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Double 18-inch SubScoop Low-Frequency Speaker
System
Features:
Subwoofer for augmenting the low-frequency performance of the
MTH-1 mid/high module, and other stage systems
Two EVX-180B woofers for reliable, extended low-frequency
output
1,200-watt long-term power capacity
Horn loading provides increased throw
Rugged, road-ready cabinet; metal grill; black carpet finish
Neutrik Speakon inputs
Rear casters for improved portability
The Electro-Voice MTL-1X is an 1,200-watt subwoofer
loudspeaker system which combines the attributes of both
horn-loaded and vented box designs.
The MTL-1X design utilizes the unique double SubScoop ™
cabinet construction with two EVX-180B woofers, as used in
X-Array TM concert systems. The design behaves like a horn
over much of its range, but without the time delay and weight
problems usually associated with conven-tional designs.
Vented-box principles take over for the lowest octave and
assist in pro-ducing exceptionally high levels of clean,
punchy bass from a modest-sized box. The reverse woofer
orientation has been used to optimize the rear chamber volume
and de-crease the horn flare rate for extended low-end
performance.
When used with the MTH-1 mid/high module, the MTL-1X provides
high-output sound reinforcement for a club, large hall, or
out-door events in a compact package which can be moved easily
by a two-person crew. Although the MTL-1X was designed for use
with the MTH-1 system, it may be used to augment the bass
performance of any Electro-Voice stage system.
Use in Multiples
The MTL-1X may be used in multiples to increase acoustic
output. When two speaker systems are placed side by side, the
woofer cones "mutually couple," causing the two
systems to act as one system with twice the effective cone
area at very-low frequencies, giving an additional 3-dB
increase in maxi-mum acoustic output. Mutual coupling will
occur when the frequency is such that the center-to-center
distance between the two woofer manifolds is less than about
one-half wavelength.
Crossover
To optimize performance, the MTL-1X should be used in
conjunction with an ac-tive crossover with a minimum slope of
12-dB per octave and a crossover fre-quency in the range of
100 Hz to 160 Hz. Due to the high efficiency of the MTL-1X,
less amplifier input is needed to achieve a given sound output
level.
Amplifier Power Recommendations
As noted in the Power-Handling Capacity section, above, the
MTL-1X has a random-noise power capacity of 1,200-watts long
term (4,800 watts peak) per EIA RS-426-A 1980. The following
guidelines will help relate this to an appropriate power
amplifier output rating.
1. To use the MTL-1X to full capacity, skilled experts in
sound system installa-tion and operation will obtain the best
re-sults if the power amplifier is 2.0 to 4.0 times the
long-term average noise power rating of the speaker system.
For the MTL-1X, this is 1,200 to 4,800 watts.
The caution cannot be made strongly enough, however, that this
arrangement is only for experts or those who can disci-pline
themselves against "pushing" the system for
ever-higher sound levels and who can avoid
"accidents" such as cata-strophic feedback or
dropped micro-phones.
2. A more conservative, "normal" amplifier size,
which will produce audible results nearly equal to those of
the "expert" rec-ommendation, is 1.0 to 1.4 times
the long-term average noise power rating of the speaker. For
the MTL-1X, this is 1,200 to 1,680 watts.
3. To 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 MTL-1X, this is 600 to 840 watts.
Request P.A. Bible Addition No. Two ("Power- Handling
Capacity") for more background on these recommendations.
Speaker Protection
When in the vented-box mode, the SubScoop ™ , like all other
vented systems, experiences rapidly increasing cone excur-sion
below the box-tuning frequency. The acoustic output is also
decreasing rapidly;therefore, it is sensible to protect the
MTL-1X and maximize the power output of the subwoofer by
inserting an active 32-Hz high-pass filter with a slope of at
least 12 dB per octave into the circuit. Such subpassband
filters are found in many commercially available crossovers
and equalizers including items manufac-tured by Electro-Voice.
Frequency Response:
The MTL-1X’s axial frequency response was measured in
Electro-Voice’s large anechoic chamber at a distance of 3
meters (10 feet) with a swept sine-wave input. Figure 1 has
been averaged and corrected for 1 watt at 1 meter.
Enclosure Construction
Intended to be used as a portable speaker system, the MTL-1X
is ruggedly constructed of 3/4-inch, void-free plywood. All
joints are dado cut, and the cabinet is finished with a
densely-woven, abuse-resistant carpet that is both attractive
and highly durable. A full-length steel grille protects the
woofer from damage. Large, heavy-duty metal corner pro-tectors,
firmly secured rubber feet, rugged casters, and recessed
handles complete the picture, ensuring that the MTL-1X speaker
system is ideally suited for a long and reli-able life on the
road.
MTL-1X Connections
The MTL-1X is equipped with two paral-leled Neutrik Speakon ®
NL4MPR-V connec-tors, selected for their ability to reliably
de-liver to the speaker components the high cur- rents
delivered by high-wattage power am-plifiers. An NL4FC mating
connector is sup-plied. The NL4FC is a four-pin connector, and
Figure 4 shows how theusual two-con-ductor speaker cable
should be wired to pins 1+ and 1– of the connector. Two
typical con-nectors at the power amplifier end of the cable
are shown: banana and 1/4-inch phone plugs. (The banana plug
provides the more reliable connection.) If it is desired to
use the MTL-1X with one amplifier for each woofer, remove the
input panel and follow the instructions. In this
con-figuration, the upper woofer is fed through pins 1+ and
1–, and the lower woofer through pins 2+ and 2–.
Specifications:
Typical Axial Frequency Response, (swept sine wave,
4 volts at 10 feet, anechoic environment, normalized for 1
watt,
1 meter into woofer: 50-160 Hz
Low-Frequency 3-dB-Down Point: 50 Hz
Usable Low-Frequency Limit (10-dB-down point): 45 Hz
Half-Space Reference Efficiency: 6.1%
Long-Term Average Power-Handling Capacity: 1200 watts
Sensitivity (SPL at 1 watt, 1 meter input,
anechoic environment, swept sine wave): 101 dB
Dispersion Angle Included by 6-dB-Down
Points on Polar Responses:
Essentially omnidirectional
Distortion, 0.1 Full Power Input into
Mid/Bass,
Second Harmonic, 100 Hz
0.3%
Third Harmonic, 100 Hz: 0.4%
Transducer Complement: Two EVX-180B's
Box Tuning Frequency: 38 Hz
Recommended Crossover Frequency: 160 Hz
Crossover Slopes, suggested: 24 dB per octave
Impedance,
Nominal: 4 ohms
Minimum: 3 ohms
Input Connections: Two paralleled Neutrik Speakon connectors
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