DALI CALLISTO User Manual

DALI CALLISTO

WHITEPAPER

INTRODUCTION

The landscape for High End Audio has been changing
for a number of years now, and the shift has been
accelerating, with no signs of it slowing down. We refer
to of course, the choice of convenience.

This ‘convenience’ has emerged in many shapes and
forms, driven by the lure of ease of use, getting started
and installation. These factors have begun to triumph
over high-quality audio, with music lovers settling for
lesser sound quality in order to get more convenience.
This is not to say that good sound is not important to
them, but simply because the wish for convenience left
them with no alternative.

The trend is that first time buyers of high-end audio
have little interest in the hassle with cables and multiple
boxes of electronics. They want easy access to all their
digitally stored music, be it online, on their phone or on a
network connected hard drive - but they want it to sound
great. In short, they long for the virtues of a traditional
Hi-Fi product that matches the audio demands of the
21th century.

At DALI we recognised this dilemma of customers
having to choose between high quality performance and
convenience in ease of use, so we set out to develop a
solution which brings together the best of both worlds.
The challenge was to create a great sounding wireless
speaker system that is easy to setup and use. A wireless
speaker system that empowers the customers to easily
access all their music in the best possible quality, and
play it back without the need for complicated electronics.

Acting as the central hub for the CALLISTO speaker
system, the DALI Sound Hub is what brings it all together.
With built-in Bluetooth, inputs for Optical (x2), Analogue
(x2), Coax and integration via dual Expansion Ports, you
can connect anything to your CALLISTO speaker system,
and, when you are done, forget all about them. The
Sound Hub automatically detects which source is active
and automatically selects the correct input, meaning
the only thing the listener really need to do is adjust
is the volume. Naturally, you can also select the input
manually; either from the Bluetooth remote control or
directly on the Sound Hub. The Sound Hub transmits the
audio signal (I2S) wirelessly to the connected speakers
in true HD audio quality (24 bit / 96 kHz) to ensure only
the best possible reproduction.

The CALLISTO speakers are designed around a DALI
manufactured 6½” wood fibre woofer with a brand new
and advanced SMC magnet motor system, and a hybrid
tweeter module. The drivers are fed by a powerful dual
channel 250W Class-D amplifier connected directly
to the drivers. This design enables us to setup each
amplifier channel to match perfectly with the driver,
and thereby maximize the performance of the drivers.
Drivers which are designed with a detailed knowledge
of the amplifier in mind can be taken well beyond
the performance levels of conventional passive driver
designs, to deliver you a transparent, detailed, coherent
and well-timed audio experience.

DALI is truly proud to introduce the CALLISTO series - a
contemporary take on traditional Hi-Fi.

With the DALI CALLISTO speakers, we deliver a speaker
series that builds on all of the DALI audio traits. A
speaker system made in Denmark, which has the
possibility to easily playback, stream, beam, select,
distribute and connect your music from any source, and
conveniently send it wirelessly to the speaker!

In the following we will dive into all the technical details
of this product. We welcome you to the world of the DALI
CALLISTO audio experience.

DALI A/S www.dali-speakers.comDALI CALLISTO 2

PRODUCTS

The DALI CALLISTO systems
consist of two stereo speaker
configurations and an optional
central Sound Hub.

CALLISTO SPEAKERS

The CALLISTO speaker series presents a unique
opportunity for DALI to deliver the best of both worlds.
Controlling the development of everything from the
drivers to the amplifier, we can optimise every single
component to match each other perfectly. This enables
us to design the woofers to be more linear than would
ever be possible in a similar priced traditional passive
speaker system. Pushing the woofer design to new
limits of performance is possible because we are
in total control of the signal path, and can therefore
ensure the control needed so not to overextend the
drivers. Leveraging this potential, we elevated the audio
performance to levels that surpass almost any speaker
amplifier combinations in this price bracket.

