Martin Audio WAVEFRONT COMPACT - APPLICATIONS GUIDE Specification

Martin Audio WAVEFRONT COMPACT - APPLICATIONS GUIDE Specification
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Wavefront Compact Series
Applications Guide
MARTIN AUDIO
L O N D O N
The Martin Experience
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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Wavefront Compact Series
Applications Guide
Contents
Introduction
Wavefront Compact Series Overview
Section 1
W8C 3-way System
Section 2
W8CT & W8CM Line Array System
Section 3
W8CS Flown Subwoofer
Section 4
WSX Folded Horn Subwoofer
Section 5
W8L Series Line Array Systems
Appendix
A1
W8 3-way System
A2
W8S HybridTM Subwoofer
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Introduction
Wavefront Compact Series Overview
Thank you for purchasing a Martin Audio Wavefront Compact Series system.
Wavefront Compact Series products make up a coherent "toolkit" of compact, live
sound enclosures covering a huge range of professional sound projects from high
quality club installations to major touring and festival systems.
Unpacking
Each Martin Audio loudspeaker is built to the highest standard and thoroughly
inspected before it leaves the factory. After unpacking the system, examine it
carefully for any signs of transit damage and inform your dealer if any such damage
is found. It is suggested that you retain the original packaging so that the system can
be repacked at a future date if necessary.
Please note that Martin Audio and its distributors cannot accept any responsibility for
damage to any returned product through the use of non-approved packaging.
Standards
Martin Audio Wavefront Compact Series products conform to the requirements of the
EMC Directive 89/336/EEC, amended by 92/31/EEC and 93/68/EEC and the
requirements of the Low Voltage Directive 73/23/EEC, amended by 93/68/EEC.
EMC Standards Applied:
Emission EN55103-1:1996
Immunity EN55103-2:1996
Electrical Safety EN60065:1993
About this Applications Guide
This Applications Guide is based on Wavefront Compact field experience and general
acoustical principles. We have provided information on the most popular system
configurations and have included simple equations for those wishing to calculate the
broadband coverage of their own cluster designs.
Going Further
Martin Audio Ltd manufactures a wide range of loudspeakers, system controllers and
power amplifier. Visit our web-site at www.martin-audio.com for the latest product
and applications news.
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Cost effective rental
The Martin Audio Wavefront Compact Series "tool kit" approach provides all the
components required to assemble high quality, truck-friendly, quick deployment
sound systems for applications ranging from small clubs, commercial and theatrical
productions using floor placed W8Cs and W8CS’...
to vast outdoor events with flown Longthrow and W8C clusters:
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Wavefront W8C systems are regularly used for audiences ranging from just a few
hundred jazz devotees to thousands of arena concert-goers. Longthrow sections can
increase touring system versatility even further and Longthrow/W8C combinations
have been very successfully used to cater for festival audiences from hundreds of
thousands to over two million at “Popestock” 2000.
The Wavefront Compact series includes both flown and floor-standing subwoofers.
W8CS’ may be flown where floor space is limited by extensive set designs or TV
camera tracks. Where floor space is available, Wavefront WSX folded horn
subwoofers may be used to implement an all-horn sound system for maximum
efficiency and projection.
Wavefront Compact system versatility satisfies rental companies' requirements to
maximise stock utilisation without compromising performance and reliability.
Wavefront W8C 3-way System
The heart of the Wavefront Compact series is the award-winning W8C (Section 1), a
compact, light weight, high performance, 3-way loudspeaker system that has been
engineered to work as well in small, stand-alone set-ups as it does in large flown
arrays.
A single Wavefront W8C cabinet will cover 55º horizontally x 30º vertically. The
W8C polar response is well defined so that it may be arrayed for high power rock
and dance applications in large venues. A smooth off-axis amplitude and phase
response allows a wide range of intercabinet angles to be used for easy coverage
tailoring.
All Wavefront Compact series cabinets are fitted with MAN load-certified flying
points to minimise set-up time. These MAN fittings are designed to comply with the
12:1 safety factor specified by the German VBG70 standard when used with
compatible MAN flying systems.
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Wavefront Longthrow W8CT & W8CM Line Array System
The Wavefront Longthrow W8CT & W8CM system (Section 2) is a compact, very
powerful, light weight, multiple horn line array loudspeaker system whose cabinets
have the same footprint and flying points as Wavefront W8C and W8CS systems.
Unlike odd-ball line arrays from other manufacturers, W8CTs and W8CMs have been
designed to integrate seamlessly into the rest of the Wavefront family. The
W8CM/CT combination may be rigged in continuous columns for high power, very
long throw applications or may be used to complement regular W8C clusters by
providing spot coverage for difficult seating areas.
The W8CT combines three horn-loaded high-mid drivers with six horn-loaded high
frequency compression drivers. Like the award-winning W8C high-mid system,
W8CT high-mid cone systems are optimally loaded to produce much lower distortion
than typical waveguide-loaded compression drivers.
The W8CM has two vertically arrayed, low-mid horns to complement W8CT highmid/high systems with seamless amplitude and polar integration.
Like all Wavefront series trapezoidal products, W8CTs and W8CMs are fitted with
MAN load-certified flying points and are designed to comply with the 12:1 safety
factor specified by the German VBG70 standard.
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Wavefront W8CS Flown Subwoofer
The W8CS (Section 3) is a compact, light weight subwoofer that has the same cabinet
footprint and flying points as the Wavefront W8C. It has been engineered to extend
the W8C's performance to below 45Hz.
The W8CS comprises a special high excursion driver coupled to an efficient mid-bass
horn and sub-bass port. This unique combination gives the W8CS the characteristic
punch of a horn-loaded system with the low frequency bass extension of a reflex
enclosure.
W8CS’ may be used as full bass subwoofers (up to120Hz) or may be flown as midbass sections (60-160Hz) to complement floor standing WSXs.
Wavefront WSX Folded Horn Subwoofer
The WSX folded horn subwoofer (Section 4) complements Wavefront Compact W8C
touring systems to provide deep bass with maximum efficiency, speed and impact. It
has a classic Martin ‘S’ shaped folded horn and couples a powerful, high excursion
driver to the airload with a modified hyperbolic expansion law.
WSXs may be used as full bass subwoofers (up to120Hz) or as low-bass headroom
extenders to complement flown W8CS sections configured for mid-bass.
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DX1 Loudspeaker Management System
The Martin Audio DX1 (Section 1.5) is a very high performance, 2 input/ 6 output
DSP-based controller providing crossover, protection, delay and alignment functions.
It comes with factory plug'n'play presets for a wide range of Martin Audio product
configurations including the Wavefront Compact family. It is ideal for combining
Wavefront Compact products into seamless systems.
For instance, two DX1s may be used to combine W8Cs, W8CS’ and WSXs to form a
stereo, 5-way, active, all horn system for the ultimate performance and impact. One
more DX1 may be used to add W8CT and W8CM Longthrow sections for difficult
venues or large outdoor events.
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Wavefront Compact Series
Applications Guide
Section 1
Wavefront W8C
3-Way System
MARTIN AUDIO
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Section 1
Wavefront W8C 3-Way System
Contents
1.1
Introduction
1.2
Specifications
1.3
Pin-outs and cabling
1.4
System patching
1.5
DX1 Loudspeaker Management System
1.6
Power amplifier recommendations
1.6.1
Martin Audio MA2.8 Power Amplifier Overview
1.7
General operational summary
1.8
Arraying and placement
1.9
Coverage calculations
1.10
W8Cs as front fills
1.11
W8Cs as side clusters
1.12
W8Cs in distributed (delay) systems
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Wavefront W8C 3-Way System
1.1 Introduction
The award-winning Wavefront W8C 3-Way System is a very compact, light weight,
high performance 3-way loudspeaker system in a trapezoidal cabinet. The Wavefront
W8C integrates a horn-loaded 12" low-mid driver with a horn-loaded 6.5" high-mid
driver and a horn-loaded 1" very high frequency compression driver. The 6.5" highmid cone driver provides a whole order better performance than a large compression
driver and is optimally loaded using a toroidal phase plug.
Wavefront series trapezoidal cabinets are fitted with MAN load-certified flying points
and are designed to comply with the 12:1 safety factor specified by the German
VBG70 standard when used with compatible 12:1 flying systems. One important
advantage of the MAN flying system is that inter-cabinet connections place a minimal
load on the cabinets and, being external, can be load certified and inspected
independently.
1.2 Specifications
Type:
3-way trapezoid, switchable active/passive
high-mid/high via rear panel
switch (see Section 1.5)
Frequency response:
120Hz - 18kHz +/- 3dB
LF limit:
-10dB @ 100Hz
Drivers:
1 x 12" (305mm) low-mid horn
1 x 6.5" (165mm) high-mid horn
1 x 1" (25mm) exit hf compression driver
Rated power:
Low-mid 300W AES, 1200Wpk
High-mid (active/passive) 150W AES, 600Wpk
High (active) 60W AES, 240Wpk
Sensitivity:
Low-mid 106dB/W
High-mid 108dB/W
High 107dB/W
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Maximum SPL:
129dB continuous, 135dB peak
Impedance:
Low-mid 8 ohms nominal
High-mid 16 ohms nominal
High 16 ohms nominal
Coverage (-6dB):
55º horizontal, 30º vertical
Crossover:
750Hz, 3.5kHz
Connectors:
2 x Neutrik NL8, 2 x EP8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (incl wheels):
(W) 562mm x (H) 799mm x (D) 925mm
(W) 22.1ins x (H) 31.5ins x (D) 36.4ins
Flown weight:
69kg (152lbs). Lid 4kg (9lb) extra
Before rigging, note colour coding!
W8C has 2 black points per side
W8CS has 1 black point per side
W8CT has 2 orange points per side
W8CM has 1 orange point per side
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1.3 Pin-outs and cabling
W8C
Connector type
W8C mode
EP8
NL8
W8C Active*
W8C Passive*
1
-1
Low Mid -
Low Mid -
2
+1
Low Mid +
Low Mid +
3
-2
High Mid -
High Mid/High -
4
+2
High Mid +
High Mid/High +
5
-3
High -
n/c
6
+3
High +
n/c
7
-4
n/c
n/c
8
+4
n/c
n/c
(*see Section 1.5 for details of the connector panel Active/Passive switch
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1.3.1 Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Cannon EP connectors
EP8-11
EP8-12
EP8-13
EP8-14
8 pin cable female
8 pin cable male
8 pin panel mount female
8 pin panel mount male
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
1.3.2 Recommended loudspeaker cable
Cable run vs copper core cross sectional area
Up to 50m
Up to 100m
Single W8C
Two W8C paralleled at the cluster.
2.5mm²
6mm²
6mm² (or 2 x 2.5mm² cores in parallel)
10mm² (or 2 x 6mm² cores in parallel)
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
1.4 System patching
A good system patch should…
1)
Be electrically safe - ie be put together by suitably qualified electrical
technicians paying attention to possible sources of moisture, connector
damage, cable damage, user and public safety.
2)
Enable the system to provide the required sound quality, coverage and level
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without feedback and without stressing its mechanical, electrical or
electro-acoustic components.
3)
Be divided into easily understood sections (eg Main, midfield, downfill etc)
and clearly labelled so that adjustments may be made quickly and efficiently.
The schematic above shows a simple system using a Martin Audio DX1 Loudspeaker
Management System configured as a 2 x 3way crossover controlling W8Cs switched
for passive high-mid/high sections and W8CS subwoofers.
See the Section 1.5 for further DX1 information and Section 2 of this applications
guide for a more complex example.
1.4.1 Cluster sub-sections
When designing a large sound system it is worth spending a little time working out a
sensible cluster patch to optimise audience coverage.
The following example is a 4 wide, 4 deep W8C classical music centre cluster
divided into farfield, midfield, nearfield and downfill horizontal rows and inner and
outer vertical columns. The active (3-way) W8Cs may be patched in pairs for
symmetrical control.
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Recommended W8C pairs:
Inner Farfield
Inner Midfield
Inner Nearfield
Inner Downfield
Outer Farfield
Outer Midfield
Outer Nearfield
Outer Downfill
Controller channel allocations
The whole cluster may be controlled from just ½ a Martin Audio DX1 controller set
up for 3-way operation. See Section 1.5 for further DX1 information.
Power amplifier channel allocations
There are 8 pairs of W8Cs each requiring high, high-mid & low-mid power amplifier
channels.
8 pairs at 3 bands per pair
= 24 amplifier channels required
= 12 x 2ch amplifiers per cluster.
2ch power amplifier allocations:
Farfield inner & outer high
Midfield inner & outer high
Nearfield inner & outer high
Downfill inner & outer high
Farfield inner & outer himid
Midfield inner & outer himid
Nearfield inner & outer himid
Downfill inner & outer himid
Farfield inner & outer lomid
Midfield inner & outer lomid
Nearfield inner & outer lomid
Downfill inner & outer lomid
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Initial inner level settings
Initial inner level settings can be calculated for each row as follows:
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The farfield inner power amplifier channels are the reference...
Initial outer level settings
Similarly, initial outer level settings can be calculated for each row as follows:
Again, the farfield inner amplifier setting (0dB) is used as a reference...
In a fairly small, wide, fan-shaped venue with heavily raked seating, we may require
the following amplifier channel settings:
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The attenuation rate shown here is 2dB per cluster row. The actual rate of vertical
attenuation will depend on the cluster height which in turn will depend on the rake of
the seats. High clusters are further from the audience at the front and require less
nearfield & downfill attenuation. The lower the cluster, the greater the required
attenuation rate.
Again, the vertical layout is...
In a narrower venue, we may require the outer sections to be attenuated a little,
particularly in the farfield section, as follows:
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1.5 DX1 Loudspeaker Management System
Martin Audio can provide factory set configuration cards for a variety of off-the-shelf
crossover systems (contact your dealer or Martin Audio Ltd for further information)
but the Martin Audio DX1 Loudspeaker Management System is strongly
recommended for all new Wavefront system designs.
The Martin Audio DX1 is a very high performance DSP-based controller and
provides crossover, protection, delay and alignment functions. As a Martin Audio
product, the DX1 is kept up-to-date with preset crossover and limiter functions
suitable for a wide range of system configurations and power amplifiers.
DX1 Factory Preset Examples
W8C Rear panel Active/Passive switch
Please note that the W8C rear connector panel is equipped with an Active/Passive
switch.
Active mode (DX1 factory presets 21, 23 or 25)
In Active mode each driver (low-mid, high-mid & high) is driven by its own power
amplifier channel. These power amplifier channels are sourced from the appropriate
DX1 output to ensure optimal crossover and limiter alignment.
The advantages of active mode are:
Ø Smoother high-mid/high amplitude and phase response
Ø Smoother high-mid/high vertical polar response
Ø Improved high-mid/high amplifier headroom
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Ø Improved high-mid/high limiter action
Three Martin Audio MA2.8 power amplifiers will drive four W8Cs (assuming W8Cs
driven in pairs).
Passive Mode (DX1 factory presets 20 & 22)
In Passive mode the high-mid and high drivers share a power amplifier channel via a
passive high-mid/high crossover network built into the loudspeaker cabinet. This
mode offers a slightly reduced performance but requires only two power amplifier
channels per 3-way W8C system.
Two MA2.8s will drive four W8Cs (assuming W8Cs driven in pairs).
The following shows the DX1 with programme 20 selected. This caters for a stereo
set-up comprising left and right W8Cs in Passive mode plus separate left and right
WSX subwoofers:
DX1 factory preset 20 (2 x 3 way configuration)
Stereo WSX+W8C (passive high-mid/high) system
Custom DX1 set-ups
Experienced users may create custom DX1 set-ups, for example…
5 way configuration
e.g. W8C (active high-mid/high) system with flown W8CS’ (low 15) used as midbass bins augmented by stacked WSXs (low 18).
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See Section 2.4 for a full system example.
1.5.1 DX1 specifications
Inputs
CMRR
Outputs
Min. Load
Max. Level
Frequency Resp.
Dynamic Range
Distortion
Maximum Delay
Output gain
Input gain
2 electronically balanced. >10k ohms
>65dB 50Hz - 10kHz
6 electronically balanced. <60 ohms
600 ohm
+20dBm into 600 ohm load
±0.5dB 20Hz - 20kHz
>110dB 20Hz -20kHz. Unwtd
<0.02% @ 1kHz, +18dBm
650mS. (Increment 2.6uS)
adjustable +15dB to -40dB in 0.1dB steps and mute
adjustable +6dB to -40dB in 0.1dB steps
Parametric Equalisation
Filters
5 Sections per output
Filter gain
+15dB to -30dB in 0.1dB step
Centre frequency
0Hz - 20kHz, 1/36 octave steps (368 positions)
Filter Q / BW
0.4 to 128 / 2.5 to 0.008
(Sections switched to shelving response)
Low frequency
20Hz - 1kHz
High frequency
1kHz - 20kHz
Shelf gains
±15dB in 0.1dB steps
Crossover (high-pass and low-pass) filters
Filters
Frequency (HPF)
Frequency (LPF)
Response
1 of each per output
10Hz - 16kHz, 1/36 octave steps
60Hz - 22kHz, 1/36 octave steps
Bessel / Butterworth 12/18/24dB per octave
Linkwitz-Riley 24dB per octave
Limiters
Threshold
Attack time
Release time
+22dBu to -10dBu
0.3 to 90 milliseconds
4, 8, 16 or 32 times the attack time
Power required
Weight
Size
60 to 250V ±15% @ 50/60Hz. < 20 watts
3.5kg Net (4.8kg Shipping)
44 (1U) x 482 x 300mm excluding connectors
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1.5.2 DX1 Output Gain and Limiter settings for W8Cs
Standardising on one good model of power amplifier (preferably the Martin Audio
MA2.8) and correctly set-up controller (preferably the Martin Audio DX1) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories.
Gain settings
The following DX1 output gain settings will enable full system performance to be
obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
W8C - assuming 300Wcont - 600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
QSC PL224
Martin MA2.8* (32dB)
Crest 4801 (x40)
Crown K1 (1.4v)
QSC PL218/218A (32dB)
QSC PL224A (32dB)
Crown MA1202 (1.4v)
Crown MA1202 (26dB)
Crown K1 (26dB)
QSC PL218A (26dB)
QSC PL224A (26dB)
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Initial DX1
Output GAIN
Lomid Himid High
dB
dB
dB
-2
-1
0
+1
+2
+3
+4
+4
+4
+4
+4
+5
+6
+7
+8
+9
+10
+10
+10
+10
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
0.62
0.69
0.77
0.87
0.98
1.09
1.23
1.23
1.23
1.23
1.23
1.38
1.55
1.73
1.95
2.18
2.45
2.45
2.45
2.45
38
37
36
35
34
33
32
32
32
32
32
31
30
29
28
27
26
26
26
26
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
-7
-6
-5
-4
-3
-2
-1
-1
-1
-1
-1
0
+1
+2
+3
+4
+5
+5
+5
+5
* Set Martin Audio MA2.8 rear MLS switch to -2dB to match peak output of
unregulated power amplifiers.
Cluster balance (eg farfield-to-nearfield or inner-to-outer) should be adjusted at the
power amplifier controls to maintain limiter tracking. See Section 1.7.
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Balancing the system using gain controls in the signal path before the power
amplifiers will cause the higher signal level upper row of a big cluster to start limiting
before the lower signal levels downfills causing tonal changes at the mix position.
Limiter settings
The Rated Power specifications in Section 1.2 show that the maximum allowable
power dissipation depends on the driver/s being driven. This is because big low and
low-mid drivers are capable of dissipating more heat than smaller high-mid and high
drivers.
Normal music and speech signals, however, are a combination of relatively low
general power levels with a multiplicity of short term transients. These short term
transients do not significantly heat the driver voice coils so it is quite permissible to
use the same 250-300W into 8Ω (500-600W into 4Ω) power amplifiers for all
sections of the W8C, W8CT and W8CM as long as they are sourced by a correctly set
controller.
When choosing power amplifiers, do not be tempted to exceed the 250-300W into 8Ω
(500-600W into 4Ω ) power rating unless the amplifier's power rails are well
regulated (see Section 1.6) - even with properly set controllers in place.
Although Martin Audio drivers are mechanically designed to survive normal road use
and the occasional operator error, over-powered or bridged amplifiers can cause overexcursions that stress and age drivers. The best way to get the clean, relaxed sound of
an overpowered amplifier is to choose an amplifier with plenty of current reserve - ie
an amplifier with good 2Ω specification - and avoid running more than two cabinets
in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
each band's high pass frequency as follows:
High pass filter range
Attack time
Release time
>31Hz
31Hz - 63Hz
63Hz - 125Hz
125Hz - 250Hz
250Hz - 500Hz
500Hz - 1KHz
1KHz - 2KHz
2KHz - 22KHz
45mS
16mS
8mS
4mS
2mS
1mS
0.5mS
0.3mS
720mS
256mS
128mS
64mS
32mS
16mS
8mS
4mS
These attack times will allow the power amplifiers to clip momentarily but not for
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long enough to be obvious to listeners or cause driver overheating. It is quite normal
to see amplifier clip indicators on the odd programme peak but continuous clipping
would indicate a cable short circuit, wrong controller settings, excessive power
amplifier gain or low mains voltage.
The following DX1 output limiter settings will avoid voice coil overheating and
minimise amplifier clipping for high quality, trouble free operation.
W8C - assuming 300Wcont - 600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
QSC PL224
Martin MA2.8* (32dB)
Crest 4801 (x40)
Crown K1 (1.4v)
QSC PL218/218A (32dB)
QSC PL224A (32dB)
Crown MA1202 (1.4v)
Crown MA1202 (26dB)
Crown K1 (26dB)
QSC PL218A (26dB)
QSC PL224A (26dB)
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Recommended
DX1 LIMITER
Lomid Himid High
dBu dBu dBu
-2
-1
0
+1
+2
+3
+4
+4
+4
+4
+4
+5
+6
+7
+8
+9
+10
+10
+10
+10
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
+3
+4
+5
+6
+7
+8
+9
+9
+9
+9
0.62
0.69
0.77
0.87
0.98
1.09
1.23
1.23
1.23
1.23
1.23
1.38
1.55
1.73
1.95
2.18
2.45
2.45
2.45
2.45
38
37
36
35
34
33
32
32
32
32
32
31
30
29
28
27
26
26
26
26
-6
-5
-4
-3
-2
-1
0
0
0
0
0
+1
+2
+3
+4
+5
+6
+6
+6
+6
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
* Set Martin Audio MA2.8 rear MLS switch to -2dB to match peak output of
unregulated power amplifiers.
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Use lower limiter settings (or more loudspeakers!) if your power amplifiers indicate
clipping on more than just the odd peak. Excessive clipping may also be caused by
cable faults or an inadequate mains supply. See Section 1.6
The DX1 may be user-programmed to many more touring and fixed installation
configurations based on its 2 input + sum, 6 output matrix. This operation is best
completed by an audio technician who is familiar with DSP-based pro-audio.
(See separate DX1 Speaker Management System Operating User's Guide for details)
1.6 Power amplifier recommendations
Wavefront Compact Series loudspeaker systems have been designed and
manufactured for very high performance and arrayability. The systems are very easy
to use - particularly if power amplifier racks and controller settings are standardised
within a system.
Power capability
W8Cs will provide full performance when driven by professional power amplifiers
capable of delivering undistorted output power into a range of loads as follows:
W8C
250-300W(AES) into 8 ohms,
500-600W(AES) into 4 ohms
and
1,000-1,200W(AES) into 2 ohms.
Please note:
Amplifiers with inadequate headroom before clipping may age high frequency
components due to excessive signal density.
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times their quoted
power for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by oversized amplifiers should be avoided.
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Martin Audio MA Series Power Amplifiers
Martin Audio MA Series amplifiers have regulated rails so it is quite permissible to
use slightly overpowered models - with suitably set controller limiters - without
risking uncontrolled power bursts. The MA series power amplifiers’ regulated power
rails also ensure maximum performance under the real-world concert conditions of
less-than-optimum mains supplies and parallel cabinets. See Section 1.6.1.
Most non-Martin power amplifiers’ 4 ohm performance figures are specified
assuming very well regulated bench supplies but fail to reach these specifications
under touring conditions. These amplifiers can be a totally false economy as they
cannot drive parallel cabinets without a very audible loss of headroom and quality.
Amplifier load tolerance
An efficient loudspeaker in live concert conditions can act as a surprisingly dynamic
and complex load. Most modern touring power amplifiers claim 2 ohm capabilities
but make sure your amplifier is also capable of driving reactive (ie inductive or
capacitive) loads without prematurely clipping or developing output stage crossover
distortion.
Mains safety!
A fully qualified technican should check mains safety and phase voltage before the
system is patched.
Power reserve
Power amplifier specifications are usually based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for musical peaks.
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load. An electrical technician
should check the mains supply vs demand using an accurate rms voltage
meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving too many W8Cs in parallel. I would suggest no more than two
so that the amplifier’s 2Ω spec is kept in reserve for musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode that to use an inadequate amplifier in
bridged mode.
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Gain or level settings
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section 1.5.2). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controller output levels and limiters have been set as tabulated in
Section 1.5.2, power amplifier level controls should be set to full (fully clockwise) for
loudspeaker sections requiring the strongest drive. Amplifiers driving nearer-field
sections within the same cluster may be backed off as required for smooth coverage.
This process will ensure that the cluster coverage remains balanced during limiting.
Rack mounting
Always leave a 1U space between power amplifiers and controllers. Although most
modern amplifiers don’t radiate significant fields it’s better to play safe and keep the
system quiet. Rear supports are recommended - check with the manufacturer.
1.6.1
Martin Audio MA2.8 Overview
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Features
Ø
Ø
Ø
Ø
Ø
Ø
Switch mode power supply
Superior sonic performance
Light weight
Advanced protection circuits
Efficient copper cooling system
Minimum load switches (MLStm)
The MA2.8 power amplifier has been designed to combine reliability and high power
output with sonic excellence. Utilising an advanced switch mode power supply, the
MA2.8 yields a very high power-to-weight ratio in a lightweight, 2U package.
See MA2.8 Power Amplifier User's Guide for detailed operating instructions.
Cooling System
The Martin Audio MA2.8 amplifier runs very cool due to a special patented copper
cooling system. The amplifier’s bi-polar output devices are mounted directly onto a
copper heat sink (copper conducts heat twice as efficiently as aluminium) and
maximum heat dissipation is achieved by turbulent airflow over the heatsink’s
geometric fins.
The MA2.8 amplifier features two proportional speed cooling fans which take in air
from the front of the amplifier and exhaust from the rear. A horizontal pressure
chamber between the heatsink and the cooling fans ensures that there is little
difference in the operating temperatures of each output device. In contrast, a
conventional tunnel design can result in a temperature variance of up to 40° between
output devices.
Switch Mode Power Supply
The MA2.8’s switch mode power supply (SMPS) is the modern solution to the
problems of size and weight. Switch mode power supplies are not new - they are
found in computers and televisions. However, the demands of high power audio are
very different to these applications. The MA2.8 overcomes the size and weight
constraints of conventional power supplies whilst at the same time avoiding the
pitfalls of typical switch mode designs.
The low output impedance of the SMPS means that rail voltages do not sag under
heavy load conditions. Additionally, the rail capacitors are being recharged at a much
faster rate than those in a conventional power supply. The result is an exceptional fast
transient low frequency performance at all power levels. Efficiency is also
maximised. With much smaller transformers than a conventional supply, there is
much less loss due to transformer resistance and much less power wasted as heat in
the power supply.
The power amplifier will produce the same power output, even if the AC line voltage
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drops by 20%.
Minimum Load Switches (MLS™)
Because the SMPS is regulated, the maximum power available for the output stages
can be adjusted without increased heat dissipation or efficiency loss. This allows the
user to match the output power with the loudspeaker impedance.
Protection
The MA2.8 amplifier has many advanced protection features that will protect both the
amplifier and the speakers connected to it, under fault conditions. All protection
circuits are independent and inaudible in normal use.
Clip Limiters
Clip limiters prevent dangerous clipped signals reaching the speaker. They work by
monitoring the output to check for signals not present at the input i.e.distortion. If
distortion exceeds 1% on an output, the limiter will reduce the input signal
proportionally.
Thermal Protection
Thermal Protection circuitry prevents the amplifier from running at an unsafe
temperature by muting the input signal when the internal temperature rises above
90°C.
