L-Acoustics 112XT User manual

Version 1.1
February 2003
L-ACOUSTICS XT LINE
112XT, 115XT
OPERATOR MANUAL

L-ACOUSTICS XT Manual V1.1 2/11/2003 1
FOREWORD
Thank you for purchasing the 112XT or 115XT sound reinforcement system.
This manual is intended to provide you with the information you require to install and operate your
XT loudspeaker enclosure in a wide variety of professional sound reinforcement applications.
Specific information and recommendations are included regarding system design, sound design and
installation. We are confident that the information provided in this manual will be sufficient for most
applications, however, should you require further assistance your distributor or L-ACOUSTICS®are
available to provide additional technical support.
MANUAL ORGANIZATION
! The Introduction gives a brief presentation of coaxial technology and the XT system.
! Chapter 1 introduces the 112XT and 115XT loudspeaker enclosures plus accessories
! Chapter 2 discusses 112XT and 115XT power amplification and cabling
! Chapter 3 describes preset selection and system operation
! Chapter 4 discusses sound design aspects
! Chapter 5 describes 112XT or 115XT installation procedures
! Chapter 6 discusses XT system operation and maintenance procedures
! Chapter 7 gives 112XT and 115XT specifications

L-ACOUSTICS XT Manual V1.1 2/11/2003 2

L-ACOUSTICS XT Manual V1.1 2/11/2003 3
TABLE OF CONTENTS
FOREWORD..............................................................................................................................................1
MANUAL ORGANIZATION....................................................................................................................1
TABLE OF CONTENTS............................................................................................................................3
LIST OF FIGURES.....................................................................................................................................4
LIST OF TABLES ......................................................................................................................................4
0. INTRODUCTION .................................................................................................................................5
1. THE XT SYSTEM..................................................................................................................................6
1.1 XT SYSTEM COMPONENTS......................................................................................................................... 6
1.2 XT OVERVIEW............................................................................................................................................. 9
1.3 112XT SPECIFICATIONS ............................................................................................................................ 10
1.4 115XT SPECIFICATIONS ............................................................................................................................ 11
2. POWERING XT ..................................................................................................................................12
2.1 POWERING 112XT.................................................................................................................................... 12
2.2 POWERING 115XT.................................................................................................................................... 14
2.3 CONNECTORS AND CABLES ..................................................................................................................... 17
3. XT CONTROL AND PROCESSING..................................................................................................17
3.1 GENERAL DESCRIPTION OF XT PRESETS.................................................................................................. 18
3.2 XT PRESET POLICY .................................................................................................................................... 18
3.3 GUIDELINES REGARDING SYSTEM PROTECTION..................................................................................... 19
3.4 XT PRESET LIBRARIES............................................................................................................................... 20
4. SOUND DESIGN ................................................................................................................................26
4.1 APPLICATIONS ........................................................................................................................................... 26
4.2 AIMING XT ENCLOSURES ......................................................................................................................... 26
4.3 ARRAYING XT ENCLOSURES ..................................................................................................................... 27
4.4 PREDICTING XT COVERAGE ..................................................................................................................... 30
4.5 DISTRIBUTED SOUND REINFORCEMENT................................................................................................. 30
4.5.1 OVERHEAD DISTRIBUTED SYSTEMS ............................................................................................ 30
4.5.2 DELAY SYSTEMS .............................................................................................................................. 30
4.5.3 COMPLEMENTARY FILL ................................................................................................................. 31
4.6 FRONT-OF-HOUSE (FOH) APPLICATIONS ................................................................................................ 32
4.7 STAGE MONITORING................................................................................................................................ 32
4.8 USING XT WITH SUBWOOFERS............................................................................................................... 34
4.8.1 COMBINING XT WITH SUBWOOFERS ........................................................................................ 35
4.8.2 GROUND STACKED SYSTEMS....................................................................................................... 35
4.8.3 SEPARATE FLOWN XT ARRAY WITH GROUND STACKED SUBWOOFERS ............................. 35
5. INSTALLATION PROCEDURES .......................................................................................................37
5.1 ETR112XT, ETR115XT U-BRACKET ATTACHMENT .................................................................................. 37
5.2 CPL112XT, CPL115XT COUPLING ADAPTER BAR ATTACHMENT ............................................................. 38
5.3 XTLIFTBAR ATTACHMENT ........................................................................................................................ 40
5.4 SAFETY RULES ........................................................................................................................................... 40
6. XT SYSTEM OPERATION .................................................................................................................41
6.1 RECOMMENDED MAINTENANCE PROCEDURES ..................................................................................... 41
6.2 SPARE PARTS.............................................................................................................................................. 42
7. SPECIFICATIONS ..............................................................................................................................43
7.1 112XT ELEMENT SPECIFICATIONS ........................................................................................................... 43
7.2 115XT ELEMENT SPECIFICATIONS ........................................................................................................... 47

