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White Paper
The MegaLine Loudspeaker System
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White Paper
The MegaLine Loudspeaker System
Introduction
Introducing the DALI MegaLine Loudspeaker System - a statement which pushes back the
boundaries of what is possible in the art and craft and science of loudspeaker design,
incorporating cutting edge acoustic and electronic technology, shaped into sculptural forms
of exceptional harmony and elegance.
The DALI MegaLine parts from decades of design conformity. The two speakers are a
seamless integration of form and function, an unapologetically monumental display which
emphasises the MegaLine’s innovative modular construction.
The MegaLine is a reference loudspeaker system capable of reproducing the full dynamics
and scale of the live music experience, revealing the subtleties of inner detail, contrast,
atmosphere, pace and rhythm, all the essential elements which makes recorded music
come alive.
The MegaLine is the result of a radical re-evaluation of the traditional approach to
loudspeaker design. Wiping the slate clean DALI's research and development engineers
questioned conventional wisdom and broke new ground on the road to a better
understanding of the crucial interaction between loudspeaker, room and listener.
The MegaLine
The MegaLine is essentially a two-way loudspeaker, based on a
vertical array of bass/midrange units alongside a second array
planar dipole ribbon tweeters.
Each array is configured to operate as a single "virtual driver"
extending from floor to ceiling.
We chose to use a stacked modular design, based on three
identical modules per channel for critical listening.
The MegaLine system requires two identical stereo amplifiers or
four identical mono blocks.
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The MegaLine Loudspeaker System
The Line Source Principle
Conventionally, a loudspeaker is viewed as a point source, radiating
sound equally in all directions in the shape of an ever-expanding
sphere. Since domestic environments rarely consist of infinite open
space, sound will at some point encounter room boundaries: floor,
ceiling a nd walls.
Sound reflected repeatedly by these surfaces will add unwanted out-ofphase components, which become a significant proportion of what
ultimately is heard at the listening position. In this way the listening room
itself exerts considerable negative influence on the final listening
experience.
In order to take the room out of the equation, a vertical array consisting
of a theoretically infinite number of point sources are created. Such a
configuration is known as a line source system and has a number of
useful characteristics for sound reproduction in enclosed spaces.
The dispersion pattern of a line source is not spherical like that of the point source, but
cylindrical as it extends outward from the loudspeaker. Of special interest here is the fact
that there is virtually no sound at the upper and lower ends of the line. Consequently, with
a line source extending from floor to ceiling, there will be no reflected sound from these
surfaces, which eliminates a major source of room colouration/influence.
The absence of floor and ceiling reflections offers two valuable advantages. Firstly, the
sonic contribution of the listening room is greatly reduced, allowing the true tonal character
of the loudspeaker to be heard much more clearly.
Secondly, there are no distracting reflections to compromise the system’s imaging abilities.
This enhances the listener's ability to perceive the musical event, sharply focused in three
dimensions, especially further away from the loudspeaker.
The line source principle provides a more immediate and direct pipeline from the
loudspeaker to the listener. Simplified one could say that the listener hears only the drivers
operating at a point that intersects a horizontal line from the ear to the speaker.
The drivers above and below this point effectively neutralise room interference, allowing
the listener to fully experience the acoustics of the original recorded space.
While the exceptional room-independent transparency of the DALI MegaLine alone would
be enough to make it a truly unique listening experience, there are further benefits to the
line source principle.
The floor-to-ceiling extension of the loudspeaker provides a very effective and uniform
coupling to the room's enclosed air volume, than what is possible with a conventional
loudspeaker. A conventional loudspeaker imposes a varying acoustical load in the vertical
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The MegaLine Loudspeaker System
plane. This has significance for the low-frequency performance of the DALI MegaLine.
Since room modes are less excited, the tight and detailed bass of the speaker is
unaffected by the room itself.