Short Circuit Protection
The MA2.8 amplifier is completely short circuit protected. The protection circuits
permit very high peak currents, but maintain the output devices within their safe
operating area.
Mains Voltage Protection
This operates if the mains voltage falls outside its permitted operating range. If this
occurs, the power supply will shut down until the correct mains voltage is restored.
DC and VHF Protection
Both DC voltages and high power VHF signals can cause damage to loudspeakers.
The MA2.8 amplifier incorporates protection circuits which are activated when
damaging DC voltages or VHF signals are present at the outputs.
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MA2.8 Specifications
Input Impedance
Gain select switch
CMRR at 1kHz
Output impedance at 1kHz
Power Bandwidth
Slew rate
Hum/Noise
Channel Separation
Mains Operating Voltage
Protection
Distortion
THD 20Hz - 20kHz and 1W –
1000W
THD at 1kHz and 1100W
DIM 30 at 500W
CCIF (13 and 14 kHz) at 500W
SMPTE (60Hz and 7kHz) at 500W
Power Matrix
20kohms (balanced) 10kohms single ended
38dB (I/P sens 0.775V), 32dB (I/P sens 1.55V)
>50dB
0.06 ohms
10Hz - 20kHz
20V/us
<-105dB
1Khz > 90dB
10Khz > 80dB
120 - 270 (minimum start voltage 190)
full output power maintained 180 - 280V.
Optional (65 - 135V) operation.
DC, High temperature, Turn on, VHF,
Over and under voltage, Clip limiters. Short
circuit.
4 ohms 0.08%
4 ohms 0.03%
4 ohms 0.02%
4 ohms 0.03%
4 ohms 0.08%
LOAD CONFIGURATION
16 ohms Stereo (2 channel)
8 ohms Stereo (2 channel)
4 ohms Stereo (2 channel)
MLS SWITCH SETTING
(-5dB)
(-4dB)
(-2dB)
160W
180W
340W
300W
350W
650W
570W
680W
1100W
2 ohms Stereo (2 channel)
1040W
1200W
16 ohms Bridged mono
8 ohms Bridged mono
4 ohms Bridged mono
600W
1200W
2100W
700W
1400W
2400W
(0dB)
520W
1100W
1400W
1900W[2]
1200W
1400W[1]
1400W[2] 2900W[2]
1300W
2000W
2200W
2800W
2400W
2800W[1]
[1] = Component tolerance
dependent
[2] = Continuous power, one channel
driven or peak power both channels
driven. Thermal protection may
occur at high continuous power.
Power in watts (EIA 1kHz, 1%
THD)
Weight
10kg (22lbs)
Dimensions
(W) 483mm x (H) 88mm x (D) 347mm
(W) 19ins x (H) 3.5ins x (D) 13.7ins
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1.7 General operational summary
1)
Always use the same model system controller and power amplifier for a
particular Wavefront product. This avoids confusion caused by different
controller topologies and power amplifiers voltage gains.
2)
It is common practice to use mixing console matrix outputs as loudspeaker
section controls. Whilst this is fine for creating a bass submix which can
easily be judged from the mix position, it can be fraught with danger if used
for audience sections which may only be audible in very specific areas. Trim
these remote sections, during listening tests with a colleague via walkie talkie,
using the relevant controller input gains. If the console matrix cannot be
avoided, try to pre-calibrate its output levels controls to their 0dB (nominal)
position initially. These settings will be easier to get back to and will avoid
embarrassing level setting mistakes during the show - particularly if the
system is being used by guest operators who may not be familiar with your
particular matrix allocations.
3)
And again, trim levels within clusters (eg farfield vs midfield or inners vs
outers) using the amplifier level controls to ensure limiter tracking.
1.8 Arraying & placement
Simple stacked systems
Single W8C
A single Wavefront W8C cabinet will cover 55º horizontally x 30º vertically and may
be used as a stand-alone system for a variety of light music and voice applications
including commercial presentations.
A W8C may be combined with a W8CS compact subwoofer or a WSX horn-loaded
subwoofer to extend its low frequency performance.
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Single W8C on W8CS subwoofer
This very compact stack may be used for as one side of a main system for a folk band
concert in a small venue, one corner of a small dance floor system, stage side fills,
stage drum fills, front fills etc.
SAFETY REMINDER!
Stacks should always be safety strapped to allow for high winds, over-exuberant
artists, crowd indicipline, scenery movements etc.
Wide coverage, broadband stack
Although a single Wavefront W8C’s horizontal coverage is 55º at high frequencies,
the system has been designed to integrate well with smaller splays for practical output
summing. A splay of 40º between axes (260mm between cabinet front corners)
provides very smooth 95º horizontal coverage with little increase in mid-band output
level whilst a smaller splay angle (typically 30º) can boost the forward output level by
2-3dB.
2-wide W8C/W8CS stack
This very compact stack may be used as one side of a small venue main system,
one corner of a dance system, high power stage side fills, drum fills, centre fills etc.
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Flown systems overview
Flown clusters are recommended for very high power music systems covering large
venues to ensure adequate coverage without excessive levels at the front of the venue.
Wavefront series products are fitted with MAN load-certified flying points and are
designed to comply with the 12:1 safety factor specified by the German VBG70
standard when used with compatible 12:1 flying systems.
MAN Transformer or Installer/Tourer flying systems allow columns of loudspeakers
to be assembled by attaching individual loudspeakers to vertically daisy-chained Drings using keyhole cabinet fittings - hence the tendency to base flown designs in this
applications guide on multiple columns. The beauty of the MAN system is that each
cabinet in a system supports only its own weight.
Each pair of vertical chains is attached to a single-width, centrally pivoted sub-bar
which, in turn, is attached to a two-way, centrally pivoted flying bar so that the
system “finds its own level”, if accidentally hoisted asymmetrically, avoiding undue
stresses and strains.
Vertical splay angles are determined by intercabinet chain lengths whilst the overall
column tilt is determined by the length of the chains between the upper cabinet and
the sub-bar. Please note that all components must have a 12:1 safety factor.
Vertical columns are splayed by tensioning a rachet strap threaded through the subbar and all of the cabinet back plates.
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Cabinets may be fitted with rear hinge back plates to allow removable hinges to be
slotted in place. These hinge assemblies provide a more rigid rear cabinet alignment.
For further information please refer to the Martin Audio Wavefront 8 Flying System
User Guide.
Rigging Schools!
Rigging should not be undertaken by untrained or unqualified personnel.
Suitable rigging training sessions may be arranged by calling Martin Audio Ltd on
+44 (0)1494 535312.
Important note on flown systems examples
Wavefront cluster examples are included in this manual to illustrate recommended
loudspeaker combinations and splay angles only. Note that very large clusters particularly those including Wavefront Longthrow elements - may need to be flown
in multiple layers to maintain the 12:1 safety factor of the standard Martin Audio
Wavefront 8 Flying System.
SAFETY NOTE!
Two female "keyhole" stud plates are fitted to each side of Wavefront cabinets to
allow cabinets to be flown up-side-down for certain applications. The upper keyhole
is the only one ever used - whatever the configuration.
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OK
No, No, No!!!
i)
NEVER suspend one cabinet from the lower flying point of the cabinet above.
ii)
NEVER suspend standard cabinets horizontally.
Two Wavefront Compact W8Cs correctly rigged using upper key-holes only
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1.9 Coverage calculations
Single W8C column
Here is an example of a 1-wide, 3 deep column of Wavefront W8Cs.
The horizontal coverage is, of course, that of a single W8C ie 55º.
The vertical coverage of a W8C cluster can be calculated as follows:
Vertical coverage of a W8C = the vertical coverage of a single W8C (30º) + the
sum of all the vertical splay angles
For a 3-deep W8C cluster with 15º vertical splay angles = 30º+15º+15º = 60º
For a 3-deep W8C cluster with 20º vertical splay angles = 30º+20º+20º = 70º
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Double W8C column
Here is a 2 wide, 3 deep column of Wavefront W8Cs.
The vertical coverage can be calculated as follows:
For a 3-deep W8C cluster with 15º vertical splay angles = 30º+15º+15º = 60º
For a 3-deep W8C cluster with 20º vertical splay angles = 30º +20º+20º = 70º
The horizontal coverage can be calculated as follows:
For a 2-wide W8C cluster with 30º horizontal splay angles = 55º+30º = 85º
For a 2-wide W8C cluster with 40º horizontal splay angles = 55º+40º = 95º
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Wide coverage cluster
4 or 6 wide, 4 deep W8C clusters may be rigged for very wide coverage. Coverage
may be calculated as follows:
6 wide cluster
The horizontal coverage now extends to:
55º+30º+30º+30º+30º+30º = 205º for 30º horizontal splays
55º+40º+40º+40º+40º+40º = 255º for 40º horizontal splays
and the vertical coverage extends to:
30º+15º+15º+15º = 75º for 15º vertical splays
30º+20º+20º+20º = 90º for 20º vertical splays
6 wide, 4 deep plan view
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Circular cluster
Two 6-wide, 4 deep W8C clusters with 30º horizontal splay angles and 20º vertical
splay angles may be flown back-to-back to provide full 360º horizontal x 90º vertical
coverage for ice shows, for example.
Column View
Note that the 90º coverage allows foldback to be provided to the ice-dancers. The
centre hole may be filled by flying a smaller cabinet underneath the main cluster.
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1.10 W8Cs as front fills
Wavefront W8Cs may be used as stage apron fills for high power rock concerts.
When carefully placed on radii converging at the centre downstage (lead vocal) area
and sychronised with the main PA downfills, these apron fills don't just balance the
subwoofers. They can focus vocals and add a detailed quality that can be beneficial
right out to the mix position.
If the apron fill loudpeaker signal is delayed by the difference between the downfill
propagation time and the apron fill propagation time and attenuated by the ratio of
those propagation times, the sound will appear to come from an area in between the
two systems for the listener shown.
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Apron fill delay line setting = t downfill - t apron fill
Apron fill gain setting wrt downfill gain = 20log10(t downfill ÷ t apron fill) dB
1.11 W8Cs as side clusters
A Wavefront Longthrow (See Section 2) centre cluster may be used with W8C
downfills for efficient operatic and orchestral amplification. Velodrome side seats can
be some distance away (typically across a wide cycle track) so fairly powerful side
clusters may be required for good projection and intelligibility.
W8Cs are ideal for this application as they blend in sonically without off-axis lobing
and stage mic colouration.
Deep orchestral stage continues this way ñ
To avoid abrupt changes in timbre between the side and centre cluster, the side
downstage W8C axis should be aimed at the seating where the centre cluster is just
beginning to lack very high frequencies.
Controller output levels and delays should be adjusted so that the side and centre
clusters are at the same level and sychronised in the same area.
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1.12 W8Cs in distributed (delay) systems
Wavefront W8C Compacts make very good high power distributed systems or delay
elements as they project sound smoothly and efficiently without local off-axis lobing.
For good overall coverage, delays are best driven in mono for most of the show
although computer controlled matrix mixes may be considered for panning spot
effects around the venue.
Flown radial delays
Flown distribution or delay loudspeakers should be placed on radii converging at the
stage and staggered for smooth coverage.
Distributed flown loudspeaker plan (stage system not shown)
Delay times should be set for synchronisation with the next most powerful source.
This would be the stage for the first row of delays (below left) or the previous row
(below right) for farfield delays.
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Synchronising flown central delays
Synchronising flown outer delays
Ideally, the sound should be perceived as coming from the stage over the whole
audience area - which means that all the delay loudspeakers should be aligned with
the stage opening. In practice, sight line, follow spot and camera shot restrictions will
affect placement for heavily raked seating areas and intelligent compromises will
need to be made.
Delay systems should be thoroughly checked over a wide listening area to ensure that
their level settings provide smooth coverage without hot spots. Delay times and levels
should be finely adjusted to minimise multiple arrivals in seating areas where systems
cannot be in line with the stage and more than one source can be heard.
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Aiming delay tower loudspeakers
Multiple delay tower loudspeakers should be tilted so that they aim towards head
height at the next tower to mask off-axis tower leakage and to minimise multiple
arrivals further out.
Synchronising multiple tower systems
(not to scale)
Small delay time errors are inevitable where delay towers are located in audience
areas (eg on a football field) due to the three dimensional geometry involved.
Initially, controller delays should be adjusted for synchronisation along a line
between staggered delay towers and then modified as necessary to minimise timing
errors around each tower and over its main coverage area.
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Wavefront Compact Series
Applications Guide
Section 2
Wavefront Longthrow
W8CT & W8CM
Line Array System
MARTIN AUDIO
L O N D O N
The Martin Experience
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Section 2
Wavefront Longthrow W8CT & W8CM Line Array System
Contents
2.1
Introduction
2.2
Specifications
2.3
Pin-outs and cabling
2.4
System patching
2.5
DX1 gain & limiter settings
2.6
Power amplifier recommendations
2.7
General system reminders
2.8
Coverage
2.9
Further examples
Section 2a
Climatic effects on sound propagation
2a.1
Introduction
2a.2
Wind effects
2a.3
Temperature effects
2a.4
Relative humidity effects
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Wavefront Longthrow W8CT & W8CM
Line Array System
2.1 Introduction
The Martin Audio Wavefront Longthrow W8CT & W8CM Line Array System is a
compact, light weight, very high power, multiple horn line array loudspeaker system
in a trapezoidal cabinet sharing design concepts and footprints with the rest of the
popular Martin Audio Wavefront Compact family.
Unlike other manufacturers who have been rushed into production to exploit the
recently recognised benefit of line array systems, Martin Audio have manufactured
modular line array systems for many years. The Martin Audio Wavefront Longthrow
system benefits from this proven track record. It uses established components and
stacked horn techniques to provide a sensible, arrayable horizontal performance
compatible with the rest of the Wavefront family.
Although designed to be rigged in continuous columns for very long throw operation,
Wavefront Longthrow elements may also be used within W8C clusters to provide
spot coverage to distant balcony or corner seating.
The Wavefront Longthrow W8CT integrates three horn-loaded 6.5" high-mid drivers
with six horn-loaded 1" high frequency compression drivers. Like the award-winning
W8C high-mid system , the W8CT high-mid driver is optimally loaded using a
toroidal phase plug to produce much lower distortion than a typical waveguide-loaded
compression driver.
The Wavefront Longthrow W8CM comprises two horn-loaded 12" low-mid drivers
to complement W8CT high-mid/high systems.
Wavefront Longthrow W8CTs and W8CMs are fitted with MAN load-certified flying
points designed to comply with the 12:1 safety factor to the German VBG70 standard
when used with compatible 12:1 flying systems.
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2.2 Specifications
W8CT
Type:
Dedicated longthrow high-mid/high enclosure
Frequency response:
750Hz-18kHz +/- 3dB
Drivers:
3 x 6.5" (165mm) high-mid horn
6 x 1" (25mm) exit hf compression driver
Rated power:
High-mid 450W AES, 1800W peak
High 360W AES, 1440W peak
Sensitivity:
High-mid 113dB
High 115dB
Maximum SPL:
High-mid: 139dB continuous, 145dB peak
High: 141dB continuous, 147dB peak
Impedance:
High-mid: 6 ohms nominal
High: 2 x 6 ohms nominal
Coverage (-6dB):
55º horizontal, Line vertical (see Section 2.8)
Crossover:
750Hz, 3.5kHz
Connectors:
2 x Neutrik NL8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (incl wheels):
(W) 562mm x (H) 799mm x (D) 925mm
(W) 22.1ins x (H) 31.5ins x (D) 36.4ins
Flown weight:
81kg (178lb). Lid 4kg (9lb) extra
W8CM
Type:
Dedicated longthrow low-mid enclosure
Frequency response:
120Hz-750Hz +/- 3dB
LF limit:
-10dB @ 80Hz
Drivers:
2 x 12" (305mm) low-mid horn
Rated power:
600W AES, 2400 peak
Sensitivity:
109dBspl/W
Maximum SPL:
136dBspl continuous, 142dBspl peak
Impedance:
4 ohms
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Coverage (-6dB):
55º horizontal, Line vertical (see Section 2.8)
Crossover:
120Hz, 750Hz
Connectors:
2 x Neutrik NL8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (incl wheels):
(W) 562mm x (H) 799mm x (D) 925mm
(W) 22.1ins x (H) 31.5ins x (D) 36.4ins
Flown weight:
72kg (158lb). Lid 4kg (9lb) extra
Before rigging, note colour coding!
W8C has 2 black points per side
W8CS has 1 black point per side
W8CT has 2 orange points per side
W8CM has 1 orange point per side
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2.3 Pin-outs and cabling
W8CT & W8CM
NL8
W8CT
W8CM
-1
Link through
Low Mid -
+1
Link through
Low Mid +
-2
High Mid -
Link through
+2
High Mid +
Link through
-3
High 1 -
Link through
+3
High 1 +
Link through
-4
High 2 -
Link through
+4
High 2 +
Link through
(See Section 1.3 for connector pin-out drawing)
2.3.1 Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels.
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
2.3.2 Recommended loudspeaker cable
Note that a standard 8-core loudspeaker cable will drive through-linked pairs of
W8CTs and W8CMs.
The following table gives suitable copper core specifications for common
applications:
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Cable run vs copper core cross sectional area
One W8CT
or W8CT/CM
combination
Two W8CTs in parallel
or two W8CT/CM
combinations in parallel
at the cluster.
Up to 50m
4mm² (or 2x 2.5mm²cores in parallel)
Up to 100m
10mm² (or 2x 4mm²cores in parallel)
10mm² (or 2x 4mm²cores
in parallel)
Not recommended but use 2x 10mm² cores
in parallel if you must.
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
2.4 System patching
A good system patch should:
1)
Be electrically safe - ie be put together by suitably qualified electrical
technicians
2)
Enable the system to provide the required sound quality, coverage and level
without feedback and without stressing its mechanical, electrical or electroacoustic components.
3)
Be divided into easily understood sections (eg Main, midfield, downfill etc)
and clearly labelled so that adjustments may be made quickly and efficiently.
Although the last two points may seem insultingly obvious to users who are naturally
well organised, they are very important. Each Longthrow section may be covering
several thousand people and fairly minor mis-patches can have major consequences
bearing in mind that outdoor events - particularly orchestral concerts - are often
competing with noise from food and drink stand generators, over-flying aircraft, local
traffic etc.
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The above schematic shows a typical system incorporating a row of Wavefront
Longthrow W8CT & W8CM elements with Wavefront Compact W8Cs and W8CS’
crossed over as flown mid-bass sections to augment floor stacked WSX subwoofers.
The system uses Martin Audio DX1 Loudspeaker Management Systems configured
as 5-way crossovers. Martin Audio can provide factory set configuration cards for a
variety of off-the-shelf crossover systems (contact your dealer or Martin Audio for
further information) but, the Martin Audio DX1 Loudspeaker Management System is
strongly recommended for all new Wavefront Longthrow system designs. See Section
1.5 for DX1 details.
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For further notes on system patching, including cluster sub-section controller and
amplifier allocations see Section 1.4.
2.5
DX1 gain & limiter settings
Standardising on one good model of power amplifier (preferably the Martin Audio
MA2.8) and correctly set-up controller (preferably the Martin Audio DX1) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories.
The Martin Audio DX1 Loudspeaker Management System may be user-programmed
for a wide range of touring configurations based on its 2 input + sum, 6 output matrix.
This operation is best completed by an audio technician who is familiar with DSP based pro-audio equipment. (See Section 1.5 and DX1 Speaker Management System
User's Guide for further details)
Gain settings
The following initial DX1 output gain settings will enable full system performance to
be obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
W8CT & W8CM - assuming 600Wcont - 1200Wpk into 4Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
-2
0.62
-1
0.69
0
0.77
+1
0.87
QSC PL224
+2
0.98
+3
1.09
Martin MA2.8* (32dB)
+4
1.23
Crest 4801 (x40)
+4
1.23
Crown K1 (1.4v)
+4
1.23
QSC PL218/218A (32dB)
+4
1.23
QSC PL224A (32dB)
+4
1.23
Crown MA1202 (1.4v)
+5
1.38
+6
1.55
+7
1.73
+8
1.95
+9
2.18
Crown MA1202 (26dB)
+10 2.45
Crown K1 (26dB)
+10 2.45
QSC PL218A (26dB)
+10 2.45
QSC PL224A (26dB)
+10 2.45
* Set MA2.8 rear MLS switch to -2dB.
38
37
36
35
34
33
32
32
32
32
32
31
30
29
28
27
26
26
26
26
Initial DX1
Output GAIN
Lomid Himid High
dB
dB
dB
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
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Cluster balance (eg inner-to-outer) should be adjusted at the power amplifier
controls to maintain limiter tracking. See Section 2.7.
Balancing the system using gain controls in the signal path before the power
amplifiers is not recommended as it will cause the higher signal level upper rows of a
big cluster to start limiting before the lower signal levels downfills causing tonal
changes at the mix position.
Limiter settings
The Rated Power specifications in Section 2.2 show that the maximum allowable
power dissipation depends on the driver/s being driven. This is because big low and
low-mid drivers are capable of dissipating more heat than smaller mid-high and high
drivers.
Normal music and speech signals, however, are a combination of relatively low
general power levels with a multiplicity of short term transients. These short term
transients do not significantly heat the driver voice coils so it is quite permissible to
use the same 250-300W into 8Ω (500-600W into 4Ω) power amplifiers for all
sections of the W8CT and W8CM as long as they are sourced by a correctly set
controller.
When choosing power amplifiers, do not be tempted to exceed the 250-300W into 8Ω
(500-600W into 4Ω ) power rating unless the amplifier's power rails are well
regulated (see Section 2.6) - even with properly set controllers in place. Although
Martin Audio drivers are mechanically designed to survive normal road use and the
occasional operator error, overpowered or bridged amplifiers can cause overexcursions that stress and age drivers. The best way to get the clean, relaxed sound of
an overpowered amplifier is to choose an amplifier with plenty of current reserve - ie
an amplifier with good 2Ω specification - and avoid running more than two cabinets
in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
each band's high pass frequency as follows:
High pass filter range
Attack time
Release time
>31Hz
31Hz - 63Hz
63Hz - 125Hz
125Hz - 250Hz
250Hz - 500Hz
500Hz - 1KHz
1KHz - 2KHz
2KHz - 22KHz
45mS
16mS
8mS
4mS
2mS
1mS
0.5mS
0.3mS
720mS
256mS
128mS
64mS
32mS
16mS
8mS
4mS
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These attack times allow the power amplifiers to clip momentarily - but not for long
enough to be obvious to listeners or cause driver overheating. It is quite normal to see
amplifier clip indicators on the odd programme peak but continuous clipping would
indicate a cable short circuit, wrong controller settings, excessive power amplifier
gain or low mains voltage.
The following DX1 output limiter settings will avoid voice coil overheating and
minimise amplifier clipping for high quality, trouble free operation.
W8CT & W8CM - assuming 600Wcont - 1200Wpk into 4Ω
Ω power amplifiers:
Typical
Amplifier
Example
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
QSC PL224
Martin MA2.8* (32dB)
Crest 4801 (x40)
Crown K1 (1.4v)
QSC PL218/218A (32dB)
QSC PL224A (32dB)
Crown MA1202 (1.4v)
Crown MA1202 (26dB)
Crown K1 (26dB)
QSC PL218A (26dB)
QSC PL224A (26dB)
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Recommended
DX1 LIMITER
Settings
Lomid Himid High
dBu dBu dBu
-2
-1
0
+1
+2
+3
+4
+4
+4
+4
+4
+5
+6
+7
+8
+9
+10
+10
+10
+10
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
+3
+4
+5
+6
+7
+8
+9
+9
+9
+9
0.62
0.69
0.77
0.87
0.98
1.09
1.23
1.23
1.23
1.23
1.23
1.38
1.55
1.73
1.95
2.18
2.45
2.45
2.45
2.45
38
37
36
35
34
33
32
32
32
32
32
31
30
29
28
27
26
26
26
26
-6
-5
-4
-3
-2
-1
0
0
0
0
0
+1
+2
+3
+4
+5
+6
+6
+6
+6
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
* Set Martin Audio MA2.8 rear MLS switch to -2dB.
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2.6 Power amplifier recommendations
Wavefront Longthrow loudspeakers have been designed and manufactured for very
high performance over great distances. They are very easy - particularly if power
amplifier racks and controllers are standardised within a system.
Power capability
W8CTs and W8CMs will provide full performance when driven by professional
power amplifiers capable of delivering undistorted output power into a range of loads
as follows:
W8CT & W8CM
250-300W(av) into 8 ohms,
500-600W(av) into 4 ohms
and
1,000-1,200W(av) into 2 ohms.
Please note:
Amplifiers with inadequate headroom before clipping may age high frequency
components due to excessive signal density.
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times their quoted
power for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by oversized amplifiers should be avoided.
Martin Audio MA series power amplifiers have regulated rails so it is quite
permissible to use slightly overpowered models - with suitably set controller limiters without risking uncontrolled power bursts. The MA series power amplifiers’
regulated power rails also ensure maximum performance under the real-world concert
conditions of less-than-optimum mains supplies and low impedance loads.
See Section 1.6.1 for information on the Martin Audio MA2.8 power amplifier.
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Amplifier load tolerance
An efficient loudspeaker in live concert conditions can act as a surprisingly dynamic
and complex load. Most modern touring power amplifiers claim 2 Ohm capabilities
but make sure your amplifier is also capable of driving reactive (ie inductive or
capacitive) loads without prematurely clipping or developing output stage crossover
distortion.
Power Reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads.
Amplifiers sound best when they have plenty of current in reserve for musical peaks.
General power amplifier reminders
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load. An electrical technician
should check the mains supply vs demand using an accurate true rms voltage
meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving more than one W8CT high-mid or high section or one W8CM
cabinet per power amplifier channel. This will keep the power amplifier’s 2
ohm capability in reserve for musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier
in bridged mode.
Gain or level settings
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section 2.5). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
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power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controller output levels and limiters have been set as tabulated in
Section 2.5, power amplifier level controls should be set to full (fully clockwise) for
loudspeaker sections requiring the strongest drive. Amplifiers, driving nearer-field
sections within the same cluster, may be backed off as required for smooth coverage.
This process will ensure that the cluster coverage remains balanced during limiting.
Rack mounting
Always leave a 1U space between power amplifiers and controllers. Although most
modern amplifiers don’t radiate significant fields it’s better to play safe and keep the
system quiet. The spare space may prove useful when last minute controller additions
are required for, say, extra audience fills. Rear supports are recommended. Check the
manufacturer's application notes for details.
2.7 General system reminders
1)
Where possible, use the same model system controller and power amplifier for
a particular Wavefront product. This avoids confusion caused by different
controller topologies or by power amplifiers with different voltage gains for
the same output specs.
2)
It is common practise to use mixing console matrix outputs as loudspeaker
section controls. Whilst this is fine for creating a bass submix which can
easily be judged from the mix position, it can be fraught with danger if used
for Longthrow loudspeaker sections which may only be audible by touring the
site on a bicycle! Trim outfield sections during listening tests with a colleague
via walkie talkie, using the relevant controller input gains.
If the console matrix is the only solution available, try to pre-calibrate the
matrix output levels controls to their 0dB (nominal) position initially. These
settings will be easier to get back to and will avoid embarrassing level setting
mistakes during the show - particularly if the system is being used by guest
operators who may not be familiar with your particular matrix allocations.
3)
And again, trim levels within clusters (eg inners vs outers) using the amplifier
level controls to ensure limiter tracking.
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2.8 Coverage
W8CT and W8CMs are designed to be flown in vertical line arrays to provide a
combination of W8C-compatible 55º horizontal coverage with tight vertical control.
The vertical coverage of a single W8CT is approximately 7.5º in the upper midrange.
When dead-hung, as illustrated below, the vertical coverage narrows with increasing
cluster height following the classic law for multi-element line arrays.
* = speed of sound (m/s).Varies with temp. (see Section 2a)
Arcsin = "the angle whose sin is..."
(Note that Nd works out to be the total height of the column in meters)
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Straight column gain and coverage
The following table shows typical Longthrow high-mid/high gain (wrt a single
Wavefront W8C) plus the mid and high frequency vertical coverage provided by
various straight vertical line arrays.
