Electro-Voice MTL-4 User's Manual
Contents
1. a Oulton company 2 LL i 1 HEAT FIGURE 1 Axial Frequency Response 1 Watt 1 Meter Model MTL 4 Manifold Technology Low Frequency Sound Reinforcement System Input Connections Cannon EP 4 14 Enclosure Materials 14 ply Baltic birch plywood Hanging Two point flying system optiona Dimensions Height 91 4 cm 36 0 in Width 91 4 cm 36 0 in Depth 76 2 30 0 Net Weight 119 kg 263 Ib Shipping Weight 134 kg 297 Ib DESCRIPTION The Electro Voice MTL 4 Manifold Technology low frequency loudspeaker system was designed for high level concert sound reinforcement in touring sound and permanent installation applications The MTL 4 is a vented box design comprised of four OL18W woofers each facing into a manifold chamber at the center of the cabinet This manifolding technique results in increased acoustic loading yielding increased low frequency efficiency and reduced distortion over conventional direct radiating designs in a remarkably small enclosure The MTL 4 is typically 2 3 dB 1 Patent pending 120 FUNDAMENTAL I TAN TTT k ATL 2ra HARMON CONT A CNTR CT Pa ETC T COONAN COON ATT Sg HARMONIC FIGURE 2 MTL 4 Polar Response icicle a a 7 octave 4 volts 10 feet FIGURE 5 MTL 4 Harmonic Distortion 0 1 Rated Power Input 160 watts 10 Feet o2. com dcarlson Q qtm net Altec Lansing DDA Dynacord Electro Voice Klark Teknik Merlin Telex Vega
3. not allow the exclusion or limitation of incidental or consequential damages so the above exclusion may not apply to you Repair by other than Electro Voice or its authorized service agencies will void this guarantee A list of authorized warranty service agencies is available from Electro Voice Inc 600 Cecil Street Buchanan MI 49107 AC 616 695 6831 Electro Voice Inc 3810 148th Avenue N E Redmond WA 98052 206 881 9555 and or Electro Voice West 8234 Doe Avenue Visalia CA 93291 AC 209 651 7777 This warranty gives you specific legal rights and you may also have other rights which vary from state to state Service and repair address for this product Electro Voice Inc 600 Cecil Street Buchanan Michigan 49107 Specifications subject to change without notice ELECTRO VOICE 600 Cecil Street Buchanan Michigan 49107 MANUFACTURING PLANTS AT BUCHANAN MI IE NEWPORT TN Ill SEVIERVILLE TN REDMOND WA E GANANOQUE ONT Electro Voice Inc 1986 B Litho In USA Part Number 530676 622 Fax Transmission To Joe Martin Fax No 317 770 1823 Number of Pages 1 From DE Carlson Date October 15 1999 Subject MTL 4 Rewiring cc ORIGINAL C 20 division of Telex Communications Acoustic Engineering R amp D Center 128 East Front Street Buchanan MI 49107 USA Tel 616 695 6831 800 234 6831 Fax 616 695 9626 e mail de carlson telex
4. 1600 w the maximum recom mended cone excursion of the DL18W woofer is not exceeded for any frequency above the box tuning frequency of 37 Hz Therefore the only limitation of the MTL 4 low frequency system in the recommended frequency range is the thermal input power Cone excursion increases substantially below box tuning and operation is not recom mended for frequencies below 37 Hz see Subpassband Speaker Protection section USE MULTIPLES MTL 4 s may be used in multiples to increase acoustic output In the following discussion it is assumed that all speaker cones are operating in unison in phase when a common signa is applied A 6 dB increase in maximum acoustic output results when two speaker systems are located side by side For operation at very low fre quencies the woofer cones mutually couple acting as one system with cone area and power handling capacity twice that of a single system 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 between the two woofer manifolds is less than about one half wavelength When the distance is greater than one half wavelength as would occur if two MTL 4 s were widely spaced the level increase tends to be limited to the 3 dB power handling increase SYSTEM POSITIONING Subwoofer system