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LIST OF FIGURES
Figure 1: XT System Components .................................................................................................................... 8
Figure 2: 112XT Enclosure.............................................................................................................................. 10
Figure 3: 115XT Enclosure.............................................................................................................................. 11
Figure 4: MLS switches on the rear panel of L-ACOUSTICS LA24a, LA48a amplifiers..................................14
Figure 5: L-ACOUSTICS preset library for XTA DP224 ................................................................................ 21
Figure 6: L-ACOUSTICS preset library for XTA DP226 ................................................................................ 22
Figure 7: L-ACOUSTICS preset library for BSS FDS-334 Minidrive ...............................................................23
Figure 8: L-ACOUSTICS preset library for BSS FDS-336 Minidrive ...............................................................24
Figure 9: L-ACOUSTICS preset library for BSS FDS-366 Omnidrive Compact Plus .................................... 25
Figure 10: General guidelines for aiming XT enclosures.................................................................................27
Figure 11: SPL mappings at octave band frequencies for a single XT enclosure............................................. 27
Figure 12: SPL mappings at octave band frequencies for two XT enclosures with 0.5 metre spacing........... 28
Figure 13: SPL mappings at octave band frequencies for two XT enclosures with 3 metre spacing.............. 28
Figure 14: General guidelines for arraying XT enclosures.. ............................................................................29
Figure 15: SPL mappings at octave band frequencies for four XT enclosures with 0.5 metre spacing........... 29
Figure 16: L-ACOUSTICS Subwoofer Continuous Unweighted SPL Comparison......................................... 34
Figure 17: Illustration of subwoofer time alignment........................................................................................ 36
Figure 18: ETR112XT, ETR115XT U-bracket installation procedure ............................................................ 38
Figure 19: CPL112XT, CPL115XT coupling adapter installation procedure.................................................. 39
Figure 20: XTLIFTBAR installation procedure ................................................................................................40
Figure 21: 112XT Line Drawing......................................................................................................................44
Figure 22: 112XT + ETR112XT Line Drawing............................................................................................... 45
Figure 23: 112XT + XTLIFTBAR Line Drawing............................................................................................. 45
Figure 24: 112XT + ETR112XT + 112CPLXT Line Drawing (0 degree) ..................................................... 46
Figure 25: 112XT + ETR112XT + 112CPLXT Line Drawing (30 degrees)..................................................46
Figure 26: 115XT Line Drawing......................................................................................................................48
Figure 27: 115XT + ETR115XT Line Drawing............................................................................................... 49
Figure 28: 115XT + XTLIFTBAR Line Drawing............................................................................................. 49
Figure 29: 115XT + ETR115XT + 115XTCPL Line Drawing (0 degrees)....................................................50
Figure 30: 115XT + ETR115XT + 115XTCPL Line Drawing (30 degrees)..................................................50
LIST OF TABLES
Table 1: Load and Power Ratings for 112XT ..................................................................................................12
Table 2: Recommended power amplification and MLS switch settings for 112XT low section .....................13
Table 3: Recommended power amplification and MLS switch settings for 112XT high section .................... 13
Table 4: Recommended MLS switch settings for powering 112XT................................................................ 14
Table 5: Load and Power Ratings for 115XT ..................................................................................................14
Table 6: Recommended power amplification and MLS switch settings for 115XT low section .....................15
Table 7: Recommended power amplification and MLS switch settings for 115XT high section .................... 15
Table 8: Recommended MLS switch settings for powering 115XT................................................................ 15
Table 9: Output Power Ratings and MLS Switch Settings for L-ACOUSTICS LAa Amplifiers .......................16
Table 10: Maximum Recommended Length for Damping Factor > 20.......................................................... 17
Table 11: Nominal floor monitor distance and monitor separation versus performer height ........................ 33
Table 12: L-ACOUSTICS Subwoofer Specification Summary......................................................................... 34

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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. Things become more complex when larger audience area coverage is
required and there are two possible approaches:
1) Multiplying the number of sound sources by dividing the audience into areas which are covered by
individual sources. In this case, the Haas effect is exploited and the goal is to reduce audible
interference effects by dissociating or decoupling the individual sound sources (delay lines can also be
introduced to provide proper localization). This is the distributed sound reinforcement, or multiple
sound source approach, and the XT line of enclosures is highly suited for this type of sound design.
2) Coupling a number of individual sound sources to form a loudspeaker array, with the objective that
each array becomes the equivalent of a single sound source.
For the second approach, conditions for achieving proper coupling of individual arrayed sound sources
have been defined by Dr. Christian Heil and Professor Marcel Urban, in "Sound Fields Radiated By
Multiple Sound Source Arrays" (AES paper preprint 3269, presented at the 92nd AES convention in
Vienna, 1992). Additional conditions were published in the AES preprint ''Wavefront Sculpture
Technology'' (WST) that was presented at the 111th Convention, NYC, 2001 (preprint 5488). The
theory that was developed defines the acoustic coupling conditions required for effectively arraying
individual sound sources. These conditions are satisfied by the ARCS®, dV-DOSC™ and V-DOSC®
products which are intended for medium- to large-scale sound reinforcement applications. However,
in most cases, it is not feasible to meet WST criteria while at the same time having a sufficient level of
versatility for small- to medium-scale applications. In other words, if a product is to be arrayable, it
typically leads to an enclosure design that cannot be used in single or very small configurations. A
different set of loudspeaker enclosure design specifications apply that are more suited to the multiple
source sound design approach.
The L-ACOUSTICS approach to distributed sound reinforcement using multiple sound sources starts
with the specification that each individual loudspeaker enclosure should behave as a totally coherent
source. This criterion can be achieved using coaxial components which are well-suited to the design of
highly versatile, small format systems. The use of coaxial components has been popularized over the
years by a famous British manufacturer for studio monitoring applications – to the best of our
knowledge, L-ACOUSTICS was the first manufacturer to use coaxial technology in professional sound
reinforcement applications and the current XT line is a continuation of the heritage that was
introduced in 1989.
Coaxial, dual concentric components provide a smooth transition between the LF and HF sections
since, by definition, the directivity of the two transducers is matched at the crossover frequency. In
addition, the directivity is horizontally, vertically and diagonally symmetric (axi-symmetric). This
results in true, single source behavior and the performance obtained is superior in terms of coherence
when compared with any combination of two independent sound sources (separate woofer plus horn-
loaded compression driver, for example). This is the case even if the independent sources are
designed to provide the same directivity behavior (which is rarely the case) since the acoustic centers
of the two sources are not located at the same physical location.
Other benefits obtained using the coaxial, axi-symmetric configuration are smooth acoustical
impedance loading for the compression driver and a short time window of reflections which is far
more acceptable than the longer reflection sequences that are produced by traditional horn designs. In
addition, the wavefront radiated by an axi-symmetric sound source has directivity that is smoothly
increasing with frequency which helps to match the acoustical environment of a typical auditorium.
Normally, the reverberation time in auditoria decreases smoothly above 1 kHz and at greater
distances in the venue, the low frequency energy is fairly constant due to the reverberant field.

