Version 1.
FOREWORD Thank you for purchasing the MTD108a, MTD112b or MTD115b sound reinforcement system. This manual is intended to provide you with the information you require to install and operate your MTD loudspeaker enclosure in a wide variety of professional sound reinforcement applications. Specific information and recommendations are included regarding system design, sound design and installation.
L-ACOUSTICS MTD Manual V1.
TABLE OF CONTENTS FOREWORD..............................................................................................................................................1 MANUAL ORGANIZATION....................................................................................................................1 TABLE OF CONTENTS............................................................................................................................3 LIST OF FIGURES...............................................
6. INSTALLATION PROCEDURES .......................................................................................................51 6.1 ETR8 U-BRACKET ATTACHMENT(MTD108a) ........................................................................................... 51 6.2 ETR1, ETR2 U-BRACKET ATTACHMENT (MTD112b, MTD115b) ...............................................................52 6.3 OMNIMOUNT BRACKET ATTACHMENT (MTD112b, MTD115b) ..............................................................53 6.
Figure 24: SPL mappings for four MTD enclosures with 0.5 metre spacing. .........................................42 Figure 25: L-ACOUSTICS Subwoofer Continuous Unweighted SPL Comparison................................48 Figure 26: Illustration of subwoofer time alignment...............................................................................50 Figure 27: ETR8 U-Bracket installation procedure ................................................................................
0. INTRODUCTION Effectively covering an audience is the goal of any sound reinforcement system design. This is straightforward in small spaces where a left/right stereo configuration is suitable provided that the available power is sufficient, i.e., a stereo pair of loudspeakers is a relatively easy system to install and the results are fairly predictable.
Loudspeaker focus or aiming can be adjusted so that maximum HF energy is directed towards the farthest listening areas, therefore balancing the SPL attenuation with distance that occurs in the direct field. At closer listening positions, the off-axis attenuation at higher frequencies provides a similar tonal balance and the attenuation with distance is less.
LINE LEVEL CONTROLLERS (7) MTD108 LLCa Stereo analog line level controller for use with the MTD108a (8) LLC112b-st Stereo analog line level controller for use with the MTD112b (9) LLC115b-st Stereo analog line level controller for use with the MTD115b in passive mode (10) LLC115b-2w Mono analog line level controller for use with the MTD115b in 2-way active mode MTD RIGGING ACCESSORIES (11) ETR 8 : Adjustable U-Bracket for ceiling, wall or scaffold mounting of the MTD108a in either horizontal or vertical ori
MTD112b ETR1 MTD115b ETR2 (for MTD115b or SB115) PION1 F-LINK CABLE DO.7 F-CABLE DO7 Figure 1: MTD System Components L-ACOUSTICS MTD Manual V1.
MTD108 LLCa (front) MTD108 LLCa (rear) LLC112b-st (front) LLC112b-st (rear) L-ACOUSTICS MTD Manual V1.
LLC115b-st (front) LLC115b-st (rear) LLC115b-2w (front) LLC115b-2w (rear) Figure 2: MTD LLC Controllers L-ACOUSTICS MTD Manual V1.
1.2 MTD OVERVIEW L-ACOUSTICS MTD108a, MTD112b and MTD115b loudspeaker enclosures along with their respective analog controllers provide highly versatile, multi-purpose systems that are designed for distributed sound reinforcement. Intended for medium-scale touring, sub-hire or fixed installation, the MTD line of enclosures benefit from the economy, packaging and “plug and play” ease of use afforded by their companion LLC analog line level controllers.
1.3 MTD108a SPECIFICATIONS The MTD108a is a passive 2-way coaxial full range loudspeaker containing one 8-inch, direct radiating low frequency component and one 1-inch titanium diaphragm, neodymium magnet, compression driver. As a full range system, the frequency response is 85 - 20k Hz with less than ± 3 dB variation and the usable bandwidth is 65 – 20k Hz (-10 dB).
1.4 MTD112b SPECIFICATIONS The MTD112b is a passive, two-way, coaxial full range loudspeaker containing one direct radiating, bass reflex-loaded 12 inch low frequency transducer and one 1.4 inch exit, 3 inch voice coil diameter, titanium alloy diaphragm compression driver. As a full range system, the frequency response is 70 Hz to 14 kHz with less than ± 3 dB variation and the usable bandwidth is 55 Hz to 16 kHz (-10 dB).