DALI A/S www.dali-speakers.comDALI CALLISTO 3

CALLISTO 2 C

This is the compact stand mount solution in the
CALLISTO system. Perfect for smaller spaces or rooms
where the speakers’ presence must be minimised,
without giving up on performance. The combination of

the 6½” low-loss wood fibre woofer, the hybrid tweeter
module and the perfectly balanced internal volume of
the cabinet, come together to form the base of a highly
accurate audio experience.

CALLISTO 6 C

When truly deep bass performance and room filling
sound-pressure is needed, the floor standing CALLISTO
6 C is the perfect choice. Gaining extra width and depth
from the added woofer and internal cabinet volume, the
CALLISTO 6 C can deliver a complete and highly detailed
three-dimensional sound stage into even large rooms.

Both speaker models have an RCA input for volume
controlled line level input. This enables you to connect an
audio device directly to the speakers if desired, although
we recommend using the DALI Sound Hub to obtain the
full convenience of the CALLISTO speakers, including
wireless audio transfer.

DALI A/S www.dali-speakers.comDALI CALLISTO 4

DALI SOUND HUB

The Sound Hub is the starting point when setting up
you CALLISTO speaker system cable free, and where
initiating the pairing process begins. It also controls
all communication with the connected speakers
and ensures that audio, volume and balance are
synchronised across the speakers. It handles all audio
inputs via the built in Bluetooth, (supporting AAC, Apt-X
and Apt-X HD) or any of the multitude of external inputs
(Optical, Coax, Analogue and the expansion ports). The
wireless 24 bit / 96 kHz connection carries the line
level signal from the Sound Hub to the speakers built-in
amplifier.

The Sound Hub’s auto source sensing system ensures
that you only rarely need think about what input you are
using. Just start playing music or turn on your TV and
the Sound Hub will automatically activate the right input,
and if in standby, also turn on the speakers. There truly is
nothing more for you to do other than enjoy.

When the need for adjusting the volume arises it is easily
done from the remote control, the Sound Hub or even
directly on top of the speakers via the built-in touch
panel. The Sound Hub transmit the volume change to the
connected speakers and the volume is changed in the
speaker amplifier.

DALI A/S www.dali-speakers.comDALI CALLISTO 5

The CALLISTO speaker system offers the ultimate in convenience, even letting you control the volume right on the speaker.

CABINET

When preparing the visual design for the CALLISTO series we
especially had two things in mind. We were seeking a design that
would allow for the introduction of the hybrid tweeter in the stand
mount model, and a look that clearly showed that this series is
something new, without losing the connection to the traditions of
the passive speaker. With the use of a round front housing for the
ribbon tweeter in combination with the distinctive tweeter front
plate, and the elegant integration of the volume control and LED’s,
we believe that we succeeded, and then some!

Manufacturing the cabinet at our large and efficient woodworking
facility in Denmark, we can keep complete control over the quality
of the speaker, handling everything from cutting out the Medium
Density Fibre board (MDF) cabinet to applying the vinyl. The
mounting of the drivers and the final tests and approvals on each
and every speaker is also handled directly at our own assembly
lines in our Danish factory.

Constructed from 25mm MDF, the cabinets employ a very
rigid construction with solid bracings across the inside of the
cabinet for extra reinforcement. Together with the very solid
MDF structure, this contributes to a stiffness and density that
practically eliminates resonance within the cabinet. However,
excessive internal bracing can disturb and hinder the crucial
airflow inside a speaker cabinet, thereby adversely affecting
sound quality. Therefore, great care is taken in the layout and
application of internal bracing in order not to reduce the internal
volume of the cabinet unnecessarily.

The high-grade vinyl is carefully selected among the finest
available. Extensive testing is carried out to make sure that
the surface and joints of the cabinet will stand the test of time.
Through strict in-house control of every aspect of production,
CALLISTO achieves a level of fit and finish typically found only in
products well beyond its price point.

DALI A/S www.dali-speakers.comDALI CALLISTO 6

WOOFER

We knew from the outset that the woofer for the
CALLISTO series would be something unique. Never
before has the entire audio chain been in the hand of
DALI’s own R&D team. This intimate knowledge helped
our acoustic team design and build a woofer that took
low loss and linearity to a whole new level.

