EAW NTL720 User manual

Is it really possible to pack 10 pounds of stu into a 5-pound
bag? Further, can all of that“stu”be painstakingly formed
into a cohesive unit capable of meeting critical challenges and
professional expectations?
EAW set out to answer these questions in the armative –
and more – with the new NTL720, an extremely compact,
self-powered line array loudspeaker system. The result is a
package that integrates fresh and genuinely exciting design
developments with a lion’s share of the most signicant
technological advances that have been pioneered over the past
three decades.
Though so small (9.4 x 24 x 14.3 inches) and light in weight (less
than 50 pounds even with onboard tri-amplication) that we’ve
nicknamed it the “baby”line array module (BLAM for short), the
NTL720 is outtted with a true three-way design that delivers
full-sized performance. From the outset, EAW committed that
its new baby would provide maximized vocal clarity via a
correctly executed three-way design with superior mid-range
performance – regardless of the miniscule footprint.
From there, the development team dened a long, detailed list
of other absolute“musts”to be accomplished for the NTL720 to
be worthy of exceeding requirements in virtually every medium-
format live and installed sound application. Every item on that
list has a big check mark next to it, and as noted, all of these
individual technologies are united as a seamless system easily
optimized under a user-friendly software interface.
A LOOK INSIDE
Let’s start with a look at the horn and driver components and
technologies of the NTL720 before moving along to other crucial
aspects. When the (stainless steel) grille is removed from the
front of the cabinet, the rst thing that stands out is that the
entire front face of the enclosure is lled by a full-sized mid/high
horn providing 110-degree (horizontal) by 12-degree (vertical)
dispersion. The extreme size of this horn – an approach rst
applied to our lauded KF730 and 760 line arrays and KF750
concert systems – has proven to insure broadband pattern
control, particularly in the entire MF/HF pass-band.
High frequencies are produced by six 1-inch dome tweeters,
congured in two vertical columns (each with three tweeters)
mounted on a manifold that feeds a single slot in the center of
the horn. This is highly eective in controlling vertical dispersion,
and with equivalent output of a 1-inch-exit, 44-millimeter voice
coil compression driver. The HF section serves the 1.5 kHz to 21
kHz frequency range.
Flanking the HF section, dual 6-inch cone woofers handle the MF
range, also loading on to the large horn. A primary design goal
was to minimize the space between the MF and HF components
in order to enhance coherency and improve overall o-axis
response. Further, a symmetric layout of the MF drivers (placed
on both sides of HF) would promote a symmetric horizontal o-
axis response.
Openings needed to be incorporated in the horn for these
MF drivers. The easiest approach would have been to provide
openings the same size as the MF cones, but this creates a large
void in the HF horn wall, causing HF energy to“escape”into this
void, reect o of the MF cone, and arrive later in time than the
direct energy.
A slot in the horn was another possible approach, reducing the
void in the horn and somewhat minimizing interference to the
HF while also decreasing the distance between the acoustic
centers of the MF drivers. Yet a large percentage of the horn wall
NTL720 Line Array System
Integrating multiple EAW technologies in a miniscule package

is missing since the void in the horn wall is still relatively large as
compared to the overall size of the horn.
The solution deployed on the NTL720 stems from a great deal
of research during the development of the acclaimed AX Series
of large-format installation loudspeakers. Called Concentric
Summation Array (CSA) technology, it calls for several smaller
openings in the horn, with a close look at the horn surface
revealing these openings to be “randomized”cutouts in
diamond-shaped patterns. The cutouts decrease the acoustic
center of the mids while also decreasing the percentage of open
area at any point along the horn. The result is greatly minimized
interference to the HF. (Figure 2)
Another EAW focus over the past several years has been beam
forming and array shading; in other words, the creation of
precise beam shapes combined with the ability to steer them as
desired for more tightly focused coverage, particularly at longer
distances. As a result, all transducers in the NTL720 are highly
ecient and capable of very high output – and packed into the
smallest space possible – while the large-mouth horn enhances
pattern control.
Called Phased Point Source Technology (PPST), it was rst
developed for the EAW KF900 Series of extreme long-throw
loudspeakers. Briey, PPST works in tandem with digital
processing to create a unied source sound impulse at all
points within the coverage area. Building upon our previous
use of phase and frequency“shading”techniques to manipulate
beam proles and to blend vertically dissimilar subsystems, the
outcome is further integration of loudspeaker modules within an
array into a single acoustical element.
In tandem with PPST principles, EAW’s Divergence Shading
technology, utilized in the KF760 large-format line array, has
been applied to further achievement of even sound pressure
levels over distance. With Divergence Shading, the pressure
remains constant throughout the source while the curvature of
the wavefront is varied. (Figure 3)
A atter wavefront produces higher pressure at distance while
a tightly curved wavefront produces lower pressure at distance.
Because the input is constant across the source, the rate of
change of pressure magnitude is small, resulting in smooth
frequency response.
BOLSTERED LOWS
During the development of the KF730 small-format line array,
the desire to employ as large of a MF/HF horn as possible led
the EAW engineering team to devise a truly innovative solution:
side-ring LF drivers. Research showed that spacing the drivers
as far apart as possible ensures delivery of the lowest possible
frequencies, with the side-mounted“gure-8”conguration
extending horizontal pattern control well into the LF range.
Figure 2
Figure 3