1.5 MTD115b SPECIFICATIONS The MTD115b is a switch-selectable active/passive, two-way, coaxial full range loudspeaker containing one direct radiating, bass reflex-loaded 15 inch low frequency transducer and one 1.4 inch exit, 3 inch voice coil diameter, titanium alloy diaphragm compression driver. As a full range system, the frequency response is 65 Hz to 14 kHz with less than ± 3 dB variation and the usable bandwidth is 50 Hz to 16 kHz (-10 dB).
2. POWERING MTD It is important that power amplifiers with sufficient power are used to power MTD108a, MTD112b or MTD115b loudspeakers since headroom is less likely to damage loudspeaker components than clipping.
2.1 POWERING MTD108a Continuous (rms) and peak power handling ratings for the MTD108a are as follows: 45 volts rms long term (pink noise with 6 dB crest factor) 250 Watts (continuous), 1000 Watts (peak) at 8 ohms Recommended power amplifier specification for powering single and multiple MTD108a enclosures are given in Table 1.
2.2 POWERING MTD112b Continuous (rms) and peak power handling ratings for the MTD112b are as follows: 45 volts rms long term (pink noise with 6 dB crest factor) 250 Watts (continuous), 1000 Watts (peak) at 8 ohms Recommended power amplifier specification for powering single and multiple MTD112b enclosures are given in Table 4.
2.3 POWERING MTD115b (PASSIVE MODE) Continuous (rms) and peak power handling ratings for the MTD11b (passive mode) are as follows: 46 volts rms long term (pink noise with 6 dB crest factor) 265 Watts (continuous), 1060 Watts (peak) at 8 ohms Recommended power amplifier specification for powering single and multiple MTD115b enclosures in passive mode are given in Table 7.
2.4 POWERING MTD115b (ACTIVE MODE) Continuous (rms) and peak power handling ratings for the MTD115b in active mode are as follows: LF Section: 46 volts rms long term (pink noise with 6 dB crest factor) 265 Watts (continuous), 1060 Watts (peak) at 8 ohms HF Section: 35 volts rms long term (pink noise with 6 dB crest factor) 150 Watts (continuous), 600 Watts (peak) at 8 ohms Recommended power amplifier specification for powering single and multiple MTD115b enclosures in active mode are given in Table 10.
Table 12: Recommended power amplification and MLS switch settings for MTD115b high section MTD115b HI SECTION AMPLIFIER OUTPUT POWER REC'D POWER (MLS SETTING) LOAD REC'D (ohms) POWER 2 2.
L-ACOUSTICS LA 15a POWER MATRIX L-ACOUSTICS LA 17a POWER MATRIX MLS SWITCH SETTING LOAD CONFIGURATION -3 dB 0 dB 16 ohms Quad (4 channel) 95 200 8 ohms Quad (4 channel) 200 4 ohms Quad (4 channel) 380 2.7 ohms Quad (4 channel) 2 ohms Quad (4 channel) MLS SWITCH SETTING LOAD CONFIGURATION -3 dB 0 dB 16 ohms Stereo (2 channel) 110 215 370 8 ohms Stereo (2 channel) 220 430 600 4 ohms Stereo (2 channel) 430 840 460 2.
2.5 CONNECTORS AND CABLES MTD108a, MTD112b and MTD115b are all supplied with dual NL4 Speakon connectors. The two Speakon connectors are internally wired in parallel, allowing for loop through connection and parallel operation of multiple MTD enclosures. For passive enclosures (MTD108a, MTD112b), Speakon wiring is 1+ / 1- for normal operation (positive polarity).
3. PROCESSING MTD 3.1 L-ACOUSTICS MTD108 LLCa DESCRIPTION The MTD108LLCa line level controller is an analog signal processing unit that optimizes the performance of the MTD108a. The stereo controller accepts two signal inputs and provides two processed outputs for the respective input channels.