W8CTs in
high-mid/high gain
(wrt single W8C)
vertical coverage (-6dB points)
high-mid
high
1 (single row)
2 (double row)
4
6
8
10
9.5dB
16dB
22dB
25dB
28dB
30dB
7.42º
3.72º
1.86º
1.24º
0.93º
0.74º
3.70º
1.86º
0.93º
0.62º
0.46º
0.37º
The above means that, for practical sound reinforcement uses, a long straight
column's mid and high frequency coverage must be regarded as being cylindrical in
nature. Low-mid vertical coverage will widen in the farfield depending on the height
of the column but users should be guided by the following coverage shape to ensure
consistent high frequency coverage.
Straight W8CT column mid/hf coverage = 55º (horizontal) x the column height
A long, straight Wavefront Longthrow column will cover vast flat outdoor areas if
you aim the column axis towards the rear of the audience. Remarkable results can be
obtained indoors using continuous columns running from stage level to the maximum
seating height.
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Unfortunately, continuous vertical columns are rarely visually acceptable particularly where the audience wraps around a thrust stage and sight lines are
critical. In such cases, shorter Longthrow columns may be flown in combination with
Wavefront W8C midfields and downfills.
Martin Audio/M.A.N. Flying System overview
Flown clusters are recommended for very high power music systems covering large
venues to ensure adequate coverage without excessive levels at the front of the venue.
Wavefront series products are fitted with MAN load-certified flying points and are
designed to comply with the 12:1 safety factor specified by the German VBG70
standard when used with compatible 12:1 flying systems.
MAN Transformer or Installer/Tourer flying systems allow columns of loudspeakers
to be assembled by attaching individual loudspeakers to vertically daisy-chained Drings using keyhole cabinet fittings - hence the tendency to base flown designs in this
applications guide on multiple columns. The beauty of the MAN system is that each
cabinet in a system supports only its own weight.
Each pair of vertical chains is attached to a single-width, centrally pivoted sub-bar
which, in turn, is attached to a two-way, centrally pivoted flying bar so that the
system “finds its own level”, if accidentally hoisted asymmetrically, avoiding undue
stresses and strains. Please note that all components must have a 12:1 safety factor.
Vertical splay angles are determined by intercabinet chain lengths whilst the overall
column tilt is determined by the length of the chains between the upper cabinet and
the sub-bar. Vertical columns are splayed by tensioning a rachet strap threaded
through the sub-bar and all of the cabinet back plates. Cabinets may be fitted with
rear hinge back plates to allow removable hinges to be slotted in place. These hinge
assemblies provide a more rigid rear cabinet alignment.
For further information please refer to the Martin Audio Wavefront 8 Flying System
User Guide.
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IMPORTANT NOTES!
Rigging should not be undertaken by untrained or unqualified personnel.
Suitable rigging training sessions may be arranged by calling Martin Audio Ltd on
+44 (0)1494 535312.
Flown systems examples
Wavefront cluster examples are included in this manual to illustrate recommended
loudspeaker combinations and splay angles only. Note that very large clusters particularly those including Wavefront Longthrow elements - may need to be flown
in multiple layers to maintain the 12:1 safety factor of the standard Martin Audio
Wavefront 8 Flying System.
Safety reminder
Two female "keyhole" stud plates are fitted to each side of Wavefront W8C and
W8CT cabinets to allow cabinets to be flown up-side-down for certain applications.
The upper keyhole is the only one ever used - whatever the configuration.
OK
i)
ii)
No, No, No!!!
NEVER suspend one cabinet from the lower flying point of the cabinet above.
NEVER suspend standard cabinets horizontally.
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2.9 Further examples
Wavefront Longthrow columns may be horizontally arrayed for wide coverage:
30
30
30
30
30
30
30
30
(left & right clusters will be mirror image)
High-mid/high horizontal coverage would be
1/2 left W8CT + 30º + 30º + 1/2 right W8CT
= one W8CT +30º + 30º
= 55º + 60º
= 115º.
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2.9.1 Flying with W8CS’
Wavefront Longthrow columns may be flown with Wavefront W8CS’ (Section 3).
The W8CS’ may be configured as fullbass systems - to leave the floor free for camera
tracks, for example - or as a mid-bass section to augment floor-stacked WSXs where
a large, standing audience is expected forward of the mix position.
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
Reminder!
Splay angles are always quoted axis-to-axis - not between cabinet sides!
ie.
30
=
|‹
0º ›|‹ 30º
›|‹ 0º ›|
As with W8Cs, the single-box horizontal coverage is 55º. Horizontal splay angles of
25-35º between axes will provide coherent polar response summations resulting in
smooth coverage with consistent tonal characteristics.
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2.9.2 Flying with W8Cs
Wavefront Longthrow columns may be flown with Wavefront Compact W8C
midfield and downfill sections.
The following example shows a wide coverage Longthrow system with W8C
midfield and downfill sections. Note that a double (vertically tightpacked) row of
W8Cs has been flown as the midfield section. Vertically tightpacking these W8Cs
extends their forward throw to help smooth the transition from Wavefront Longthrow
to Wavefront W8C. The vertical splay angle between the main Longthrow column
and the double W8C midfield section is kept small to avoid vertical coverage gaps.
8
20
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
15
8
8
8
8
8
8
8
15
15
15
15
15
15
15
15
20
20
15
20
20
15
20
20
20
15
8
8
20
20
15
Note that the Longthrow system's output is considerably greater than the Compact's
for the same input voltage so some level tailoring tends to be required to provide
smooth coverage with distance.
FAQ: Why do you use powerful Longthrow and tight-packed sections and then
turn them down?
A:
The tight vertical coverage of the Longthrow and tight-pack sections allows
us to concentrate high quality sound onto the audience without exciting roof
resonances. They help maintain excellent direct-to-reverb ratios.
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A typical arena gain set-up may be as follows:
Main Longthrow section
Double W8C midfield section
W8C downfills
-12dB to -6dB
-6dB to 0dB
-4dB to 0dB
2.9.3 Adding Longthrow elements to W8C/W8CS clusters
Wavefront Longthrow elements may be added to conventional W8C/CS clusters for
larger venues, to improve overall sound projection to, for example, upper rear seats.
Note that when just a few Wavefront Longthrow elements are used to supplement a
large W8C system, high-mid/high W8CTs may be used without low-mid W8CMs as
low-mid energy is provided by adjacent W8C low-mid sections.
= W8CT,
= W8C,
= W8CS
15
15
8
8
8
15
15
20
20
20
20
15
20
15
15
20
8
20
20
15
A simplified maximum horizontal coverage calculation is:
27.5º (left ½ W8C/W8CT) + 15º + 15º + 27.5º (right ½ W8C/W8CT) = 85º
A simplified maximum vertical coverage calculation is:
3.75º (top ½ W8CT) + 8º + 20º + 20º + 15º (bottom ½ W8C) = 66.75º
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Climatic effects on sound propagation
2a.1 Introduction
When working in large venues or outdoors we should always remember that sound
propagates through air and is affected by air temperature, humidity and wind.
The most audible of these effects is wind as it can vary dramatically in less than a
second causing rapidly swept filter effects that change middle and high frequency
content into incoherent noise.
Air temperature can change suddenly with very audible effects (eg when backstage
doors are opened during sound checks, venue doors are opened near the end of a
show in winter or cold air displaces the warm air trapped in a stadium during a clear
summer evening). Although quite rare, rapid air temperature changes can cause
sudden changes in propagation direction and major coverage problems for a few
fretful minutes before clearing. These sudden coverage changes often trigger sound
system investigations as they tend to sound like mid or high frequency component
failures or tripped amplifiers.
Humidity tends to change slowly with time and affects the higher frequencies. This
slow change can be missed as our ear-brain system tends to compensate for subtle
high frequency losses. If the relative humidity changes from, say, 25% at the
beginning of a hot afternoon's sound check to 40% as the weather turns sultry, we
may not notice the gradual 6dB increase in high frequency at the back of the field
(3dB at the mix position) until the guest engineer arrives, having walked the field
with a clean* pair of ears, and wants to change everything.
*Be aware that the human ear discharges more wax in humid conditions and this will tend to negate the
improved high frequency propagation.
Although it is not possible to control the climate outdoors at the moment, a
knowledge of its various effects on sound system performance will allow good
system designers to minimise problems as follows:
1)
Avoid trying to cover large outdoor areas with multiple, horizontally parallel
arrays. Keep mid & high frequency sections closely coupled at their optimum
horizontal splay angles to minimise audible combing effects with crosswinds.
2)
Avoid high, heavily tilted point source clusters as their propagation can be
refracted by temperature gradients or reflected by strong air layers causing
major coverage problems. Use large, continuous vertical columns (from stage
height to crane hook) to propagate sound almost parallel to the ground.
3)
Design for at least 5º excess vertical and horizontal coverage to allow for
propagation shifts. If you don't have the extra equipment for this contingency,
be prepared to retrim cluster tilts until the doors are about to open.
4)
Where possible, take regular breaks outside the venue to avoid adapting to
humidity changes. If there is no time for breaks, ask trusted crew members for
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their opinions or compare the system’s high frequency sound quality with a
pair of high quality mix position monitors delayed back to the PA. The PA
should sound warmer and more punchy but should never sound brighter than
good monitors unless the man with the cheque book wants it that way.
5)
Always get trusted sound crew members to walk the field during the show.
Their reports will be telling you more about climate changes than your system
setup so don't be surprised if they ask for subsection level changes and eq
adjustments. Major changes can occur when:
i.
the audience floods in (temperature gradients get disturbed and
humidity can rise)
ii.
around sunset (temperature and local wind changes)
2a.2 Wind effects
Side winds
Gusting side winds can dramatically effect mid and high frequency sound by
changing the propagation direction (and, therefore, the way adjacent radiators
interact) as follows:
Single sound source
For example a 50km per hour (31 mph) side gust = approx 13.9m/s.
The temporary change in direction during the gust = arctan 13.9/340
= approx arctan 0.041 = approx 2.3º
This may seem trivial until you realise that this sudden 2.3º change will shift a poorly
arrayed system's polar pattern undulations about 2m to right at a typical outdoor mix
position. Easily enough to swap high-mid and high frequency peaks and troughs
several times in just a few seconds - an effect that went out of fashion in the 60s!
Variable combing (phasing) caused by wind effects should be minimised by avoiding
widely spaced, parallel high frequency sections carrying the same signals.
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Spaced, parallel loudspeakers will comb (add or subtract their outputs) depending on
their distance or time offset from us (see Section 4.10). A 150mm/0.5ms offset at the
listening position will cause nulls at 1KHz, 3KHz, 5KHz, 7KHz, 9KHz, 11KHz etc
but we wouldn't be aware of the combing under casual listening conditions because
we are used to listening to natural sounds in the presence of multiple arrivals (echoes)
and our ear-brain system adapts to them. We don't adapt to varying comb structures
though, especially in the horizontal plane, as our horizontally spaced ears act as a
sensitive interferometer.
Martin Audio Wavefront Longthrow horns are stacked vertically and adjacent
W8CTs may be flown in mirror image and splayed 30-40º (for coherent arraying) to
minimise high frequency combing in breezy outdoor conditions. Widely spaced,
parallel columns – carrying the same signal - should be avoided.
Where budgets allow, mono centre clusters should be used for lead vocals and
instrumentals. Large ensembles (such as large string sections or large choirs) should
be divided into multiple subgroups which are sent to separate clusters.
|< 0º >|<
W8CM W8CT
0º
>|< 0º >|
W8CT W8CT
Spaced, parallel columns – Bad in windy conditions
|< 0º >|<30-40º>|< 0º >|
W8CM W8CT W8CT W8CT
Splayed, tightly packed columns – Better in windy conditions
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Wind gradient
Air movement is slowed by friction so wind is usually lighter near the ground than it
is higher up. Ground level wind speeds can vary from over 90% of the main wind
speed in the daytime, when the air is being mixed by being warmed by the ground, to
under 30% at night, when air - cooled by the ground - looses buoyancy.
This varying wind speed with height is called the wind gradient.
A wind gradient associated with wind blowing towards a loudspeaker will "slow" its
vertical wavefront differentially. The vertical wavefront will be slowed less near the
ground and its sound path will veer upwards.
30m
Wind Stronger
20m
10m
Wind Weaker
0m
0m 10m 20m 30m 40m 50m 60m 70m 80m 90m
Sound path tilting upwards outdoors due to wind
blowing towards loudspeakers
Conversely, a wind gradient associated with wind blowing from behind a loudspeaker
system will "speed up" its vertical wavefront differentially. The vertical wavefront
will be speeded up less near the ground and its sound path will veer downwards.
30m
20m
Wind Stronger
10m
Wind Weaker
0m
0m 10m 20m 30m 40m 50m 60m 70m 80m 90m
Sound path tilting downwards outdoors due to wind
blowing away from loudspeakers
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Local winds
Air absorbs very little heat from the sun's rays. It is indirectly heated by contact with
warm surfaces. It also relies on contact with cooling surfaces to lose heat.
A local, anabatic wind can be set up by air rising up a slope warmed by the morning
sun.
The same slope may cool the air at night causing it to flow down hill to form a
katabatic wind. To maintain coverage, loudspeaker cluster tilts may need to be
readjusted between morning orchestral rehearsals for a major outdoor event and the
actual show.
Gusts and squalls
On a fair day when the ground is warm and clouds are forming and being moved by a
very light breeze, local winds may vary in direction and strength as illustrated below.
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Local winds may be even more erratic in showery weather. Dramatic down-drafts of
cold air may occur causing local squalls.
Graph showing main wind speed (dark colour) and gusts (light colour)
over several hours
The above main wind and gust plot shows that gusts can be more erratic in nature and
several times stronger than the main wind. Their effects will be far more audible than
a steady wind.
Anti-phasing eq
It may be advisable to roll off the system's high frequency response during gusts and
squalls as a decreasing hf response sounds more natural than the incoherent swishing
noise associated with phasing. A single pole (6dB per octave) high cut filter with a
variable knee control down to 8KHz works well.
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2a.3 Temperature effects
The speed of sound varies with air temperature:
This means that the speed of sound can vary from 331.5m/s to 354.9m/s between 0ºC
and +40ºC.
Temperature Gradient
As mentioned in Section 2a.2, air is a poor heat conductor and relies on its contact
with surfaces to heat up and cool down.
On a clear, warm, sunny day the ground will warm low level air and the atmosphere
will heat up, by convection, from bottom to top. Warm air cannot rise to the top of the
atmosphere because air pressure drops with height and air temperature falls as the
pressure falls.
Sound will travel faster near the ground and slower higher up causing its path to be
tilted upwards.
Cooler
30m
20m
10m
Warmer
0m
0m 10m 20m 30m 40m 50m 60m 70m 80m 90m
Sound path tilting upwards outdoors due to normal
temperature decrease with height
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If the sky remains clear after sunset, the ground will cool and draw heat from the air
in contact with it. Air nearest the ground may get cooler than the air above it. In the
absence of wind, this cool air may stay near the ground on a still night.
60m
50m
40m
30m
20m
Temperature
inversion
10m
0m
0˚C
10˚C
20˚C
The same "inverse temperature gradient" can form above ice rinks and in most indoor
venues. Sound will now travel slower near the ground and faster higher up causing its
path to be tilted downwards.
30m
20m
Warmer
10m
Cooler
0m
0m 10m 20m 30m 40m 50m 60m 70m 80m 90m
Sound path tilting down indoors due to high level heating or low
level cooling (eg. ice rink) or outdoors due to cooling ground
2a.4 Relative humidity effects
Air absorption is quoted in dB/m and occurs over and above the usual sound pressure
level changes caused by an expanding wavefront quoted in dB/doubling of distance.
Air absorption changes with relative humidity and temperature but these changes are
complex - particularly where the humidity is low and the temperature varies a lot.
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0.3dB/m
10KHz
0.2dB/m
6KHz
0.1dB/m
3KHz
1.5KHz
0dB/m
Absorption
coefficient
0
10% 20% 30% 40% 50% 60% 70% 80% 90%
Relative Humidity
In this example, high-mid and high frequency air absorption characteristics are
quite complex at low relative humidity. Mid frequency absorption increases with
increasing humidity, reaches maximum attenuation at about 5% RH and then starts to
drop again. High-mid frequency absorption increases with increasing humidity,
reaches maximum attenuation between 5 and 15% RH and then starts to drop again.
High frequency absorption increases with increasing humidity, reaches maximum
attenuation between 15 and 20% RH and then starts to drop again.
At the higher relative humidity (above 20% RH) found in temperate latitudes,
absorption generally decreases with increasing relative humidity. This means that
high frequency sound propagation improves as the relative humidity rises … but this
is not always obvious in warmer weather as our ears produce more secretions when
we perspire.
Note that, even at high relative humidity, we will still loose 10dB at 10KHz over
100m. Martin Audio Wavefront Longthrow systems provide the extra high-mid and
high frequency headroom to cope with this air absorption.
Humidity changes can be a problem indoors too. On rainy days, damp audiences in
large venues can cause temporary humidity increases that can make a well soundchecked system sound too harsh and fizzy. Be prepared to back off any mid and high
frequency compensation until the venue's air conditioning has caught up.
Longthrow systems should be corrected with caution and distant audience areas
rechecked at regular intervals during large events.
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Wavefront Compact Series
Applications Guide
Section 3
Wavefront W8CS
Flown Subwoofer
MARTIN AUDIO
L O N D O N
The Martin Experience
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Section 3
Wavefront W8CS Flown Subwoofer
Contents
3.1
Introduction
3.2
Specifications
3.3
Pin-outs and cabling
3.4
System patching
3.5
DX1 Loudspeaker Management System
3.6
Power amplifier recommendations
3.6.1
Martin Audio MA4.2 Power Amplifier Overview
3.7
Adding W8CS’ to flown W8C systems
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Wavefront W8CS Flown Subwoofer
3.1 Introduction
The Martin Audio Wavefront W8CS Flown Subwoofer comprises a special 15" high
excursion driver coupled to an efficient mid-bass horn with a sub-bass port. This
unique combination gives the W8CS the characteristic punch of a horn-loaded system
with the low frequency bass extension of a reflex enclosure.
The W8CS is a compact, light weight system in a trapezoidal cabinet. It has the same
footprint as the popular W8C (Section 1) and has been engineered to extend the
Wavefront Compact W8C's performance to below 45Hz.
W8CS’ may either be used as full bass subwoofers (up to120Hz) or may be flown as
mid-bass sections (60-160Hz) to complement floor standing WSXs.
Like all flown Wavefront products, W8CS’ are fitted with MAN load-certified flying
points and are designed to comply with the 12:1 safety factor specified by the German
VBG70 standard when used with the compatible 12:1 flying systems. One important
advantage of the MAN flying system is that inter-cabinet connections place a minimal
load on the cabinets and, being external, can be load certified and inspected
independently.
3.2 Specifications
Type:
Compact folded bass horn, port assisted
Frequency response:
45-200Hz +/- 3dB
Low frequency limit:
-10dB @ 35Hz
Driver:
1 x 15" (380mm) long excursion
Rated Power:
Sensitivity:
800W into 8 ohms, 3200W peak
105dB/W
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Maximum SPL:
132dB continuous, 138dB peak
Impedance:
8 ohms nominal
Connectors:
2 x Neutrik NL8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (inc wheels):
(W) 562mm x (H) 799mm x (D) 925mm
(W) 22.1ins x (H) 31.5ins x (D) 36.4ins
Flown weight:
61kg (134lb). Lid 4kg (9lb) extra
Before rigging, note colour coding!
W8C has 2 black points per side
W8CS has 1 black point per side
W8CT has 2 orange points per side
W8CM has 1 orange point per side
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3.3 Pin-outs and cabling
W8CS
NL8
W8CS
-1
Driver -
+1
Driver +
-2
Driver -
+2
Driver +
-3
n/c
+3
n/c
-4
n/c
+4
n/c
(See Section 1.3 for connector pin-out drawing)
3.3.1 Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
3.3.2 Recommended loudspeaker cable
Although only 4-core cable is required for W8CS’, many users will find it convenient
to standardise on 8-core NL8 cables to avoid confusion when using other
loudspeakers in the Wavefront range.
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Cable run vs copper core cross sectional area
Up to 50m
Up to 100m
Single W8CS
Two W8CS’ paralleled at the
cluster.
2.5mm²
6mm²
6mm² (or 2 x 2.5mm² cores in parallel)
10mm² (or 2 x 6mm² cores in parallel)
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
3.4 System patching
Refer to Section 1.4 and Section 2.4 for general Wavefront patching suggestions and
examples.
Bass sub-mix operation
Many mix operators prefer to create a separate sub-mix for bass/mid-bass sections.
This is good practice as it helps provide main system headroom for those allimportant vocals and solos whilst allowing for larger-than-life percussion and bass
instrument mixes without intermodulation and distortion.
This configuration can easily be programmed into the Martin Audio DX1
Loudspeaker Management System. The following illustrates a DX1 set up to control
an active (3-way) Wavefront W8C system with W8CS’ (configured as a flown midbass section) augmenting floor-stacked WSXs.
Flying W8CS’ as a mid-bass section eliminates the problem of mid-bass absorption
experienced with densely packed standing crowds.
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3.5 DX1 Loudspeaker Management System
Refer to Section 1.5 for general information on the Martin Audio DX1 Loudspeaker
Management System including configuration examples.
3.5.1 DX1 Output Gain and Limiter settings for W8CS’
Standardising on one good model of power amplifier (preferably the Martin Audio
MA4.2)and correctly set-up controller (preferably the Martin Audio DX1) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories. (See Section 1.5 and DX1 Speaker
Management System User's Guide for further details)
Gain settings
The following initial DX1 output gain settings will enable full system performance to
be obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
W8CS - assuming 800Wcont - 1600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Initial DX1
Output GAIN
dB
Crown MA5002VZ (0.775v)
Martin MA4.2** (41dB)
Crest CA18 (x115)
Crown MA3600VZ (0.775v)
-2
0.62 42
-9
-1
0.69 41
-8
-1
0.69 41
-8
-1
0.69 41
-8
0
0.77 40
-7
+1
0.87 39
-6
+2
0.98 38
-5
+3
1.09 37
-4
QSC PL236/PL236A (36dB) +4
1.23 36
-3
+5
1.38 35
-2
+6
1.55 34
-1
+7
1.73 33
0
Martin MA4.2** (32dB)
+8
1.95 32
+1
Crest 8001 (x40)
+8
1.95 32
+1
Crest 9001 (x40)
+8
1.95 32
+1
QSC PL236A (32dB)
+8
1.95 32
+1
+9
2.18 31
+2
+10 2.45 30
+3
+11 2.75 29
+4
+12 3.08 28
+5
+13 3.46 27
+6
Crown MA3600VZ (26dB) +14 3.88 26
+7
Crown MA5002VZ (26dB) +14 3.88 26
+7
QSC PL236A (26dB)
+14 3.88 26
+7
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers.
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Cluster balance (eg farfield-to-midfield or inner-to-outer) should be adjusted at the
power amplifier controls to maintain limiter tracking. See Section 3.7.
Balancing the system using gain controls in the signal path before the power
amplifiers is not recommended as it will cause the higher signal level upper rows of a
big cluster to start limiting before the lower signal levels downfills causing tonal
changes at the mix position.
Limiter settings
The Rated Power specification in Section 3.1 indicates the maximum long-term
power dissipation that can be tolerated before driver ageing or damage occurs through
overheating or over-excursion.
When choosing power amplifiers, do not be tempted to exceed the 800W into 8Ω
power rating unless the amplifier's power rails are well regulated (see Section 3.6) even with properly set controllers in place. Although Martin Audio drivers are
mechanically designed to survive normal road use and the occasional operator error,
overpowered or bridged amplifiers can cause over-excursions that stress and age
drivers. The best way to get the clean, relaxed sound of an overpowered amplifier is
to choose an amplifier with plenty of current reserve - ie an amplifier with good 2Ω
specification - and avoid running more than two cabinets in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
the subwoofer's high pass frequency as follows:
High pass filter range
Attack time
Release time
>31Hz
45mS
720mS
31Hz - 63Hz
16mS
256mS
(63Hz high pass may be used when W8CS crossing in as a mid-bass)
These attack times allow the power amplifiers to clip momentarily but not for long
enough to be obvious to listeners or cause driver overheating. It is quite normal to see
amplifier clip indicators on the odd programme peak but continuous clipping would
indicate a cable short circuit, wrong controller settings, excessive power amplifier
gain or low mains voltage.
The following initial DX1 output limiter settings will avoid voice coil overheating
and minimise amplifier clipping for high quality, trouble free operation.
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W8CS - assuming 800Wcont - 1600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Crown MA5002VZ (0.775v)
Martin MA4.2** (41dB)
Crest CA18 (x115)
Crown MA3600VZ (0.775v)
-2
-1
-1
-1
0
+1
+2
+3
QSC PL236/PL236A (36dB) +4
+5
+6
+7
Martin MA4.2** (32dB)
+8
Crest 8001 (x40)
+8
Crest 9001 (x40)
+8
QSC PL236A (32dB)
+8
+9
+10
+11
+12
+13
Crown MA3600VZ (26dB) +14
Crown MA5002VZ (26dB) +14
QSC PL236A (26dB)
+14
0.62
0.69
0.69
0.69
0.77
0.87
0.98
1.09
1.23
1.38
1.55
1.73
1.95
1.95
1.95
1.95
2.18
2.45
2.75
3.08
3.46
3.88
3.88
3.88
42
41
41
41
40
39
38
37
36
35
34
33
32
32
32
32
31
30
29
28
27
26
26
26
Recommended
DX1 LIMITER
Settings
dBu
-3
-2
-2
-2
-1
0
+1
+2
+3
+4
+5
+6
+7
+7
+7
+7
+8
+9
+10
+11
+12
+13
+13
+13
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers.
Use lower settings (or more subwoofers!) if your power amplifiers indicate clipping
on more than just the odd peak. Excessive clipping may also be caused by inadequate
power amplifier reserve or an inadequate mains supply. See Section 3.6.
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3.6 Power amplifier recommendations
The Wavefront Compact Subwoofer has been designed and manufactured for very
high performance but will not give that performance unless power amplifiers are
chosen and used intelligently.
Power capability
W8CS’ provide full performance when driven by professional power amplifiers
capable of delivering undistorted output power into a range of loads as follows:
W8CS
800 W(AES) into 8 ohms
1,600 W(AES) into 4 ohms
and
3,200 W(AES) into 2 ohms
Please note:
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times their quoted
power for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by over-sized amplifiers should be avoided.
Martin Audio MA series power amplifiers have regulated rails so it is quite
permissible to use slightly overpowered models - with suitably set controller limiters
- without risking uncontrolled power bursts. The MA series power amplifiers’
regulated power rails also ensure maximum performance under the real-world concert
conditions of less-than-optimum mains supplies and low impedance loads. See
Section 3.6.1 for further details.
Amplifier load tolerance
An efficient subwoofer system in live concert conditions can act as a surprisingly
dynamic and complex load. Most modern touring power amplifiers claim 2 ohm
capabilities but make sure your amplifier is also capable of driving reactive (ie
inductive or capacitive) loads without prematurely clipping or developing output
stage crossover distortion.
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Power reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for percussive peaks and sustained bass
notes.
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load.
An electrical technician should check the mains supply vs demand using an
accurate rms voltage meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving too many W8CS’ in parallel. I would suggest no more
than two so that the power amplifier’s 2 ohm spec is kept in reserve for
musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
Power amplifier gain or level settings reminder
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section 3.5). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controllers have been set as tabulated in Section 3.5, power amplifier
level controls should be set to full (fully clockwise) for loudspeaker sections requiring
the strongest drive. Amplifiers driving nearer-field sections within the same cluster
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may be backed off as required for smooth coverage. This process will ensure that
the cluster coverage remains balanced during limiting.
Rack mounting
As with main W8C systems, always leave a 1U space between big subwoofer power
amplifiers and controllers. Although most modern amplifiers don’t radiate significant
fields it's better to play safe and keep the system free from hum & buzz. Rear
supports are recommended. Check the manufacturer's application notes for details.
3.6.1
Martin Audio MA4.2 Overview
Features
Ø
Ø
Ø
Ø
Ø
Ø
Switch mode power supply
Superior sonic performance
Light weight
Advanced protection circuits
Efficient copper cooling system
Minimum load switches (MLStm)
The MA4.2 power amplifier has been designed to combine reliability and high power
output with sonic excellence. Utilising an advanced switch mode power supply, the
MA4.2 is characterised by a very high power-to-weight ratio, in a lightweight, 2U
package.
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See MA4.2 Power Amplifier User's Guide for detailed operating instructions.