Working with well known elements from the OPTICON
and RUBICON woofers, we used advanced computer
simulation and a whole lot of listening hours, to
optimise the magnet motor to deliver the ultimate in
flux saturation and Bl linearity within the voice coils
excursion span. The rear membrane suspension (spider)
geometry was likewise optimised to work in close
harmony with the amplifier. Knowing that we controlled
the maximum signal impulse, we could soften up the
spider and obtain a very linear and perfectly symmetrical
suspension within the working area of the voice coil
and membrane, only taking control and slowing down
the membrane movement at the outer most excursion
points.

The extra linearity obtained both around the voice-coil
and in the spider manifests itself in reduction in mechan­ical distortion and less strain on the amplifier, which
leads to more detailing and a better defined sound stage.

The CALLISTO woofers also benefits from the use of
SMC in the pole piece. Soft Magnetic Compound (SMC)
is a coated magnet granule that can be shaped into any
form that you would want. SMC has many advantages,
and when used in a speaker magnet motor system,
it results in a significant reduction of distortion from
mechanical loss. SMC’s unique ability to deliver a
high magnetic conductivity and a very low electrical

Every part of the CALLISTO woofer is optimised
to work perfectly with the build in amplifier.

conductivity delivers all the wanted qualities of a really
good speaker magnet without the traditional downsides.

Like in the RUBICON magnet motor system, the
CALLISTO’s SMC pole piece is covered by a copper cap
that helps focus the flux field surrounding the voice coil,
and in conjunction with the SMC pole piece, the flux
modulation is significantly less influenced by the current
in the voice coil. As a result, we manage to reduce the
distortion from current generated flux variations greatly.
Furthermore by surrounding the SMC pole piece with a
copper cap, and controlling the effect via small slits in
the copper cap, we focus the effect of the SMC around
the voice coil and linearise the inductance generated in
the voice coil to a degree that it is seen as almost flat.

As a result of these optimisations and especially through
use of SMC, the CALLISO series benefits from an
extremely agile, well behaved and ultra low loss woofer,
that when working in conjunction with the amplifier,
is able to deliver a detail rich, time coherent and very
powerful audio signal.

Computer simulation helped optimise the magnet
system for optimal flux saturation

The Bl in the CALLISTO woofer is not only very linear
but perfectly symmetrical

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The dome tweeter is constructed
to match the CALLISTO amplifier
and to works seamlessly with
the ribbon tweeter.

HYBRID TWEETER

DALI’s trademark hybrid tweeter module combines the
dome tweeter with a ribbon tweeter for an amazing
rendering of the high frequencies, and a dispersion of
high frequency audio that outperforms all other tweeter
technologies.

In the CALLISTO series, DALI makes use of the hybrid
tweeter configuration in both the stand-mount and the
floor-standing model, with a great deal of work carried
out to optimise the module specifically for the CALLISTO
series.

The dome membrane is very soft and ultra-lightweight,
and actually so thin that a coating has to be applied
to hold the material together and be uniform in
construction. Using computer simulation we were able
to optimise the magnet system and maximize flux

Through the help of simulation the dimensions of the
magnet was optimized for almost perfect flux saturation.

saturation right at the voice coil area. This optimisation
combined with the use of an ultra-thin magnetic fluid for
cooling, enables the dome tweeter to deliver a very linear
BL in the entire excursion range. This results in better
control, power handling and greatly limits distortion.

The ribbon part of the hybrid module is a magneto-static
type tweeter. Four bands of conductive material make
up the active diaphragm that is controlled by a strong
magnetic field formed around it. The ribbon tweeter is
the master of wide dispersion, and combining it with the
soft dome, we get a tweeter module that can be utilised
as low as 2.0 KHz and continues to perform well above
30 KHz. This extreme bandwidth combined with the ultra
wide dispersion is an important part of the DALI sonic
definition.