OVER mode, a 100 Hz high pass filter is applied since the MTD112b is intended to be used with additional subwoofers. For subwoofer drive, the second front panel switch allows for selection of bandpass filtering and equalization that is optimized for either SB115, SB118 or SB218 subwoofers. The processed subwoofer signal output is then available on the XLR connectors provided on the front or rear panels of the controller.
amplifier inputs with the amplifier outputs then connected to the controller "Sense Return" input Speakon connector (Ch A = 1+/1-, Ch B = 2+/2-). Since the amplifier is connected in a loop, LLC sense return protection circuitry can monitor the signal applied to the loudspeakers and provide thermal protection of speaker components plus voltage- and frequency-dependent cone excursion limiting provided that the power amplifier has 32 dB gain.
4.1 MTD108a FLOOR MONITOR SYSTEM Figure 7a: MTD108a Floor Monitor System Block Diagram L-ACOUSTICS MTD Manual V1.
4.2 MTD108a FOH SYSTEM (MONO SUBS) Figure 8a: MTD108a FOH System Block Diagram (mono subwoofers) L-ACOUSTICS MTD Manual V1.
4.3 MTD108a FOH SYSTEM (STEREO SUBS) Figure 9a: MTD108a FOH System Block Diagram (stereo subwoofers) (note: LLC ChA to ChB link provides +6 dB increase for subwoofer drive) L-ACOUSTICS MTD Manual V1.
4.4 MTD112b FLOOR MONITOR SYSTEM Figure 10a: MTD112b Floor Monitor System Block Diagram L-ACOUSTICS MTD Manual V1.
4.5 MTD112b FOH SYSTEM (MONO SUB) Figure 11a: MTD112b FOH System Block Diagram (mono subwoofers) L-ACOUSTICS MTD Manual V1.
4.6 MTD112b FOH SYSTEM (STEREO SUBS) Figure 12a: MTD112b FOH System Block Diagram (stereo subwoofers) (note: LLC ChA to ChB link provides +6 dB increase for subwoofer drive) L-ACOUSTICS MTD Manual V1.
4.7 MTD115b (PASSIVE) FLOOR MONITOR SYSTEM Figure 13a: MTD115b (passive) Floor Monitor System Block Diagram L-ACOUSTICS MTD Manual V1.
4.8 MTD115b (PASSIVE) FOH SYSTEM (MONO SUB) Figure 14a: MTD115b (passive) FOH System Block Diagram (mono subs) L-ACOUSTICS MTD Manual V1.
4.9 MTD115b (PASSIVE) FOH SYSTEM (STEREO SUBS) Figure 15a: MTD115b (passive) FOH System Block Diagram (stereo subs) (note: LLC ChA to ChB link provides +6 dB increase for subwoofer drive) L-ACOUSTICS MTD Manual V1.
4.10 MTD115b (ACTIVE) FLOOR MONITOR SYSTEM Figure 16a: MTD115b (active) Floor Monitor System Block Diagram L-ACOUSTICS MTD Manual V1.
4.11 MTD115b (ACTIVE) FOH SYSTEM (STEREO SB118 SUBS) Figure 17a: MTD115b (active) FOH System Block Diagram (stereo SB118) Figure 17b: MTD115b (active) FOH System Cabling Detail (stereo SB118) L-ACOUSTICS MTD Manual V1.
4.12 MTD115b (ACTIVE) FOH SYSTEM (STEREO SB218 SUBS) Figure 18b: MTD115b (active) FOH System Cabling Detail (stereo SB218) Figure 18a: MTD115b (active) FOH System Block Diagram (stereo SB218) L-ACOUSTICS MTD Manual V1.
5. SOUND DESIGN 5.1 APPLICATIONS The art of designing a sound system is a profession in itself and a complete description of all sound system design aspects is beyond the scope of this manual. If necessary, we recommend the use of a specialized sound engineer or consultant since the best products can produce the worst results if improperly set-up.
Figure 19: General guidelines for aiming MTD enclosures 5.3 ARRAYING MTD ENCLOSURES Figure 20 shows SPL mappings at octave band frequencies for a single MTD enclosure (generated using CATT-Acoustic modeling software), demonstrating the evenness of coverage and single point source behavior that is obtained using coaxial technology. Note: For color versions of figures 20, 21, 22 and 24 please see the MTD manual PDF file that is available for download from www.l-acoustics.