Cooling System
The Martin Audio MA4.2 amplifier runs very cool due to a special patented copper
cooling system. The amplifier’s bi-polar output devices are mounted directly onto a
copper heat sink (copper conducts heat twice as efficiently as aluminium) and
maximum heat dissipation is achieved by turbulent airflow over the heatsink’s
geometric fins.
The MA4.2 amplifier features two proportional speed cooling fans which take in air
from the front of the amplifier and exhaust from the rear. A horizontal pressure
chamber between the heatsink and the cooling fans ensures that there is little
difference in the operating temperatures of each output device. In contrast, a
conventional tunnel design can result in a temperature variance of up to 40° between
output devices.
Switch Mode Power Supply
The MA4.2’s switch mode power supply (SMPS) is the modern solution to the
problems of size and weight. Switch mode power supplies are not new - they are
found in computers and televisions. However, the demands of high power audio are
very different to these applications. The MA4.2 overcomes the size and weight
constraints of conventional power supplies whilst at the same time avoiding the
pitfalls of typical switch mode designs.
The low output impedance of the SMPS means that rail voltages do not sag under
heavy load conditions. Additionally, the rail capacitors are being recharged at a much
faster rate than those in a conventional power supply. The result is an exceptional fast
transient low frequency performance at all power levels.
Efficiency is also maximised. With much smaller transformers than a conventional
supply, there is much less loss due to transformer resistance and much less power
wasted as heat in the power supply.
Regulation of the SMPS means that the power amplifier will produce the same power
output, even if the AC line voltage drops by 20%.
Minimum Load Switches (MLS™)
Because the SMPS is regulated, the maximum power available for the output stages
can be adjusted without increased heat dissipation or efficiency loss. This allows the
user to match the output power with the loudspeaker impedance.
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Protection
The MA4.2 amplifier has many advanced protection features that will protect both the
amplifier and the speakers connected to it, under fault conditions. All protection
circuits are independent and inaudible in normal use.
Clip Limiters
Clip limiters prevent dangerous clipped signals reaching the speaker. They work by
monitoring the output to check for signals not present at the input i.e.distortion. If
distortion exceeds 1% on an output, the limiter will reduce the input signal
proportionally.
Thermal Protection
Thermal Protection circuitry prevents the amplifier from running at an unsafe
temperature by muting the input signal when the internal temperature rises above
90°C.
Short Circuit Protection
The MA4.2 amplifier is completely short circuit protected. The protection circuits
permit very high peak currents, but maintain the output devices within their safe
operating area.
Mains Voltage Protection
This operates if the mains voltage falls outside its permitted operating range. If this
occurs, the power supply will shut down until the correct mains voltage is restored.
DC and VHF Protection
Both DC voltages and high power VHF signals can cause damage to loudspeakers.
The MA4.2 amplifier incorporates protection circuits which are activated when
damaging DC voltages or VHF signals are present at the outputs.
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MA4.2 Specifications
Input Impedance
Gain select switch
CMRR at 1KHz
Output impedance at 1KHz
Power Bandwidth
Slew rate
Hum/Noise
Channel Separation
Mains Operating Voltage
Protection
Distortion
THD 20Hz - 20kHz and 1W –
1000W
THD at 1 kHz and 2000W
DIM 30 at 500W
CCIF (13 and 14kHz) at 500W
SMPTE (60Hz and 7kHz) at 500W
20kohms (balanced) 10kohms single ended
41dB (I/P sens 0.775V), 32dB (I/P sens 2.26V)
>50dB
<0.06 ohms
5Hz - 20kHz
20V/us
<-95dB
1kHz > 80dB
10kHz > 70dB
120 – 270 (minimum start voltage 190)
full output power maintained 180 – 280V.
Optional (65 - 135V) operation.
DC, High temperature, Turn on, VHF,
Over and under voltage, Clip limiters.
AFS Short circuit.
4 ohms 0.1%
4 ohms 0.04%
4 ohms 0.04%
4 ohms 0.04%
4 ohms 0.04%
Power Matrix
LOAD CONFIGURATION
16 ohms Stereo (2 channel)
8 ohms Stereo (2 channel)
4 ohms Stereo (2 channel)
2 ohms Stereo (2 channel)
16 ohms Bridged mono
8 ohms Bridged mono
4 ohms Bridged mono
MLS SWITCH SETTING
(-5dB)
(-4dB)
(-2dB)
220W
260W
410W
430W
520W
820W
830W
1000W
1600W
1660W
2000W
2200W
3050W[2]
860W
1040W
1640W
1660W
2000W
3200W
3320W
4000W
4400W
(0dB)
650W
1300W
2100W
2400W[1]
3200W[2]
2600W
4200W
4800W[1]
[1] = Component tolerance
dependent [2] = Continuous power,
one channel driven or peak power
both channels driven. Thermal
protection may occur at high
continuous power. Power in watts
(EIA 1kHz, 1% THD)
Weight
Dimensions
10kg (22lbs)
(W) 483mm x (H) 88mm x (D) 347mm
(W) 19ins x (H) 3.5ins x (D) 13.7ins
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3.7 Adding W8CS’ to flown W8C systems
Although the Wavefront W8C is often used as a base for smaller floor-stacked or
stage-stacked systems (see Section 1.8), flying W8CS’ with main W8C systems can
keep the floor tidy and free up floor space for scenery, TV camera tracks etc.
As mentioned earlier, very large outdoor festival crowds will absorb mid-bass from
low-profile, ground stacked subwoofers. Flying W8CS’ as horn-loaded mid-bass
complements the horn-loaded WSX subwoofers to provide an incredibly tight,
efficient and detailed bass performance that will shift air and provide a phenomenal
kick drum punch.
3.7.1 W8CS/W8C configurations
For medium power amplications - amplifying an large orchestra, for example, where
low frequency stability is important - a single row of W8CS’ may be added to a
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standard W8C cluster extending its low frequency response to below 45Hz. This
configuration can be very efficient as it uses the rest of the cluster as a baffle,
increasing forward projection allowing high gain before feedback.
The following iconic layout may be used to represent the above cluster:
30
30
30
30
30
30
20
20
30
20
20
30
30
30
20
20
20
20
30
30
Important reminder:
Splay angles are always quoted axis-to-axis - not between cabinet sides!
ie.
30
=
|‹ 30º ›|
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W8CS’ flown in rows with W8Cs
30
30
30
30
30
30
20
20
20
20
30
30
30
30
30
30
20
20
30
20
30
20
30
Multiple rows of W8CS’ increase low frequency headroom for higher power rock,
dance club applications.
Note that flying W8CS’ in rows keeps clusters relatively narrow where width is at a
premium.
Coverage would be 145º horizontal x 70º vertical.
For very high power rock or dance applications, the above W8CS’ may be configured
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as flown mid-bass elements (crossed in at 60Hz and out at 160Hz) to augment floorstacked WSXs working as low subs below 60Hz. Refer to Section 2.4.
Power amplifier monitoring at real-world gigs have shown that half of the total
system power is demanded between 60Hz & 160Hz during heavy rock and dance
music.
W8CS’ flown in columns with W8Cs
15
15
15
15
15
15
20
20
20
20
20
20
20
20
20
20
20
20
20
20
15
15
15
15
15
15
Again, coverage would be 145º Horizontal x 70º Vertical.
Flying W8CS’ in columns between W8C columns keeps clusters shorter whilst
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providing good vertical control for minimum roof excitation.
W8CS’ may be flown as fullbass where floor space is required for TV cameras or
may be configured as flown mid-bass elements to complement floor-stacked WSXs.
For further information on suitable Wavefront subwoofer systems and a brief tutorial
on bass stack sizes and shapes vs coverage see Section 4.
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Wavefront Compact Series
Applications Guide
Section 4
Wavefront WSX
Folded Horn
Subwoofer
MARTIN AUDIO
L O N D O N
The Martin Experience
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Section 4
Wavefront WSX Folded Horn Subwoofer
Contents
4.1
Introduction
4.2
Specifications
4.3
Pin-outs and cabling
4.4
System patching
4.5
DX1 Loudspeaker Management System
4.6
Power amplifier recommendations
4.7
Placement
4.8
WSX application examples
4.9
Further examples
4.10
Spaced systems
4.11
Electronic steering
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Wavefront WSX Folded Horn
Subwoofer
4.1 Introduction
The powerful WSX folded horn subwoofer is designed to complement Wavefront
Series W8C touring systems to provide deep bass with maximum efficiency, speed
and impact. Its classic Martin ‘S’ shaped folded horn is over 7 feet (2.1m) long and
couples a powerful 18” (460mm) long excursion driver to the airload with a modified
hyperbolic expansion law.
4.2 Specifications
Freq response:
38-150Hz +/- 3dB (half space)
LF limit:
-10dB @ 28Hz
Rated Power:
600W into 8 ohms, 2400W peak
Sensitivity:
105dB (half space with band limited pink noise)
Maximum SPL:
Impedance:
132dB continuous, 138dB peak (half space with band limited
pink noise)
8 ohms nominal
Crossover Freq:
150Hz or below
Crossover System:
Martin Audio DX1 Loudspeaker Management System,
MX4 or MX5. (See operating instructions)
Connectors:
2 x Neutrik NL8
Dimensions:
(W) 572mm x (H) 1066mm x (D incl wheels) 1065mm
(W) 22.5ins x (H) 41.9ins x (D incl wheels) 41.9ins
Weight:
96kg (211 lbs)
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4.3 Pin-outs and cabling
WSX
NL8
WSX
-1
Driver -
+1
Driver +
-2
Driver -
+2
Driver +
-3
n/c
+3
n/c
-4
n/c
+4
n/c
(See Section 1.3 for connector pin-out drawing)
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4.3.1 Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
4.3.2 Recommended loudspeaker cable
Although only 4-core cable is required for WSXs, many users will find it convenient
to standardise on 8-core NL8 cables to avoid confusion when using other
loudspeakers in the Wavefront range.
Cable run vs copper core cross sectional area
Up to 50m
Up to 100m
Single WSX
Two WSXs paralleled
2.5mm²
6mm²
6mm² (or 2 x 2.5mm² cores in parallel)
10mm² (or 2 x 6mm² cores in parallel)
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
4.4 System patching
Refer to Section 1.4 and Section 2.4 for general Wavefront patching suggestions and
examples.
Bass sub-mix operation
Many mix operators prefer to create a separate sub-mix for bass/mid-bass sections.
This is good practice as it helps provide main system headroom for those allimportant vocals and solos whilst allowing for larger-than-life percussion and bass
instrument mixes without intermodulation and distortion.
This configuration can easily be programmed into the Martin Audio DX1
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Loudspeaker Management System. The following illustrates a DX1 set up to control
an active (3-way) Wavefront W8C system with floor-stacked WSXs augmented by
W8CS’ configured as flown mid-bass sections.
Augmenting WSXs with flown W8CS’ as mid-bass sections eliminates the problem
of mid-bass absorption experienced with densely packed standing crowds.
4.5 DX1 Loudspeaker Management System
Refer to Section 1.5 for general information on the Martin Audio DX1 Loudspeaker
Management System including configuration examples.
4.5.1 DX1 Output Gain and Limiter settings for Wavefront WSXs
Standardising on one good model of power amplifier and correctly set-up controller
(preferably the Martin Audio DX1) will provide the most dynamic system
performance and protection whilst simplifying design and reducing spares
inventories.
The Martin Audio DX1 Loudspeaker Management System may be user-programmed
for a wide range of touring configurations based on its 2 input + sum, 6 output matrix.
This operation is best completed by an audio technician who is familiar with DSP based pro-audio equipment.
(See Section 1.5 and DX1 Speaker Management System User's Guide for further
details)
Gain settings
The following initial DX1 output gain settings will enable full system performance to
be obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
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WSX - assuming 600Wcont - 1200Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Initial DX1
Amplifier
Amplifier
Output GAIN
Sensitivity
Gain
When used as:
Sub-bass
Full bass
dBu Vrms dB
(>60Hz)
(>160Hz)
dB
dB
Crown MA5002VZ (0.775v) -2
0.62 42
-4
-9
Martin MA4.2** (41dB)
-1
0.69 41
-3
-8
Crest CA18 (x115)
-1
0.69 41
-3
-8
Crown MA3600VZ (0.775v) -1
0.69 41
-3
-8
0
0.77 40
-2
-7
+1
0.87 39
-1
-6
+2
0.98 38
0
-5
+3
1.09 37
+1
-4
QSC PL236/236A (36dB)
+4
1.23 36
+2
-3
+5
1.38 35
+3
-2
+6
1.55 34
+4
-1
+7
1.73 33
+5
0
Martin MA4.2** (32dB)
+8
1.95 32
+6
+1
Crest 8001 (x40)
+8
1.95 32
+6
+1
Crest 9001 (x40)
+8
1.95 32
+6
+1
QSC PL236A (32dB)
+8
1.95 32
+6
+1
+9
2.18 31
+7
+2
+10 2.45 30
+8
+3
+11 2.75 29
+9
+4
+12 3.08 28
+10
+5
+13 3.46 27
+11
+6
Crown MA3600VZ (26dB) +14 3.88 26
+12
+7
Crown MA5002VZ (26dB) +14 3.88 26
+12
+7
QSC PL236A (26dB)
+14 3.88 26
+12
+7
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers.
Limiter settings
The Rated Power specification in Section 4.2 indicates the maximum long-term
power dissipation that can be tolerated before driver ageing or damage occurs through
overheating or over-excursion.
When choosing power amplifiers, do not be tempted to exceed the 600W into 8Ω
power rating unless the amplifier's power rails are well regulated (see Section 4.6) even with properly set controllers in place. Although Martin Audio drivers are
mechanically designed to survive normal road use and the occasional operator error,
overpowered or bridged amplifiers can cause over-excursions that stress and age
drivers. The best way to get the clean, relaxed sound of an overpowered amplifier is
to choose an amplifier with plenty of current reserve - ie an amplifier with good 2Ω
specification - and avoid running more than two cabinets in parallel.
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To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
the subwoofer's high pass frequency. These attack times allow the power amplifiers to
clip momentarily but not for long enough to be obvious to listeners or cause driver
overheating. It is quite normal to see amplifiers momentarily clipping on the odd
programme peak but continuous clipping would indicate a cable short circuit, wrong
controller settings, excessive power amplifier gain or low mains voltage.
High pass filter range
Attack time
Release time
>31Hz
31Hz - 63Hz
45mS
16mS
720mS
256mS
The following initial DX1 output limiter settings will avoid voice coil overheating
and minimise amplifier clipping for high quality, trouble free operation.
WSX - assuming 600 W into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Crown MA5002VZ (0.775v)
Martin MA4.2** (41dB)
Crest CA18 (x115)
Crown MA3600VZ (0.775v)
-2
-1
-1
-1
0
+1
+2
+3
QSC PL236/PL236A (36dB) +4
+5
+6
+7
Martin MA4.2** (32dB)
+8
Crest 8001 (x40)
+8
Crest 9001 (x40)
+8
QSC PL236A (32dB)
+8
+9
+10
+11
+12
+13
Crown MA3600VZ (26dB) +14
Crown MA5002VZ (26dB) +14
QSC PL236A (26dB)
+14
0.62
0.69
0.69
0.69
0.77
0.87
0.98
1.09
1.23
1.38
1.55
1.73
1.95
1.95
1.95
1.95
2.18
2.45
2.75
3.08
3.46
3.88
3.88
3.88
42
41
41
41
40
39
38
37
36
35
34
33
32
32
32
32
31
30
29
28
27
26
26
26
Recommended
DX1 LIMITER
Settings
dBu
-3
-2
-2
-2
-1
0
+1
+2
+3
+4
+5
+6
+7
+7
+7
+7
+8
+9
+10
+11
+12
+13
+13
+13
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers. (See illustration in Section 3.5.1)
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NOTE!
Use lower settings (or more subwoofers!) if your power amplifiers indicate clipping
on more than just the odd peak. Excessive clipping may also be caused by inadequate
power amplifier reserve or an inadequate mains supply. See Section 4.6.
4.6 Power amplifier recommendations
The Wavefront WSX Subwoofer has been designed and manufactured for very high
performance but will not give that performance unless power amplifiers are chosen
and used intelligently.
Power capability
WSXs provide full performance when driven by professional power amplifiers
capable of delivering undistorted output power into a range of loads as follows:
WSX
600 W(AES) into 8 ohms
1,200 W(AES) into 4 ohms
and
2,400 W(AES) into 2 ohms
Please note:
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times the power
quoted for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by over-sized amplifiers should be avoided.
Martin Audio MA series power amplifiers have regulated rails so it is quite
permissible to use slightly overpowered models - with suitably set controller limiters
- without risking uncontrolled power bursts. The MA series power amplifiers’
regulated power rails also ensure maximum performance under the real-world concert
conditions of less-than-optimum mains supplies and low impedance loads. (See
Section 3.6.1)
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Amplifier load tolerance
An efficient subwoofer system in live concert conditions can act as a surprisingly
dynamic and complex load. Most modern touring power amplifiers claim 2 ohm
capabilities but make sure your amplifier is also capable of driving reactive (ie
inductive or capacitive) loads without prematurely clipping or developing output
stage crossover distortion.
Mains safety!
A fully qualified technican should check mains safety and phase voltage before the
system is patched.
Power reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for percussive peaks and sustained bass
notes.
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load.
An electrical technician should check the mains supply vs demand using an
accurate rms voltage meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving too many WSXs in parallel. I would suggest no more than two
so that the power amplifier’s 2 ohm spec is kept in reserve for musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
Gain or level settings
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
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Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section 4.5.1). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controller output levels and limiters have been set as tabulated in
Section 4.5.1, power amplifier level controls should be set to full (fully clockwise) for
loudspeaker sections requiring the strongest drive. Other amplifiers - driving apron
subwoofer sections, for instance - may be backed off as required for smooth coverage.
This process will ensure that the system remains balanced during limiting.
Rack mounting
As with main W8C systems, always leave a 1U space between subwoofer power
amplifiers and controllers. Although most modern amplifiers don’t radiate significant
fields it's better to play safe and keep the system free from hum & buzz. Rear
supports are recommended. Check the manufacturer's application notes for details.
4.7 Placement
The WSX is designed to be ground stacked. Ground stacking maintains maximum
efficiency and provides the solid mounting essential for good dynamics.
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WSX horns flare away from the label end. They can be symmetrically coupled by
placing them label-to-label …
Symmetrically coupled 2-wide columns show a slight improvement in mid-bass
amplitude and polar response - but the effect becomes insignificant in large, flat
fronted arrays or widely spaced stage apron systems.
2-wide symmetrical columns of WSXs may be horizontally arrayed just like main
cluster systems.
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4.7.1 Array shapes vs coverage
WSXs may be stacked and arrayed to increase sound pressure and tailor coverage.
The sound pressure increase is intuitive but the significance of subwoofer array
shapes and sizes is often overlooked.
The following table shows the sound pressure boost and coverage provided by a
variety of flat fronted arrays:
Array
Approx Boost
(wrt single unit)
Horizontal
coverage
Vertical
coverage
-
Wide
Wide
+12dB
Wide
Narrow
+12dB
Narrow
Wide
+24dB
Narrow
Narrow
In these examples “wide” means that there are no coverage nulls within the forward
180º at mid-bass crossover frequencies. Wide coverage arrays have significant output
beyond 180º making them more prone to room colouration.
“Narrow” means that coverage will drop significantly before 180º coverage is reached
at the mid-bass crossover frequency.
General rules:
♦ The larger the array the more directional it becomes
♦ A larger, directional system will be less affected by the room
♦ We get a 6dB far field sound pressure boost every time we double the number of
cabinets
Stacking safety!
Stacked WSXs should always be blocked, strapped and anchored from above by
a qualified rigger.
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4.7.2 Coverage angle for tightly packed flat fronted arrays
-6dB Coverage
Here is a simplified formula for calculating the main coverage angle of a tightly
packed flat fronted array.
* = approximate speed of sound in m/s. Varies with temperature (see Section 2a).
Arcsin means “the angle whose sin is ...”
Flat fronted cluster coverage patterns will be confined to one main lobe whose midbass crossover directivity is proportional to the size of the cluster.
The medium sized array (left) has significant output to ±90º whereas the large array’s
±90º output is dramatically reduced.
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A note on coverage nulls
It is useful to be able to calculate where these first response nulls will occur for
various frequencies as they indicate areas where coverage, transient response and
directional information would be poor without fill systems. For symmetrical arrays
nulls will occur either side of the on-axis line. We can calculate the overall “null-tonull” angle using the simple formula:
As a very rough guide, the null-to-null angle will be approximately twice the -6dB
coverage angle.
Interpreting polar plots
i) It is conventional to “normalise” polar plot on-axis amplitudes so that different polar shapes may be
readily compared. In practice, the large array (right example) would have a higher on-axis amplitude
than the medium array.
ii) It is also conventional to plot polar amplitudes on a logarithmic scale. This is fine when working in
sound pressure level terms but is not suitable for superimposing a polar plot onto a venue plan. Venue
plans are drawn to a linear scale so polar plots with linear amplitude scales would be more suitable.
iii) Polar plots have been simplified in this article for clarity. Real-world off-axis lobe amplitudes and
shapes would vary considerably depending on boundary loading, echoes, reverberation and other
audio sources affecting the same space.
Vertical -6dB coverage
The following table gives the approximate vertical coverage angles of typical WSX
arrays - ignoring boundary effects (see later).
WSXs High
(on sides)
40Hz
3
4
8
16
Wide
Wide
Wide
69º
Vertical coverage
80Hz
Wide
Wide
69º
33º
160Hz
98º
69º
33º
16º
♦ Use tall stacks for long shots. Useful for long distances in low-roofed venues
with raked seating up to the height of the stack
♦ Use short stacks for short, wide vertical shots
♦ Use tall, electronically steered, stacks to project to high, distant seating - see
Section 4.11
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Vertical Boundary effects
A solid floor will act as a reflector. This will cause a vertical stack to perform as if it
were double the length, giving a useful low frequency boost accompanied by a
narrower, more complex polar response.
For instance, an 8 high ground-based stack of WSXs will act like the top half of a 16
high stack.
At 80Hz its smoothest vertical coverage will be from the floor to its own height
(4.6m) + 16.5º. It will, therefore, cover seats 19m above floor level at a distance of
50m and 34m above floor level at 100m.
It is possible to reach higher seating areas whilst retaining the long throw
characteristics of a tall vertical stack by electronically “tilting” the system - see
Section 4.11.
Note that flexible floors may actually absorb sound at some frequencies so the
situation isn’t always so simple in practice.
Horizontal - 6dB coverage
The following table gives the approximate horizontal coverage angles of typical WSX
arrays - ignoring boundary effects.
WSXs Wide
(on sides)
Horizontal coverage
40Hz
80Hz
160Hz
2
4
8
16
Wide
Wide
75º
35º
Wide
75º
35º
17º
75º
35º
17º
9º
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WSXs Wide
(standing upright)
Horizontal coverage
40Hz
80Hz
160Hz
3
4
8
16
Wide
Wide
Wide
69º
Wide
Wide
69º
33º
98º
69º
33º
16º
With WSXs standing upright, flat fronted cluster coverage patterns will be confined
to one main lobe whose mid-bass crossover width is inversely proportional to the size
of the cluster as long as horizontal gaps are less than 500mm.
♦ Use wide arrays for long shots. Useful for long, narrow venues
♦ Use narrow arrays for short, wide shots
Horizontal Boundary effects
A solid wall near an array will act as a reflector. This will cause a horizontal array to
perform as if it were twice as wide, giving a useful low frequency boost accompanied
by a narrower, more complex polar response.
Again, a flexible side wall may absorb sound at certain low frequencies. Boundaries
should always be treated with caution.
4.7.3 Spacing
It is possible to space out WSXs to provide a larger frontal area with fewer units but
care must be taken to avoid irregular coverage at higher, mid-bass frequencies.
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The following formula gives the pressure ratio p(h) (wrt to the on-axis pressure) for
any off-axis angle of a regularly spaced linear array:
Far field polar patterns can be quite complicated - even for a simple pair of
subwoofers driven in unison.
Wide spacing will cause off axis irregularities (combing) because time offsets start to
become significant. See Section 4.10 for a more detailed explanation.
♦ An odd number of half wavelengths will cause nulls along the line of the
loudspeakers (the 90º lines) - see the 2½ wavelength example above.
♦ An even number of half wavelengths will cause lobes along the line of the
loudspeakers - see the 2 wavelength example below.
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The following tables give the maximum recommended gap (between WSX sides) for
the relevant frequency range.
WSXs standing upright
Gap
Smooth coverage range
0.5m
1.0m
2.0m
38 - 160Hz
38 - 110Hz
38 - 80Hz
WSXs lying horizontally
Gap
Smooth coverage range
0.0m
0.5m
1.0m
2.0m
38 - 160Hz
38 - 115Hz
38 - 86Hz
38 - 60Hz
To avoid combing...
♦ Keep horizontal gaps below 1m for upright WSXs
♦ Keeps horizontal gaps below 0.2m for horizontal WSXs
4.7.4 Horizontal splays
Splaying WSX arrays horizontally will widen their mid-bass coverage.
The following sketch shows an 8 wide x 3 high WSX array arranged in four
symmetrical pairs for smooth mid-bass coverage.
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WSXs Wide
(On sides.
Splayed with
Radius = width)
Horizontal coverage
40Hz
80Hz
160Hz
2
4
8
16
Wide
90º
60º
30º
90º
60º
30º
36º
60º
30º
36º
40º
Note that lower frequencies remain focussed when large arrays are used with large
radii. Smaller systems with small radii will widen coverage at all frequencies but may
cause low frequency build-up on thrust and island stages. Avoid this problem
by augmenting small stage corner systems with WSXs placed along the stage apron.
For a smooth polar crossover:
♦ Array the WSXs to match the curvature of the main clusters' low-mid or midbass section whenever possible but avoid making the front horizontal gaps
greater than 200mm
♦ Avoid large gaps between the main system and the WSXs whenever possible
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4.8 WSX application examples
The following sketches show how WSXs may be deployed for a wide range of
productions and types of venue. All productions and venues present their own unique
requirements and these examples are intended as a template or starting point for your
own specific design.
Examples 1 and 2 show typical set-ups for smaller venues.
(1) WSX set-up for small, high power variety/orchestral production
Gives medium vertical & wide horizontal coverage up to 120Hz - allowing for ground effects.
Example 1 uses small stacks of WSXs for a high power variety or orchestral
production as it is quite desirable to excite the natural room acoustic for this type of
application.
(2) WSX set-up for small, very high power dance/rock production
Gives very narrow vertical & wide horizontal coverage up to 120Hz - allowing for ground effects.
Example 2 shows a tight vertical set-up for a very high power dance or rock event
where it is desirable to keep low frequency energy concentrated on the audience for
maximum bass/mid-bass punch without excessive roof excitation. Note that the apron
WSXs are there to provide smooth nearfield coverage, balance backline leakage and
keep the overall sound image locked onto the stage. The closer spacing, used for the
very high power set-ups, helps maintain bass/mid-bass focus out to the midfield/mix
position.
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(3) WSX set-up for very high power dance/rock production in
narrow arena
Gives narrow horizontal & vertical coverage up to 120Hz - allowing for ground effects.
Example 3 shows a very high power dance or rock set-up for a narrow “shoe box”
venue. Note the four-wide left and right WSX arrays for tight horizontal control and
the more tightly packed apron systems for central focusing.
(4) WSX set-up for very high power dance/rock production in wide
arena
Gives wide horizontal & very narrow vertical coverage up to 120Hz - allowing for ground effects.
Example 4 shows a similar set-up - but this time for a wider venue. Note the narrower
left and right WSX stacks for wider horizontal coverage.
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(5) Alternative set-up for wide venues
Splayed WSX arrays for wide horizontal coverage.
Example 5 shows a set-up for a TV shoot in a similar wide venue where sight-lines
are critical. Note the lower profile, splayed left and right WSX arrays.
4.8.1 System alignment
As with all sound system components, a few moments setting up the subwoofer
system for smooth coverage and maximum impact will ensure that the mix operator is
hearing a true representation of the auditorium sound and save a lot of surprises and
head scratching later.
In all cases...
1)
Set the main L&R WSX stacks to match the main L&R system farfield levels
around 120Hz, fine-tuning system delays as required.
2)
Set the L&R stack front-fills to balance the main L&R systems + WSXs in the
nearfield - again, using system delays as required.
