Description
The Electro-Voice S
b
121 bass module is a
compact, low-frequency enhancement sys-
tem designed for sound reinforcement.
Through the extensive use of computer-aided
design and modeling, Electro-Voice engi-
neers have developed a state-of-the-art por-
table system that combines the advantages
of a long-throw 12-inch woofer in a high-
impact polypropylene structural-foam cabi-
net that is light in weight (only 32.2 lb over-
all).
Low-Frequency Driver Description
The DL12Sx low-frequency driver was spe-
cially developed for the S
b
121. Its deep-
frame geometry provides high-peak excur-
sion ability. At the heart of this driver, is a
magnetic structure optimized to yield the best
possible Thiele-Small parameters to match
the tuned enclosure.
The woofer features beryllium copper lead
wires, a low-mass edge-wound voice coil and
high-temperature materials. The part of the
magnet structure adjacent to the coil is insu-
lated using the exclusive EV PROTEF
TM
process (U.S. Patent #4,547,632). The coil
is driven by a massive, 16-lb magnet struc-
ture.
Enclosure Description
The enclosure is constructed of high-impact
polypropylene structural foam. It provides a
stiff and extremely durable enclosure.
Molded into the cabinet are an integral
carrying handle and a stand socket for
mounting on 1
3
/
8
-inch stands such as the
100BK. Rubber feet that are attached to the
bottom of the cabinet and the mating sock-
ets that are molded into the top provide a
means of stacking systems. Four hanging
inserts are also provided (four metric M8 x
1.25).
Xp200A Electronic System Controller
The optional Xp200A electronic system con-
troller complements the characteristics of the
S
b
121. Its mono-summed subwoofer outputs
provide crossover and infrasonic protection
(see Crossover and Subpassband Protection
sections). Its 24-db-per-octave filters roll-off
response below 37 Hz and above 100 Hz.
The Xp200A also includes a special low-fre-
quency profile circuit that enhances the per-
formance of the S
b
121. The amount of en-
hancement can be adjusted to suit the user’s
personal preference.
Crossover
The S
b
121 should be used in conjunction
with an active crossover to roll-off response
above 100-200 Hz, so that bass enhancement
does not “muddy up” vocals or call atten-
tion to the physical location of the S
b
121.
(The closer the roll-off point is to 100 Hz,
the least the overall sound quality will be
affected by the enhancement of the bass
module.) The roll-off rate should be a mini-
mum of 12-dB per octave.
The optional Xp200A electronic controller
provides a 24-dB-per-octave roll-off above
134 Hz.
Subpassband Speaker Protection
The S
b
121, like all other vented systems,
experiences rapidly increasing cone excur-
sion below the box-tuning frequency (60 Hz
for the S
b
121). Acoustic output is also de-
creasing rapidly. Therefore, it is sensible to
protect the S
b
121 and maximize its undis-
torted output by inserting an active high-pass
filter at a corner frequency somewhat below
box tuning. The roll-off rate should be at least
12-dB per octave. At this minimum rate, a
corner frequency of about 0.8 the box tun-
ing frequency (48 Hz for the S
b
121) is ap-
Sb
121
300-Watts
Nonpowered
Bass
Module
• Lightweight (32 lb) and compact
• Very durable structural-foam
enclosure with integral handle
• Stand mountable and arrayable
• 300-watts continuous power
handling (1,200-watts short term)
for
high
output
• DL12Sx 12-inch woofer with Kevlar
®
Reinforced cone
• Neutrik Speakon
®
high-current
connectors
(
1
/
4
-in. phone jacks
also
provided)
• Four molded-in attachment points
(metric M8 x 1.25) for secure
suspension
