S12 Two-Way Stage Speaker System
S12 Two-Way Stage Speaker System
ensure that the S12 speaker system is ide-
ally suited to a long and reliable life on the
road.
Frequency Response
The combination of a 12-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 S12 is equipped with two parallel
1/4-inch phone jacks. (The S12-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 coverage
pattern remains constant and the vertical pat-
tern smoothly transitions to a 40° angle above
5,000 Hz. Response within the 60°x 40° rated
coverage angle is uniform, which means de-
pendable audience coverage without “hot
spots” or dead zones at certain frequencies.
The 60° x 40° dispersion characteristic also
helps avoid early reflections from nearby
floor or side-wall surfaces which could de-
grade performance. The controlled directiv-
ity of the high- and low-frequency transduc-
ers also eliminates response irregularities
caused by diffraction off nearby enclosure
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 S12 is the con-
stant-directivity dispersion provided by
the 60° x 40° horn. The polar response of
the system at selected one-third-octave band-
widths is shown in Figure 5. These polar
responses were measured in an anechoic en-
vironment at 6.1 meters (20 feet) using one-
third-octave pink-noise inputs. The frequen-
cies selected are fully representative of the
polar response of the system. Beamwidth
of the system utilizing the complete one-
third-octave polar data is shown in Figure 6.
Directivity 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 S12 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 S12, 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 sec-
tion, above, the S12 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 rat-
ing.
1. To use the S12 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 S12
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 S12 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 S12 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 S12 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.
Stand Mounting
The S12 can be mounted on the 100BK
speaker stand, or any other stand with
a 1-3/8-inch diameter shaft.
