Naim OVATOR S-600 BROCHURE

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Ovator S-600: Design, engineering and technology

Southampton Road, Salisbury SP1 2LN, ENGLAND

Introduction

High-end hi-fi speaker design is a multidisciplinary
endeavour embracing elements of acoustics,
mechanics, materials, vibration, electronics and musical
psychology. And thanks both to the extraordinary
discrimination of our ears, and our hard-wired sensitivity
to ideas and emotions expressed through music,
success in speaker design requires that the elements of
each discipline be thoroughly optimised. A successful
high-end speaker is truly more than the sum of its parts.
So the story of the Ovator S-600 is not simply that of a
new drive unit technology, it is one of the optimisation of
a multitude of interdependent elements where even the
apparently mundane can have an influential role to play.

The Ovator S-600 builds on proven Naim speaker
design techniques while simultaneously introducing new
technologies, new ideas and new refinements; all
incorporated in a scheme that offers a striking yet subtle
aesthetic and provides great ease of installation.

Paul Neville

Naim Audio

Fig. 1 Plinth and Floor Spikes
The Ovator S-600 Plinth, Cabinet and Driver Chassis

The foundation of the Ovator S-600 is its plinth. An
extremely rigid high pressure aluminium die-casting, the
plinth provides location for the cabinet, floor spike
fittings, and mounting points for the passive crossover
module (or active loom interface) and terminal panel.
The floor spike fittings comprise conventional M8
tapped holes at the front, but at the rear the form of the
plinth and the detail design of the spikes enables them
to be conveniently adjusted and locked from above. The
spikes themselves are manufactured from hardened
stainless steel.

Connection Bosses

Fig. 2

Plinth Leaf Spring

Leaf Spring

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The Ovator S-600 cabinet is attached to the plinth at
two locations towards the front and via a leaf-spring at
the rear. The leaf spring is a 200mm stainless steel
bar that runs laterally underneath the cabinet and
attaches centrally to its underside. At each end the
leaf-spring is bolted, via tapped bosses, to the plinth.
The front locations comprise stand-off bosses through
which a bolt is inserted and screwed into the cabinet.
A slot feature either side of each boss introduces
some controlled compliance to the front cabinet
locations that in combination with the leaf-spring
results in the cabinet rotationally (forward and
backward) decoupling from the plinth above 12Hz.

The entire plinth and cabinet system was the subject
of Finite Element Analysis modelling to analyze,
predict and fine-tune its vibration characteristics with
the aim of ensuring that any resonant behaviour within
the audible band is minimised. Limited decoupling of
the system outside the audible band is inherent in
achieving this aim. The cabinet/plinth leaf-spring was
first introduced on the Naim Allae loudspeaker
although the leaf-sprung cabinet concept goes back to
the Intro and Credo.

Fig. 3 8” Drive Unit Basket

Contact Points

Fig. 4

BMR Sub-assembly

The Ovator S-600 BMR Drive Unit

The Ovator S-600 BMR (Balanced Mode Radiator) has
its own separate enclosure formed by a 12.7mm thick
aluminium alloy cylinder nested within the cabinet. A
unique suspension system comprising two, four
element, duralumin circumferential leaf-springs
decouples the BMR module from the rest of the cabinet.
The suspension system prevents low frequency
mechanical energy from the bass drivers interacting
with the BMR and stops mid/high frequency mechanical
energy being transmitted to the cabinet. The cylinder is
held by one leaf-spring at the front of the cabinet and
one at the back. The system was Finite Element
Analysis modelled and the design optimised to provide
a decoupling from 4Hz – more than six octaves below
the beginning of the BMR pass-band. The BMR
enclosure is gradient filled with a mix of wool felt and
reticulated foam and has a vent at the back so that
changes in temperature or atmospheric pressure do not
impact upon performance. A simple transit system
locks-up and protects the suspension system during
shipping.