5. SPECIFICATIONS Frequency Response 10 Feet on Axis Swept One Third Octave Pink Noise Anechoic Environment see Figure 1 40 225 Hz Low Frequency 3 dB Down Point 40 Hz Usable Low Frequency Limit 10 dB down point 32 Hz Half Space Reference Efficiency 12 5 Long Term Average Power Handling Capacity per EIA Standard RS 426A see Power Handling Capacity section 1600 watts Short Term Power Handling Capacity 10 milliseconds 6400 watts Maximum Long Term Average Midband Acoustic Output 200 watts Sound Pressure Level at 1 Meter Indicated Input Power Anechoic Environ ment Band Limited Pink Noise Signal 50 200 Hz 1 Watt 102 dB 1600 Watts 134 dB 6400 Watts 140 dB Dispersion Angle Included by 6 dB Down Points on Polar Responses Indicated One Third Octave Bands of Pink Noise 80 160 Hz Horizontal and Vertical see Figure 3 177997 Directivity Factor Median over 80 160 Hz Range see Figure 4 2 84 Directivity Index Median over 80 160 Hz Range see Figure 4 4 5 Distortion 0 1 Full Power Input see Figure 5 Second Harmonic 50 Hz 0 6 100 Hz 0 5 Third Harmonic 50 Hz 0 6 100 Hz 0 2 Distortion Full Power Input see Figure 6 Second Harmonic 50 Hz 1 4 100 Hz 1 8 Third Harmonic 50 Hz 2 0 100 Hz 0 8 Transducer Complement Four DL18W Box Tuning Frequency 37 Hz Impedance Nominal Two 4 ohm loads Minimum Two 4 ohm loads Eleciro Voice
6. ause the MTL 4 is essentially symmetrical only a single polar response curve is shown Additional typical information is provided in Figure 3 which shows 6 dB down beamwidth versus frequency Figure 4 shows the directivity 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 5 Figure 6 shows distortion at full 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 simultaneously just like real voice or instru ment program Second our signa contains more energy at extremely high and low fre quencies than typical actual program adding an extra measure of reliability Third the test signal includes not only the overall long term average or continuous level which our ears interpret as loudness but also short duration peaks which are many times higher than the average just like actual program The long term average level stresses the speaker thermally heat The in stantaneous peaks test mechanical reliability cone and diaphragm excursion Note that the sine wave test signals sometimes used have a much less demanding peak value relative
7. concert system CONNECTION The MTL 4 has four 8 ohm loudspeakers wired in paralleled pairs resulting in two 4 ohm loads accessed by a 4 pin connector at the back of the enclosure The connector used is the Cannon EP 4 14 male and the pin out arrangement and wiring diagram is shown in Figure 7 The mating connector for the cable end is the Cannon 4 11 1 HANGING The MTL 4 may be ordered with an optional two point flying hardware system In addition to a time savings in setup this unique two point system permits wide range of angle adjust ments and offers maximum flexibility in array design and implementation for both the sound touring company and the sound contractor a gultan 1 company WARRANTY Limited Electro Voice Speakers and Speaker Systems excluding active electronics are guaranteed for five years from date of original purchase against malfunction due to defects in workmanship and materials If such malfunc tion occurs unit will be repaired or replaced at our option without charge for materials or labor if delivered prepaid to the proper Electro Voice service facility Unit will be returned prepaid Warranty does not extend to finish appearance items burned coils or malfunction due to abuse or operation under other than specified conditions including cone and or coil damage resulting from improperly designed enclosures nor does it extend to incidental or consequential damages Some states do
8. lle and have flying hardware and removable dolly options APPLICATIONS The MTL 4 is ideal for any professional touring or installation application requiring low frequency reproduction at high sound pressure levels with low distortion Manifold technology maximizes the acoustic output per bulk volume and frontal area of the enclosure enabling more compact systems and arrays than would be obtainable with conventional sound reinforcement enclosure designs Additionally the MTL 4 is more directional than most low frequency loudspeaker systems The dimensions of the MTL 4 were chosen for efficient truck pack and high density array design The cabinets may be stacked three high and three wide in a standard tractor trailer allowing for over 14 000 wattts of bass system to be accommodated in only three feet of truck floor length Careful attention was paid to details to provide both the tour ing company and the sound contractor with a convenient and time saving professional sound reinforcement package FREQUENCY RESPONSE The MTL 4 frequency response was measured in an anechoic environment at one meter on axis with a one watt swept one third octave pink noise input See Figure 1 DIRECTIVITY The MTL 4 directional characteristics were measured by running a set of polar response curves in EV s large anechoic chamber The test signal was one third octave pseudo random pink noise centered at the frequencies indicated in Figure 2 Bec