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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.
The coaxial configuration therefore provides the optimum directivity required in order to obtain even
coverage and constant tonal balance in a typical semi-reverberant auditorium. Extensive sound design
and installation experience acquired by L-ACOUSTICS over the years confirms this and we are
confident that coaxial, axi-symmetric loudspeaker enclosures are the best tools for multiple source,
distributed sound design.
The coaxial performance of the 112XT and 115XT loudspeaker enclosures provide the basic starting
tools for distributed sound reinforcement design.
1. THE XT SYSTEM
The XT line consists of: 112XT, 115XT loudspeaker enclosures, XT rigging accessories and SB115,
SB118, SB218 or dV-SUB subwoofers. OEM factory presets are provided for approved digital signal
processors (XTA DP224, DP226 and BSS 366). Please note that amplifier racks plus loudspeaker
cables are not specified but should meet the minimum specification requirements outlined below.
1.1 XT SYSTEM COMPONENTS
LOUDSPEAKER ENCLOSURES
(1) 112XT
Active 2-way coaxial loudspeaker with 90 degree axi-symmetrical coverage, containing 12”
loudspeaker, 1.4” exit high frequency compression driver
(2) 115XT
Active 2-way coaxial loudspeaker with 80 degree axi-symmetrical coverage, containing 15”
loudspeaker, 1.4” exit high frequency compression driver
SUBWOOFER ENCLOSURES
(3) SB115
Front-loaded, bass-reflex design, single 15’’ subwoofer for low frequency extension
(4) SB118
Dual-vented bandpass-loaded, single 18’’ subwoofer for high level, extended bandwidth
(5) SB218
Front-loaded, bass-reflex design, dual 18’’ subwoofer for high level, extended bandwidth
(6) dV-SUB
Dual-vented bandpass-loaded triple 15” subwoofer for high level, low frequency extension
For more information concerning SB115, SB118 and SB218 subwoofer enclosures please consult the SB
Subwoofer User’s Manual

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XT RIGGING ACCESSORIES
(7) ETR112XT
Adjustable U-Bracket for ceiling, wall or scaffold mounting of the 112XT in either horizontal or
vertical orientations
(8) CPL112XT
Coupling adapter bars used in conjunction with ETR112XT to array two 112XT enclosures
vertically with independent tilt adjustment for both enclosures
(9) ETR115XT
Adjustable U-Bracket for ceiling, wall or scaffold mounting of the 115XT in either horizontal or
vertical orientations
(10) CPL115XT
Coupling adapter bars used in conjunction with ETR115XT to array two 115XT enclosures
vertically with independent tilt adjustment for both enclosures
(11) XTLIFTBAR
Allows for single point rigging of 112XT or 115XT loudspeaker enclosures with 5 pick points
available for tilt adjustment
(12) PION 2
Double stud Aeroquip flytrack fitting-to-ring for permanent installation of 112XT or 115XT
enclosures or for use in conjunction with ETR112XT or ETR115XT as a safety attachment
LOUDSPEAKER CABLES
(13) F-CABLE (SP7, SP25)
Loudspeaker cable, 4 conductor, 4mm2conductor cross-section, 7 m (20 ft) or 25 m (80 ft)
length, equipped with 2 x Speakon connectors
(14) F-LINK CABLE (SP.7)
Loudspeaker link cable, 4 conductor, 4mm2conductor cross-section, 0.7 m (2 ft) length,
equipped with 2 x Speakon connectors (for paralleling XT enclosures).
112XT
115XT

L-ACOUSTICS XT Manual V1.1 2/11/2003 8
ETR112XT
ETR115XT
CPL112XT
CPL115XT
XTLIFTBAR
PION2
F-CABLE DO7 F-LINK CABLE DO.7
Figure 1: XT System Components