125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz Figure 21: SPL mappings at octave band frequencies for two MTD enclosures with 0.5 metre spacing (arrayed system corresponding to the “works” case shown in Figure 23) Figure 22 shows SPL mappings for a distributed system of two MTD enclosures with a spacing of 3 meters. Interference now occurs lower in frequency and tends to be masked by room reverberation. Compared with the closely spaced (arrayed) system of Fig.
WORKS AVOID BEST Figure 23: General guidelines for arraying MTD enclosures. The “avoid” case corresponds to the SPL mappings shown in Figure 24, “works” corresponds to Figure 21 and “best” corresponds to Figure 22. 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz Figure 24: SPL mappings at octave band frequencies for four MTD enclosures with 0.5 metre spacing (arrayed system corresponding to the “avoid” case shown in Figure 23). L-ACOUSTICS MTD Manual V1.
5.4 PREDICTING MTD COVERAGE Polar data files are available for modeling MTD108a, MTD112b and MTD115b coverage using industry-standard EASE or CATT-Acoustic room acoustics modeling software packages (see Figures 20-22 for examples of typical SPL mappings). For more information on these modeling programs, please consult: www.ada-acousticdesign.com www.catt.se for EASE information for CATT. MTD108a, MTD112b and MTD115b polar data (EASE or CATT format) is available for download from: www.l-acoustics.com. 5.
binoculars can provide a good starting point by simply measuring the distance from the delay location to the main system, i.e., the geometric path difference. 5.5.3 COMPLEMENTARY FILL For large-scale sound reinforcement (typically when V-DOSC, dV-DOSC or ARCS are used as the main FOH system), MTD enclosures can be used for distributed front fill (ground stacked), flown center cluster downfill, stereo in-fill, offstage fill or as distributed delays.
possible in order to reduce the increase in SPL over the first few rows relative to the audience further back in the coverage region. OFFSTAGE FILL When the horizontal coverage of the main left/right FOH arrays is not sufficient to cover the entire audience area, MTD enclosures can also be used for offstage fill. Typically, throw distance requirements are shorter and vertical coverage angles are greater, making MTD a possible solution for this application.
5.7 STAGE MONITORING Given the optimum signal processing and protection provided by their respective LLC analog controllers and due to their compact, wedge-shaped format and axi-symmetrical directivity, MTD enclosures provide a high performance, “plug and play” stage monitoring solution. FLOOR MONITORING For floor monitoring applications, the coaxial component configuration employed in the MTD108a, MTD112b and MTD115b provides a high degree of image and coverage stability.
Table 16: Nominal floor monitor distance (to performer) and separation versus performer height MTD108a (short-throw: 22.
SIDE FILL OR DRUM FILL MONITORING When used in conjunction with SB115, SB118 or SB218 subwoofers, MTD108a, MTD112b or MTD115b enclosures provide an excellent solution for side fill or drum fill monitoring. Single or double enclosure stacked configurations are the most common set-up for these applications and the MTD can also be used without subwoofers depending on the amount of LF extension expected by the monitor engineer or performing artist.
The subwoofer output for all LLC analog controllers has been calibrated to provide approximately 6 dB of low frequency contour when subwoofers are used with MTD108a, MTD112b or MTD115b enclosures in a 1:1 MTD:subwoofer ratio.
5.8.3 Separate Flown MTD with Ground Stacked Subwoofers For a separate flown MTD system with ground stacked subwoofers, time alignment of subwoofers is required due to the geometric path difference between the two systems. This is illustrated in Figure 26, where the distance from the measurement microphone position to the subwoofers is dSUB while the distance to the flown MTD system: dFLOWN = dSUB + PATH DIFFERENCE.
6. INSTALLATION PROCEDURES 6.
6.
6.3 OMNIMOUNT ATTACHMENT (MTD112b, MTD115b) (1) Remove Omnimount attachment screws (5 mm allen key) (2) Attach Omnimount plate to enclosure (3) Omnimount adapter can be used for installation in horizontal or vertical orientation with continuous angle adjustment (4) Angle adjustment Figure 29: Omnimount installation procedure 6.
