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T I 5i Two-Way Trapezodlal Speaker System
All Electro-Voice HS- and HST- systems
follow the same principles. Put minimum
stress on the cabinet and make each cabinet
hang independently of any other device.
Suspending the Electro-Voice T15i
Speaker System
Part of the TlSi's versatility is that it can be
mounted either vertically or horizontally, and
has a rotatable horn. The mounting system
is conceptually very simple. Two aluminum
tubes pass vertically through the cabinet and
each is secured via two oversize cast brack¬
ets (threaded flanges). The enclosure is sand¬
wiched between the four (two on each end)
brackets. The enclosure is essentially rest¬
ing between the brackets.
When installing the T15i, two of the three
supplied forged eyebolts are screwed into the
upper two brackets. The third eyebolt should
be screwed into the appropriate T-nut on the
rear panel of the enclosure. When mount¬
ing the enclosure vertically, use the lower
T-nut. When mounting the enclosure hori¬
zontally. use the T-nut located in the center
of the rear panel of the enclosure. This is
necessary for aiming the system. The center
of gravity is arranged so the enclosure is di¬
rected towards the ceiling. In order to pro¬
vide a downward or horizontal projection
angle, the pull-up point must be used,
if multiple cabinets are to be suspended, each
system requires its own rigging points. Sys¬
tems must not be suspended from each
other. The eyebolts must be connected us¬
ing suitably rated chain with connectors such
as shackles or threaded chain connectors, or
suitably rated aircrafl cables to sus-pend and
aim the system.
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 (appro.ximately 90" cir¬
cular coverage patterns for each) to create a
.special system type—the constant-directiv¬
ity system. At higher frequencies the hori¬
zontal coverage pattern remains constant and
the vertical pattern smoothly transitions to a
40° angle above 4,000 Hz. Response within
the 60° X 40° rated coverage angle is uni¬
form. which means dependable audience
coverage without hot spots or dead zones at
certain frequencies. The 60° x 40° disper¬
sion characteristic also helps avoid early re¬
flections from nearby floor-or side-wall sur¬
faces which could degrade intelligibility.
The controlled directivity of the high- and
low-fiequency transducers also eliminates
response irregularities caused by diffraction
off nearby enclosure edges and, in combina¬
tion with an essentially flat on-axis frequency
response, produces a total acoustic power
output that is uniform with frequency.
Enclosure Construction
A combination of dado-cut joints, tough ad¬
hesives and proper bracing ensures a soni-
cally dead enclosure free from panel reso¬
nances. The flying hardware is preinstalled
in the TI5i. The exterior of the T15i is cov¬
ered w'ith a white, textured paint that is
palntable if the installer desires.
Rotating the High-Frequency Horn
The T15i high-frequency horn may be eas¬
ily rotated about its major axis, providing
coverage independent of enclosure orienta¬
tion. First remove the enclosure grille, then
the horn. Both are affixed with #2 Phillips-
head screws. Rotate the horn 90° about its
axis and reinstall the components.
Connections
Power connection to the T15i is made
through Neutrik Speakon* connectors. Both
connectors are wired in parallel. Pins 1 -r/l-
is wired to the system. Pins 2+/2- in each
connector are linked together allowing cus¬
tom wiring schemes.
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 respon.se shown in Figure 1.
The TlSi's axial frequency response was
measured in Electro-Voice's large ancchoic
chamber at a distance of 10 feet with a swept
sine-wave input of 4 volts. Figure 1 has been
averaged and corrected for 1 watt/1 meter.
Directisity
A unique feature of the T15i is the con¬
stant-directivity dispersion provided by
the 60°
X
40° horn. The polar response of
the system at selected one-third-octave
bandwidths is shown in Figure S. These
polar responses were measured in an
ancchoic environment at 10 feet using one-
third-octave pink-noise inputs. The frequen¬
cies selected are fully representative of the
polar response of the system. Beam width of
the system utilizing the complete one-third-
octave polar data is shown in Figure 6. R^
and directivity index (D^) are plotted in Fig¬
ure 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 Rat¬
ing Full Range (ANSl/EIA RS-426-A 1980)
uses a noise spectrum which mimics typical
music and tests the thermal and mechanical
capabilities of the components. Electro-Voice
will support relevant additional standards as
and when they become available. Extreme,
in-house power tests, which push the per¬
formance boundaries of the w'oofers, are also
performed and passed to ensure years of
trouble-free service.
Specifically, the T15i passes ANSI/EIA RS-426-A
1980 with the followii^ \'alucs:
R,.^ = 5.98 ohms (1.15 x R,,)
Pt,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 SI5, 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
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