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1.2 XT OVERVIEW
L-ACOUSTICS 112XT or 115XT loudspeaker enclosures are intended for distributed sound
reinforcement and can be used for either high performance touring or fixed installation. Both XT
loudspeaker enclosures feature highly-advanced coaxial components and rigging accessories while also
benefiting from the flexibility afforded by OEM digital presets.
The 112XT is an active 2-way loudspeaker containing a 1.4" exit compression driver that is directly
loaded by the 12" loudspeaker in a coaxial configuration while the 115XT features a 15” loudspeaker.
As discussed in the introduction, advantages of the coaxial approach include: single point source
radiation and excellent phase response, total wavefront coherency at all frequencies and axi-
symmetrical directivity that produces identical horizontal and vertical coverage. Coaxial design also
provides LF/HF superimposed dispersion characteristics that are free of polar lobing effects typical of
traditional horn and woofer combinations. The end result is natural, studio monitor level sound
quality, ideal for proximity use and perfectly matching semi-reverberant environments.
The 112XT or 115XT are ideal for distributed sound reinforcement and can also be used in medium
power front-of-house (FOH) applications for theatres, clubs, multi-purpose venues or corporate
events. Examples of distributed systems include delay rings for large-scale installations, surround
effects channels for theatre or multimedia, distributed reinforcement for sports venues, and delays for
speech reinforcement in convention centre ballrooms. Although optimized for single operation,
112XT or 115XT loudspeakers can be used in vertical arrays of two enclosures to enhance either SPL
or coverage. Due to their compact, wedge-shaped format and axi-symmetrical directivity, XT
enclosures also provide an exceptionally high performance floor monitor solution. When used with
the SB118 (or other L-ACOUSTICS subwoofers), XTs are also excellent for side fill and drum
monitoring applications.
OEM factory presets are available for approved digital processors, providing flexible solutions for a
wide variety of 2- and 3-way operating modes. For 2-way operation, three types of presets are
provided:
FRONT presets are for standalone FOH operation (without subwoofers) where low and high
frequency shelving equalization provides a frequency response contour suitable for music
applications.
FILL presets provide nominally flat response for use in speech reinforcement and classical music
applications or when XT enclosures are used as a close proximity fill enclosure.
Both FRONT and FILL presets are derived under freefield measurement conditions.
MONITOR presets include additional low frequency equalization to account for half-space
loading conditions and are intended for floor monitoring applications or fixed installations where
the XT is wall- or ceiling-mounted.
MONITOR presets are derived under half-space measurement conditions.
A variety of 3-way presets are provided for use of the 112XT or 115XT with SB115, SB118, SB218 or
dV-SUB subwoofers. Standard 3W presets utilize a complimentary 100 Hz crossover point for the XT
and its companion subwoofer and are recommended for closely coupled applications. Alternatively,
when XT enclosures are flown and subwoofers are ground stacked, 3WX presets can be employed
where an 80 Hz low pass filter is applied to the subwoofers and 112XT or 115XT low frequency
response extends to 55 or 50 Hz, respectively.
Pole mount sockets and side-mounted fly track sections are included as standard on XT enclosures
and optional rigging accessories include an adjustable U-bracket for ceiling, wall or scaffold mounting
(vertical or horizontal orientations), coupling adapter bars for vertical coupling of two XT enclosures
(independent tilt adjustment for each enclosure) and the XTLIFTBAR accessory for single point rigging
(5 pick points available allowing for tilt adjustment).

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1.3 112XT SPECIFICATIONS
The 112XT is an active, 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 65 Hz
to 18 kHz with less than ± 3 dB variation and the usable bandwidth is 55 Hz to 18 kHz (-10 dB).
The cone body of the low frequency component provides pattern control loading of the compression
driver and yields a 90-degree (± 20 degrees) conical dispersion pattern that is axi-symmetrical. The
crossover point between low and high frequency components is 1 kHz with 24 dB per octave
Linkwitz-Riley characteristics. Long term power handling is 290 Wrms for the low section and 135
Wrms for the high section at a nominal 8 ohm impedance. Connection to the loudspeaker is made via
two parallel 4-pin Neutrik Speakon connectors.
The 112XT has a truncated wedge shape with a curved front profile. Dimensions are 54 cm (21.3 in)
high, 41 cm (16.1 in) wide at the front of the enclosure, 16.5 cm (6.5 in) wide at the rear of the
enclosure and 37.5 cm (14.8 in) deep. When used on its rear side, the front baffle of the enclosure is
oriented at a 45 degree angle with respect to vertical, allowing the enclosure to be used as a floor
monitor. Enclosure weight is 27 kg (59.5 lbs).
Cabinet construction consists of 30 mm (1.18 in) and 18 mm (0.70 in) Baltic birch plywood with
internal steel bracing and joints that are sealed, screwed and rabbeted. The finish is maroon-gray high
resilient paint. The front of the enclosure is protected by a black powder-coated, 1.5 mm (0.06 in)
thick steel grill that is covered with 10 mm (0.4 in) thick acoustically transparent open cell foam.
The 112XT has two side-recessed flytrack sections and 36 mm (1.42 in) diameter pole mount sockets
mounted on the top and bottom sides. Pole mount sockets function with the ETR112XT U-bracket
accessory for rigging the enclosure in either horizontal or vertical orientations, providing angular
adjustment with 10 degree resolution. Two CPL112XT coupling adapter bars can be used in
conjunction with the ETR112XT U-bracket, allowing two 112XT enclosures to be flown vertically
while providing independent tilt adjustment for each enclosure. The XTLIFTBAR accessory functions
with either of the pole mount sockets and provides five attachment points for rigging purposes.
The 112XT loudspeaker is used with an approved digital processor with OEM factory presets for
active 2-way operation or 3-way operation in conjunction with additional subwoofers (L-ACOUSTICS
SB115, SB118, SB218 or dV-SUB).
Figure 2: 112XT Enclosure