This proprietary approach, called Phase Aligned, also creates
an o-axis null in the horizontal plane, putting more acoustical
energy on axis. Sure, the look of drivers ring out the side of
the box is dierent, but extensive listening tests backed by
measurement proved the design.
This proven LF method was again deployed in the NTL720. Like
the MF section, the LF woofers are 6-inch, with all four of these
drivers outtted with powerful neodymium magnet structures
that also reduce weight.
While these drivers may seem a bit on the small side, the ability
of the Phase Aligned drivers to extend LF performance is
particularly advantageous in meeting the needs of applications
requiring a bit of added punch. In addition, the response of the
MF drivers is also extended down to 100 Hz, furthering low-end
presence and impact. (A low-pass lter on the LF drivers curtails
their output at about 300 Hz.) (Note the NTL720 crossover points
presented in Figure 4.)
THE GUNNESS FOCUSING™ DIFFERENCE
The onboard self-powering technology developed and proven
in the EAW NT Series, has been further extended for the NTL720.
It includes three individual modied 500-watt Class D (digital)
amplier modules tailored for their respective subsections (LF,
LF/MF, and HF – all 4-ohm loads) and also precisely matched to
their own digital signal processors.
This reliable and very lightweight (9 lbs) amplication package
is easily eld-replaceable (more on this later). It includes an
intelligent power supply control that aords optimum eciency
with rock- solid immunity from AC line variations, with self-
resetting protection circuitry guarding against output overload,
overheating, power supply faults and excess output current.
Convection cooling eliminates the need for fans. (Figure 5)
Each DSP is tailored to best optimize its respective subsection,
providing response correction as well as EQ, delay, level, and
delay for additional tailoring and alignment control. Excursion
limiters add another layer of protection for the components.
Headlining the processing, however, is EAW’s revolutionary
Gunness Focusing™ alignment and driver processing algorithms
that deliver horn-loaded performance comparable to premium
direct-radiating studio monitors. Also rst unveiled in the NT
Series, Gunness Focusing is now available – via the UX8800
digital processor – for an ever-increasing number of conventional
EAW loudspeakers, but it’s already onboard the NTL720.
To the point, Gunness Focusing eliminates the traditional
characteristics of “honk” and“splashiness” that can plague horn-
loaded loudspeaker designs. The honk of a horn is normally
heard in the lower frequencies of its band pass, while splashiness
(an attribute of compression drivers) is usually heard at the
highest frequencies and obscures the ne detail in instruments,
such as cymbals.
Likewise, cone drivers have inherent resonances in their upper
frequency range that result in “muddiness” in the middle of the
vocal range. These HF and LF behaviors combine to produce a
sonic signature commonly referred to as“coloration.”
DSP is the primary tool available for dealing with these types
of loudspeaker anomalies, with the EAW engineering team
recognizing that the key is understanding the trade-os of
traditional DSP implementation. Therefore, the team rst
developed a proprietary, software-based spectrograph for
acoustical analysis. This spectrograph, along with other analysis
tools, was used to investigate the unprocessed responses of HF
and LF subsystems in various directions and at various levels.
The analysis allowed various performance anomalies to be
isolated from each other. In this way, those anomalies that
were linear, time invariant, spatially consistent, and therefore
correctable, could be distinguished from anomalies without
those characteristics, and which were therefore not correctable.
The next step was to apply appropriate DSP to the correctable
anomalies.
Another analysis was performed on the standard, universally
used DSP algorithms. This test proved that these standard
algorithms simply did not produce lters with response shapes,
temporal behaviors, or resolutions with anywhere near the
required precisions or accuracies necessary to correct those
anomalies to which they were being applied. (Figure 6 presents
before and after spectrographs of the dramatic impact made by
Gunness Focusing.)
Figure 4
Figure 5