3)
Set the flown centre-fills to balance the main L&R systems + WSXs in the
centre midfield/mix position.
4)
Set the apron-fill loudspeakers to focus the central nearfield region. For opera
recitals, some of these may be used for voice imaging only and be
progressively delayed to the principal vocal microphone position.
5)
Set the apron WSX levels to match the band/orchestra apron-fill loudspeakers
around 120Hz.
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4.9 Further examples
Thrust stages
Examples 6 and 7 show typical set-ups for large, thrust stage productions.
(6) WSX set-up for high power variety/orchestral production on
large thrust stage
front view
side view
Gives medium vertical & wide horizontal coverage up to 120Hz for audience on 3 sides - allowing for
ground effects.
1)
2)
3)
4)
5)
Set the front & rear WSX arrays to match the main front & rear system farfield levels
around 120Hz
Set the front & rear W8Cs to balance the main systems + WSXs in the nearfield
Set the flown centre W8Cs to balance the main systems + WSXs + W8Cs in the L, R &
centre/mix position midfield areas
Set the apron W2s to fill the L, R & centre nearfield region
Set the apron WSXs to match the W2s around 120Hz
Again, left and right WSX arrays (but this time at front and rear) are augmented by
apron fills. The system set-ups may be thought of as three-sided versions of examples
3 and 5.
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(7) WSX set-up for very high power dance/rock production on large
thrust stage
front view
side view
Gives narrow vertical & wide horizontal coverage up to 120Hz for audience on 3 sides - allowing for
ground effects - with tighter apron WSX spacing for more coherent nearfield mid-bass coverage and
punch.
1)
2)
3)
4)
5)
Set the front & rear WSX arrays to match the main front & rear corner system farfield
levels around 120Hz
Set the front & rear W8Cs to balance the main systems + WSXs in the nearfield
Set the flown centre W8Cs to balance the main systems + WSXs + W8Cs in the L, R &
centre/mix position midfield areas
Set the apron W3s to fill the L, R & centre nearfield region
Set the apron WSXs to match the W3s around 120Hz
Island stages (not shown)
Island stages are simply four-sided versions of examples 3 and 5 and should be
aligned using the same process.
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4.10 Spaced systems
Whenever two or more loudspeaker systems are fed with the same signal and their
coverage overlaps, sound addition and subtraction will take place depending on the
listener’s position.
In the following example, the off-axis listener may hear delayed sound from the right
hand system.
The two loudspeakers are driven in phase (both were +ve just before the instant
shown) but the extra distance travelled by the second (R) signal causes it to be out of
phase at the listener position at that particular frequency (R is -ve while L is +ve).
Reflections
Remember that a strong side wall reflection will act like a second source and the
direct and reflected signal will combine as if they were two sources.
The following illustration shows what will happen. The direct signal will combine
with the reflected signal as if it were a phantom source in the position shown.
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Addition & Subtraction
The above shows how two pairs of sine waves (with identical amplitude and
frequency characteristics) will sum. Pair (a) are in phase and add. Pair (b) are out of
phase and cancel.
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Polar variations with frequency
Whether particular frequency components add or subtract in the far field will depend
on the loudspeaker system spacing, the angular offset of the listener with respect to
the centre line, and the wavelength.
The following polar responses show what happens when subwoofers are placed 8.6m
apart and are driven in unison at various frequencies:
100Hz
The polar plot shows the far field polar response of the two subwoofers when driven
in phase with the same 100Hz signal. Subwoofer interaction causes irregular coverage
either side of the centre line.
Response nulls (cancellations) occur at the sides because the spacing is an odd
number of half-wavelengths causing this frequency component to cancel in the far
field.
80Hz
The above shows the same system at 80Hz.
At this frequency the central position remains well covered but the polar pattern has
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changed dramatically around the sides. There are now strong lobes at the sides
because the spacing is now an even number of half-wavelengths at this particular
frequency. These lobes could cause low frequency feedback problems on stage with
the high microphone gains used for orchestral low string (cello, double bass) sections
or for “unplugged” performances.
60Hz
At 60Hz the spacing is an odd number of half-wavelengths again so we see side nulls
again.
40Hz
When the frequency drops to 40Hz, the 8.6m spacing = 1 wavelength.
Again, the central response is maintained but there is a dip in response over wide
areas either side of the centre. The spacing is an even number of half-wavelengths
again so we see side lobes again.
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40 Hz reduced spacing
The above shows what happens at 40Hz if we reduce the spacing between the
subwoofers to 4.3m.
We get better central coverage without 40Hz side lobes - adequate for long, narrow
“shoe-box” venues but wider coverage would be required for most arenas.
40Hz close coupled
Close coupling would give a wider coverage at that frequency but the spacing could
still give coverage irregularities at mid-bass frequencies due to the shorter
wavelengths at higher frequencies.
The real world
Bass notes usually include harmonic components each with a different wavelength.
Some will add giving an amplitude peak whilst others will subtract giving an
amplitude dip. This will give tonal changes with listening position and emphasise
particular notes and timbres.
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In the following example, listeners over a wide central area will hear a warm bass
note rich in harmonics whereas those around the sides (in line with the subwoofers at
90º) will hear less of the fundamental but more of the harmonics whose full
wavelengths coincide with the subwoofer spacing.
Listeners in the 60º zone will hear the note at a reduced level and may be more aware
of room reverberation because the direct-to-reverberation ratio would be poorer for
that note. Other notes would give different effects.
In practice, these peaks and troughs can be smoothed out with additional fill systems.
4.11 Electronic steering
It is possible to “aim” ground-stacks towards distant raked seating or balconies or
away from problematic areas by electronically “tilting” the system using multichannel digital delay lines.
The illustration below shows the basic schematic plus the staircase effect** (greyed
out) produced by the progressive increase in drive delay from bottom to top.
**Important Note:
The staggered stack (shown greyed out) illustrates the effect of electronic
steering.
For safety reasons, never try to tilt or stagger a real subwoofer stack.
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Note that it is important to keep the subwoofers tightly packed to avoid polar
anomolies caused by spacing.
Procedure
The normal procedure is to measure the angle from the top of the vertical subwoofer
stack to the highest/most distant seats (using an inclinometer) and to calculate the
required delay increment with the formula shown.
Example
We wish to project bass/mid-bass punch to stadium balcony seats 30º higher than the
top of our WSX stacks.
The WSXs are 572mm wide giving a centre-to-centre spacing of 0.572m.
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This means that our delay increment (in ms)
= tan 30º x 0.572 x 1000
340
= 0.577 x 0.572 x 2.94
= 0.97mS or 970uS.
The following delay line taps would be required for the above system:
t0
t1
t2
t3
t4
t5
t6
=
=
=
=
=
=
=
0ms
0.97mS
1.94mS
2.91mS
3.88mS
4.85mS
5.82mS
Going further
It is possible to apply electronic shaping to horizontal arrays. For instance, it is
common to use curved main clusters for smooth mid and high frequency coverage.
Ground-based subwoofer arrays should follow the same curvature to maintain midbass crossover coherence but this is often difficult due to flat-fronted stage structures.
The following illustration shows an example of a flat-fronted horizontal array
electronically splayed to emulate the greyed-out example shown.
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Section 5
Application Guide
Wavefront W8L Series Line Arrays
W8L, W8LC & W8LM
plus
W8LS and WLX Sub-woofers
Simply need controller and amplifier rack information?
Skip to sections 5.10, 5.11 & 5.12
5.1
Introduction
5.2
Specifications, outline drawings and performance plots
5.3
Classic line array behavior
5.4
How many do I need?
5.5
ViewPointtm 3.03 and System control
5.6
Horizontal considerations
5.7
Sub-woofers and Front Fills
5.8
Climatic effects
5.9
Delay Systems
5.10
W8L Quick Start Guide
5.11
W8LC Quick Start Guide
5.12
W8LM Quick Start Guide
General information
W8L Series Applications Guide
Version 2
Copyright by Martin Audio Ltd 2004; all rights reserved.
19th February 2004
Martin Audio Ltd, Century Point, Halifax Road,
Cressex Business Park, High Wycombe, Buckinghamshire. UK.
The information presented in this document is, to the best of our knowledge, correct. Martin Audio
Limited will not, however, be held responsible for the consequences of any errors or omissions.
Technical specifications, weights and dimensions should always be confirmed with Martin Audio
Limited before inclusion in any additional documentation.
In our efforts to develop and improve our products we reserve the right to change the technical
specification of our products without notice. Martin Audio Limited tries, whenever possible, to
minimise the effects of product changes on equipment compatibility.
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Wavefront W8L Series Line Arrays
5.1 Introduction
Martin Audio W8L Series line arrays are next generation line array systems which
combine innovative loudspeaker design techniques with line array technology to
produce a family of very powerful line arrays with extended frequency response,
smooth coverage and maximum dynamic impact.
The series includes:
The W8L 3-way full-range line array
The W8LC 3-way compact line array
The W8LM 3-way mini line array
The W8L and W8LC systems are fully horn-loaded tri-amplified systems. All
sections are 8 ohms for easy paralleling in pairs.
The W8LM system combines direct radiating and horn-loaded cone drivers for low
and mid frequency coverage with a horn-loaded high frequency section. The system
may be bi-amplified (low/mid & high) or driven using a single amplifier channel via
its internal 3-way passive crossover. W8LMs are 12 ohms for easy paralleling in
threes or fours.
Where low frequency extension is required, W8L Series line arrays will integrate
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with a range of Martin Audio sub-woofers including the Martin Audio W8LS direct
radiating sub-woofer system or the Martin Audio WLX horn-loaded & ported
(Hybridtm) sub-woofer system. See Section 5.7.
W8L, W8LC and W8LM systems combine patentable driver loading techniques researched and proven by Martin Audio over many years - with no-compromise
vertically-coupled waveguides and true constant directivity horns to achieve a level of
efficiency and coverage consistency not usually found in this popular format. W8L
Series horns develop low curvature vertical wavefronts for smooth, comb-free
coupling at practical vertical splay angles. A feature not possible with spaced, pointsource drivers.
W8L Midrange section
Wavefront W8L Series line arrays feature integral, quick deployment flyware systems
which allow progressive curvature columns of up to 16 cabinets to be assembled. By
hinging at the front rather than the rear, the rigging system minimises gaps between
the acoustic elements which would otherwise interfere with the line array effect.
Viewed from the side, W8L Series enclosures are trapezoidal in shape with 3.75º wall
angles to allow arrays of varying curvature to be constructed. A series of inter-cabinet
splay angles from 0º to 7.5º are selected by links at the rear of the enclosure. The 7.5º
maximum splay angle allows tight curvature at the bottom of the array, obviating the
need for dedicated down-fill systems. All hardware is integral and captive.
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W8L rear rigging
Caution:
W8L Series columns should be rigged and flown by
professional riggers or trained personnel under professional
riggers' supervision. Flying professional loudspeaker systems is
not a job for amateurs!
See the appropriate Flying System User Manual for further
details.
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5.2 W8L, W8LC, W8LM line array element specifications
(single enclosure)
Specification
Type
Frequency Resp (±3dB)
Hor Coverage (-6dB)
(-10dB)
Vert Coverage (-6dB)
Driver complement
Rated Power
W8L
W8LC
W8LM
Full-range
3-way line
array element
50Hz-18KHz
90deg
120deg
7.5deg
LF: 1 x 15”
Hybridtm
horn-loaded
cone drivers
Compact
3-way line
array element
60Hz-18KHz
90deg
120deg
7.5deg
LF: 1 x 12”
Hybridtm
horn-loaded
cone drivers
MF: 2 x 8”
horn-loaded
cone drivers
MF: 2 x 6.5”
horn-loaded
cone drivers
Ultra-compact
3-way line
array element
60Hz-18KHz
100deg
120deg
7.5deg
LF+MF:
2 x 8” cone
drivers.
1 ported direct
radiating LF,
1 Hybridtm
horn-loaded
LF/MF.
HF: 3 x 1”
horn-loaded
compression
drivers
LF:
700W AES,
2800W peak
HF: 3 x 1”
horn-loaded
compression
drivers
LF:
400W AES,
1600W peak
MF:
400W AES,
1600W peak
MF:
200W AES,
800W peak
HF
200W AES,
800W peak
HF
100W AES,
400W peak
LF: 106dB
LF: 103dB
MF: 108dB
MF: 106dB
HF: 113dB
HF: 109dB
LF:
134dB cont.,
140dB peak.
LF:
129dB cont.,
135dB peak.
Passive
99dB LF rising
to 105dB HF
Bi-amplified
LF+MF:
125dB cont.,
131dB peak.
MF:
MF:
HF:
HF: 2 x 1”
horn-loaded
compression
drivers
Bi-amplified
LF+MF:
400W AES,
1600W peak
HF: 75W AES,
300W peak
Passive
400W AES,
1600W peak
Bi-amplified
LF+MF:
100dB
HF: 106dB
Sensitivity (spl at 1m, 1W)
Max SPL (spl calc 1m)
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134dB cont.,
140dB peak.
129dB cont.,
135dB peak.
125dB cont.,
131dB peak.
HF:
136dB cont.,
142dB peak.
HF:
129dB cont.,
135dB peak.
LF: 8 ohms
LF: 8 ohms
MF: 8 ohms
MF: 8 ohms
Passive
124dB cont.,
130dB peak.
Bi-amplified
LF+MF:
12 ohms
HF:
12 ohms
HF: 8 ohms
HF: 8 ohms
Nominal Impedance
Crossover
Connectors
Enclosure
Finish
Grille
Dimensions
mm
inches
(*incl wheelboard)
Weight (incl. steel hardware)
Passive
12 ohms
LF to MF:
300Hz passive,
LF to MF:
220Hz active,
LF to MF:
300Hz active,
MF to HF
2.5KHz active
MF to HF
3KHz active
2 x Neutrik
NL8 or PAcon
sockets
(Input & Link)
Vertical
trapezoid
3.75 deg top &
bottom walls.
Multi-laminate
birch ply
Textured paint
Perforated
steel
(W) 1314
(H) 490
(D) 755/855*
2 x Neutrik
NL8 or PAcon
sockets
(Input & Link)
Vertical
trapezoid
3.75 deg top &
bottom walls.
Multi-laminate
birch ply
Textured paint
Perforated
steel
(W) 1000
(H) 367
(D) 550/683*
Vertical
trapezoid
3.75 deg top &
bottom walls.
Multi-laminate
birch ply
Textured paint
Perforated
steel
(W) 620
(H) 241
(D) 400
(W) 51.7
(H) 19.3
(D) 29.7/33.7*
127Kg
(279lbs)
(W) 39.4
(H) 14.5
(D) 21.7/26.9*
58Kg (128lbs)
(W) 24.4
(H) 9.5
(D) 15.75
24Kg (53lbs)
MF to HF
2.2KHz active
or passive
2 x Neutrik
NL4 sockets
(Input & Link)
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W8L & W8LS outline dimensions
(W8L shown)
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W8LC outline dimensions
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W8LM outline dimensions
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W8LX outline dimensions
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W8L polar plot
W8L beamwidth plot
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W8LC polar plot
W8LC beamwidth plot
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W8LM polar plot
W8LM beamwidth plot
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5.3 Classic line array behavior
Although the vertical coverage of a single point source may be wide, when arrayed in
a straight line, multiple sources vector sum to form a tight vertical coverage pattern
that narrows with increasing cluster height and frequency following the classic law
for multiple source line arrays.
* = speed of sound (m/s).Varies with temp.
Arcsin = "the angle whose sin is…"
Nd = the total height of the column in meters
Propagation
Under normal conditions a wavefront moves through air at about 340m per second.
Air gets its properties from the weight and speed of its molecules. Molecules of
different weight (other gases maybe) or different velocity (that translates into
temperature) will exhibit different speeds of sound. Motion of the sound source, the
listener, or the air itself has no effect on the speed of sound, nor does the pressure of
the air.
An impulse applies energy to the air. (This energy becomes a difference in pressure in
front of and behind the wavefront.) As the front expands, the energy is spread over a
larger and larger area, in a way suggested by the relationship between the radius and
area of a sphere. The total energy stays the same, the area expands, so the energy in
one unit of area decreases with the square of the distance from the source.
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Point Sources
The effects of geometric spreading are well known for the three idealised sound
sources; the point, line and plane. The behaviour of each is based solely on the
assumption that, in a homogeneous medium, sound propagation from a single point
source is purely spherical. Thus the sound energy in any particular direction is
inversely proportional to the increasing surface area of the sphere. If SWL represents
the continuous sound power output of the source measured at 1 metre, then at a
distance of r metres (where r must always be divided by the measurement distance,
which is usually 1m), the sound pressure level becomes;
SPL = SWL(point) - 10log (4 π r²)
and I = W / (4 π r²)
This is can be rewritten simply as;
SPL = SWL(point) - 20log (r) - 11
which is known as the standard inverse square law for point sources.
For a point source it represents a 6dB reduction in sound pressure level
per doubling of distance.
If the ground is quite hard and reflective, compensation must be made for these
ground reflections. In this case 11 is replaced by 8dB.
Line Sources (e.g. line array loudspeakers)
Classic line and plane sources can then be considered to consist of an infinite number
of evenly distributed individual point sources. The overall behaviour is then found by
integrating the individual effects of each point source over the full length or area. In
the case of an ideal line of infinite length, the results approximate that of purely
cylindrical propagation. Thus the sound energy in any perpendicular direction is
inversely proportional to the increasing circumference of the cylinder. Using the same
nomenclature as above, the sound pressure level becomes;
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SPL = SWL(line) - 10log(4 p r)
For a line source this results in only a 3dB reduction in sound pressure
level per doubling of distance in the nearfield . . .
But note: This nearfield -3dB/doubling distance varies with frequency
and straight line array length
Plane Sources
For a plane source (e.g. a flat wall of sub-woofers), integrating an infinite number of
point sources distributed in two dimensions produces a flat surface. Thus, propagation
away from a planar source approximates a plane wave. The sound energy of each
point source is therefore assumed to propagate in a straight line perpendicular to the
plane, meaning that no geometric spreading need be considered as there is no change
in distributed surface area as the wave propagates.
Obviously there will be some at the edges of an finite planar source, however, at close
range near the centre of the plane there is no diminution with distance. Therefore, the
sound pressure level can be written as:
SPL = SWL(plane)
Unfortunately, most real line and plane sources are of a finite size. This means that
their overall behaviour becomes a definite integral. Considering this, it is easy to
imagine that, at a very great distance or very small size, both sources will ultimately
approximate an ideal point source.
This suggests that for such sources, there is a gradual change in behavior as a function
of both size and distance.
A straight line array will maintain it's low loss characteristics (3dB decrease in spl per
doubling of distance + air absorption) for a distance that depends on it's length with
respect to the wavelength of the sound being projected. Beyond this distance the line
effect breaks down and the spl characteristic weakens from -3dB/doubling of distance
plus air absorption to -6dB/doubling of distance plus air absorption. This transition
distance depends on the square of the straight line array's length and is proportional to
frequency following the generally accepted formula:
Where distances and length are given in metres and the frequency is in Hertz.
The speed of sound is approximately 340metres/second but varies with temperature.
Simplified, this means that you need a long line array to project low-mid frequencies
efficiently. Doubling the line array length will almost quadruple its low-mid
frequency nearfield throw. See Section 5.4.
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Stacked general purpose horns vs low curvature line array elements
The following illustrations compare the poor coverage characteristics of vertically
stacked general purpose horns with the properly designed low curvature horns found
in the W8L Series line arrays.
Three 30º horns 1m apart, 8kHz
Three tightly arrayed low curvature horns at 8kHz
Vertically spaced, wide coverage horns will have hot spots directly in front of each
horn and will comb (add or subtract depending on the wavelength and relative
propagation times) in the mid and far field. Tightly arrayed low curvature horns
project more coherently. As the number of low curvature line elements is increased
forward projection strengthens and the side lobes decrease.
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The listener hears the vector sum of more and more cabinets as he moves further
away from a straight line array. These increasing contributions partially compensate
for the normal reduction in sound pressure with distance from source.
Note that farfield spl levels will increase towards the centre of the array where more
elements add.
W8L Series
The classic explanation of line array behavior assumes omni-directional point source
drive elements that must be positioned within ¼ wavelength at their highest operating
frequency for coherent summation. Martin Audio designs comprise directional hornloaded sections. This closely coupled horn technique modifies the equations allowing
greater driver spacing. See our Institute of Acoustics, Reproduced Sound 2003 paper,
Advances in Line Array Technology for Live Sound.
Note that our mid and hf designs do not try to emulate a dead straight ribbon.
Practical loudspeaker columns must have vertical coverage patterns tailored to suit
the audience size and shape and our line array systems have been designed with this
in mind. The W8L Series are deliberately designed to produce slightly curved vertical
wavefronts - enough to allow up to 7.5º of vertical splay to be introduced between
boxes but not enough to affect straight line performance.
Progressive Curvature arrays
Straight columns (0º splay angles) produce far-field high-mid frequency sound
pressure levels that increase approximately 6dB for every doubling of W8L quantities
but, as inter-box splay angles increase, the vector sum of multiple W8Ls decreases
through 3dB for a 3º splay to 0dB (no summation) at 7.5º. This Progressive
Curvature provides smooth level coverage without amplifier channel trimming for
most applications.
Martin Audio’s ViewPointtm software calculates the optimum progressive curvature
for a given audience area. The progressive curvature produces a more consistent
frequency response from the front rows to the rear seats than often used J-shaped
arrays having a straight, long throw section at the top and a curved lower section. An
over-angular J-shaped array acts like a foreshortened straight array above a point
source array and creates vertical lobes that result in irregular coverage.
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Irregular coverage from a J-Shaped Array
Smoother coverage from a Martin Audio Progressive Curvature Array
ViewPointtm calculates the maximum summation point (near the top of a
progressively curved array) and aims this towards the furthest listening area. A
progressive curvature array’s HF coverage weakens dramatically above the maximum
summation point so this point is regarded as the Coverage Stop – see Section 5.5.12
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5.4 How many do I need?
There are four major factors to take into account when specifying line array columns
for a specific application.
1)
2)
3)
4)
Will I need delays? Very important - see Section 5.9.
Spectral Balance - the minimum column length required for spectral
balance over the full audience distance or just beyond the 1st delays.
Maximum SPL - the number & model required to achieve maximum spl.
Horizontal Coverage – see Section 5.6.
5.4.1 Spectral Balance
Users new to line array technology can be confused by items 2 & 3. The minimum
column length for spectral balance cannot be reduced simply because the band is a
quiet traditional folk combo. A short line array column would project only mid
frequencies to the far field. It would lack warmth and sparkle as it would not be long
enough for the line affect to take effect at low mid frequencies and may not have the
headroom at high frequencies. Boosting the system’s LF and HF would simply cause
too much bass in the front seats and a lack of headroom at HF.
As we saw earlier, a straight line array will maintain it's low loss characteristics (3dB
decrease in spl + air absorption per doubling of distance) for a distance that depends
on the line length with respect to the wavelength of the sound being projected.
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The transition distance is not the system’s maximum throw. It is the distance that the
system’s near-field characteristic will reach – or, if you prefer, the 3dB per doubling
of distance attenuation range (ignoring air absorption). Beyond this distance the
attenuation rate will increase to 6dB/doubling of distance (ignoring air absorption).
The transition distance can be thought of as the distance that the line array’s
advantageous low attenuation rate will reach.
The distance from the stage to the furthest seats in a typical football stadium is in
excess of 120m. The line array advantage (the effect of moving the near-field
characteristic closer to the audience) will be proportional to frequency and the square
of the line length so it will be less for short arrays at low frequencies.
It is very important that you use a line array that is long enough for the low-mid
frequency projection to follow the superior mid and high frequency projection
out far enough for mid-high air absorption to have a balancing effect.
The following curves show the spectral balance of 4 and 12 W8L cabinets vs distance
taking air absorption into account for about 40% relative humidity.
The 4 x W8L system low mid projection is less efficient than its upper mid projection
because too few cabinets have been used for the line to be effective at low
frequencies. The smaller system would project clean vocals but it would sound thin –
lacking warmth and authority.
The 12 x W8L system 200Hz, 600Hz and 6KHz responses are closer together (and,
obviously, at a higher amplitude). The longer line has "kicked" the low-mid
frequencies out further so that they can keep up with the mid and high frequencies.
A 12 x line array provides excellent spectral tracking over typical stadium distances
whilst providing the extra high frequency headroom required to partially counter air
absorption.
Note that, as air absorption increases, upper mid frequency characteristics tend to
track lower mid characteristics with high frequencies tailing off.
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Model and quantity for a balanced spectral response
A spectrally balanced system will provide a useful far-field response within an octave
of the product’s LF and HF specification.
A system’s LF response may be enhanced by extending the effective column length
with sub-woofers flown above or stacked immediately below the array.
HF air absorption is the dominant factor beyond 50m. Be cautious about specifying
very long throw systems where the air may be dry (e.g. for outdoor events during hot,
dry weather, for desert regions or for venues with warm air heating). See Sections 5.8
& Section 5.9.
The following chart indicates the minimum quantity and model for the required
throw. The chart is based on applications experience and line array physics as it is
currently understood.
Quantity
W8L
(no subs)
W8LC
(no subs)
W8LM
(no subs)
Cabinets
arrayed with
2° or less
inter-cabinet
splay
4
6
8
10
12
14
16
Throw
(in meters)
for spectral
balance
Throw
(in meters)
for spectral
balance
Throw
(in meters)
for spectral
balance
25
40
60*
80*
100*
130**
155**
18
29
40
58*
70*
88*
105**
12
18
25
32
41
50*
60*
* Assumes relative humidity 50% or higher
** Assumes relative humidity 70% or higher
Lower humidity will cause unacceptable HF absorption.
Note: The cabinet quantities refer to low curvature arrays or the low curvature (upper)
sections of progressively curved arrays.
The following ViewPointtm examples indicate the quantity of cabinets that can be
regarded as contributing to the system’s mid and high frequency far-field
characteristic.
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Example 1
12 x W8L (at 1°) per side festival system in side wings for 100m throw
Example 2
16 x W8L per side arena system
Upper 12 cabinets at 1 & 2° for 100m throw
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Example 3
12 x W8LM per side 41m concert hall system
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5.4.2 Maximum far-field on-axis SPL Calculations
Simplified maximum far-field on-axis spl estimates for a single column may be made
using the following simple arithmetic and look-up tables . . .
Far-field Sound Pressure Level (spl) = A minus B minus C
where A = the effective source spl referred to 1m distance
B = the radial attenuation with distance
C = excess air attenuation
(A) - The effective source spl is calculated for far-field estimates only (in practice,
large array outputs do not integrate as close as 1m).
This “source spl” will depend on the W8L Series model’s maximum spl, the
number of cabinets and the splay angle between the cabinets. W8L Series
cabinets have a nominal vertical MF & HF coverage of 7.5° so calculations
have been restricted to 8 cabinets for 1° splay and 4 cabinets for 2° splay on
the assumption that progressive curvature arrays start with minimal splay at
the top for far-field projection, increasing towards the bottom. 0° (straight)
arrays are calculated for up to 16 cabinets as curvature losses are not
applicable.
See look-up table below.
(B) - Radial attenuation is the reduction in sound pressure due to the radial
expansion of the wavefront. This attenuation varies from 3dB per doubling of
distance in the nearfield to 6dB per doubling in the farfield and depends on
the length of the array.
See look-up table below.
(C) - Excess air attenuation is caused by air absorption. It is heavily dependent on
humidity and temperature and is worse at mid and high frequencies.
See look-up table below.