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1.4 115XT SPECIFICATIONS
The 115XT is an active, 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, neodymium compression driver. As a full range system, frequency response
is 60 Hz to 18 kHz with less than ± 3 dB variation and the usable bandwidth is 50 Hz to 18 kHz (-10
dB).
The cone body of the low frequency component provides pattern control loading of the compression
driver and yields an 80-degree (± 20 degree) conical dispersion pattern that is axi-symmetrical. The
crossover point between low and high frequency components is 1 kHz with 24 dB per octave
Linkwitz-Riley characteristics. Long term power handling is 250 Wrms for the low section and 85
Wrms for the high section at a nominal 8 ohm impedance. Connection to the loudspeaker is made via
two parallel 4-pin Neutrik Speakon connectors.
The 115XT enclosure has a truncated wedge shape with a curved front profile. Dimensions are 58 cm
(22.8 in) high, 44 cm (17.3 in) wide at the front of the enclosure, 16.7 cm (6.6 in) wide at the rear of
the enclosure and 47.5 cm (18.7 in) deep. When used on its rear side, the front baffle of the 115XT is
oriented at a 41 degree angle with respect to vertical, allowing the enclosure to be used as a floor
monitor. Enclosure weight is 29.5 kg (65.0 lbs).
Cabinet construction consists of 30 mm (1.18 in) and 18 mm (0.70 in) Baltic birch plywood with
internal steel bracing and joints that are sealed, screwed and rabbeted. The finish is maroon-gray high
resilient paint. The front of the enclosure is protected by a black powder-coated, 1.5 mm (0.06 in)
thick steel grill that is covered with 10 mm (0.39 in) thick acoustically transparent open cell foam.
The 115XT has two side-recessed flytrack sections and 36 mm (1.42 in) diameter pole mount sockets
mounted on the top and bottom sides. Pole mount sockets function with the ETR115XT U-bracket
accessory for rigging the enclosure in either horizontal or vertical orientations, providing angular
adjustment with 10 degree resolution. Two CPL115XT coupling adapter bars can also be used in
conjunction with the ETR115XT U-bracket, allowing two 115XT enclosures to be flown vertically
while providing independent tilt adjustment for each enclosure. The XTLIFTBAR accessory functions
with either of the pole mount sockets and provides five attachment points for rigging purposes.
The 115XT loudspeaker is used with an approved digital processor with OEM factory presets for
active 2-way operation or 3-way operation in conjunction with additional subwoofers (L-ACOUSTICS
SB115, SB118, SB218 or dV-SUB).
Figure 3: 115XT Enclosure

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2. POWERING XT
It is important that power amplifiers with sufficient power are used to power the 112XT or 115XT
since headroom is less likely to damage loudspeaker components than clipping. Apart from normal
standards regarding construction, protection, cooling and damping factor that are expected of any
professional sound reinforcement amplifier, the XT system has been calibrated to be used with
amplifiers with the following specifications:
GAIN STRUCTURE
All amplifiers should have 32 dB gain for all sections (sub, low and high). The limiter thresholds and
output channel gains of OEM digital crossover presets have been adjusted to be used with amplifiers
having 32 dB gain.
LIMITERS
Peak limiters on all amplifier outputs with soft clipping characteristics; attack time less than 3msec
COOLING
Temperature speed-controlled fan recommended
In practice, L-ACOUSTICS specifies power amplifiers with output power equivalent to twice the RMS
power handling for the low section and equivalent to the peak power handling for the high section.
These requirements typically allow the same amplifier to be used for both sections since the drive
level for the HF section is attenuated relative to the LF section to account for efficiency differences
(i.e., full continuous power will never be delivered to the HF section due to this attenuation). When
the same amplifier is used for the HF section, the extra available power then translates into headroom
for improved high frequency transient response.
Sections 2.1 and 2.2 give a summary of rms and peak power handling along with recommended power
amplifier output specifications for operation of single 112XT or 115XT enclosures or multiple XT
enclosures in parallel.
2.1 POWERING 112XT
Continuous (rms) and peak power handling ratings for the 112XT are as follows:
LF Section: 48 volts rms long term (pink noise with 6 dB crest factor)
290 Watts (continuous), 1160 Watts (peak) at 8 ohms
HF Section: 33 volts rms long term (pink noise with 6 dB crest factor)
135 Watts (continuous), 540 Watts (peak) at 8 ohms
Table 1: Load and Power Ratings for 112XT
112XT ENCLOSURE RATINGS
ONE 112XT TWO 112XT THREE 112XT FOUR 112XT
SECTION LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D
LOW 8 290 1160 580 4 580 2320 1160 2.7 870.0 3480 1740 2 1160 4640 2320
HIGH 8 135 540 540 4 270 1080 1080 2.7 400.0 1600 1600 2 540 2160 2160
For amplifying 2 112XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1160 W into 4 ohms
* HIGH Amplifier Output Power: 1080 W into 4 ohms
For amplifying 3 112XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1740 W into 2.7 ohms
* HIGH Amplifier Output Power: 1600 W into 2.7 ohms