Sound pressure from a line source decreases much more gradually as the listener is
moving away from the speakers, than with conventional designs. This means that the DALI
MegaLine can provide uniform sound pressure levels over a very large listening area. Not
too loud for listeners closer to the speakers, yet not too soft for listeners further away.
Multiple Drivers
There is a school of thought in high-end audio that swears to the virtues of compact, twoway box loudspeakers. This is based on the assumption that a simple, yet carefully
executed construction of limited dimensions sidesteps many of the problems
that afflict larger enclosures.
However, aficionados of compact loudspeakers must accept extreme
limitations on available sound pressure levels, which are far from true concert
hall levels. Stand-mounted boxes are typically extremely critical in regards to
placement, if they are to deliver their best.
The MegaLine could be viewed as the worlds most advanced two-way
loudspeaker. It shares the positive aspects of the finest compact designs,
while eliminating the flaws that are inherent to the genre. The MegaLine does
this by delivering virtually unlimited dynamic headroom, minimal distortion
and a high level of sonic performance and all this independent of the physical
limitations of the listening environment.
The shape and surface area of the two "virtual transducers" which make up
the MegaLine are unique in many ways. High frequencies are handled by an
array of DALI's custome made dipole ribbon tweeters, with a total radiating area
corresponding to more than 80 conventional 1" dome units per channel.
The bass/midrange system of the MegaLine provides a surface area ten times greater
than any conventional two-way systems.
Finally the radiating surfaces of the many dynamic drivers are coupled to powerful
magnetic assemblies. This sets the room’s air volume in motion as it would with by a huge
and powerful piston, providing exceptionally efficient coupling of the loudspeaker to the air
volume's mass and resistance.
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The MegaLine Loudspeaker System
The Dipole Planar Ribbon Tweeter
The custom-made dipole planar ribbon tweeter reproduces the high frequencies. This is
designed and assembled completely in-house. Years of refinement and experimentation
have led to the special version of the ribbon used in the
MegaLine.
The voice coil of the driver is etched on the ribbon itself, which is
then precision-mounted in the powerful magnetic system.
The long ribbon driver is mounted on the side of the
bass/midrange enclosure. The shape and position of the wood
profiles alongside the ribbon are carefully calculated to enhance
the acoustic transfer characteristics of the ribbon.
Among its many virtues, the ribbon tweeter has a large surface area in direct contact with
the air volume that is to be set in motion. There is minimal loss in the "surround", since the
ribbon is only mounted at its narrow ends, allowing the motion of the ribbon to be a faithful
copy of the electrical input signal. The low-mass ribbon is placed in a uniform and powerful
magnetic field for strict motion control.
The air mass surrounding the ribbon also provides damping, unlike conventional tweeters,
whose surface area is too small to usefully exploit air damping as a means of controlling
diaphragm motion.
The resonant frequency of the ribbon is approximately 10 Hz. Since the driver operates
exclusively above 1,200 Hz, this eliminates any possibility of audible distortion arising from
excitation of the resonant frequency.
As a dipole driver, the ribbon tweeter radiates sound equally to the front and rear,
eliminating the distortion and colourations that occur in a conventional dome tweeter due
to the compressed air volume behind the diaphragm. With carefully optimised operating
conditions, the ribbon tweeter redefines key concepts such as speed, accuracy ,
transparency and clarity in high frequency reproduction. Its critical inner damping allows
the driver to track extreme transient signals with full control.
The MegaLine bass/midrange drivers, bass reflex & cabinet
The MegaLine employs 6½" drivers customised with a wide frequency
range that makes them ideal for this two-way application.
A key factor in the bass and midrange performance of the drivers is the
specially designed magnetic system, which generates a uniform and
highly focused magnetic field.
Tight control over diaphragm motion allows the drivers to operate up to
10 kHz. The MegaLine benefits fully from our ongoing research into the resolution of
micro-contrasts in drive units.