Value of A
W8LM
W8LC
W8L
Max dB spl
Max dB spl
Max dB spl
cont. pk
cont. pk
cont. pk
1
134
140
129
135
125
131
2
140
146
135
141
131
137
4
146
152
141
147
137
143
6
150
156
145
151
141
147
8
152
158
147
153
143
149
10
154
160
149
155
145
151
12
156
162
151
157
147
153
14
157
163
152
158
148
154
16
158
166
153
159
149
155
Effective source spl (referred to 1m) vs model & quantity
Quantity
(splayed at 0°)
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W8LM
W8LC
W8L
Max dB spl
Max dB spl
Max dB spl
cont. pk
cont. pk
cont. pk
1
134
140
129
135
125
131
2
140
146
135
141
131
137
4
145
151
140
146
136
142
6
148
154
143
149
139
145
8
150
156
145
151
141
147
Effective source spl (referred to 1m) vs model & quantity
Quantity
(splayed at 1°)
W8LM
W8LC
W8L
Max dB spl
Max dB spl
Max dB spl
cont. pk
cont. pk
cont. pk
1
134
140
129
135
125
131
2
139
145
134
140
130
136
4
143
149
138
144
134
140
Effective source spl (referred to 1m) vs model & quantity
Quantity
(splayed at 2°)
Value of B
8m
6m
4m
2m
1m
array
array
array
array
array
(8xW8L,
(4xW8L,
(2xW8L,
5xW8LC 11xW8LC (12xW8L (16xW8L)
3xW8LC
or
or
or
or
4xW8LM) 8xW8LM) 16xW8M) 16xW8LC)
16m
15dB
12dB
12dB
12dB
12dB
32m
21dB
15dB
15dB
15dB
15dB
64m
27dB
21dB
18dB
18dB
18dB
128m
33dB
27dB
21dB
21dB
21dB
256m
39dB
33dB
27dB
24dB
24dB
Radial attenuation vs line array length & distance at 6KHz
(inter-cabinet splay = 1° or less)
Distance from
array
↓
Value of C
Distance from array
25% R.H.
50% R.H.
75% R.H.
100% R.H.
↓
16m
2dB
1dB
0.7dB
0.6dB
32m
4dB
2dB
1.4dB
1.2dB
64m
8dB
4dB
2.8dB
2.3dB
128m
16dB
8dB
5.6dB
4.6dB
256m
32dB
16dB
11dB
9.2dB
Excess air attenuation vs distance at 6KHz (20°C at sea level)
Stereo Approximation
The above figures are for a single column. Centre-field maximum spl may increase by
approximately 3dB at mid frequencies for stereo systems and may approach a 6dB
increase at low frequencies.
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Horizontal off-axis attenuation
Off-axis figures will be less than single column on-axis figures at mid and high
frequencies as follows:
Horizontal
off-axis
attenuation
-3dB
-6dB
-10dB
W8L
(± off-axis angle)
22.5°
45°
60°
W8LC
(± off-axis angle)
22.5°
45°
60°
W8LM
(± off-axis angle)
25°
50°
60°
Note! Gusting side winds may affect these figures erratically.
5.5
ViewPointtm (Version 3.03)
Contents
5.5.1
Introduction
5.5.2
Installing ViewPointtm
5.5.3
Using ViewPointtm
5.5.4
Entering venue data
5.5.5
Coverage start and stop
5.5.6
Array type
5.5.7
Array fixing
5.5.8
Designing a flown array
5.5.9
Stacked systems
5.5.10
Venue name
5.5.11
Editing ViewPointtm designs
5.5.12
Frequently asked questions
5.5.13
Using ViewPointtm for systems with sub-woofers
5.5.14
Manual array editing
5.5.15
Array page
5.5.16
Processor page
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5.5.17
Saving a design
5.5.18
Loading a design
5.5.19
Printing ViewPointtm
5.5.20
Exiting the programme
5.5.21
ViewPointtm support
ViewPointtm (Version 3.03)
5.5.1
Introduction
ViewPointtm software will automatically calculate the splay angles of a W8L Series
array and will indicate the optimum controller (processor) preset and amplifier patch
information once venue and array data has been entered. You can print out array,
venue, rigging and patch information and save your work to disk.
Please Note:
ViewPointtm produces sonically accurate results based on high resolution
loudspeaker data and the audience coverage but you must use the amplifier
patch and one of the controller preset indicated for accurate Band Zoning and
smooth coverage.
1)
The controller preset names shown on ViewPointtm correspond to the
preset names on our DX1, XTA DP226 or XTA AudioCore data files.
2)
Please ensure that your controllers are running our standard reference
presets for the W8L Series loudspeaker in use.
3)
Users should start with a unity gain, zero delay, flat frequency response
controller input section and revert back to our standard presets at the
beginning of each venue setup to avoid using settings contaminated with
room equalization from a previous gig.
5.5.2
Installing ViewPointtm
ViewPointtm is supplied in a zip folder which contains a setup executable file
ViewPoint 3.03.exe.
Double-click on this and follow the on-screen prompts.
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Using ViewPointtm
Once you have installed ViewPointtm, it will be visible as a shortcut in All Programs
via your Windows Start button.
A single click on the viewpoint v3.03 tab will open the following page:
ViewPointtm will indicate splay angles and controller presets for these flown systems:
W8L (Full-range line array)
W8LS (Sub-woofer)
W8LC (Compact line array)
W8LM (Mini line array)
WLX (Sub-woofer)
and these flown combinations of the above:
W8LS (Sub) above W8L
W8L above W8LC
W8LS (Sub) above W8LC
W8LC above W8LM
WLX (Sub) above W8LC
WLX (Sub) above W8LM
and the following ground-stacks:
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W8L
W8LC
W8LM
5.5.4
Entering venue data
Choose metric or imperial units using the Units box on the Venue page.
Click on the button adjacent to the units that you would like to use.
Note: if you enter dimensions in one unit system and then click on the button of the
other system all dimensions will be converted, i.e. 1m will become 3.28ft.
PLEASE NOTE!
ViewPointtm is designed as a line array design aid. It does not claim to be a high
resolution drawing programme.
It indicates optimum line array curvature based on simple audience dimensions that
may be gathered from basic venue drawings or from a quick on-site survey.
For best results, planes should be used as follows:
Plane 1 is used to simulate the main floor area from the stage to a rear bleacher or
boundary.
Plane 2 is used to simulate any audience continuation behind Plane 1 (e.g. a rear
bleacher) from the end of the main floor to furthest and highest seat below Plane 3.
Plane 3 is used to simulate the furthest/highest audience area.
Example:
Plane 1, plane 2 and plane 3 decisions
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Overlayed ViewPointtm display (front fills not shown)
There are 3 methods for entering venue Dimensions.
5.5.4.1
Direct
If you have the venue plans available then this is the easiest method:
Enter the height, length and elevation of up to three planes.
For all planes Length refers to the horizontal length of that plane
For all planes Height refers to the height of the rear of the plane. Plane 1
height can be negative or positive.
For planes two and three Elev refers to the elevation (height) of the front of
the plane.
For plane three Distance relates to the actual distance from the front of the
array to the start of the third plane.
For all planes selecting Seated or Standing places ear level at 1.4 or 1.8m
above the respective plane.
5.5.4.2
Individual Plane R-A
To enter diagonal distance (R) and angle of elevation (A) instead of length (X) and
height (Y) click on the symbol in the bottom left hand corner of a plane.
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The following pop-up window will appear.
Enter R and A in the right hand boxes and click on Get X-Y.
Click on Close and Update to copy the X and Y data in to the Length and Height
boxes and close the pop-up window or click on the x symbol in the top right hand
corner of the pop-up window to close it without copying.
Note: you can also use this in reverse to calculate angles from X and Y data.
5.5.4.3
Single Point Survey
This option enables you to enter all plane data from a single reference point directly
under the intended flying point or above the stack position.
We recommend that you use a tripod to mount your laser distance measurement
device and your inclinometer since the data entered is very sensitive to small errors.
Click
and a tool will appear that details the diagonal
length and angle for each plane beginning and end.
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It also details the height of your distance measuring device above plane 1. If the stage
is raised then include this height as well as the height of the device above the stage.
Note: It is assumed that plane 1 begins at the point where you mount the tripod and
the array will be flown directly above it.
To enter data for each plane aim your device at the beginning and end of the plane
and enter the values into the spaces provided. The units of measurement will be
determined by the choice made in the main window and negative aiming angles imply
the point aimed for is below the device.
Ensure that you have enabled or disabled the planes you require by checking the
enable tick box for each plane.
When you are satisfied with the data click Update venue, a conversion will then be
made to the direct form of venue dimension.
You can switch back and forth between the single point survey and direct form at any
time.
5.5.5
Coverage start and stop
Specify the horizontal coverage distances from the front of the array. Coverage start
and stop are shown as vertical grey bars on the view of the venue.
Please note:
A flown array’s overall curvature will be significantly increased by very close
coverage starts because the lower cabinets will need to aim further down. This will
decrease the number of straighter cabinets towards the top of the array decreasing the
efficiency of the far-field coverage.
See W8L Series Applications Guide Section 5.4 to relate maximum source spl to
loudspeaker quantity and curvature.
Always use a sensible choice of coverage start for the number of line array cabinets
available, using front-fill loudspeakers for the first 5 or 6 rows if at all possible.
Front-fills will also improve imaging. See Sect. 5.7.2
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Array Type
The choice of loudspeaker type depends on the application. See W8L Series
Applications Guide Section 5.4
If a mixed system is selected a further section to the right allows you to define the
quantity of the lower cabinets.
5.5.7
Array Fixing
Select either Fly or Stack in the Fixing section to determines how the array is
supported.
In Fly mode the grid is suspended and cabinets are attached beneath
In Stack mode the grid forms a base and cabinets are placed on top. Ground
Stack Bars are fixed between the grid and the rear splay holes of the lowest
cabinet to set the overall system tilt.
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5.5.8
GUIDES
Designing a flown array
Minimum trim height
This is the low limit for the array and is defined as the smallest allowable distance
from the lowest point of the array to the ground below.
You should set the minimum allowable trim height by sight line considerations.
Work this out from venue information gathered from venue and stage set information.
Make sure the array does not restrict the audience view from 1.8m above the highest
audience plane to 2m above the highest upstage artist position.
Maximum pick height
Set this to the maximum array height allowable (usually the highest part of the flying
frame).
The maximum pick height is usually chosen to allow for the maximum flying point
height minus a sensible allowance for any shackles, stingers, bridles or flying hooks.
1m should be allowed for a stinger between each grid flying lug and the relevant
motor hook to ensure that motor chain bags do not rest on the grid or top cabinet and
upset its tilt angle.
Array Height
Set the array height for best coverage. It refers to the highest point of the array but
does not include shackles, stingers, bridles or flying hooks.
Array height is an important aspect of line array system design.
A low flown system may interfere with sightlines and may be too straight to provide
the smooth coverage that would be provided by a progressively curved array.
A high flown system may provide smooth coverage – but at the expense of maximum
sound pressure level if the system curvature does not allow small enough intercabinet splay angles for efficient far-field projection. Again, see W8L Series
Applications Guide Section 5.4 to relate maximum source spl to loudspeaker quantity
and curvature.
A system flown too high will be uncomfortable for the audience as the sound source
will not coincide with the performance area.
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Example
Venue view – inefficient design
Array too high and, therefore, too curved for efficient cabinet-to-cabinet
summation
Array view – inefficient design
Array too curved for efficient cabinet-to-cabinet summation
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Venue view – efficient design
Lower curvature - for efficient cabinet-to-cabinet summation
Array view – efficient design
Lower curvature for efficient cabinet-to-cabinet summation
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Number of cabinets
The default value is 10 cabinets and this is a good starting point for most situations.
Click the Design button to see coverage, array length and splay angles.
You may wish to edit the number of cabinets to see how coverage, array length and
splay angles are affected.
Note: the software will attempt to cover as wide an area as set by the coverage start
and stop values. If the coverage (Start to Stop) cannot be met with the number of
cabinets selected, a screen message will appear.
VERY IMPORTANT NOTE!!!
Long throw applications will require arrays long enough to ensure the appropriate
vector summation for the distance to be covered. Too few cabinets may result in an
inappropriate design. Once again, see W8L Series Applications Guide Section 5.4.
Mixed systems
The number of cabinets in mixed systems relates to the total number of cabinets in the
array. A separate control dictates how many of the lower cabinet types are present.
See later.
5.5.9
Stacked systems
When Stack is selected the maximum number of cabinets is limited and instead of
Array Height, Stage Height appears in its place.
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Set Stage Height to the vertical distance from the first plane to the floor of the stage.
The Add Subs button allows the stack to be mounted on popular Martin Audio subwoofers – with the sub-woofers either on the stage or stacked directly on the floor.
Note: If Stage Height is below the ear level of the first plane then the ear height
becomes equal to the stage height.
5.5.10
Venue name
Enter the name of the venue. Previously saved venue names will appear here.
5.5.11
Editing ViewPointtm designs
Once the initial venue and array parameters have been entered and the Design button
has been clicked, venue and array data, can only be edited by clicking on the up or
down symbols next to the appropriate data box.
Whenever a value is altered the software will automatically recalculate splay angles.
5.5.12
Q.
Frequently asked questions
Why is the top cabinet overshooting the furthest seat?
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A.
The auto calculation routine will tend to aim the top cabinet slightly beyond
the coverage stop distance to give maximum vector summation at the furthest
listening position. This is physics at work and is not a shortcoming of the W8 Series
line arrays.
One benefit of this overshoot is that it can act as a hedge against coverage shortfalls
caused by temperature and wind gradients bending the projected sound downwards.
See W8L Series Applications Guide for further information about temperature and
wind gradients.
Reducing reflections and overspill
ViewPointtm's auto calculation routine is based on a combination of theoretical
modeling* and practical experience and aims to give the most consistent frequency
response over the audience surfaces as well as an even SPL distribution. We strongly
recommend using ViewPointtm's recommendations before attempting radically
different schemes.
If there are highly reflective surfaces (or level sensitive neighbours) immediately
beyond the Coverage stop point you may wish to reduce the level and overshoot at
that point. This may be done by reducing the coverage stop distance until the top
cabinet ray coincides with the highest/furthest audience area.
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Q.
The cabinet rays are spaced further apart in the 45 – 75m area. Surely this
means that just one cabinet is covering more than fifteen meters of the audience?
A.
The rays shown on ViewPointtm can be a little misleading because a series of
rays arriving at a shallow angle will appear to be widely spaced.
Many users equate this with the sun’s rays which weaken as the sun sets. In fact, the
setting sun’s power weakens due to greater absorption of shorter wavelengths through
the earth’s curved atmosphere not because the rays are arriving at a shallow angle.
With W8L Series arrays, the sound pressure level at any point in the room can be
thought of as the vector sum of all the cabinets +/-7.5 degrees from that point, not
simply due to the cabinet whose ray is aiming there. The example above shows that
the “cabinet 7” area receives contributions from cabinets 3 to 11, not just cabinet 7.
ViewPointtm’s Progressive Curvature calculations ensure that inter-cabinet splay
angles increase gradually from the array and arrays are driven slightly harder towards
the top of the array to partially compensate for air losses. This combination of
Progressive Curvature and Band Zoning gives maximum projection to the furthest
seats and the smoothest coverage.
5.5.13
Using ViewPointtm for systems with sub-woofers
Flown W8LS sub-woofers
By default all W8LS splay angles are set to zero. If possible raise the array height so
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that the W8LS cabinets are pointing downwards - or consider a parallel (side) W8LS
or WLX sub-woofer array.
W8LS side arrays
Matching a W8LS side array to the curvature of a main W8L array is easy. Simply
copy the W8L angles.
WLX side arrays
If you specify a WLX side array it should be designed to match the curvature of the
main array. Matching adjacent WLX and W8LC array shapes is difficult (as they are
different shapes and sizes) so ViewPointtm does this for you:
Enter the number of WLXs you wish to use in the number box to the right of the
Match WLX button, then click the Match WLX button.
A WLX array is generated that has a similar shape to your original main array.
Splaying WLX cabinets in mixed systems
In mixed WLX/W8LC systems ViewPointtm may be used to aim the upper WLXs as
close to the main audience area as the rigging system will allow whilst keeping the
lower W8LC array pointing in the correct position for best coverage.
Click the Splay WLX control to enable/disable this feature.
Sub-woofer placement and alignment? – see Section 5.7
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5.5.14
GUIDES
Manual array editing (experts only!!!)
Should you wish to ignore ViewPointtm’s accurate coverage advice, continue with
great caution, as follows:
Click on the Manual button (in Venue view) to manually edit splay angles and the
array tilt angle.
1) Position the cross-hair over the dark blue squares at the end of each ray until
the box turns red.
2) Use the left and right mouse buttons to increase or decrease the array tilt (top
cabinet only) or inter-cabinet splay angles of the cabinets below.
Alternatively . . .
1) Click on the splay angle to be altered to select a cabinet.
2) Move the mouse pointer into the top half of the screen.
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3) Use the mouse buttons as described to change the angle. This is useful when the
blue squares at the end of the uppermost rays lie outside the displayable area.
Note that the ray colours relate to Planes 1, 2 and 3. Occasionally, when a venue
involves three planes or the second plane is a balcony which is above the level of the
first plane, the auto calculation routine will indicate black ray(s) not pointing at the
audience. This occurs when rays hit a vertical surface such as a balcony front.
Do not be tempted to switch off or heavily attenuate cabinets indicating a black ray as
this could upset the line effect producing lobes and causing room colouration.
The user has the choice of ignoring the warning, which may be advisable if the
balcony front is small or non-reflective, or manually editing the splay angles to miss
the reflective surface.
It is not advisable to miss the surface completely as temperature gradients in the air
can steer high frequencies upwards or downwards by 5° or more from the direction
the cabinets are pointing in.
5.5.15
Array Page
Please note!
ViewPointtm’s Array page is for design/decision making only.
It does not guarantee safety. Safety will depend on the
condition of the product, the suitability of supporting
structures and personnel, weather conditions etc.
ViewPointtm information should be passed to suitably qualified
and experienced riggers for final decisions about loading,
stability and safety.
5.5.15.1
Flown arrays
Click on the Array tab to show the rigging configuration and mechanical parameters.
This shows a close up of the array along with dimensions and splay angles. The
gridlines are calibrated in 0.2m or 0.5ft increments, depending on which unit system
is selected. Using the gridlines it is possible to read off dimensions such as the depth
of any part of the array.
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Note: the top corner of the top cabinet is always positioned above the reference point
on the venue view. This is shown by the blue vertical line on the Array view which
indicates the datum point from which coverage Start/Stop distances are measured.
Pick Points and Cabinet Positions
Two grid pick points (front & rear) are shown for flown arrays.
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The cabinet grid position can be selected as either Front or Rear depending on the
amount of system tilt required. The rear positions makes more down-tilt (+ve angle)
available and the front position makes more up-tilt (-ve angle) available.
Lifting Bar Option
A Lifting Bar option is available for W8LC, WLX and W8LM flown arrays.
When Lifting Bar is selected further options become available.
The lifting bar can be placed in the Rear or Front position and can be lifted at either
one or two points.
Single Point Lift
This displays the Nearest hole in the lifting bar and the Actual Angle of the grid
when lifted at that hole.
Note that ViewPointtm will display a warning if there is no suitable hole available.
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Adjusting the array height slightly on the Venue page will often position the system
on a suitable hole or narrow the gap between the required angle and the angle given
by the nearest hole. Flip between Venue and Array pages to set and recheck.
(If the required lifting point is too far back, make sure that the lifting bar is in the rear
position and that the cabinet is mounted at the front of the grid before trying an
alternative height. Similarly, if the required lifting point is too far forward, make sure
that the lifting bar is in the front position and the cabinet is mounted at the rear of the
grid before trying an alternative height)
Two Point Lift
This places a pick point at each end of the bar.
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A two-motor lift from a lifting bar will…
Enable more extreme up-tilts and down-tilts because the lifting bar extends
beyond the front lifting point forward of the normal grid tab in the front
position and extends the rear lifting point behind the normal grid tab in the
rear position
Spread the array load across two rigging points
Allow fine angular control using the motors
Load Indicators
Depending on the grid configuration the 'Rear Pick Load' and 'Front Pick Load' are
displayed as well as total mass. These loads as well as the forces between cabinets are
checked after each change of the array or grid.
Should either of the pick loads become less than zero or the inter-cabinet forces
become too high then a mechanical warning window will appear.
5.5.15.2
Stacked arrays
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When designing ground-stacked arrays, inspect the array view and check that the
center of gravity is in a safe place.
Stack stability
Red stability limits are indicated within the grid on the Array page – circled on the
right below.
If the centre of gravity crosses this red region the force required to push or pull the
array over is less than that shown in the box beside the array view and a mechanical
warning is raised.
Please note: This assumes that no sliding takes place. Grids should be securely
attached to the ground in all cases.
The push value (in Newtons) – shown circled on the left below - can be varied to
simulate wind load.
Zoom In
This shows the ground-stack bar position required for the lowest cabinet angle.
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5.5.16
GUIDES
Processor page
The Processor page shows a controller-to-amplifier patch table and indicates which
controller settings to use for the design.
The page also shows power amplifier rack layouts to ensure that the amplifiers share
the power demand adequately (see Quick Start sections for advice on rack layouts and
mains distribution). Move your mouse cursor over the greyed out amplifier racks to
see further rack details.
Historically, array cabinets have been numbered from top to bottom (see Quick Start
sections). W8L and W8LC line array section impedances are all 8 ohms and usually
driven in pairs so that each power amplifier channel sees a 4 ohm load. W8LM line
array section impedances are about 13 ohms and are usually driven in fours to present
a 3.25 ohm load.
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In practice, multipurpose racks are more easily configured for a wide variety of array
sizes by driving the arrays in the opposite direction - from the bottom up. Smaller line
array configurations can be driven from large multipurpose racks by leaving the
upper, more equalized, outlets unused. This is indicated on the Processor page by
lettering the amplifier channel/loudspeaker outlets A-H with A at the bottom.
The following example relates 16-speaker rack outlets to the top-to-bottom cabinet
numbering. Note that W8Ls and W8LCs are driven in pairs whereas W8LMs are
driven in fours.
Speaker Outlet
H
G
F
E
D
C
B
A
Cabinet number
W8L/W8LC
(pairs)
W8LM
(fours)
1&2
3&4
5&6
7&8
9 & 10
11 & 12
13 & 14
15 & 16
1–4
5–8
9 – 12
13 – 16
Controller presets
The recommended DX1 or DP226 controller preset is shown on the Processor page.
Most of our line array controller presets include extra channels for Band Zoning.
Band Zoning is a technique of splitting the array into various MF and HF zones to
provide more air absorption compensation for the upper (longer throw) sections.
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A typical large scale system will have its LF sections driven in unison, its MF split
into upper (far-field) and lower (near-field) zones and its HF split into upper (farfield), middle (mid-field) and lower (near-field) zones. See Section 5.9 for more
on Band Zoning and Sections 5.10 (W8L), 5.11 (W8LC) or 5.12 (W8LM) for rack info.
Note that W8L and W8LC presets also offer a choice of settings –
HFCUT
HFNORMAL
HFBOOST
These are intended to cater for differing propagation conditions and, of course,
personal taste.
We recommend the following settings for differing humidity conditions:
HF BOOST when RH = 10 to 30%
HF NORMAL when RH = 30 to 50%
HF CUT
when RH = 50 to 100%.
W8L presets have an HF VARIABLE setting to allow the user to manually adjust HF
equalisation for atmospheric effects and personal taste.
A reminder …
ViewPointtm produces sonically accurate results based on high resolution
loudspeaker data and the audience coverage. You must use the exact reference
preset and amplifier patch for accurate Band Zoning and smooth coverage.
1)
The controller preset names shown on ViewPointtm correspond to the
preset names on our published Martin Audio DX1, XTA DP226 or XTA
AudioCore data files.
2)
Please ensure that controllers are loaded with our standard reference
presets for the W8L Series loudspeaker in use.
3)
Users should start with a unity gain, zero delay, flat frequency response
controller input section and revert back to our standard presets at the
beginning of each venue setup to avoid using settings contaminated with
room equalization from a previous gig.
5.5.17
Saving a venue or array design to disk
Select the Venue page and click on Save.
CONTINUED..
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Appendix 1
Wavefront W8 3-Way System
Contents
A1.1
Introduction
A1.2
Specifications
A1.3
Pin-outs and cabling
A1.4
System patching
A1.5
DX1 Loudspeaker Management System
A1.6
Power amplifier recommendations
A1.6.1
Martin Audio MA2.8 Power Amplifier Overview
A1.7
General operational summary
A1.8
Arraying and placement
A1.9
Coverage calculations
A1.10
W8 front fills
A1.11
W8 side clusters
A1.12
W8 distributed (delay) systems
A1.13
Combining W8s with other Wavefront systems
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Wavefront W8 3-Way System
A1.1 Introduction
The Wavefront W8 3-Way System is a high performance 3-way loudspeaker system
in a trapezoidal cabinet. The Wavefront W8 integrates two horn-loaded 12" low-mid
drivers with a horn-loaded 6.5" high-mid driver and a horn-loaded 1" very high
frequency compression driver. The 6.5" high-mid cone driver provides a better order
of performance than a large compression driver and is optimally loaded using a
toroidal phase plug.
Wavefront series trapezoidal cabinets are fitted with MAN load-certified flying points
and are designed to comply with the 12:1 safety factor specified by the German
VBG70 standard when used with compatible 12:1 flying systems. One important
advantage of the MAN flying system is that inter-cabinet connections place a minimal
load on the cabinets and, being external, can be load certified and inspected independently.
A1.2 Specifications
Type:
3-way trapezoid, switchable active/passive
high-mid/high via rear panel
switch (see Section A1.5)
Frequency response:
120Hz - 18kHz +/- 3dB
LF limit:
-10dB @ 80Hz
Drivers:
2 x 12" (305mm) low-mid horn
1 x 6.5" (165mm) high-mid horn
1 x 1" (25mm) exit hf compression driver
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Rated power:
Low-mid 400W AES, 1600Wpk
High-mid (active/passive) 150WAES, 600Wpk
High (active) 60W AES, 240Wpk
Sensitivity:
Low-mid 106dB/W
High-mid 108dB/W
High 107dB/W
Maximum SPL:
129dB continuous, 135dB peak
Impedance:
Low-mid 8 ohms nominal
High-mid 16 ohms nominal
High 16 ohms nominal
Coverage (-6dB):
55º horizontal, 30º vertical
Crossover:
750Hz, 3.5kHz
Connectors:
2 x Neutrik NL8, 2 x EP8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (incl wheels):
(W) 562mm x (H) 1066mm x (D) 925mm
(W) 22.1ins x (H) 42.0ins x (D) 36.5ins
Weight:
90kg (198lbs)
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A1.3 Pin-outs and cabling
W8
Connector type
W8 mode
EP8
NL8
W8 Active*
W8 Passive*
1
-1
Low Mid -
Low Mid -
2
+1
Low Mid +
Low Mid +
3
-2
High Mid -
High Mid/High -
4
+2
High Mid +
High Mid/High +
5
-3
High -
n/c
6
+3
High +
n/c
7
-4
n/c
n/c
8
+4
n/c
n/c
(*see Section A1.5 for details of the connector panel Active/Passive switch)
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A1.3.1
Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Cannon EP connectors
EP8-11
EP8-12
EP8-13
EP8-14
8 pin cable female
8 pin cable male
8 pin panel mount female
8 pin panel mount male
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
A1.3.2
Recommended loudspeaker cable
Cable run vs copper core cross sectional area
Up to 50m
Up to 100m
Single W8
Two W8 paralleled at the cluster.
2.5mm²
6mm²
6mm² (or 2 x 2.5mm² cores in parallel)
10mm² (or 2 x 6mm² cores in parallel)
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
A1.4 System patching
A good system patch should…
1)
Be electrically safe - ie be put together by suitably qualified electrical
technicians paying attention to possible sources of moisture, connector
damage, cable damage, user and public safety.
2)
Enable the system to provide the required sound quality, coverage and level
without feedback and without stressing its mechanical, electrical or
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electro-acoustic components.
3)
Be divided into easily understood sections (eg Main, midfield, downfill etc)
and clearly labelled so that adjustments may be made quickly and efficiently.
The schematic above shows a simple stereo PA set-up using two Martin Audio DX1
Loudspeaker Management Systems configured as 5-way crossovers controlling 3 x
W8 per side switched for fully active (3-way) operation augmented with W8S
subwoofers.
Larger systems may be assembled using the same two DX1 units - but with extra
"slave" amplifiers and loudspeakers.
See Section A1.5 for further DX1 information.
A1.4.1
Cluster sub-sections
When designing a large sound system it is worth spending a little time working out a
sensible cluster patch to optimise audience coverage.
The following example is a 4 wide, 4 deep W8 classical music centre cluster divided
into farfield, midfield, nearfield and downfill horizontal rows and inner and outer
vertical columns. The active W8s may be patched in pairs for symmetrical control.
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Recommended W8 pairs:
Inner Farfield
Inner Midfield
Inner Nearfield
Inner Downfield
Outer Farfield
Outer Midfield
Outer Nearfield
Outer Downfill
Controller channel allocations
The whole cluster may be controlled from just ½ a Martin Audio DX1 controller set
up for 3-way operation. See Section A1.5 for further DX1 information.