L-ACOUSTICS XT Manual V1.1 2/11/2003 13
For amplifying 4 112XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 2320 W into 2 ohms
* HIGH Amplifier Output Power: 2160 W into 2 ohms
Based on these specifications, recommended L-ACOUSTICS LA power amplifier specifications and
MLS switch settings are summarized in Tables 2 and 3. In these tables, boldface settings indicate a
good power match based on the recommended power amplifier specification.
Table 2: Recommended power amplification and MLS switch settings for 112XT low section
112XT LOW SECTION AMPLIFIER OUTPUT POWER
REC'D POWER (MLS SETTING)
LOAD POWER LA 17a LA 24a LA 48a
(ohms) (W)
2 2320 do not use do not use 2400
(-2 dB)
2.7 1740 1080 1635 2130
(0 dB) (0 dB) (-2 dB)
4 1160 840 1300 1600
(0 dB) (-2 dB) (-2 dB)
8 580 430 700 820
(0 dB) (-2 dB) (-2 dB)
Table 3: Recommended power amplification and MLS switch settings for 112XT high section
112XT HI SECTION AMPLIFIER OUTPUT POWER
REC'D POWER (MLS SETTING)
LOAD REC'D LA 17a LA 24a LA 48a
(ohms) POWER
2 2160 do not use do not use 2000
(-4 dB)
2.7 1600 1080 1635 1665
(0 dB) (0 dB) (-4 dB)
4 1080 840 1300 1000
(0 dB) (-2 dB) (-4 dB)
8 540 430 700 520
(0 dB) (-2 dB) (-4 dB)
L-ACOUSTICS LA amplifier MLS switch settings for powering the 112XT are summarized in Table 4
and Figure 4 shows the location of MLS switches on the LA24a and LA48a rear panel.

L-ACOUSTICS XT Manual V1.1 2/11/2003 14
Table 4: Recommended MLS switch settings for powering 112XT
MLS SWITCH SETTING
LA17a LA24a LA48a
112XT LO SECTION 0 dB -2 dB -2 dB
112XT HI SECTION 0 dB -2 dB -4 dB
Figure 4: MLS switches on the rear panel of L-ACOUSTICS LA24a, LA48a amplifiers
2.2 POWERING 115XT
Continuous (rms) and peak power handling ratings for the 115XT are as follows:
LF Section: 45 volts rms long term (pink noise with 6 dB crest factor)
250 Watts (continuous), 1000 Watts (peak) at 8 ohms
HF Section: 26 volts rms long term (pink noise with 6 dB crest factor)
85 Watts (continuous), 350 Watts (peak) at 8 ohms
Table 5: Load and Power Ratings for 115XT
115XT ENCLOSURE RATINGS
ONE 115XT TWO 115XT THREE 115XT FOUR 115XT
SECTION LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D LOAD RMS PEAK REC'D
LOW 8 250 1000 500 4 500 2000 1000 2.7 750.0 3000 1500 2100040002000
HIGH 8 85 350 350 4 170 700 700 2.7 250.0 1000 1000 2 350 1400 1400
For amplifying 2 115XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1000 W into 4 ohms
* HIGH Amplifier Output Power: 700 W into 4 ohms
For amplifying 3 115XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 1500 W into 2.7 ohms
* HIGH Amplifier Output Power: 1000 W into 2.7 ohms
For amplifying 4 115XT in parallel, the recommended amplifier specifications are:
* LOW Amplifier Output Power: 2000 W into 2 ohms
* HIGH Amplifier Output Power: 1400 W into 2 ohms

L-ACOUSTICS XT Manual V1.1 2/11/2003 15
Based on these specifications, recommended L-ACOUSTICS LA power amplifier specifications and
MLS switch settings are summarized below in Tables 6 and 7.
Table 6: Recommended power amplification and MLS switch settings for 115XT low section
115XT LOW SECTION AMPLIFIER OUTPUT POWER
REC'D POWER (MLS SETTING)
LOAD POWER LA 17a LA 24a LA 48a
(ohms) (W)
2 2000 do not use do not use 2000
(-4 dB)
2.7 1500 1080 1635 1665
(0 dB) (0 dB) (-4 dB)
4 1000 840 1300 1000
(0 dB) (-2 dB) (-4 dB)
8 500 430 700 520
(0 dB) (-2 dB) (-4 dB)
Table 7: Recommended power amplification and MLS switch settings for 115XT high section
115XT HI SECTION AMPLIFIER OUTPUT POWER
REC'D POWER (MLS SETTING)
LOAD REC'D LA 17a LA 24a LA 48a
(ohms) POWER
2 1400 1200 1400 1660
(0 dB) (-4 dB) (-5 dB)
2.7 1000 1080 1180 1380
(0 dB) (-4 dB) (-5 dB)
4 700 840 750 830
(0 dB) (-4 dB) (-5 dB)
8 350 430 400 430
(0 dB) (-4 dB) (-5 dB)
MLS switch settings for powering the 115XT are summarized in Table 8.
Table 8: Recommended MLS switch settings for powering 115XT
MLS SWITCH SETTING
LA17a LA24a LA48a
115XT LO SECTION 0 dB -2 dB -4 dB
115XT HI SECTION 0 dB -4 dB -5 dB