9. n Axis 110 100 LEVEL dB 3 5 125 Hz FUNDAMENTAL ATT Leti o A f asl PEI EE eN 100 1 9 x 209 HARMONIC 2 2 he etit nu 8 8 d w a og Pet EEEE ee ANT VAS 2 3 20 50 100 200 HARMONIC III 60 FREQUENCY IN HERTZ 4 Beamwidth vs Frequency FREQUENCY m FIGURE 6 MTL 4 Harmonic Distortion 1 0 Rated Power Input 1600 watts 10 Feet on Axis Pin 4 i 4 ohms Pin 3 LEE LLL LED E TUE Pin 2 4 ohms FREQUENCY IN HERTZ Pin 1 FIGURE 4 MTL 4 Directivity Factor and Directivity index vs Frequency E ES c e Fc 5 54 az FIGURE 7 MTL 4 Wiring Diagram more efficient than horn loaded enclosures of equivalent size in the 40 80 Hz region Additionally this radical design allows for efficient heat transfer from the loudspeakers to minimize thermal build up during extended periods of high power operation Designed to survive the rigors of the road the MTL 4 is constructed of 14 ply Baltic birch plywood and is covered with black Ozite Super TNT carpeting the most rugged in the industry For permanent installations the MTL 4 is available with a black textured paint finish Both versions feature a black nylon cloth gri
10. s such as the MTL 4 are often located on the floor This is both con venient and can provide a desired high acoustic impact when the speakers are for example placed near the periphery of a dance floor other installations such as a theatre or auditorium the audible location of a subwoofer operating at 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 12 5 system efficiency noted in the Specifications section Location at a floor wall junction acoustic quarter space doubles effi ciency 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 maximum overall bass output in the room Corner placement acoustic eighth space doubles efficiency again and guarantees excitation of all room modes Such placement for maximum efficiency and room mode excitation is not necessary and may not be desirable or possible for a variety of reasons including esthetics and practicality The MTL 4 can also be successfully operated away from any nearby acoustic boundaries particularly when multiple systems are used for increased output ability see Use in Multiples section such as in a flown
11. stem with signals much below the tuning frequency While such signals may be in the program material they are often extraneous such as from record surface irregularities strong 5 25 Hz components or a dropeed microphone The DL18W very low frequency reproducer is ruggedly designed and has a high maximum excursion before damage t 0 5 inch However high output subwoofer systems such as the MTL 4 should be protected by high pass filter with a 3 dB down corner frequency of about 0 8 the enclosure tuning frequency approximately 30 Hz Below the corner frequency a rolloff of at least 12 dB per octave should be used Without protection subpassband signals may bottom the DL18W Damage will probably result especially after repeated occurrences Even if bottoming does not occur the sub passband signals waste amplifier power and modulate distort the frequencies which are within the MTL 4 s operating range Much woofer distortion or muddy bass can be attributed to lack of subpassband protection LARGE SIGNAL PERFORMANCE Speakers have two limitations that govern their large signal or maximum output perfor mance capabilities One is the speaker s long term average power capacity related to thermal or heat destruction The second is its maximum linear cone excursion ability as expressed in the Thiele Small parameter Xmax One of the benefits of the MTL 4 manifold technology design is that with full power input
12. 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 adding another extra measure of reliability Specifically the MTL 4 is designed to withstand 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 band width 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 spectrum 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 amplifiers with continuous power set at 800 watts into each of the 3 45 ohms EIA equivalent impedance inputs 52 5 volts true RMS resulting in a total of 1600 watts of continuous power being delivered to the MTL 4 Amplifier clipping sets instantaneous peaks at 6 dB above the continuous power or 6400 watts peak 105 volts peak per input 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 falling rapidly there is no utility in driving the sy
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