Like on the woofer the Bl in the CALLISTO tweeter is
very linear and very symmetrical.

DALI A/S www.dali-speakers.comDALI CALLISTO 8

DALI SOUND HUB

The elegantly designed Sound Hub is the central hub
in the CALLISTO system. It houses all the potential
connections, has built-in controls for Power On/Off,
Volume control, Source select, Mute and Speaker pairing,
and also visual indications for Volume, Source and
Speaker placement. It is also the base of the distribution
of the wireless audio signal.

Hidden away, but easily accessible on the back of the
Sound Hub is the broad array of possible connections.
This is also where the two expansions bays are placed,
and the location of the Link button that initiates the
pairing process.

The Sound Hub remote control is connected to the Sound
Hub via Bluetooth ensuring the optimal in operating
distance, stability and visual feedback from the Sound
Hub. This also enables the user to place the Sound Hub
anywhere in the same room as the speakers. Offering
the possibility to place the Sound Hub in a central
position, wherever it looks its best or hiding it away
completely.

DALI A/S www.dali-speakers.comDALI CALLISTO 9

Hidden away on the back of the

Sound Hub the link button, every input

and output connector, and the expansion

ports is readily accessible.

EXPANSION PORTS

One of the most innovative features of the DALI Sound
Hub is actually hidden away from view. The two modular
expansion ports on the back panel open the Sound
Hub to a world of possibilities. Via the DALI designed
open standard connector, any type of audio module
can integrate 100% with the Sound Hub system.
Supporting I2S audio transfer on up to 8 channels, and
command transfer to control volume and other essential
information. This enables a total seamless addition of
extra functions to the Sound Hub, not only allowing
for streaming, multi-room or even multi-channel
expansions, but also future proofing the Sound Hub
and any connected speakers by separating the quickly
evolving music delivery technologies from the more
robust and time durable speaker technology.

WIRELESS AUDIO TRANSFER

The wireless connection between the Sound Hub and the
speakers, is an extremely stable digital connection, made
on either the 2.4 GHz or the 5.8 GHz band depending on
location and quality of the connection. The proprietary 30
bit protocol transfers an uncompressed I2S audio signal
in 24 bit 96 kHz, utilising the remaining bits to control
volume, speaker ID and other control data. Because
it works on a less trafficked band, and the protocol is
specially designed for transporting an audio signal,
the connection is highly stable introducing next to no
packet loss. The protocol uses forward error correction
to remove the result of packet loss should they occur.
The high bandwidth low latency protocol functions as a
point to multipoint connection. This allows for multiple
speakers to connect to the same stereo signal. With
latency below 25 ms, sync between video and audio
from a movie or TV source is obtained well within
conventionally acceptable limits.

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SOUND HUB INPUTS

Bluetooth

This proven and very well-known wireless technology
is built-in as standard, offering the possibility to transfer
sound to the CALLISTO system from almost any device.
Even if the basis of Bluetooth is more than 20 years old,
new advances in audio quality is still being made. DALI
wants to enable you to listen to Bluetooth transferred
music in the best possible quality, and have therefore
added support for AAC and Apt-X HD in the Sound Hub.

AAC is an improved audio protocol that despite still
being lossy, supports a larger amount of audio data
to be transferred via the Bluetooth connection. AAC
is supported by a host of mobile platforms, and is
mainly used by Apple products as the highest quality of
Bluetooth transfer.

Apt-X HD is an expansion of the well-known Apt-X audio
protocol, allowing for compression of up to 24 bit 48
kHz audio streams and a wider bandwidth transfer than
Apt-X. This allows for high quality playback of not just
traditional audio files, but also HD quality music over
Bluetooth, along with full backward compatibility with
Apt-X.

The TV input is activated by the carrier signal. This
enables the Sound Hub to power up the CALLISTO
speaker system the second the TV is turned on, they are
therefore ready to play as soon as there is sound from
the TV, without any delay.