L-ACOUSTICS XT Manual V1.1 2/11/2003 16
L-ACOUSTICS LA 15a POWER MATRIX L-ACOUSTICS LA 17a POWER MATRIX
MLS SWITCH SETTING MLS SWITCH SETTING
LOAD CONFIGURATION -3 dB 0 dB LOAD CONFIGURATION -3 dB 0 dB
16 ohms Quad (4 channel) 95 200 16 ohms Stereo (2 channel) 110 215
8 ohms Quad (4 channel) 200 370 8 ohms Stereo (2 channel) 220 430
4 ohms Quad (4 channel) 380 600 4 ohms Stereo (2 channel) 430 840
2.7 ohms Quad (4 channel) 460 2.7 ohms Stereo (2 channel) 720 1080
2 ohms Quad (4 channel) 500 2 ohms Stereo (2 channel) 870 1200
L-ACOUSTICS LA 24a POWER MATRIX L-ACOUSTICS LA 48a POWER MATRIX
MLS SWITCH SETTING MLS SWITCH SETTING
LOAD CONFIGURATION -5 dB -4 dB -2 dB 0 dB LOAD CONFIGURATION -5 dB -4 dB -2 dB 0 dB
16 ohms Stereo (2 channel) 160 200 340 520 16 ohms Stereo (2 channel) 220 260 410 650
8 ohms Stereo (2 channel) 300 400 700 1100 8 ohms Stereo (2 channel) 430 520 820 1300
4 ohms Stereo (2 channel) 600 750 1300 1500 4 ohms Stereo (2 channel) 830 1000 1600 2300
2.7 ohms Stereo (2 channel) 1000 1180 1465 1635 2.7 ohms Stereo (2 channel) 1380 1665 2130 2700
2 ohms Stereo (2 channel) 1200 1400 1550 1700 2 ohms Stereo (2 channel) 1660 2000 2400 2900
Table 9: Output Power Ratings and MLS Switch Settings for L-ACOUSTICS LAa Amplifiers

L-ACOUSTICS XT Manual V1.1 2/11/2003 17
2.3 CONNECTORS AND CABLES
112XT and 115XT are 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 XT
enclosures. Speakon connectors are wired as follows:
1+ = LF+
1 - = LF -
2+ = HF+
2 - = HF –
In order to preserve high damping factor (essential to the sonic qualities of the system and to prevent
overshoot of cone displacement which can result in mechanical damage), it is desirable to keep
loudspeaker cables as short as possible and with a gauge offering low resistance per unit length. The
following chart provides information regarding the minimum wire cross-section versus length:
Table 10: Maximum Recommended Length for Damping Factor > 20
Cross Section Gauge 8 ohms 4 ohms
Metric (mm2) Imperial Metric Imperial Metric Imperial
2.5 13 30 m 100 ft 15 m 45 ft
4 11 50 m 150 ft 25 m 75 ft
6 8 75 m 225 ft 37 m 110 ft
10 6 120 m 360 ft 60 m 180 ft
As standard, L-ACOUSTICS F-CABLE (SP7, SP25) and F-LINK CABLE (SP.7) loudspeaker cables are 4
conductor cables with 4 mm2conductor cross-section (11 gauge). SP25 cables can be used for 25
meter cable runs to power a 4 ohm load (2 x 112XT or 115XT enclosures in parallel) while
maintaining a damping factor greater than 20.
3. XT CONTROL AND PROCESSING
A digital processor is specified for use with XT enclosures in order to provide the following functions:
crossover filtering, component time alignment, corrective component equalization, system protection
and system equalization. OEM factory presets are provided for a number of approved digital
processors including: BSS FDS-366 Omnidrive Compact Plus, BSS FDS-334 Minidrive, BSS FDS-336
Minidrive, XTA DP224 and XTA DP226. All presets (except for Minidrive) are distributed via
PCMCIA card and can also be downloaded from the L-ACOUSTICS website (www.l-acoustics.com).
Since the XTA DP226 is a 2 input by 6 output unit, the DP224 is 2 x 4, the FDS-334 is 2 x 4, the FDS-
336 is 2 x 6 and the FDS-366 is 3 x 6, exact internal wiring of your FOH drive rack and digital
processor channel assignments will vary depending on the selected processor and the application.
Carefully consider your flexibility requirements before selecting the type of processor to specify.
NOTE: ALWAYS REFER TO THE PRESET DESCRIPTION SHEET FOR YOUR PROCESSOR WHEN
SELECTING PRESETS AND CONFIGURING YOUR DRIVE RACK.