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The MegaLine Loudspeaker System
The MegaLine employs a total of 12 bass/mid driver per channel for high sensitivity. As
each individual driver does much less work at any given sound pressure level than in a
traditional two-driver loudspeaker. It is crucial that each driver responds to the presence of
even extreme low-level signals.
This is ensured by the use of a low-loss surround and an optimal diaphragm profile that
contributes to the unique ability of the MegaLine to render the miniscule ambience
information, which defines the recorded space. With its massive array of bass/midrange
drivers, the MegaLine delivers extreme dynamic headroom.
Sharing the work between so many drivers allows for high sound pressure levels with no
stress, neither to the drivers nor for the listener. This is a significant contributing factor to
the smooth, relaxed sound of the DALI MegaLine. Even at high listening levels for
extended periods the listener will experience very little listening fatigue.
The MegaLine takes even the most dynamic passages in its stride, with none of the
crippling dynamic compression that plagues lesser systems. Even when operated at
average levels of 100 dB the MegaLine still has ample headroom for clean peaks well
beyond 120 dB.
Bass reflex enclosure
The basic MegaLine cabinet module is an 80-liter enclosure with two separate internal
chambers. A pair of 6½” bass/midrange drivers is mounted in each
chamber with a bass reflex tuning which is vented at the rear of the
cabinet.
The ports are mounted on the rear panel to reduce the audible effects
of port turbulence. The partition between the chambers also provides
internal bracing and resonance damping for the large panel surfaces.
Internal bracing in conjunction with the angled exterior surfaces effectively divides the
panels into smaller sections, substantially reducing any resonant tendencies.
Our extensive experiments with various bass loading technologies have resulted in a bass
reflex enclosure which combines the advantages of reflex loading - higher maximum
sound pressure levels, higher sensitivity and greater low frequency extension - without
sacrificing the fast transient response and outstanding bass definition normally associated
with sealed enclosures.
The special reflex loading employed in the MegaLine reduces driver distortion by damping
cone motion at the port resonance frequency and permits the use of low-Q drivers with
powerful magnetic systems.
Modular cabinet design
The line source principle can only be realised in a loudspeaker, which extends from floor to
ceiling. For maximum flexibility as well as ease of installation, the MegaLine consists of a
number of identical 755 mm modules with four 6½" bass/midrange drivers and an
externally mounted ribbon tweeter.
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The impedance of each module is 1.6Ω. Coupling three modules in series per channel
yields a total system impedance of 4.8 Ω (4 modules = 6.4 Ω, 5 modules = 8 Ω).
The modules are stacked on a low-profile foundation fitted with four high quality banana
sockets of gold-plated copper for optimum contact to the amplifier output.
The base houses connections to the modules as well as DC protection for the ribbon driver
via a high-grade polypropylene capacitor.
In order to ensure that the tall and heavy DALI MegaLine stands perpendicular on an
uneven or unstable surface, gold-plated brass screws at the four corners of the base allow
precise adjustment in the vertical plane.
Cable connectors are recessed in a groove at the rear of each module. An aluminium
cover fits neatly over the groove to conceal all wiring. The internal wiring and the cable
provided for connection between modules are of the highest quality.
The Active Crossover
The MegaLine utilizes an outboard active crossover for intrinsic superiority to passive filter
types with their unacceptable levels of insertion loss and component distortion.
We cut no costs nor effort to achieve a level of transparency,
neutrality and dynamics in the crossover in order to equal the
performance of the MegaLine loudspeakers.
As of this the active crossover is based solely on discrete
components with no degrading integrated circuits in the signal
path. Only an active device can fine-tune crossover frequencies
with extreme accuracy, maintain phase integrity, optimise
frequency and power response as well as handling and match the sensitivities of the
drivers.
Because the active crossover is inserted between the preamplifier and the power
amplifiers, the full damping factor of the amplifiers is uncompromised. The crossover is
completely isolated from unwanted effects of dynamic impedance variations in the driver
units. This reduces distortion and provides smoother frequency response, especially at
high volume levels.