The audio input on the other hand, is activated by an
audio signal. Since many audio units do not turn off
the carrier signal when put into standby, a simple light
detection is not enough. By analysing the audio signal,
the Sound Hub can determine if audio is played back,
and if not, will automatically power off the system,
turning it back on again when a signal is detected.

The optical input accepts any data rate from 16 bit / 32
kHz to 24 bit / 192 kHz. The signal will be converted to
work optimally with the 24 bit / 96 kHz wireless transfer
audio protocol before being passed on to the connected
speakers.

Coaxial RCA

For direct digital connection between an audio device
and the Sound Hub. Like the optical input, it will accept
from 16 bit / 32 kHz to 24 bit / 192 kHz.

Optical

The two optical inputs are controlled differently with a
clear focus on TV and audio use.

SOUND HUB OUTPUTS

Sub-out

LFE type subwoofer output. When a subwoofer is
connected, everything below 100 Hz is sent through this
output to a connected subwoofer.

Pre-out

Line level RCA output. This output allows you to use
the DALI Sound Hub as a pre-amplifier for your existing
setup, making it possible to enjoy the benefits of the
modular extensions and the auto source sensing
capabilities. The Pre-out can also be used to connect

Analogue (RCA and mini/jack)

The high-quality ADC samples the analogue signal in 24
bit / 96 kHz using the system master clock for optimal
wireless transfer to the CALLISTO speakers.

to the CALLISTO speakers via a cable in cases where
wireless transfer is not preferable.

USB Power

The built in USB A port delivers a 5V 1A output to power
connected devices like a Google Chromecast Audio, or
charge a mobile device whilst playing. It is also used to
update the Sound Hub’s firmware. The built in USB port
does not offer the ability to playback audio stored on a
connected device.

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On the back of the
speakers the mains
power connector, link
button, setup display,
the line-in connector
and USB port for
firmware upgrades
is located.

AMPLIFIER

Designing a ‘best in class’ active speaker system is
the sum of many parts. One truly important part is
the amplifier, or more correctly the amplifier module.
Any quality amplifier module consists of three equally
important parts that need to be designed to work

together in perfect harmony: the amplifier itself, the PSU
and the signal processing. The delivery from the signal
processing and the PSU to the amplifier circuitry must
adhere precisely to the amplifiers needs and demands.
Only in this way can you achieve an undistorted,
uncoloured and coherent amplification.

The amplifier

The CALLISTO Class D amplifier is based on patented
state-of-the-art technology with a global feedback, self­oscillating design chosen for its very musical properties.
Being able to deliver 250 Watts for up to 5 seconds,
there is plenty of power to ensure more than enough
sound pressure even in complex musical passages or
massive explosions in movies.

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Simple diagram of the amplifier structure showing the self oscillating global feedback loop.

Buffer

and filter

Enable and

Standby

Resonant
Feedback

circuit

Error
correction

Clipping

detection and

clamping

Phaselag

Comparator

The self-oscillating loop PWM amplifier enjoys improved
performance over conventional fixed-frequency triangle­based PWM amplifiers because the bandwidth of the
feedback loop is higher than that of a conventional
feedback loop which must obey conservative stability
criteria. The post filter feedback reduces distortion and
provides best in class load invariance. To keep control
of the self-oscillating switching frequency and to ensure
fast recovery after a clipping situation, the limiter circuit
acts whenever the voltage difference between the input
and output of the error amplifier exceeds a hardware
defined threshold. This threshold is tuned so that THD
levels will not exceed approximately 1% at the speaker
output.

Power Stage

MOSFET

gate driver

Overcurrent

protecCon

Overtemperature,

Clipping detection

LC-filter

Total Harmonic Distortion is below 0.005% across
the entire frequency range.

The Total Harmonic Distortion (THD) of the amplifier
is below 0.005% across the audio bandwidth 20-20
kHz measured at 1W output power into 4Ω. At 30W
output power the amplifier meets THD levels between

0.015% and 0.03% which is successfully independent
of frequency. Traditional amplifiers typically show
increasing levels of THD towards higher frequencies.