7. MTD SYSTEM OPERATION Please refer to Section 4 for cabling and configuration details for typical MTD system configurations. Once the system is cabled (LLC controllers, amplifiers and loudspeakers), connect program signal lines (L/R outputs from a mixing console, for example) to the appropriate input channels of the LLC Controller(s). Recall that LLC Controllers are calibrated for use with power amplifiers having 32 dB gain (i.e., 40 x voltage gain or 1 volt input = 40 volts output).
b) LF Service The 8”, 12” or 15'' loudspeaker components of the coaxial assemblies used in the MTD108a, MTD112b and MTD115b are not field-serviceable. For field service, the entire coaxial assembly should be removed and replaced. To remove the front grille, lift the edges of the acoustic foam and remove the screws. Screws can be found where the edges of the foam are not glued onto the grille - there is no need to completely remove the acoustic foam in order to remove the loudspeaker grille.
8. SPECIFICATIONS 8.1 MTD108a SPECIFICATIONS Frequency Response Frequency response: Usable bandwidth: 85 – 20k Hz (± 3 dB) 65 – 20k Hz (-10 dB) Sensitivity (2.
Figure 30: MTD108a line drawing L-ACOUSTICS MTD Manual V1.
Figure 31: MTD108a plus ETR8 line drawings L-ACOUSTICS MTD Manual V1.
8.2 MTD108LLCa SPECIFICATIONS Technical Inputs Outputs Input Headroom Nominal Gain at 200 Hz Signal to Noise Dynamic Range THD Bandpass/Equalization Filters 3 modes: Speaker Protection Front & Rear Panel Indicators Front Panel Controls Rear Panel Control Electronically balanced 10 kΩ input (pin 2 hot) Electronically balanced 50 Ω output (pin 2 hot) +20 dBV 0 dB (unity gain) > 84 dB > 104 dB <0.
8.3 MTD112b SPECIFICATIONS Frequency Response Frequency response: Usable bandwidth: 70 – 14k Hz (± 3 dB) 55 – 16k Hz (-10 dB) Sensitivity (2.
Figure 32: MTD112b line drawing L-ACOUSTICS MTD Manual V1.
Figure 33: MTD112b plus ETR1 line drawings L-ACOUSTICS MTD Manual V1.
8.4 LLC112b-st SPECIFICATIONS Technical Inputs Outputs Input Headroom Nominal Gain at 200 Hz Signal to Noise Dynamic Range THD Electronically balanced 10 kΩ input (pin 2 hot) Electronically balanced 50 Ω output (pin 2 hot) +20 dBV 0 dB (unity gain) in X-OVER mode > 84 dB > 104 dB <0.
8.5 MTD115b SPECIFICATIONS Frequency Response Frequency response: Usable bandwidth: 65 – 14k Hz (± 3 dB) 50 – 16k Hz (-10 dB) Sensitivity PASSIVE (2.83 Vrms at 1 m) ACTIVE LF (2.83 Vrms at 1 m) HF (2.83 Vrms at 1 m) (LLC FRONT position) 98.5 dB SPL (65 – 14k Hz) 96 dB SPL (65 – 1.2k Hz) 106 dB SPL (1.
Figure 34: MTD115b line drawing L-ACOUSTICS MTD Manual V1.
Figure 35: MTD115b plus ETR2 line drawings L-ACOUSTICS MTD Manual V1.
8.6 LLC115b-st, LLC115b-2w SPECIFICATIONS Technical Inputs Outputs Input Headroom Nominal Gain at 200 Hz Signal to Noise Dynamic Range THD Bandpass/Equalization Filters 3 modes: Electronically balanced 10 kΩ input (pin 2 hot) Electronically balanced 50 Ω output (pin 2 hot) +20 dBV 0 dB (unity gain) in X-OVER mode Low-mid section > 84 dB High section > 92 dB > 104 dB <0.
Rear Panel Connectors LLC115b-st Ch A, B XLR line outputs (LLC 115b-st) MONO SUB XLR output (in parallel with front panel XLR) Sense Return: 1x 4-pin Neutrik speakon Ch A=1+/1-, Ch B=2+/2LLC115b-2w LF, HF XLR line outputs (LLC 115b-2w) MONO SUB XLR output (in parallel with front panel XLR) Sense Return: 1x 4-pin Neutrik speakon LF=1+/1-, HF=2+/2Power Requirement Power Consumption 100 V - 240 V 50/60 Hz 15 W Physical Finish Black anodized front panel, white serigraphy Net Dimensions 483 x 44 x 305 mm 19