L-ACOUSTICS XT Manual V1.1 2/11/2003 18
3.1 GENERAL DESCRIPTION OF XT PRESETS
For 2-way operation, three types of presets are provided:
FRONT presets are for standalone FOH operation (without subwoofers) where low and high
frequency shelving equalization provides a frequency response contour suitable for music
applications.
FILL presets provide nominally flat response for use in speech reinforcement and classical music
applications or when XT enclosures are used as a close proximity fill enclosure.
FRONT and FILL presets are derived under freefield measurement conditions.
MONITOR presets include additional low frequency equalization to account for half-space
loading conditions and are intended for floor monitoring applications or fixed installations where
the XT is wall- or ceiling-mounted.
MONITOR presets are derived under half space measurement conditions.
A variety of 3-way presets are provided for use of 112XT or 115XT loudspeaker enclosures with
SB115, SB118, SB218 or dV-SUB subwoofers. Standard 3W presets utilize a complimentary 100 Hz
crossover point for the XT and its companion subwoofer and are recommended for closely coupled
applications. Alternatively, when XT enclosures are flown and subwoofers are ground stacked, 3WX
presets can be employed where an 80 Hz low pass filter is applied to the subwoofers and 112XT or
115XT low frequency response extends to 55 or 50 Hz, respectively.
3.2 XT PRESET POLICY
According to L-ACOUSTICS policy, key parameters are software-protected and preset data or
passwords are not available in order to preserve quality control, confidentiality and to maintain the
integrity of L-ACOUSTICS system presets. Restricting access to presets is in no way meant to restrict
flexibility or the creative process – on the contrary, software-protected presets are intended to
enhance creativity by ensuring quality control and repeatability.
Extensive engineering and real world testing goes into determining optimum presets – detailed polar
measurements and weighted spatial averaging are used to determine component equalization, time
alignment, crossover points and crossover filter slopes, for example. As a result, L-ACOUSTICS
presets give the user an optimum starting point – system tuning should be done using band
attenuation, subwoofer time alignment and system equalization using input section parametric filters –
not by altering presets for the following reason:
Without proper instrumentation and spatial averaging, adjustments made at one location (e.g. the mix
position) are not optimum at all other locations within the defined coverage region of the system.
When made by ear, such adjustments are often misguided – the user may be in a local room mode
(low frequency pressure maximum or minimum) and/or may be hearing a cancellation or addition due
to crossover misalignment that sounds good at that specific location but what about all others?
Meanwhile, the same result could have been achieved while preserving the power response of the
system by using the correct crossover preset and a simple equalization cut or correct time alignment
of subwoofers.
Preset libraries are distributed via PCMCIA Card which are available from L-ACOUSTICS
headquarters in France , L-ACOUSTICS US, L-ACOUSTICS UK or your L-ACOUSTICS distributor.
Preset libraries and upgrades can also be downloaded from www.l-acoustics.com.

L-ACOUSTICS XT Manual V1.1 2/11/2003 19
3.3 GUIDELINES REGARDING SYSTEM PROTECTION
As standard, limit thresholds for XTA and BSS Processors are initially set at 3 dBu above the RMS
power handling for both low and high sections of the 112XT and 115XT as follows:
112XT low section : +6 dBu
112XT high section : +3 dBu
115XT low section : +6 dBu
115XT high section : +2 dBu
Amplifier input sensitivities (0 dB MLS switch setting) are as follows:
LA17a : +5.5 dBu
LA24a : +7.7 dBu
LA48a : +9.5 dBu
For the 112XT and 115XT low section, the +6 dBu limit threshold corresponds to 3 dBu above the
RMS power handling of the low section as well as the input sensitivity of the L-ACOUSTICS LA17a
(+5.5 dBu) and LA 24a (+7.7 dBu) so that system protection is performed by a combination of the
clip limiting circuits of the amplifier and the output channel limiters of the digital signal processor.
Note: L-ACOUSTICS recommends that LA power amplifier clip limiters be engaged at all times (CLIP switch
depressed in the “IN” position).
L-ACOUSTICS LA amplifier clip limiters are sonically transparent and function by monitoring the
output signal and comparing the distortion produced between the input and output of the amplifier. If
the distortion exceeds 1% THD for any reason (voltage or current clipping), the limiter reduces the
input signal proportionally (2 msec attack, 150 msec release). Under normal operation, clip limiting is
inaudible and L-ACOUSTICS recommends leaving the Channel A and B clip limiters switched ''on''
(rear panel button depressed) at all times.
As shown in Sections 2.1 and 2.2, additional protection can be obtained by using the following MLS
switch settings for power matching of the amplifier output to the power handling capacity of the XT
low and high sections:
MLS SWITCH SETTING
LA17a LA24a LA48a
112XT LO SECTION 0 dB -2 dB -2 dB
112XT HI SECTION 0 dB -2 dB -4 dB
MLS SWITCH SETTING
LA17a LA24a LA48a
115XT LO SECTION 0 dB -2 dB -4 dB
115XT HI SECTION 0 dB -4 dB -5 dB
For the 112XT and 115XT high section, the +3 dBu (112XT) or +2 dBu (115XT) limit thresholds
correspond to 3 dBu above the RMS power handling of the high section and system protection is
performed by the limiting circuitry of the digital signal processor.
Example: For the 112XT, the high section limit threshold is set to 3 dBu below the peak power
handling in order to provide secure operation, i.e, the RMS power handling is 135 W, peak power
handling is 540 W and assuming 32 dB amplifier gain, these power ratings correspond to limit
thresholds of 0 dBu (135 W) and +6 dBu (540 W). As standard, the 112XT HF limiter threshold is set
to +3 dBu (3 dB less than the peak power handling).