By connecting the amplifiers directly to the drivers, the active crossover filter function
optimises system phase linearity to a degree which would be impossible with a passive
crossover.
Dual mono design right down to separate external power supplies provides infinite channel
separation in all stages. The power supply also incorporates separate regulation stages for
the bass/midrange and high frequency sections, eliminating any risk of crosstalk.
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The MegaLine Loudspeaker System
Due to the comprehensive separation of the high frequency and bass/midrange sections,
harmonics generated by amplifier clipping in the bass section are effectively isolated from
the tweeter system.
The crossover operates in Class A with no negative feedback, for optimal dynamic
characteristics even under the most extreme signal and load conditions.
Unlike typical circuits which rely heavily on feedback, the performance of the crossover
cannot be compromised by dynamic distortion phenomena. Thanks to its zero feedback
output buffer stages, the MegaLine crossover can also drive long cable lengths for
maximum flexibility.
The crossover is designed to be left on at all times in order to ensure optimum working
temperature and operating conditions throughout every listening session. When the
crossover is turned on, a ten-second soft-start cycle allows both channels to stabilise.
Output relays protect the amplifiers and loudspeakers from overload when the filter is
turned on or off, or when fluctuations occur in the mains voltage. The MegaLine crossover
is housed in a black low-profile heavy gauge aluminium cabinet specially treated to
maximise durability, heat dissipation and resistance to corrosion.
In short the MegaLine has four features that stands out from the crowd and makes it quite
unique;
The Line Source Principle
• Eliminates floor and ceiling reflections
• Reduces audible effects of listening room bass modes
• Provides a larger listening area
• Has a large driver surface area for uniform dispersion
regardless of frequency
Multiple Drivers
• Allows for a two-way system with only one crossover frequency
• Reduce distortion due to the number of drivers that share the reproduction
• Provides higher power handling and higher maximum sound pressure levels
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The MegaLine Loudspeaker System
The Dipole Planar Ribbon Tweeter
• Drastically reduces cabinet resonances
• Provides surface area equal to more than 80 conventional 1" dome tweeters
• Extreme low mass for high speed and sonic accuracy
• Eliminates loss of energy compared to traditional drivers
The Active Crossover
• Provides for a more precise fine-tuning of crossover frequencies and roll-off slopes
• Eliminates insertion loss and component distortion inherent in passive filters
• Connects the power amplifiers directly to the drivers for improved control/higher
damping factor.
• Ideal signal processing without unwanted crossover/driver interaction
The MegaLine is the materialization of our extensive research and experience in
loudspeaker development, design and production.
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The MegaLine Loudspeaker System
Technical Specifications :
Frequency range ± 3 dB (Hz): 35 – 22000
Nominal Impedance Ω: 6
Crossover frequency: 1200 Hz (via external active crossover)
Bass reflex tuning frequency (Hz): 38.5
Enclosure type: Reflex
Placement: Floor
Recommended amp. Power (Watts): 100-1000 (2 channels per speaker)
High frequency drivers: 3 x proprietary dipole ribbon driver
Low frequency drivers: 12 x 6½”
Dimensions : (H x W x D): 231 x 36.5 x 49.2 cm (3 modules)
Weight: 110 kg, per channel
222 lb , per channel
Finish: Alpi
DALI MegaLine AC-U Active Crossover :
Frequency response : (± 0.5 dB): 5 Hz-200 kHz
Filter precision : (20 Hz - 20 kHz): ± 0.25 dB
Input impedance: 20 k
Output impedance: 50
Connections: phono
Max. cable length to power amplifier: 10 m
Dimensions (H x W x D): 48 x 440 x 305 mm
Weight: 4.8 kg (ex. power supplies)
Power consumption: 13 Watts per channel
91 x 14.4 x 19.4 in.
6.1 kg (w. power supplies)
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