A large study presented in 2014 analysed more than
400 different musical tracks, and concluded that there
needs to be a 10x peak-to-average power in an amplifier
to ensure the dynamics of music without limiting and in
worst case clipping. The amplifier in CALLISTO delivers
30 Watts continuous power, and up to 300 Watts power
for very short bursts, delivering perfectly on the 10x
peak-to-average power ratio. The obvious advantage
of leveraging this knowledge is the amplifier design
draws less running power, and thereby reduces the risk
of introducing PSU noise leaks and shutdowns due to
overheating.

There is a 10x peak to average power ratio for normal
music, and with 250 Watts for up to 5 seconds the
CALLISTO amplifier has more power than most amplifiers.

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The compact but very powerful

PSU is able to deliver up to

300 Watts peak power.

THE POWER SUPPLY UNIT

The power supply for the system is a universal mains
input switch mode PSU, capable of delivering 50 Watts
continuous and 250 Watts power for 5 seconds. The
voltage regulation is done from both the negative and
positive rail voltage to suppress uneven bus pumping on
the rails through the half-bridge amplifier design.

The power supply is a 130 kHz switching fly-back type,
making use of the alternating energy stored in the
transformer. The size of the transformer is optimized for
the power dynamics of the amplifier, maintaining stable
operation from 300W down to less than 1 W.

THE SIGNAL PROCESSING

The core of the signal processing is comprised of a
50MIPS Digital Signal Processor, and an audiophile 24bit
Digital to Analogue Converter.

The DSP boasts an audio processor capable of up to
1024 instructions per cycle. On the output side, the
DSP is connected through I2S to a Burr Brown DAC
that makes use of advanced segment architecture to
achieve excellent 123 dB dynamic range performance.
Differential current outputs are provided to suppress
common mode noise and, by nature of the analogue
interface, clock jitter is eliminated on the audio interface
to the class D power amplifier. The current to voltage
conversion is done at the power amplifier input, securing
the shortest possible signal path without the need of
sound quality degrading AC-coupling capacitors.

The master volume control takes effect in the signal
chain just before the analogue amplification stage, to
ensure optimal Signal-to-Noise-Ratio, and true 24 bit HD
resolution at all volume levels. This means that no matter
which of the many possible volume controls is used for
adjusting the master volume, the actual volume change
is done at the very end of the signal chain.

Every part of the amplifier module is design
and developed by DALI.

The amplifier output is connected directly to the driver,
with all of the crossover filtering done in DSP. Having
complete control over every step of the audio handling
has the clear benefit of being able to maximize the
utilisation of every component in the audio chain.
Optimising the crossover parameters with the knowledge
of precisely how the driver is going to react, pushing
the performance of the individual driver right to the limit
without ever going beyond. Combined with the well­known DALI driver performance, this is a large part of
the ‘best in class’ sound of the CALLISTO speakers.

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CALLISTO IN PRACTICAL USE

The DALI CALLISTO speaker series is at the same time
something brand new, never seen before, and something
very familiar and well-known. This is precisely what
sets it apart from every other speaker system in the
market today. The CALLISTO speaker system speaks to
a broader audience than traditional Hi-Fi, without ever
loosing foothold with the current Hi-Fi customer.

Built on traditional virtues and technology, they sound
every bit as good, and most likely better, than the best
traditional combinations out there at the same price
level. At the same time, they offer ease of use in both
setup and operation to an extent not seen before. This
combination is extremely powerful, and offers customers
an exciting new option.

Since the CALLISTO speaker system is at heart a
traditional Hi-Fi speaker system, the user scenarios is
for the most part found in the normal primary listening
setup. Both the CALLISTO 2 C and the CALLISTO 6 C
have the ability to deliver a room filling audio experience,
either from a musical source or if connected to the TV.

If you are looking for the best in audio quality, the best in
connectivity, the most convenient audio system, a future
proof modular audio system and a truly elegant looking

audio system, then the answer is simple.....the all new

DALI CALLISTO.

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