Power amplifier channel allocations
There are 8 pairs of W8 loudspeakers each requiring high, high-mid & low-mid
power amplifier channels.
8 pairs at 3 bands per pair
= 24 amplifier channels required
= 12 x 2ch amplifiers per cluster
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2ch power amplifier allocations:
Farfield inner & outer high
Midfield inner & outer high
Nearfield inner & outer high
Downfill inner & outer high
Farfield inner & outer himid
Midfield inner & outer himid
Nearfield inner & outer himid
Downfill inner & outer himid
Farfield inner & outer lomid
Midfield inner & outer lomid
Nearfield inner & outer lomid
Downfill inner & outer lomid
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Initial inner level settings
Initial inner level settings can be calculated for each row as follows:
The farfield inner power amplifier channels are the reference...
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Initial outer level settings
Similarly, initial outer level settings can be calculated for each row as follows:
Again, the farfield inner amplifier setting (0dB) is used as a reference...
In a fairly small, wide, fan-shaped venue with heavily raked seating, we may require
the following amplifier channel settings:
The attenuation rate shown here is 2dB per cluster row. The actual rate of vertical
attenuation will depend on the cluster height which in turn will depend on the rake of
the seats. High clusters are further from the audience at the front and require less
nearfield & downfill attenuation. The lower the cluster, the greater the required
attenuation rate.
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Again, the vertical layout is...
In a narrower venue, we may require the outer sections to be attenuated a little,
particularly in the farfield section, as follows:
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A1.5 DX1 Loudspeaker Management System
Martin Audio can provide factory set configuration cards for a variety of off-the-shelf
crossover systems (contact your dealer or Martin Audio Ltd for further information)
but the Martin Audio DX1 Loudspeaker Management System is strongly
recommended for all new Wavefront system designs.
The Martin Audio DX1 is a very high performance DSP-based controller and
provides crossover, protection, delay and alignment functions. As a Martin Audio
product, the DX1 is kept up-to-date with preset crossover and limiter functions
suitable for a wide range of system configurations and power amplifiers.
DX1 Factory Preset Examples
W8 Rear panel Active/Passive switch
Please note that the W8 rear connector panel is equipped with an Active/Passive
switch.
Active mode (DX1 factory presets 21, 23, 24 or 25)
In Active mode each driver (low-mid, high-mid & high) is driven by its own power
amplifier channel. These power amplifier channels are sourced from the appropriate
DX1 output to ensure optimal crossover and limiter alignment.
The advantages of active mode are:
Ø
Ø
Ø
Ø
Smoother high-mid/high amplitude and phase response
Smoother high-mid/high vertical polar response
Improved high-mid/high amplifier headroom
Improved high-mid/high limiter action
Three Martin Audio MA2.8 power amplifiers will drive four W8s (assuming W8s
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driven in pairs).
Passive Mode (DX1 factory presets 20 & 22)
In Passive mode the W8 high-mid and high drivers share a power amplifier channel
via a passive high-mid/high crossover network built into the loudspeaker cabinet.
This mode offers a slightly reduced performance but requires only two power
amplifier channels per 3-way W8 system.
Two MA2.8s and will drive W8s (assuming W8s driven in pairs).
The following shows the DX1 with programme 20 selected. This caters for a stereo
set-up comprising left and right W8s in Passive mode plus separate left and right
WSX folded-horn subwoofers. For more WSX information see Section 4.
DX1 factory preset 20 (2 x 3 way configuration)
Stereo W8 system (passive) with WSX subwoofers
Custom DX1 set-ups
Experienced users may create custom DX1 set-ups, for example…
3 + 2-way configuration
e.g. W8 3-way system with W8S subs (passive) & W8 (passive) front fills
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A1.5.1
GUIDES
DX1 specifications
Inputs
CMRR
Outputs
Min. Load
Max. Level
Frequency Resp.
Dynamic Range
Distortion
Maximum Delay
Output gain
Input gain
2 electronically balanced. >10k ohms
>65dB 50Hz - 10kHz
6 electronically balanced. <60 ohms
600 ohm
+20dBm into 600 ohm load
±0.5dB 20Hz - 20kHz
>110dB 20Hz -20kHz Unwtd
<0.02% @ 1kHz, +18dBm
650mS. (Increment 2.6uS)
adjustable +15dB to -40dB in 0.1dB steps and mute
adjustable +6dB to -40dB in 0.1dB steps
Parametric Equalisation
Filters
5 Sections per output
Filter gain
+15dB to -30dB in 0.1dB steps.
Centre frequency
0Hz - 20kHz, 1/36 octave steps (368 positions)
Filter Q / BW
0.4 to 128 / 2.5 to 0.008
(Sections switched to shelving response)
Low frequency
20Hz - 1kHz
High frequency
1kHz - 20kHz
Shelf gains
±15dB in 0.1dB steps
Crossover (high-pass and low-pass) filters
Filters
Frequency (HPF)
Frequency (LPF)
Response
1 of each per output
10Hz - 16kHz, 1/36 octave steps
60Hz - 22kHz, 1/36 octave steps
Bessel / Butterworth 12/18/24dB per octave
Linkwitz-Riley 24dB per octave
Limiters
Threshold
Attack time
Release time
+22dBu to -10dBu
0.3 to 90 milliseconds
4, 8, 16 or 32 times the attack time
Power required
Weight
Size
60 to 250V ±15% @ 50/60Hz. < 20W
3.5kg. Net (4.8kg. Shipping)
44 (1U) x 482 x 300mm excluding connectors
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1.5.2 DX1 Output Gain and Limiter settings for the W8
Standardising on one good model of power amplifier (preferably the Martin Audio
MA2.8) and correctly set-up controller (preferably the Martin Audio DX1) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories.
Gain settings
The following DX1 output gain settings will enable full system performance to be
obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
W8 - assuming 300Wcont - 600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Initial DX1
Output GAIN
Lomid Himid High
dB
dB
dB
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
-2
0.62 38
-9
-9
-7
-1
0.69 37
-8
-8
-6
0
0.77 36
-7
-7
-5
+1
0.87 35
-6
-6
-4
QSC PL224
+2
0.98 34
-5
-5
-3
+3
1.09 33
-4
-4
-2
Martin MA2.8* (32dB)
+4
1.23 32
-3
-3
-1
Crest 4801 (x40)
+4
1.23 32
-3
-3
-1
Crown K1 (1.4v)
+4
1.23 32
-3
-3
-1
QSC PL218/218A (32dB)
+4
1.23 32
-3
-3
-1
QSC PL224A (32dB)
+4
1.23 32
-3
-3
-1
Crown MA1202 (1.4v)
+5
1.38 31
-2
-2
0
+6
1.55 30
-1
-1
+1
+7
1.73 29
0
0
+2
+8
1.95 28
+1
+1
+3
+9
2.18 27
+2
+2
+4
Crown MA1202 (26dB)
+10 2.45 26
+3
+3
+5
Crown K1 (26dB)
+10 2.45 26
+3
+3
+5
QSC PL218A (26dB)
+10 2.45 26
+3
+3
+5
QSC PL224A (26dB)
+10 2.45 26
+3
+3
+5
* Set Martin Audio MA2.8 rear MLS switch to -2dB to match peak output of
unregulated power amplifiers.
Cluster balance (eg farfield-to-nearfield or inner-to-outer) should be adjusted at the
power amplifier controls to maintain limiter tracking. See Section A1.7.
Balancing the system using gain controls in the signal path before the power
amplifiers will cause the higher signal level upper row of a big cluster to start limiting
before the lower signal levels downfills causing tonal changes at the mix position.
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Limiter settings
The Rated Power specifications in Section A1.2 show that the maximum allowable
power dissipation depends on the driver/s being driven. This is because big low and
low-mid drivers are capable of dissipating more heat than smaller high-mid and high
drivers.
Normal music and speech signals, however, are a combination of relatively low
general power levels with a multiplicity of short term transients. These short term
transients do not significantly heat the driver voice coils so it is quite permissible to
use the same 250-300W into 8Ω (500-600W into 4Ω) power amplifiers for all
sections of the W8 as long as they are sourced by a correctly set controller.
When choosing power amplifiers, do not be tempted to exceed the 250-300W into 8Ω
(500-600W into 4Ω ) power rating unless the amplifier's power rails are well
regulated (see Section A1.6) - even with properly set controllers in place.
Although Martin Audio drivers are mechanically designed to survive normal road use
and the occasional operator error, over-powered or bridged amplifiers can cause overexcursions that stress and age drivers. The best way to get the clean, relaxed sound of
an overpowered amplifier is to choose an amplifier with plenty of current reserve - ie
an amplifier with good 2Ω specification - and avoid running more than two cabinets
in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
each band's high pass frequency as follows:
High pass filter range
Attack time
Release time
>31Hz
31Hz - 63Hz
63Hz - 125Hz
125Hz - 250Hz
250Hz - 500Hz
500Hz - 1KHz
1KHz - 2KHz
2KHz - 22KHz
45mS
16mS
8mS
4mS
2mS
1mS
0.5mS
0.3mS
720mS
256mS
128mS
64mS
32mS
16mS
8mS
4mS
These attack times will allow the power amplifiers to clip momentarily but not for
long enough to be obvious to listeners or cause driver overheating. It is quite normal
to see amplifier clip indicators on the odd programme peak but continuous clipping
would indicate a cable short circuit, wrong controller settings, excessive power
amplifier gain or low mains voltage.
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The following DX1 output limiter settings will avoid voice coil overheating and
minimise amplifier clipping for high quality, trouble free operation.
W8 - assuming 300Wcont - 600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Martin MA2.8* (38dB)
Crest CA9 (x68)
Crown MA1202 (0.775v)
QSC PL224
Martin MA2.8* (32dB)
Crest 4801 (x40)
Crown K1 (1.4v)
QSC PL218/218A (32dB)
QSC PL224A (32dB)
Crown MA1202 (1.4v)
Crown MA1202 (26dB)
Crown K1 (26dB)
QSC PL218A (26dB)
QSC PL224A (26dB)
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Recommended
DX1 LIMITER
Lomid Himid High
dBu dBu dBu
-2
-1
0
+1
+2
+3
+4
+4
+4
+4
+4
+5
+6
+7
+8
+9
+10
+10
+10
+10
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
+3
+4
+5
+6
+7
+8
+9
+9
+9
+9
0.62
0.69
0.77
0.87
0.98
1.09
1.23
1.23
1.23
1.23
1.23
1.38
1.55
1.73
1.95
2.18
2.45
2.45
2.45
2.45
38
37
36
35
34
33
32
32
32
32
32
31
30
29
28
27
26
26
26
26
-6
-5
-4
-3
-2
-1
0
0
0
0
0
+1
+2
+3
+4
+5
+6
+6
+6
+6
-9
-8
-7
-6
-5
-4
-3
-3
-3
-3
-3
-2
-1
0
+1
+2
+3
+3
+3
+3
* Set Martin Audio MA2.8 rear MLS switch to -2dB to match peak output of
unregulated power amplifiers.
Use lower limiter settings (or more loudspeakers!) if your power amplifiers indicate
clipping on more than just the odd peak. Excessive clipping may also be caused by
cable faults or an inadequate mains supply. See Section A1.6.
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The DX1 may be user-programmed to many more touring and fixed installation
configurations based on its 2 input + sum, 6 output matrix. This operation is best
completed by an audio technician who is familiar with DSP-based pro-audio.
(See separate DX1 Speaker Management System User's Guide for details)
A1.6 Power amplifier recommendations
Wavefront Series loudspeaker systems have been designed and manufactured for very
high performance and arrayability. The systems are very easy to use - particularly if
power amplifier racks and controller settings are standardised within a system.
Power capability
The Wavefront W8 will provide full performance when driven by professional power
amplifiers capable of delivering undistorted output power into a range of loads as
follows:
W8
250-300W(AES) into 8 ohms,
500-600W(AES) into 4 ohms
and
1,000-1,200W(AES) into 2 ohms.
Please note:
Amplifiers with inadequate headroom before clipping may age high frequency
components due to excessive signal density.
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times their quoted
power for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by oversized amplifiers should be avoided.
Martin Audio MA Series Power Amplifiers
Martin Audio MA Series amplifiers have regulated rails so it is quite permissible to
use slightly overpowered models - with suitably set controller limiters - without
risking uncontrolled power bursts. The MA series power amplifiers’ regulated power
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rails also ensure maximum performance under the real-world concert conditions of
less-than-optimum mains supplies and parallel cabinets. See Section A1.6.1.
Most non-Martin power amplifiers’ 4 ohm performance figures are specified
assuming very well regulated bench supplies but fail to reach these specifications
under touring conditions. These amplifiers can be a totally false economy as they
cannot drive parallel cabinets without a very audible loss of headroom and quality.
Amplifier load tolerance
An efficient loudspeaker in live concert conditions can act as a surprisingly dynamic
and complex load. Most modern touring power amplifiers claim 2 ohm capabilities
but make sure your amplifier is also capable of driving reactive (ie inductive or
capacitive) loads without prematurely clipping or developing output stage crossover
distortion.
Mains safety!
A fully qualified technican should check mains safety and phase voltage before the
system is patched.
Power reserve
Power amplifier specifications are usually based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for musical peaks.
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load. An electrical technician
should check the mains supply vs demand using an accurate rms voltage
meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving too many W8s in parallel. I would suggest no more than two
so that the amplifier’s 2Ω spec is kept in reserve for musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
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Gain or level settings
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section A1.5.2). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controller output levels and limiters have been set as tabulated in
Section A1.5.2, power amplifier level controls should be set to full (fully clockwise)
for loudspeaker sections requiring the strongest drive. Amplifiers driving nearer-field
sections within the same cluster may be backed off as required for smooth coverage.
This process will ensure that the system remains balanced during limiting.
Rack mounting
Always leave a 1U space between power amplifiers and controllers. Although most
modern amplifiers don’t radiate significant fields it’s better to play safe and keep the
system quiet. Rear supports are recommended - check with the manufacturer.
A1.6.1
Martin Audio MA2.8 Overview
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Features
Ø
Ø
Ø
Ø
Ø
Ø
Switch mode power supply
Superior sonic performance
Light weight
Advanced protection circuits
Efficient copper cooling system
Minimum load switches (MLStm)
The MA2.8 power amplifier has been designed to combine reliability and high power
output with sonic excellence. Utilising an advanced switch mode power supply, the
MA2.8 yields a very high power-to-weight ratio in a lightweight, 2U package.
See MA2.8 Amplifier User's Guide for detailed operating instructions.
Cooling System
The Martin Audio MA2.8 amplifier runs very cool due to a special patented copper
cooling system. The amplifier’s bi-polar output devices are mounted directly onto a
copper heat sink (copper conducts heat twice as efficiently as aluminium) and
maximum heat dissipation is achieved by turbulent airflow over the heatsink’s
geometric fins.
The MA2.8 amplifier features two proportional speed cooling fans which take in air
from the front of the amplifier and exhaust from the rear. A horizontal pressure
chamber between the heatsink and the cooling fans ensures that there is little
difference in the operating temperatures of each output device. In contrast, a
conventional tunnel design can result in a temperature variance of up to 40° between
output devices.
Switch Mode Power Supply
The MA2.8’s switch mode power supply (SMPS) is the modern solution to the
problems of size and weight. Switch mode power supplies are not new - they are
found in computers and televisions. However, the demands of high power audio are
very different to these applications. The MA2.8 overcomes the size and weight
constraints of conventional power supplies whilst at the same time avoiding the
pitfalls of typical switch mode designs.
The low output impedance of the SMPS means that rail voltages do not sag under
heavy load conditions. Additionally, the rail capacitors are being recharged at a much
faster rate than those in a conventional power supply. The result is an exceptional fast
transient low frequency performance at all power levels. Efficiency is also
maximised. With much smaller transformers than a conventional supply, there is
much less loss due to transformer resistance and much less power wasted as heat in
the power supply.
The power amplifier will produce the same power output, even if the AC line voltage
drops by 20%.
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Minimum Load Switches (MLS™)
Because the SMPS is regulated, the maximum power available for the output stages
can be adjusted without increased heat dissipation or efficiency loss. This allows the
user to match the output power with the loudspeaker impedance.
Protection
The MA2.8 amplifier has many advanced protection features that will protect both the
amplifier and the speakers connected to it, under fault conditions. All protection
circuits are independent and inaudible in normal use.
Clip Limiters
Clip limiters prevent dangerous clipped signals reaching the speaker. They work by
monitoring the output to check for signals not present at the input i.e.distortion. If
distortion exceeds 1% on an output, the limiter will reduce the input signal
proportionally.
Thermal Protection
Thermal Protection circuitry prevents the amplifier from running at an unsafe
temperature by muting the input signal when the internal temperature rises above
90°C.
Short Circuit Protection
The MA2.8 amplifier is completely short circuit protected. The protection circuits
permit very high peak currents, but maintain the output devices within their safe
operating area.
Mains Voltage Protection
This operates if the mains voltage falls outside its permitted operating range. If this
occurs, the power supply will shut down until the correct mains voltage is restored.
DC and VHF Protection
Both DC voltages and high power VHF signals can cause damage to loudspeakers.
The MA2.8 amplifier incorporates protection circuits which are activated when
damaging DC voltages or VHF signals are present at the outputs.
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MA2.8 Specifications
Input Impedance
Gain select switch
CMRR at 1kHz
Output impedance at 1kHz
Power Bandwidth
Slew rate
Hum/Noise
Channel Separation
Mains Operating Voltage
Protection
Distortion
THD 20Hz - 20kHz and 1W –
1000W
THD at 1kHz and 1100W
DIM 30 at 500W
CCIF (13 and 14 kHz) at 500W
SMPTE (60Hz and 7kHz) at 500W
Power Matrix
20kohms (balanced) 10kohms single ended
38dB (I/P sens 0.775V), 32dB (I/P sens 1.55V)
>50dB
0.06 ohms
10Hz - 20kHz
20V/us
<-105dB
1Khz > 90dB
10Khz > 80dB
120 - 270 (minimum start voltage 190)
full output power maintained 180 - 280V
Optional (65 - 135V) operation
DC, High temperature, Turn on, VHF,
Over and under voltage, Clip limiters. Short
circuit
4 ohms 0.08%
4 ohms 0.03%
4 ohms 0.02%
4 ohms 0.03%
4 ohms 0.08%
LOAD CONFIGURATION
16 ohms Stereo (2 channel)
8 ohms Stereo (2 channel)
4 ohms Stereo (2 channel)
MLS SWITCH SETTING
(-5dB)
(-4dB)
(-2dB)
160W
180W
340W
300W
350W
650W
570W
680W
1100W
2 ohms Stereo (2 channel)
1040W
1200W
16 ohms Bridged mono
8 ohms Bridged mono
4 ohms Bridged mono
600W
1200W
2100W
700W
1400W
2400W
(0dB)
520W
1100W
1400W
1900W[2]
1200W
1400W[1]
1400W[2] 2900W[2]
1300W
2000W
2200W
2800W
2400W
2800W[1]
[1] = Component tolerance
dependent
[2] = Continuous power, one channel
driven or peak power both channels
driven. Thermal protection may
occur at high continuous power.
Power in watts (EIA 1kHz, 1%
THD)
Weight
10kg (22lbs)
Dimensions
(W) 483mm x (H) 88mm x (D) 347mm
(W) 19ins x (H) 3.5ins x (D) 13.7ins
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A1.7 General operational summary
1)
Always use the same model system controller and power amplifier for a
particular Wavefront product. This avoids confusion caused by different
controller topologies and power amplifiers voltage gains.
2)
It is common practice to use mixing console matrix outputs as loudspeaker
section controls. Whilst this is fine for creating a bass submix which can
easily be judged from the mix position, it can be fraught with danger if used
for audience sections which may only be audible in very specific areas. Trim
these remote sections, during listening tests with a colleague via walkie talkie,
using the relevant controller input gains. If the console matrix cannot be
avoided, try to pre-calibrate its output levels controls to their 0dB (nominal)
position initially. These settings will be easier to get back to and will avoid
embarrassing level setting mistakes during the show - particularly if the
system is being used by guest operators who may not be familiar with your
particular matrix allocations.
3)
And again, trim levels within clusters (eg farfield vs midfield or inners vs
outers) using the amplifier level controls to ensure limiter tracking.
A1.8 Arraying & placement
Simple stacked systems
Single W8
A single Wavefront W8 cabinet will cover 55º horizontally x 30º vertically and may
be used as a stand-alone system for a variety of light music and voice applications
including commercial presentations.
A W8 may be combined with a W8S compact subwoofer or a WSX horn-loaded
subwoofer to extend its low frequency performance.
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Single W8 on W8S subwoofer
This very compact stack may be used as one side of a main system for a folk band
concert in a small venue, one corner of a small dance floor system, stage side fills,
stage drum fills, front fills etc.
SAFETY REMINDER!
Stacks should always be safety strapped to allow for high winds, over-exuberant
artists, crowd indicipline, scenery movements etc.
Wide coverage, broadband stack
Although a single Wavefront W8’s horizontal coverage is 55º at high frequencies, the
system has been designed to integrate well with smaller splays for practical output
summing. A splay of 40º between axes (260mm between cabinet front corners)
provides very smooth 95º horizontal coverage with little increase in mid-band output
level whilst a smaller splay angle can boost the forward output level by 2-3dB.
2-wide W8/W8S ground-stack
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This very compact stack may be used for as one side of a small venue main system,
one corner of a dance system, high power stage side fills, drum fills, centre fills etc.
Flown systems overview
Flown clusters are recommended for very high power music systems covering large
venues to ensure adequate coverage without excessive levels at the front of the venue.
Wavefront series products are fitted with MAN load-certified flying points and are
designed to comply with the 12:1 safety factor specified by the German VBG70
standard when used with compatible 12:1 flying systems.
MAN Transformer or Installer/Tourer flying systems allow columns of loudspeakers
to be assembled by attaching individual loudspeakers to vertically daisy-chained Drings using keyhole cabinet fittings - hence the tendency to base flown designs in this
applications guide on multiple columns. The beauty of the MAN system is that each
cabinet in a system supports only its own weight.
See Section 1.8 for further details and illustrations.
Rigging Schools!
Rigging should not be undertaken by untrained or unqualified personnel.
Suitable rigging training sessions may be arranged by calling Martin Audio Ltd on
+44 (0)1494 535312.
Important note on flown systems examples
Wavefront cluster examples are included in this manual to illustrate recommended
loudspeaker combinations and splay angles only. Note that very large clusters particularly those including Wavefront Longthrow elements - may need to be flown
in multiple layers to maintain the 12:1 safety factor of the standard Martin Audio
Wavefront 8 Flying System.
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A1.9 Coverage calculations
Single W8 column
Here is an example of a 1-wide, 3 deep column of Wavefront W8s.
The horizontal coverage is, of course, that of a single W8 ie 55º.
The vertical coverage of a W8 cluster can be calculated as follows:
Vertical coverage of a W8 = the vertical coverage of a single W8 (30º) + the sum
of all the vertical splay angles
For a 3-deep W8 cluster with 15º vertical splay angles = 30º+15º+15º = 60º
For a 3-deep W8 cluster with 20º vertical splay angles = 30º+20º+20º = 70º
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Double W8 column
Here is a 2 wide, 4 deep column of Wavefront W8s.
Vertical coverage of a W8 cluster = the vertical coverage of a single W8 (30º) +
the sum of all the vertical splay angles
For a 4-deep W8 cluster with 20º vertical splay angles = 30º+20º+20º+20º = 90º
Horizontal coverage of a W8 cluster = the horizontal coverage of a single W8
(55º) + the sum of all the horizontal splay angles
For a 2-wide W8 cluster with 30º horizontal splay angles = 55º+30º = 85º
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Wide coverage cluster
4 or 6 wide, 4 deep W8 clusters may be rigged for very wide coverage. Coverage may
be calculated as follows:
6 wide cluster
6 wide, 4 deep plan view
The horizontal coverage now extends to:
55º+30º+30º+30º+30º+30º = 205º for 30º horizontal splays
and the vertical coverage extends to:
30º+20º+20º+20º = 90º for 20º vertical splays
Circular cluster
Two 6-wide, 4 deep W8 clusters with 30º horizontal splay angles and 20º vertical
splay angles may be flown back-to-back to provide full 360º horizontal x 90º vertical
coverage for, for example, ice shows.
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Column View
Note that the 90º coverage allows foldback to be provided to the ice-dancers. The
centre hole may be filled by flying a smaller cabinet underneath the main cluster.
Circular, 4-deep W8 cluster
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W8s as front fills
Wavefront W8s may be used as stage apron fills for high power rock concerts. When
carefully placed on radii converging at the centre downstage (lead vocal) area and
sychronised with the main PA downfills, these apron fills don't just balance the
subwoofers. They can focus vocals and add a detailed quality that can be beneficial
right out to the mix position.
If the apron fill loudpeaker signal is delayed by the difference between the downfill
propagation time and the apron fill propagation time and attenuated by the ratio of
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those propagation times, the sound will appear to come from an area in between the
two systems for the listener shown.
Apron fill delay line setting = t downfill - t apron fill
Apron fill gain setting wrt downfill gain = 20log10(t downfill ÷ t apron fill) dB
A1.11
W8s as side clusters
A Wavefront Longthrow (See Section 2) centre cluster may be used with W8
downfills for efficient operatic and orchestral amplification. Velodrome side seats can
be some distance away (typically across a wide cycle track) so fairly powerful side
clusters may be required for good projection and intelligibility.
W8s blend in sonically without off-axis lobing and stage mic colouration.
Deep orchestral stage continues this way ñ
To avoid abrupt changes in timbre between the side and centre cluster, the side
downstage W8 axis should be aimed at the seating where the centre cluster is just
beginning to lack very high frequencies.
Controller output levels and delays should be adjusted so that the side and centre
clusters are at the same level and sychronised in the same area.
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A1.12
GUIDES
W8s in distributed (delay) systems
Wavefront W8s make very good high power distributed systems or delay elements as
they project sound smoothly and efficiently without local off-axis lobing.
For good overall coverage, delays are best driven in mono for most of the show
although computer controlled matrix mixes may be considered for panning spot
effects around the venue.
Flown radial delays
Flown distribution or delay loudspeakers should be placed on radii converging at the
stage and staggered for smooth coverage.
Distributed flown loudspeaker plan (stage system not shown)
Delay times should be set for synchronisation with the next most powerful source.
This would be the stage for the first row of delays (below left) or the previous row
(below right) for farfield delays.
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Synchronising flown central delays
Synchronising flown outer delays
Ideally, the sound should be perceived as coming from the stage over the whole
audience area - which means that all the delay loudspeakers should be aligned with
the stage opening. In practice, sight line, follow spot and camera shot restrictions will
affect placement for heavily raked seating areas and intelligent compromises will
need to be made.
Delay systems should be thoroughly checked over a wide listening area to ensure that
their level settings provide smooth coverage without hot spots. Delay times and levels
should be finely adjusted to minimise multiple arrivals in seating areas where systems
cannot be in line with the stage and more than one source can be heard.
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Aiming delay tower loudspeakers
Multiple delay tower loudspeakers should be tilted so that they aim towards head
height at the next tower to mask off-axis tower leakage and to minimise multiple
arrivals further out.
Synchronising multiple tower systems
(not to scale)
Small delay time errors are inevitable where delay towers are located in audience
areas (eg on a football field) due to the three dimensional geometry involved.
Controller delays should be adjusted, initially, for synchronisation along a line
between staggered delay towers and then modified as necessary to minimise timing
errors around each tower and over its main coverage area.
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A1.13
GUIDES
Combining W8s with other Wavefront systems
The full-sized Wavefront W8 3-way loudspeaker is a member of the comprehensive
Wavefront 8 family which includes:
•
•
•
•
It's single-12" brother - the W8C 3-way system (Section 1).
The W8CT & W8CM Longthrow line array system (Section 2).
The W8S Hybrid™ flown subwoofer (Section A2) and its single-15" brother - the
W8CS flown subwoofer (Section 3).
The WSX folded horn subwoofer (Section 4).
Wavefront Compact W8C and W8CS systems fulfill the requirement for smaller
touring components with a slight reduction of low frequency performance as follows:
Model
LF components
LF limit (-10dB)
W8
W8C
2 x 12" horn-loaded
1 x 12" horn-loaded
80Hz
100Hz
W8S
W8CS
1 x 18" (ported) + 1 x 15" (horn-loaded)
1 x 15" (horn-loaded)
30Hz
35Hz
Wavefront 8 family members can be combined successfully to make larger systems
out of the available enclosures because they use similar high-mid and HF driver and
horn components and compatible rigging.
