. The 60° x 40° dispersion charac-
teristic also helps avoid early reflections from
nearby floor or side-wall surfaces which
could degrade performance. The controlled
directivity of the high- and low-frequency
transducers also eliminates response irregu-
larities caused by diffraction off nearby en-
closure edges and, in combination with an
essentially flat on-axis frequency response,
produces a total acoustic power output that
is uniform with frequency.
Directivity
A unique feature of the S15 is the constant-di-
rectivity dispersion provided by the 60° x 40°
horn. The polar response of the system at
selected one-third-octave bandwidths is
shown in Figure 5. These polar responses
were measured in an anechoic environment
at 6.1 meters (20 feet) using one-third-oc-
tave pink-noise inputs. The frequencies se-
lected are fully representative of the polar
response of the system. Beamwidth of the
system utilizing the complete one-third-oc-
tave polar data is shown in Figure 6. Direc-
tivity factor, R
θ
, and directivity index, D
i
, are
plotted in Figure 7.
Power-Handling Capacity
Electro-Voice components and systems are
manufactured to exacting standards, ensur-
ing they will hold up, not only through the
most rigorous of power tests, but also
through continued use in arduous, real-life
conditions. The EIA Loudspeaker Power
Rating Full Range (ANSI/EIA RS-426-A
1980) uses a noise spectrum which mimics
typical music and tests the thermal and me-
chanical capabilities of the components.
Electro-Voice will support relevant addi-
tional standards as and when they become
available. Extreme, in-house power tests,
which push the performance boundaries of
the woofers, are also performed and passed
to ensure years of trouble-free service.
Specifically, the S15 passes ANSI/EIA
RS-426-A 1980 with the following values:
R
SR
= 5.98 ohms (1.15 x R
E
)
P
E(MAX)
= 250 watts
Test voltage = 38.67 volts rms,
77.33 volts peak (+6dB)
The “peak” power-handling capacity of a
woofer is determined by the peak test volt-
age amount. For the S15, a 77.33-volt peak
test voltage translates into 1,000-watts short-
term peak power-handling capacity. This is
the equivalent of four times the “average”
power-handling capacity, and is a peak that
can be sustained for only a few milliseconds.
However, this sort of short-duration peak is
very typical in speech and music. Provided
the amplifier can reproduce the signal accu-
rately, without clipping, the system will per-
form accurately and reliably, even at these
levels.
Amplifier Power Recommendations
As noted in the Power-Handling Capacity
section, above, the S15 has a random-noise
power capacity of 250 watts long term
(1,000 watts peak) per ANSI/EIA RS-426-A
1980. The following guidelines will help
relate this to an appropriate power amplifier
output rating.
1. To use the S15 to full capacity, skilled
experts in sound system installation and
operation will obtain the best results if
the power amplifier is 2.0 to 4.0 times
the long-term average noise power rat-
ing of the speaker system. For the S15
this is 500 to 1,000 watts.
The caution cannot be made strongly
enough, however, that this arrange-
ment is only for experts or those who
can discipline themselves against
“pushing” the system for ever-higher
sound levels and who can avoid “acci-
dents” such as catastrophic feedback
or dropped microphones.
2. A more conservative, “normal” amplifier
size, which will produce audible results
nearly equal to those of the “expert” rec-
ommendation, is 1.0 to 1.4 times the
long-term average noise power rating of
the speaker. For the S15 this is 250 to
350 watts.
3. To be very conservative, one can use an
amplifier rated at 0.5 to 0.7 times the
long-term average noise power rating of
the loudspeaker. For the S15 this is 125
to 175 watts.
Request P.A. Bible Addition No. Two
(“Power Handling Capacity”) for more back-
ground on these recommendations.
Service
In the unlikely event the S15 requires ser-
vice, the woofer and driver can both be re-
placed or serviced from the front. A service
data sheet is available from Electro-Voice.
