Electro-Voice S15M Specfications

S15M

Floor Monitor

• PRO™ circuit provides HF driver

protection

• Constant-directivity 80° x 55° horn

• Usable monitor angles of 50° and 65°

• 250-watt long-term rms power

capacity

• Roadworthy enclosure with metal

corners, a metal grille and a
durable black carpet finish

• Dual 1/4-inch phone jack or dual

Neutrik Speakon

1

See Connections section

®

inputs

1

Description

The Electro-V oice S15M is a 250-watt, two­way, high-efficiency, constant-directivity
stage floor monitor system, featuring a
vented, direct-radiating woofer section.
Pos sible system orientations are 50°, 65°,
and perpendicular to the floor. It combines
professional-quality Electro-Voice compo­nents arranged in a vertical array with an
unusually durable, lightweight enclosure.
The result is wide-range accurate sound re­production with transparent highs and ex­tended bass response.

The high-frequency section of the S15M uti­lizes an 80° x 55° constant-directivity horn
driven by a one-inch throat, wide-bandwidth,
titanium-diaphragm driver. The DH2010A
high-frequency compression driver uses a
unique, convex-drive Time Path
plug structure (U.S. Patent #4,525,604) for
smooth and extended high-frequency perfor­mance. The voice coil is coupled to the dia­phragm with EV’s exclusive Resonant
Drive™ Technology. This increases and
smooths the high-frequency response and re­duces the amount of internal equalization
required for flat frequency response.
Driver output extends to 20,000 Hz.

A self-resetting high-frequency protection

™

phasing

circuit, EV’s PRO™ circuit, is included with
the S15M to prevent against accidental over­drive and improve system reliability. If the
input power to the high-frequency driver
exceeds the nominal rating, the protection
circuit is activated and reduces the power
delivered to the driver by 6 dB. The system
will remain in this mode of operation until
the input power is reduced to a safe level.

The bass section of the S15M is designed
using Thiele-Small parameters for solid per­formance to 77 Hz. The 381-mm (15-in.)
SG15 woofer used is a specially designed
unit featuring an extended-length voice coil
and high-temperature construction materials.
The system combines professional-quality
components arranged in an unusually durable
Thiele-Small-aligned vented enclosure. The
result is clear and articulate, high-quality
sound.

Speaker Protection

The S15M, like all other vented systems,
experiences rapidly increasing cone excur­sion below the box-tuning frequency, while
the acoustic output decreases rapidly. There­fore, to protect the S15M and maximize the
power output of the system, it is necessary
to insert an active 45- to 80-Hz high-pass
filter into the circuit. The filter should have

a slope of at least 12 dB per octave. Such
subpassband filters are found in many cross­overs and equalizers manufactured by
Electro-V oice, as well as other commercially
available equipment.

Enclosure Construction

The S15M enclosure is constructed of Road­W ood™, a structural material that combines
the strength of high-quality plywood with the
density and acoustic damping of particle
board without brittleness. Road-Wood™
uses the same principle of crossbanding ve­neers, as in plywood, in order to achieve its
very high rigidity. A tough liquid-phenolic
resin is blended with long, narrow strands
of hardwood. Alternate layers are perpen­dicularly bonded under intense heat and
pressure to form panels of superior unifor­mity. Unlike many grades of plywood,
Road-Wood™ is dimensionally stable,
water resistant and free from voids.

A combination of dado-cut joints and tough
adhesives ensure a sonically dead enclosure
free from panel resonances.

The densely woven, industrial-grade, abuse­resistant carpeting provides a finish that is
both attractive and highly durable. Heavy­duty metal corner protectors, firmly secured
rubber feet, recessed handles and a protec-

S15M Floor Monitor

tive metal grille complete the picture and
ensure that the S15M speaker system is ide­ally suited to a long and reliable life on the
road.

Frequency Response

The combination of a 15-inch woofer, wide­bandwidth 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

S15M Floor Monitor

(10 feet), using a 4-volt swept sine-wave in­put in an anechoic chamber. No external
equalization was used. Figure 1 has been
averaged and corrected for 1 watt at 1 meter.

Connections

The S15M is equipped with two parallel
1/4-inch phone jacks. (The S15M-E has two
parallel Neutrik Speakon

®

NL4MP connec­tors.) 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 com­ponent 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 sys­tem type — the constant-directivity system.
At higher frequencies the vertical coverage
pattern remains constant and the horizontal
pattern smoothly transitions to a 55° angle
above 5,000 Hz. Response within the 80° x 55°
rated coverage angle is uniform, which
means dependable coverage without “hot
spots” or dead zones at certain frequencies.
The 80° x 55° dispersion characteristic also
helps avoid early reflections from nearby
surfaces which could degrade performance.
The controlled directivity of the high- and
low-frequency transducers 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 S15M is the con­stant-directivity dispersion provided by the

80° x 55° 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-octave pink-noise inputs. The fre­quencies selected are fully representative of
the polar response of the system. Beamwidth
of the system utilizing the complete one­third-octave polar data is shown in Figure 6.
Directivity factor, R
D

, are plotted in Figure 7.

i

and directivity index,

,

Power-Handling Capacity

Electro-Voice components and systems are
manufactured to exacting standards, ensur­ing 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
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 performance boundaries of
the woofers, are also performed and passed
to ensure years of trouble-free service.

Specifically, the S15M passes ANSI/EIA
RS-426-A 1980 with the following values:

R

= 5.98 ohms (1.15 x RE)

SR

P

= 250 watts

E(MAX)

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 volt­age amount. For the S15M, a 77.33-volt­peak-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 accurately, without clipping, the
woofer will also perform accurately and re­liably, even at these levels.

Amplifier Power Recommendations

As noted in the Power-Handling Capacity
section, above, the S15M has a random­noise power capacity of 250 watts long­term (1,000-watts peak) per ANSI/EIA RS­426-A 1980. The following guidelines will
help relate this to an appropriate power am­plifier output rating.

1. To use the S15M 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 rat­ing of the speaker system. For the S15M
this is 500 to 1,000 watts.

The caution cannot be made strongly
enough, however, that this arrangement
is only for experts or those who can disci­pline themselves against “pushing” the
system for ever-higher sound levels and
who can avoid “accidents” 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” rec­ommendation, is 1.0 to 1.4 times the
long-term average noise power rating
of the speaker. For the S15M this is
250 to 350 watts.

3. T o 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 S15M this
is 125 to 175 watts.

Request P.A. Bible Addition No. Two
(“Power-Handling Capacity”) for more back­ground on these recommendations.

Service

In the unlikely event the S15M requires
ser vice, the woofer and driver can both be
replaced or serviced from the front. A service
data sheet is available from Electro-Voice.

Architects’ and Engineers’
Specifications

The loudspeaker shall be a compact vented­box type. The low frequencies shall be
reproduced with one 250-watt (ANSI/EIA