Martin Audio DX1 controllers are pre-loaded with a wide range of system
programmes to combine Wavefront 8 components using the correct crossover
characteristics and delay settings. Experienced users may mix and match DX1s with
standard crossover settings for custom combinations. See the DX1 Speaker
Management System Operating Instructions (issued with the DX1) for further details.
For instance, two Wavefront users may combine their smaller systems for a larger
event. If one user has W8S Hybrid™ subwoofers and the other has WSX folded-horn
subwoofers, their systems would need to be set up so that the subwoofer systems
combine in phase with the correct time alignment.
A quick interrogation of DX1 programmes 24 (for W8+W8S) and 21 (for W8+WSX)
shows that the W8+W8S settings would need their delays increasing by 3.771mS to
align with the W8+WSX settings. This is because the WSX's long folded horn gives it
a longer acoustical delay than the W8S' shorter mid-bass horn.
The extra W8 delay is catered for in the DX1 set to programme 21 but not in the DX1
set to programme 24 - which is set up for the W8S.
WSX ------------------------------------4.361mS---------------------------------W8 Low mid
WSX ------------------------------------3.771mS--------------W8S--0.59mS--W8 Low mid
The extra 3.771mS may be added to the DX1 set to programme 24 as an input delay.
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Combining Subwoofers
The following illustration shows WSX and W8S subwoofers combined for a larger
event as discussed.
Combining Wavefront W8 and Wavefront Longthrow systems
(See next page)
The left cluster for an athletic field is shown. The main forward section includes 4
rows of Longthrow with another 2 rows of W8CTs being used to augment the outer
columns.
The W8-to-W8CT vertical splay angle is kept very small (3º - just one M.A.N. flying
system chain link) to provide a smooth transition between the two sections.
Wavefront Longthrow (Line Array) systems have more forward gain than regular W8
systems so amplifier gains should be set to allow for this. The W8CT/CM amplifier
channels are usually attenuated by 6-9dB wrt the W8 amplifiers.
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See Section 2 for further Wavefront W8CT/CM information.
See Section A2 for guidance on W8/W8S combinations.
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Appendix 2
Wavefront W8S Hybrid™ Subwoofer
Contents
A2.1
Introduction
A2.2
Specifications
A2.3
Pin-outs and cabling
A2.4
System patching
A2.5
DX1 Loudspeaker Management System
A2.6
Power amplifier recommendations
A2.6.1
Martin Audio MA4.2 Power Amplifier Overview
A2.7
Adding W8S’ to flown W8 systems
A2.8
W8S Ground Arrays
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Wavefront W8S Hybrid™ Subwoofer
A2.1 Introduction
The Martin Audio Wavefront W8S Hybrid™ Subwoofer combines a horn-loaded 15"
driver with a ported 18" high-excursion direct radiator. This powerful combination
gives the W8S the characteristic punch of a horn-loaded system with the low
frequency bass extension of a reflex enclosure.
The W8S is a light weight system in a trapezoidal cabinet. It has the same footprint as
the W8 3-way system and has been engineered to extend the Wavefront W8's
performance to below 40Hz.
Like all flown Wavefront products, the W8S is fitted with MAN load-certified flying
points and is designed to comply with the 12:1 safety factor specified by the German
VBG70 standard when used with compatible 12:1 flying flying systems. One important
advantage of the MAN flying system is that inter-cabinet connections place a minimal
load on the cabinets and, being external, can be load certified and inspected
independently.
A2.2 Specifications
Type:
Hybrid™ bass system
Frequency response:
40-150Hz +/- 3dB
Low frequency limit:
-10dB at 30Hz
Driver:
1 x 15" (380mm) horn loaded
1 x 18" (460mm) reflex loaded
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Rated Power:
Sensitivity:
800W into 8 ohms, 3200W peak
104dB/W
Maximum SPL:
131dB continuous, 137dB peak
Impedance:
8 ohms nominal per driver
Connectors:
2 x Neutrik NL8, 2 x EP8
Cabinet construction:
Birch Ply
Cabinet finish:
Slate textured paint
Protective grille:
Perforated steel
Grille finish:
Grey paint
Dimensions (inc wheels):
(W) 562mm x (H) 1066mm x (D) 925mm
(W) 22.1ins x (H) 42.0ins x (D) 36.4ins
Weight:
90kg (198lb)
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A2.3 Pin-outs and cabling
W8S
EP8
NL8
W8S
1
-1
18" Driver -
2
+1
18" Driver +
3
-2
18" Driver -
4
+2
18" Driver +
5
-3
15" Driver -
6
+3
15" Driver +
7
-4
15" Driver -
8
+4
15" Driver +
(See Section A1.3 for NL connector pin-out drawing)
A2.3.1
Cable and panel connector part numbers
Please note the following part numbers when ordering loudspeaker connectors to
make up cables and patch panels:
Neutrik NL connectors
NL8FC
NL8MPR
NL8MM
8 pole cable (female)
8 pole panel (male)
8 pole inline coupler (male-male)
Cannon EP connectors
EP8-11
EP8-12
EP8-13
EP8-14
8 pin cable female
8 pin cable male
8 pin panel mount female
8 pin panel mount male
Connectors should be kept in good, clean, uncorroded condition to ensure full,
undistorted loudspeaker performance. Corroded or damaged pins and sockets can
cause severe distortion or loss of signal.
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A2.3.2
GUIDES
Recommended loudspeaker cable
Cable run vs copper core cross sectional area
Up to 50m
Up to 100m
Single W8S
Two W8S’ paralleled at the
cluster.
2.5mm²
6mm²
6mm² (or 2 x 2.5mm² cores in parallel)
10mm² (or 2 x 6mm² cores in parallel)
Q. Why the odd sizes?
A. Loudspeaker cables are available in a limited range of standard copper core sizes ie. 1.5mm², 2.5mm², 4mm², 6mm², 10mm² and 35mm².
A2.4 System patching
Refer to Section A1.4 for general Wavefront patching suggestions and examples.
Bass sub-mix operation
Many mix operators prefer to create a separate sub-mix for bass/mid-bass sections.
This is good practice as it helps provide main system headroom for those allimportant vocals and solos whilst allowing for larger-than-life percussion and bass
instrument mixes without intermodulation and distortion.
This configuration can easily be programmed into the Martin Audio DX1
Loudspeaker Management System. The following illustrates a DX1 set up to control
an active (3-way) Wavefront W8 system with a separate W8S sub-mix.
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A2.5 DX1 Loudspeaker Management System
Note:
W8S systems may be driven 2-way for maximum performance. Time aligning the
W8s' 18" reflex-loaded driver with its 15" horn-loaded section provides exceptional
mid-bass punch and impact.
DX1 Programme 24 should be used as your default setting. (See Section A1.5)
A2.5.1
DX1 Output Gain and Limiter settings for W8S’
Gain settings
The following initial DX1 output gain settings will enable full system performance to
be obtained whilst keeping the console and drive system noise floors inaudible and
avoiding amplifier slew-rate limiting:
W8S - assuming 800Wcont - 1600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Amplifier
Amplifier
Sensitivity
Gain
dBu Vrms dB
Initial DX1
Output GAIN
(Lo15" & Lo18" o/ps)
dB
Crown MA5002VZ (0.775v)
Martin MA4.2** (41dB)
Crest CA18 (x115)
Crown MA3600VZ (0.775v)
-2
0.62 42
-9
-1
0.69 41
-8
-1
0.69 41
-8
-1
0.69 41
-8
0
0.77 40
-7
+1
0.87 39
-6
+2
0.98 38
-5
+3
1.09 37
-4
QSC PL236/PL236A (36dB) +4
1.23 36
-3
+5
1.38 35
-2
+6
1.55 34
-1
+7
1.73 33
0
Martin MA4.2** (32dB)
+8
1.95 32
+1
Crest 8001 (x40)
+8
1.95 32
+1
Crest 9001 (x40)
+8
1.95 32
+1
QSC PL236A (32dB)
+8
1.95 32
+1
+9
2.18 31
+2
+10 2.45 30
+3
+11 2.75 29
+4
+12 3.08 28
+5
+13 3.46 27
+6
Crown MA3600VZ (26dB) +14 3.88 26
+7
Crown MA5002VZ (26dB) +14 3.88 26
+7
QSC PL236A (26dB)
+14 3.88 26
+7
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers.
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Standardising on one good model of power amplifier (preferably the Martin Audio
MA4.2) and correctly set-up controller (preferably the Martin Audio DX1) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories. (See Section A1.5 and DX1 Speaker
Management System User's Guide for further details)
Cluster balance (eg farfield-to-midfield or inner-to-outer) should be adjusted at the
power amplifier controls to maintain limiter tracking. See Section A2.7.
Balancing the system using gain controls in the signal path before the power
amplifiers is not recommended as it will cause the higher signal level upper rows of a
big cluster to start limiting before the lower signal levels downfills resulting in tonal
changes at the mix position.
Limiter settings
The Rated Power specification in Section A2.2 indicates the maximum long-term
power dissipation that can be tolerated before driver ageing or damage occurs through
overheating or over-excursion.
When choosing power amplifiers, do not be tempted to exceed the 800W into 8Ω
power rating unless the amplifier's power rails are well regulated (see Section A2.6) even with properly set controllers in place. Although Martin Audio drivers are
mechanically designed to survive normal road use and the occasional operator error,
overpowered or bridged amplifiers can cause over-excursions that stress and age
drivers. The best way to get the clean, relaxed sound of an overpowered amplifier is
to choose an amplifier with plenty of current reserve - ie an amplifier with good 2Ω
specification - and avoid running more than two cabinets in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
the subwoofer's high pass frequency as follows:
High pass filter range
Attack time
Release time
>31Hz
31Hz - 63Hz
45mS
16mS
720mS
256mS
These attack times allow the power amplifiers to clip momentarily but not for long
enough to be obvious to listeners or cause driver overheating. It is quite normal to see
amplifier clip indicators on the odd programme peak but continuous clipping would
indicate a cable short circuit, wrong controller settings, excessive power amplifier
gain or low mains voltage.
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The following initial DX1 output limiter settings will avoid voice coil overheating
and minimise amplifier clipping for high quality, trouble free operation.
W8S - assuming 800Wcont - 1600Wpk into 8Ω
Ω power amplifiers:
Best-fit
Amplifier
Example
Vrms dB
Recommended
DX1 LIMITER
Settings
(Lo15" & Lo18" o/ps)
dBu
0.62
0.69
0.69
0.69
0.77
0.87
0.98
1.09
1.23
1.38
1.55
1.73
1.95
1.95
1.95
1.95
2.18
2.45
2.75
3.08
3.46
3.88
3.88
3.88
-3
-2
-2
-2
-1
0
+1
+2
+3
+4
+5
+6
+7
+7
+7
+7
+8
+9
+10
+11
+12
+13
+13
+13
Amplifier
Sensitivity
dBu
Crown MA5002VZ (0.775v)
Martin MA4.2** (41dB)
Crest CA18 (x115)
Crown MA3600VZ (0.775v)
-2
-1
-1
-1
0
+1
+2
+3
QSC PL236/PL236A (36dB) +4
+5
+6
+7
Martin MA4.2** (32dB)
+8
Crest 8001 (x40)
+8
Crest 9001 (x40)
+8
QSC PL236A (32dB)
+8
+9
+10
+11
+12
+13
Crown MA3600VZ (26dB) +14
Crown MA5002VZ (26dB) +14
QSC PL236A (26dB)
+14
Amplifier
Gain
42
41
41
41
40
39
38
37
36
35
34
33
32
32
32
32
31
30
29
28
27
26
26
26
** Set Martin Audio MA4.2 rear MLS switch to 0dB to match peak output of
unregulated power amplifiers.
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Use lower limiter settings (or more subwoofers!) if your power amplifiers indicate
clipping on more than just the odd peak. Excessive clipping may also be caused by
inadequate power amplifier reserve or an inadequate mains supply. See below.
A2.6 Power amplifier recommendations
The Wavefront W8S Subwoofer has been designed and manufactured for very high
performance but will not give that performance unless power amplifiers are chosen
and used intelligently.
Power capability
W8S’ provide full performance when driven by professional power amplifiers
capable of delivering undistorted output power into a range of loads as follows:
W8S
800 W(AES) into 8 ohms
1,600 W(AES) into 4 ohms
and
3,200 W(AES) into 2 ohms
Please note:
Amplifiers with excessive output may damage voice-coils or age driver suspensions
due to excessive heat dissipation and excursion.
A note about power amplifier output specifications
Most power amplifier manufacturers keep their costs down by using unregulated
supply rails which sag under load. To allow for this sag, manufacturers set their rails
high so that they still meet their quoted output into specified loads. These high rail
voltages allow such power amplifiers to provide outputs 1.5 - 2 times their quoted
power for short-term bursts. Martin Audio products will withstand this potential
doubling of instantaneous power - with suitably set controller limiters - but further,
long-term increases caused by over-sized amplifiers should be avoided.
Martin Audio MA series power amplifiers have regulated rails so it is quite
permissible to use slightly overpowered models - with suitably set controller limiters
- without risking uncontrolled power bursts. The MA series power amplifiers’
regulated power rails also ensure maximum performance under the real-world concert
conditions of less-than-optimum mains supplies and low impedance loads.
See Section A2.6.1 for further details.
Amplifier load tolerance
An efficient subwoofer system in live concert conditions can act as a surprisingly
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dynamic and complex load. Most modern touring power amplifiers claim 2 ohm
capabilities but make sure your amplifier is also capable of driving reactive (ie
inductive or capacitive) loads without prematurely clipping or developing output
stage crossover distortion.
Power reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for percussive peaks and sustained bass
notes.
1)
Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load.
An electrical technician should check the mains supply vs demand using an
accurate rms voltage meter.
2)
If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3)
Avoid driving too many W8S drivers in parallel. I would suggest no more
than 2 x 15" or 2 x 18" per amplifier channel so that the power amplifier’s 2
ohm spec is kept in reserve for musical peaks.
4)
Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
Note that W8S 15" and 18" drivers may be driven in parallel - i.e. in passive mode
(DX1 programmes 22 or 23) to save amplifier channels on smaller systems … but
with reduced punch and slam.
W8S' should always be driven actively (DX1 programme 24) when power amplifier
budgets allow.
Power amplifier gain or level settings reminder
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
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Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section A2.5.1). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controllers have been set as tabulated in Section A2.5.1, power
amplifier level controls should be set to full (fully clockwise) for loudspeaker sections
requiring the strongest drive. Amplifiers driving nearer-field section within the same
cluster may be backed off as required for smooth coverage. This process will ensure
that the cluster coverage remains balanced during limiting.
Rack mounting
As with main W8 systems, always leave a 1U space between big subwoofer power
amplifiers and controllers. Although most modern amplifiers don’t radiate significant
fields it's better to play safe and keep the system free from hum & buzz. Rear
supports are recommended. Check the manufacturer's application notes for details.
A2.6.1
Martin Audio MA4.2 Overview
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Features
Ø
Ø
Ø
Ø
Ø
Ø
Switch mode power supply
Superior sonic performance
Light weight
Advanced protection circuits
Efficient copper cooling system
Minimum load switches (MLStm)
The MA4.2 power amplifier has been designed to combine reliability and high power
output with sonic excellence. Utilising an advanced switch mode power supply, the
MA4.2 is characterised by a very high power-to-weight ratio, in a lightweight, 2U
package.
See MA4.2 Amplifier User's Guide for detailed operating instruction.
Cooling System
The Martin Audio MA4.2 amplifier runs very cool due to a special patented copper
cooling system. The amplifier’s bi-polar output devices are mounted directly onto a
copper heat sink (copper conducts heat twice as efficiently as aluminium) and
maximum heat dissipation is achieved by turbulent airflow over the heatsink’s
geometric fins.
The MA4.2 amplifier features two proportional speed cooling fans which take in air
from the front of the amplifier and exhaust from the rear. A horizontal pressure
chamber between the heatsink and the cooling fans ensures that there is little
difference in the operating temperatures of each output device. In contrast, a
conventional tunnel design can result in a temperature variance of up to 40° between
output devices.
Switch Mode Power Supply
The MA4.2’s switch mode power supply (SMPS) is the modern solution to the
problems of size and weight. Switch mode power supplies are not new - they are
found in computers and televisions. However, the demands of high power audio are
very different to these applications. The MA4.2 overcomes the size and weight
constraints of conventional power supplies whilst at the same time avoiding the
pitfalls of typical switch mode designs.
The low output impedance of the SMPS means that rail voltages do not sag under
heavy load conditions. Additionally, the rail capacitors are being recharged at a much
faster rate than those in a conventional power supply. The result is an exceptional fast
transient low frequency performance at all power levels.
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Efficiency is also maximised. With much smaller transformers than a conventional
supply, there is much less loss due to transformer resistance and much less power
wasted as heat in the power supply.
Regulation of the SMPS means that the power amplifier will produce the same power
output, even if the AC line voltage drops by 20%.
Minimum Load Switches (MLS™)
Because the SMPS is regulated, the maximum power available for the output stages
can be adjusted without increased heat dissipation or efficiency loss. This allows the
user to match the output power with the loudspeaker impedance.
Protection
The MA4.2 amplifier has many advanced protection features that will protect both the
amplifier and the speakers connected to it, under fault conditions. All protection
circuits are independent and inaudible in normal use.
Clip Limiters
Clip limiters prevent dangerous clipped signals reaching the speaker. They work by
monitoring the output to check for signals not present at the input i.e.distortion. If
distortion exceeds 1% on an output, the limiter will reduce the input signal
proportionally.
Thermal Protection
Thermal Protection circuitry prevents the amplifier from running at an unsafe
temperature by muting the input signal when the internal temperature rises above
90°C.
Short Circuit Protection
The MA4.2 amplifier is completely short circuit protected. The protection circuits
permit very high peak currents, but maintain the output devices within their safe
operating area.
Mains Voltage Protection
This operates if the mains voltage falls outside its permitted operating range. If this
occurs, the power supply will shut down until the correct mains voltage is restored.
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DC and VHF Protection
Both DC voltages and high power VHF signals can cause damage to loudspeakers.
The MA4.2 amplifier incorporates protection circuits which are activated when
damaging DC voltages or VHF signals are present at the outputs.
MA4.2 Specifications
Input Impedance
Gain select switch
CMRR at 1KHz
Output impedance at 1KHz
Power Bandwidth
Slew rate
Hum/Noise
Channel Separation
Mains Operating Voltage
Protection
Distortion
THD 20Hz - 20kHz and 1W –
1000W
THD at 1 kHz and 2000W
DIM 30 at 500W
CCIF (13 and 14kHz) at 500W
SMPTE (60Hz and 7kHz) at 500W
20kohms (balanced) 10kohms single ended
41dB (I/P sens 0.775V), 32dB (I/P sens 2.26V)
>50dB
<0.06 ohms
5Hz - 20kHz
20V/us
<-95dB
1kHz > 80dB
10kHz > 70dB
120 – 270 (minimum start voltage 190)
full output power maintained 180 – 280V
Optional (65 - 135V) operation.
DC, High temperature, Turn on, VHF,
Over and under voltage, Clip limiters
AFS Short circuit
4 ohms 0.1%
4 ohms 0.04%
4 ohms 0.04%
4 ohms 0.04%
4 ohms 0.04%
Power Matrix
LOAD CONFIGURATION
16 ohms Stereo (2 channel)
8 ohms Stereo (2 channel)
4 ohms Stereo (2 channel)
2 ohms Stereo (2 channel)
16 ohms Bridged mono
8 ohms Bridged mono
4 ohms Bridged mono
MLS SWITCH SETTING
(-5dB)
(-4dB)
(-2dB)
220W
260W
410W
430W
520W
820W
830W
1000W
1600W
1660W
2000W
2200W
3050W[2]
860W
1040W
1640W
1660W
2000W
3200W
3320W
4000W
4400W
(0dB)
650W
1300W
2100W
2400W[1]
3200W[2]
2600W
4200W
4800W[1]
[1] = Component tolerance
dependent [2] = Continuous power,
one channel driven or peak power
both channels driven. Thermal
protection may occur at high
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continuous power. Power in watts
(EIA 1kHz, 1% THD)
Weight
Dimensions
10kg (22lbs)
(W) 483mm x (H) 88mm x (D) 347mm
(W) 19ins x (H) 3.5ins x (D) 13.7ins
A2.7 Adding W8S’ to flown W8 systems
Although the Wavefront W8S is often used as a base for smaller floor-stacked or
stage-stacked systems, flying W8S’ with main W8 systems can keep the floor tidy
and free up floor space for scenery, TV camera tracks etc.
As mentioned earlier, very large outdoor festival crowds will absorb mid-bass from
low-profile, ground stacked subwoofers. Flying W8S’ will provide a tight, efficient
and detailed bass performance without audience mid-bass absorption.
A2.7.1
W8S/W8 configurations
For medium power amplications - amplifying a large orchestra, for example, where
low frequency stability is important - a single row of W8S’ may be added to a
standard W8 cluster extending its low frequency response to below 40Hz. This
configuration can be very efficient as it uses the rest of the cluster as a baffle,
increasing forward projection allowing high gain before feedback.
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The following iconic layout may be used to represent the above cluster:
Important reminder:
Splay angles are always quoted axis-to-axis - not between cabinet sides!
ie.
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Multiple rows of W8S'
Multiple rows of W8S’ increase low frequency headroom for higher power rock,
dance club applications. Flying W8S’ in rows keeps clusters relatively narrow where
width is at a premium.
Coverage would be 145º horizontal x 70º vertical.
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For very high power rock or dance applications, the above W8S’ may be configured
as flown mid-bass elements (crossed in at 80Hz and out at 150Hz) to augment floorstacked WSX folded-horn subwoofers working as low subs below 80Hz. Refer to
Section 4 for further information on WSX folded-horn subwoofers.
Power amplifier monitoring at real-world gigs have shown that half of the total
system power is demanded between 60Hz & 160Hz during heavy rock and dance
music.
W8S’ flown in columns with W8s
Flying W8S’ in columns between W8 columns keeps clusters shorter whilst providing
good vertical control for minimum roof excitation.
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Again, coverage would be 145º Horizontal x 70º Vertical.
A2.8
W8S Ground Arrays
W8S Hybrid™ subwoofers provide maximum coherence when flown with the main
system but may be arrayed on the ground if flying weights are restricted or the
ground's boundary effects are required to maximise system headroom.
Stacking safety!
Stacked W8S' should always be blocked, strapped and anchored from above by
a qualified rigger.
Coverage angle for tightly packed flat fronted arrays
-6dB Coverage
Here is a simplified formula for calculating the main coverage angle of a tightly
packed flat fronted array.
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* = approximate speed of sound in m/s. Varies with temperature (see Section 2a).
Arcsin means “the angle whose sin is ...”
Flat fronted cluster coverage patterns will be confined to one main lobe whose midbass crossover directivity is proportional to the size of the cluster.
The medium sized array (left) has significant output to ±90º whereas the large array’s
±90º output is dramatically reduced.
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A note on coverage nulls
It is useful to be able to calculate where these first response nulls will occur for
various frequencies as they indicate areas where coverage, transient response and
directional information would be poor without fill systems. For symmetrical arrays
nulls will occur either side of the on-axis line. We can calculate the overall “null-tonull” angle using the simple formula:
As a very rough guide, the null-to-null angle will be approximately twice the -6dB
coverage angle.
Interpreting polar plots
i) It is conventional to “normalise” polar plot on-axis amplitudes so that different polar shapes may be
readily compared. In practice, the large array (right example) would have a higher on-axis amplitude
than the medium array.
ii) It is also conventional to plot polar amplitudes on a logarithmic scale. This is fine when working in
sound pressure level terms but is not suitable for superimposing a polar plot onto a venue plan. Venue
plans are drawn to a linear scale so polar plots with linear amplitude scales would be more suitable.
iii) Polar plots have been simplified in this article for clarity. Real-world off-axis lobe amplitudes and
shapes would vary considerably depending on boundary loading, echoes, reverberation and other
audio sources affecting the same space.
Vertical -6dB coverage
The following table gives the approximate vertical coverage angles of typical W8S
arrays - ignoring boundary effects (see later).
W8S' High
(standing upright)
40Hz
2
3
4
Wide
Wide
Wide
Vertical coverage
80Hz
Wide
Wide
80º
160Hz
80º
53º
40º
♦ Use tall stacks for long shots. Useful for long distances in low-roofed venues
with raked seating up to the height of the stack.
(Important: see safety note above)
♦ Use short stacks for short, wide vertical shots.
Vertical Boundary effects
A solid floor will act as a reflector. This will cause a vertical stack to perform as if it
were double the length, giving a useful low frequency boost accompanied by a
narrower, more complex polar response.
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For instance, a 4 high ground-stack of W8S' will act like the top half of an 8 high
stack. (Important: see safety note above)
Note that flexible floors may actually absorb sound at some frequencies so the
situation isn’t always so simple in practice.
Horizontal - 6dB coverage
The following table gives the approximate horizontal coverage angles of typical W8S
arrays - ignoring boundary effects.
W8S' Wide
(standing upright)
40Hz
3
4
8
16
Wide
Wide
Wide
69º
Horizontal coverage
80Hz
160Hz
Wide
Wide
69º
33º
98º
69º
33º
16º
With W8S' standing upright, flat fronted cluster coverage patterns will be confined to
one main lobe whose mid-bass crossover width is inversely proportional to the size of
the cluster as long as horizontal gaps are less than 500mm.
♦ Use wide arrays for long shots. Useful for long, narrow venues
♦ Use narrow arrays for short, wide shots
Horizontal Boundary effects
A solid wall near an array will act as a reflector. This will cause a horizontal array to
perform as if it were twice as wide, giving a useful low frequency boost accompanied
by a narrower, more complex polar response.
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Again, a flexible side wall may absorb sound at certain low frequencies. Boundaries
should always be treated with caution.
Spacing
It is possible to space out W8S' to provide a larger frontal area with fewer units but
care must be taken to avoid irregular coverage at higher, mid-bass frequencies.
The following formula gives the pressure ratio (wrt the on-axis pressure) for
any off-axis angle of a regularly spaced linear array:
Far field polar patterns can be quite complicated - even for a simple pair of
subwoofers driven in unison.
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Wide spacing will cause off axis irregularities (combing) because time offsets start to
become significant. See Section 4.10 for a more detailed explanation.
♦ An odd number of half wavelengths will cause nulls along the line of the
loudspeakers (the 90º lines) - see the 2½ wavelength example above
♦ An even number of half wavelengths will cause lobes along the line of the
loudspeakers - see the 2 wavelength example below
The following tables give the maximum recommended gap (between W8S sides) for
the relevant frequency range.
W8S' standing upright
Gap
Smooth coverage range
0.5m
1.0m
2.0m
38 - 160Hz
38 - 110Hz
38 - 80Hz
To avoid mid-bass combing keep horizontal gaps below 500mm for upright W8S'
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Horizontal splays
Splaying W8S' arrays horizontally will widen their mid-bass coverage.
The following sketch shows a very high power, tightly packed 8-wide x 3 high W8S
ground array - splayed for smooth mid-bass coverage.
Note the four W8 front fills included in the stack. These alternate with the top row of
W8S' to give the W8 front fills their nominal 30º axis-to-axis splay.
W8S' are normally used upright with the 18" unit at the bottom. This ensures that the
side rigging points are nearest the top for safe rigging. Straps and rigging systems
should be used to prevent ground stacks from falling over under the influence of high
winds or over-exuberant fans.
For a smooth polar crossover:
♦ Array the W8S' to match the curvature of the main clusters' bottom section
whenever possible but avoid making the front horizontal gaps greater than
500mm.
♦ Avoid large gaps between the main system and the ground array whenever
possible.
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W8S Apron Fills
To avoid irregular subwoofer coverage due to widely-spaced left-right systems, it is
wise to place equally spaced W8S subwoofers along the stage apron between the
main left and right ground stacks.
This practice improves low frequency consistency - particularly at and around the
typical central auditorium mix position.
Note that W8S subwoofers may be used with other members of the Wavefront family
of products including the WSX folded-horn subwoofer. See Section A1.13.
(For detailed info on other Wavefront Series ground-stacks see Section 4.8)
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