DESCRIPTION
The DTH
®
118b is a low-
frequency, folded-horn enclosure
designed to augment bass rein-
forcement for a full-range system.
Its folded-horn design combines
efficiency and low-frequency
bandwidth into a compact, yet very
powerful, bass enclosure.
The DTH 118b uses one 18"
1888-8 HP Black Widow
®
woofer in
the compression chamber of the
horn. The amount of compression
both from the rear of the woofer
cone and into the slot-loaded horn
throat effectively raises the imped-
ance enough to rate the system at
8 ohms .
The cabinet is constructed of
7-ply, 3/4" high-density plywood
with a black polyurethane coating.
Recessed handles on each side
and rear casters aid in convenient
transport. Feet on the side as
well as bottom allow flexibility in
stacking other mid- and high-
frequency enclosures using the
DTH 118b as a stable base.
Rear panel connections are
designed to allow a simple
four-conductor input for the DTH
118b alone, or eight-conductor
input with a four-conductor output
for bi-amping to other systems. For
example, if an eight-conductor
cable is used, then two pair can be
parallelled into a four conductor for
high current capacity, and drive the
DTH 118b from its low-frequency
amplifier; while the other four can
be configured as bi-amp output for
an upper frequency two-way
system.
PERFORMANCE
OPTIMIZATION
The DTH 118b can be placed
relative to stage, floor and/or wall
surfaces in a variety of ways to
extend its already impressive low
frequency performance. Using
existing surfaces in this way creates
a virtual coupling of the horn to
those surfaces that guide the
expansion of the sound wavefronts
radiated by the mouth of the horn,
which can result in as much as a
6 dB increase in efficiency at
frequencies below 50 Hz.
Placement suggestions include
freestanding the DTH 118b on its
bottom or side on a floor or stage
with at least four feet of clear floor
space in front of the horn mouth.
Another novel placement
approach is to stand the horn
upright and then face the horn
mouth into a room corner at an
angle of 45
°
, 15 inches from the
walls. Thus, the room itself
becomes an extension of the horn
mouth. This placement into the
room corner can be further
enhanced by using a triangular
3/4" or thicker plywood “cover” (not
supplied by Peavey) that serves the
purpose of sealing the top of the
DTH 118b to the walls, much like
the floor seals the bottom to the
same walls. This cover need not
extend farther into the room than
the rear of the DTH 118b, and if
constructed appropriately, can also
be used to support the mid- and
high-frequency enclosures of a full-
range system.
FREQUENCY RESPONSE
This measurement is useful in
determining how accurately a given
enclosure reproduces an input
signal. The frequency response of
the DTH 118b is measured at
1 meter using a 2.8-volt swept sine
input. As shown in Figure 1, the
DTH 118b provides a smooth
frequency response below 60 Hz
and up to the crossover frequency.
Low frequencies can be extended
downward by using the optional
Peavey DTH 118b Sub Processor.
The DTH 118b Sub Processor
specifically provides all the neces-
sary elements to optimize the
performance of the DTH 118b and
the earlier DTH 118 folded horn
bass cabinets. Subsonic filtering is
included, which allows maximum
power handling at low frequencies.
Moderate Q filtering maximizes the
output of the DTH 118b near horn
cutoff. Additionally, optimized
highpass outputs are provided for
the DTH 4000 series speakers.
An anechoic low frequency
response curve of the DTH 118b
after processing is shown in Figure
2. The amount of low frequency
extension when the DTH 118b is
used in a room will be better than
shown in the figure. This is due to
the room placement of the cabinet
as discussed in the previous
section.
POWER HANDLING
There are many different
approaches to power handling
ratings. Peavey rates this speaker
system’s power handling using a
modified form of the AES Standard
2-1984. Utilizing audio band (20 Hz
to 20 kHz) pink noise with peaks
over four times the RMS level, this
strenuous test signal assures the
user that every portion of this
system can withstand today’s high-
technology music. The test signal
contains large amounts of very low
frequency energy, effectively
simulating the frequency content of
live music situations. The full
measure of high frequencies in the
test signal allow for exposure of the
speaker system to synthesized
tones that may extend beyond
audibility. This rating is contingent
upon having a minimum 3 dB of
amplifier headroom available.
ARCHITECTURAL
AND ENGINEERING
SPECIFICATIONS
The loudspeaker system shall
have an operating bandwidth of
58 Hz to 300 Hz. The output level
shall be 104 dB when measured at
a distance of one meter with
an input of one watt. The nominal
impedance shall be 8 ohms. The
continuous power handling shall be
400 watts, with maximum program
power of 800 watts and minimum
amplifier headroom of 3 dB. The
outside dimensions shall be 26
inches wide by 40 1/4 inches high
by 31 3/4 inches deep. The weight
shall be 172 lbs. The loudspeaker
system shall be a Peavey model
DTH 118b.
2