To solve this dilemma, the company undertook development
of custom (and rather radical) DSP algorithms specically
engineered to provide the required lters for correcting
loudspeaker anomalies. The resulting lters had to possess the
required precision and accuracy in both the frequency and time
domain. At the same time, any uncorrectable anomalies would
have to be ignored by the lters.
This advanced processing, now called Gunness Focusing, cannot
be applied“as is”to just any loudspeaker, let alone be something
that even the most astute of users can set up. The anomalies and
resonance problems cured by Gunness Focusing are very specic
to each loudspeaker design.
Thus, the internal physical details must be known, the anomalies
must be carefully analyzed, with appropriate lters custom
designed by EAW and implemented via the UX8800 processor –
or, in the case of the NTL720, it’s incorporated within the system.
CONTROL & MUCH MORE
EAWPilot control software provides comprehensive DSP control
as well as monitoring of amplier status for each NTL720 module
in an array. And it does much, much more. When connected, all
loudspeakers in the audio system comprise a network in which
EAWPilot recognizes each individual loudspeaker as well as
arrays of loudspeakers acting as a single unit.
The roots of this software package stem from the KF900 project’s
optimization program, FChart, which uses high-resolution
measurements of each individual driver in an array to predict and
optimize total array performance. EAWPilot employs this same
approach to control multiple loudspeakers in a total system
environment.
Not only does EAWPilot assist in optimizing a wide range of
loudspeaker and array parameters, but its Wizard modeling
software helps in automatically conguring array DSP for optimal
performance tting specic audience areas, greatly simplifying
system setup and alignment. This even extends to providing
the user with input on building optimum array structures and
selecting correct pickpoints on the array ybars for a given array
conguration. (Figure 7)
Input selection provided on NTL720 cabinets is both simple
and exible – the user has a choice of analog, AES left/right, and
EAW’s proprietary U-Net. Drawn from the UX8800 and other EAW
products, U-Net provides full digital control of each device in a
system, including audio signal, processing parameters, routing –
in addition to accommodating EAW Smaart tuning and analysis
platform. (Figure 8)
Figure 6
Figure 7
Figure 8

Communication connection options also include U-Net, as well
as a USB port on the back panel for interfacing with the DSP.
In addition, each back panel also oers HF boost and neareld
contour controls, as well as a range of LED indicators for signal,
limiter, clip, input selection, U-Net status, amplier status, HF
boost engagement and neareld contour engagement.
SIMPLE, FLEXIBLE RIGGING
One of the most exciting aspects of the NTL720 is its proprietary
FastLatch™ integral rigging system. Representing more than two
decades of tireless eort in getting this crucial facet exactly right,
the rigging design oers an easy, convenient “hinge-and-latch”
design, with the essential components being two heavy-duty
hinge mechanisms on the back of each cabinet and a latch
mechanism on the underside of each cabinet.
When ying an array, the rst module attaches to the ybar,
and then each subsequent module is lifted up (remember, total
weight is under 50 lbs) and hooked to the hinges on the rear
corners of the above cabinet, and then the box is simply pushed
forward by the bottom of the cabinet until it swings up to be
secured by the latch. This process is repeated until the desired
array size is achieved, with cabinet splay angles (a choice of 12,
9, 6, 3, and 0 degrees is provided) easily selectable by carrier
brackets that accompany the hinges. (Figure 9)
The hinges hold so securely that the rigger can actually walk
away from the array, and then return later to swing the box up to
its latch above. And because of the light weight, it’s also easy to
y two modules at once, further saving time. Once the latch has
locked into place, two safety pins are inserted to further secure
the attachment.
Striking NTL720 arrays proves to be as easy – just reverse the
process, including the ability to take down two boxes at a time.
Anyone working with this rigging system nds it extremely fast
and intuitive, with a 10-box array able to be assembled and own
within about ve minutes.
The ybar can also be used as a stable, safe groundstack
platform. It’s outtted with (optional) threaded feet for adjusting
the level and tilt angle of the array with the use of a hex bit on a
power drill. (Figure 10)
REPLACE IT IN PLACE
The rigging design allows individual components and even
entire modules to be replaced within built array structures,
whether own or stacked. In other words, a cabinet can be
removed for service without having to take down the array.
Removal is easy and safe, with just four integral spring bolts
on each side of the cabinet needing to be loosened to free the
cabinet. And the spring loading keeps the bolts in place within
the array frame so they don’t fall out.
Another option allows removal of the amplier package
by loosening just six screws on the back panel. Two plug
connectors that directly connect the amplier to the PCB inside
of the cabinet not only ensure a solid, lock-tight t, but it also
eliminates the hassles of cable connections.
Yet one more option allows the user to easily remove the front
grille to access the horn, which itself can also be removed to
access all of the drivers. Loosen several screws, and the entire MF
and HF assembly can be lifted out.
Finally, NTL720 cabinets are nished with a tough RoadCoat™
nish that is highly scratch-resistant, and the grille is durable
stainless steel. Cabinets come in black as standard, and EAW can
meet any specialty paint color and nish needs that are desirable
in certain xed installation situations.
Figure 9
Figure 10
Testing and optimization of NTL720 arrays was done
in real-world conditions at the Stadium Theater in
Woonsocket, Rhode Island.

SMALL BUT MIGHTY
EAW likes to call the NTL720 a“small system born of big ideas,”
encompassing the creative thinking and hard work of the full
force of the company’s engineering team over the course of
more than a quarter century. As a result, it’s no wonder that a lot
of us consider it a new baby, small stature notwithstanding.
And the company believes that the purpose-motivated
integration of the sheer number of useful, proven technologies
contained within the NTL720 will soon have users considering it
their own baby as well.
The EAW engineering team that collaborated on the
development of the NTL720.