ment applications in permanently installed
sound systems. Typical venues include
cinemas, auditoriums, theaters, performing arts
centers, night clubs and concert halls. The
TL606DW is designed to serve as the primary
low-frequency section in extended-response
two-way systems with excellent bass perfor-
mance to 40 Hz and controlled dispersion to
800 Hza typical crossover frequency of two-
way systems. When used with the dedicated
XEQ-504 crossover/equalizer, the TL606DW
can be combined with appropriate Electro-
Voice TransPlanarTM horns and DH series driv-
ers to form a passive two-way system of
unprecedented wide-range response and lin-
earity. However, to extract the maximum per-
formance from the TL606DW, a multiamp con-
figuration using the XEQ-2 or XEQ-3 cross-
over/equalizer units is recommended so that
full rated power may be applied to the low-
frequency system. With a half-power point of
40 Hz, the TL606DW can also serve as the
subwoofer component in large, multiway sys-
tems.
FREQUENCY RESPONSE
The TL606DW frequency response was mea-
sured in an anechoic environment at 10 feet on
axis with swept one-third-octave pink noise.
The frequency response curve for the TL606DW
are shown in Figure 1.
DIRECTIVITY
The TL606DW directional characteristics were
measured by running a set of polar-response
curves in EVs large, anechoic chamber. The
test signal was one-third-octave pseudo-ran-
dom pink noise centered at the frequencies
indicated in Figure 2. The curves show horizon-
tal (side-to-side) dispersion when the
enclosures long axis is vertical. The vertical
(up-and-down) polar responses are also shown.
Additional typical information is provided in
Figure 3 which shows 6-dB-down beamwidth
versus frequency. Figure 4 shows the directiv-
ity factor and directivity index versus frequency.
DISTORTION
Following AES (Audio Engineering Society)
recommended practice, plots of second- and
third-order harmonic distortion for 0.1 rated
input power are shown in Figure 6. Figure 5
shows distortion at 0.01 rated input power.
POWER HANDLING CAPACITY
To our knowledge, Electro-Voice was the first
U.S. manufacturer to develop and publish a
power test closely related to real-life condi-
tions. First, we use a random noise input signal
because it contains many frequencies simulta-
neously, just like real voice or instrument pro-
gram. Second, our signal contains more en-
ergy at extremely high and low frequencies
than typical actual program, adding an extra
measure of reliability. Third, the test signal
includes not only the overall long-term aver-
age or continuous levelwhich our ears
interpret as loudnessbut also short-duration
peaks which are many times higher than the
average, just like actual program. The long-
term average level stresses the speaker ther-
mally (heat). The instantaneous peaks test
mechanical reliability (cone and diaphragm
excursion). Note that the sine-wave test sig-
nals sometimes used have a much less de-
manding peak value relative to their average
level. In actual use, long-term average levels
exist from several seconds on up, but we apply
the long-term average for several hours, add-
ing another extra measure of reliability.
Specifically, the TL606DW is designed to with-
stand the power test described in EIA Standard
RS-426A. The EIA test spectrum is applied for
eight hours. To obtain the spectrum, the output
of a white noise generator (white noise is a
particular type of random noise with equal
energy per bandwidth in Hz) is fed to a shaping
filter with 6-dB-per-octave slopes below 40 Hz
and above 318 Hz. When measured with the
usual constant-percentage analyzer (one-third-
octave), this shaping filter produces a spec-
trum whose 3-dB-down points are at 100 Hz
and 1,200 Hz with a 3-dB-per-octave slope
above 1,200 Hz. This shaped signal is sent to
the power amplifier with the continuous power
set at 800 watts into the 3.5 ohms EIA equiva-
lent impedance for the TL606DW (52.9 volts
true rms).
Amplifier clipping sets instantaneous peaks at
6 dB above the continuous power, or 3,200
watts peak (105 volts peak). This procedure
provides a rigorous test of both thermal and
mechanical failure modes.
SUBPASSBAND SPEAKER PROTECTION
Below the enclosure tuning frequency, cone
excursion increases rapidly. Since acoustic
output is also failing rapidly, there is no utility in
driving the system with signals much below the
tuning frequency. While such signals may be in
the program material, they are often extrane-
oussuch as from record-surface irregulari-
ties (strong 5- to 25-Hz components) or a
dropped microphone. The DL15W very-low-
frequency reproducer is ruggedly designed and
has a high maximum excursion before damage
(±0.5 inch). However, high-output subwoofer
systems such as the TL606DW should be
protected by a high-pass filter with a 3-dB-
down corner frequency of about 0.8 the enclo-
sure tuning frequency. Below the corner fre-
quency, a roll-off of 12-dB-per-octave is usually
sufficient.
Without protection, subpassband signals may
bottom the DL15Ws. Damage will probably
result, especially after repeated occurrences.
Even if bottoming does not occur, the subpass-
band signals waste amplifier power and modu-
late (distort) the frequencies which are within
the TL606DWs operating range. Much woofer
distortion or muddy bass can be attributed to
lack of subpassband protection.
The Electro-Voice EX-24, XEQ-2 and XEQ-3
electronic crossover/equalizers provide sub-
passband protection. The 3-dB-down points
are 30 Hz (EX-24 and XEQ-2) and 16 Hz or 32
Hz (XEQ-3).
Other high-pass filters are available, and one-
third-octave equalizers can also be effective at
providing the required protection.
USE IN MULTIPLES
TL606DWs may be used in multiples to in-
crease acoustic output. In the following discus-
sion, it is assumed that all speaker cones are
operating in unison (in phase) when a common
signal is applied. A 6-dB increase in maximum
acoustic output results when two speakers are
located side by side. For operation at very low
frequencies, the woofer cones mutually
couple, acting as one speaker with cone area
and power-handling capacity twice that of a
single speaker. The doubling of cone area
doubles efficiency, providing a 3-dB increase in
sound pressure level. The second 3 dB comes
from the doubling of power capacity.
Mutual coupling occurs when the frequency is
such that the center-to-center distance be-
tween the two speaker cones is less than about
one-quarter wavelength. For a given center-to-
center distance, the highest frequency at which
mutual coupling will occur can be calculated
from the following formula:
3,000
f = ,
Dmax
where Dmax is the distance in inches and f is
frequency in Hz. When Dmax is greater than
one-quarter wavelength, as would occur if
two TL606DWs were widely spaced, the
level increase tends to be limited to the 3-dB
power-handling increase.
More than two TL606DWs can be used for
increased output. In general, maximum acous-
tic power output ability increases as the square
of the number of mutually coupled cones. For
example, four cones would provide 42 or 16
times the power output of a single cone, an
increase of 12 dB (10 log10 16 = 12 dB). Note
that the associated increased efficiency
(2.9% X 4 = 12%) approaches that of a fully
horn-loaded design, but in a much smaller
enclosure.
SYSTEM POSITIONING
Subwoofer systems such as the TL606DW are
often located on the floor. This is both conve-
nient and can provide a desired high acoustic
impact when the speakers are, for example,
placed near the periphery of a dance floor. In
other installations, such as a theater or audito-
rium, the audible location of a subwoofer oper-
ating at a sufficiently low crossover frequency
(below about 125 Hz) will not be particularly
evident. The other system elements operating
above the subwoofer range can be positioned
for the desired locational cues and uniform
audience coverage.
Floor location provides the acoustic half-space
environment associated with the 5.8% system
efficiency noted in the Specifications section.
Location at a floor-wall junction (acoustic quar-
ter space) doubles efficiency (a 3-dB increase
in sound pressure level) and tends to promote
the full excitation of more room modes, or
standing waves, important in achieving maxi-
mum overall bass output in the room. Corner
placement (acoustic eighth space) doubles
efficiency again and guarantees excitation of
all room modes. (Such placement for maxi-
mum efficiency and room-mode excitation is
not necessary and may not be desirable or
possible for a variety of reasons, including
aesthetics and building design.)