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The Ovator S-600 cabinet is of composite construction
with 25mm thick curved sides created from the
lamination of nine MDF sheets bonded under heat and
pressure. This construction effectively incorporates
constrained layer damping within the structure of the
material to create an immensely rigid and non-resonant
panel. The 50mm thick front baffle is created from the
lamination of four layers of 12.5mm MDF to create a
significantly more rigid and better damped panel than
would be achieved through the use of a single sheet.
The outside edges of the front baffle are radiused to
minimise diffracted radiation and internal bracing and
strategic mass damping contribute further to a cabinet
that, in acoustic terms, is fundamentally benign. The
cabinet is internally lined with 20mm wool felt.

The lower portion of the cabinet is divided into two
separate 30 Litre closed box enclosures – one for each
bass driver. Closed box loading was chosen thanks to
the distinct advantages it offers over other loading
techniques in terms of time domain performance and
dynamic compression. The Ovator S-600 low frequency
system resonance is at 38Hz with a Q of 0.6. The free
field -3dB point is 50Hz.

Both the Ovator S-600 bass driver and BMR chassis are
custom designed high-pressure die-castings modelled
using Finite Element Analysis to optimise their
performance by managing the vibration energy that is
an unavoidable consequence of their operation. The
bass driver chassis for example is characterised by a
triangulated structure that not only provides great rigidity
but also maximises the open area behind the cone.
Additionally, it features minimal interface mating
surfaces so that mechanical energy transfer to the
cabinet is controlled and predictable.

Fig. 5

Speaker Cross-section

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The Ovator S-600 Crossover

A significant benefit of the of using a BMR to cover the
entire mid and high frequency band is that the typical
2kHz – 3kHz crossover, with its unavoidable phase and
dispersion discontinuities, is not required. The Ovator S­600 crossover between bass drivers and BMR operates
at 380Hz with fourth order acoustic slopes and minimal
phase discontinuity. Thanks to the similarly wide
dispersion of the bass drivers and BMR at crossover
there is no dispersion discontinuity,

The crossover module itself is attached to the underside
of the plinth and comprises a MDF panel carrying a
glass-fibre printed circuit board. It is suspended from the
plinth via an elastomeric mounting system and selected
crossover components also benefit from discrete
mechanical decoupling. The topology of the printed
circuit board borrows many of the layout and earthing
principles of Naim power amplifiers. Components are all
of extremely high quality, each selected following
extensive technical analysis and listening. Four different
types of metalised polypropylene ClarityCap capacitors
are used including the new and outstanding ESA type
employed as the main BMR feed capacitor. The
inductors are a combination of air core and laminate
steel core. The LF feed inductor is a huge laminated
steel core item of 2.8mH with only 0.08Ω series
resistance. The crossover filter and equalisation curves
were extensively computer modelled and correlated with
measurement and listening. The crossover presents a
benign load to driving amplifiers with a minimum
impedance of 3.2Ω at 100Hz and a maximum phase
shift throughout the entire audible band of ±30°.

For bi-amp or tri-amp active operation the entire
crossover can be simply removed and replaced with an
active wiring loom adaptor. The terminal panel is also
exchanged for one carrying three sets of terminals.

The Ovator S-600 Connectors

The Ovator S-600 features custom designed input
terminals that offer a significant advance on
conventional items. The conception and design of the
terminals was informed by the experience gained from
the Naim Hi-Line and Power-Line projects to generate
an innovative and high performance speaker connection
solution.

The terminal is designed to work optimally with the new
Naim high conductivity copper alloy speaker pins but
can also accept standard banana plugs. The sprung
contacts optimise contact pressure and minimise
contact resistance. They are manufactured from a
unique grade of copper alloy with an IACS (International
Annealed Copper Standard) of over 90% and enhanced
spring properties. The terminal housing is designed to
eliminate eddy currents and allow the contacts to float in
order to minimise microphonic effects. The complete
housing is also designed to float within the aluminium
back plate of the speaker.

Silver plate on both the contacts and the pins were

chosen from listening tests, which confirmed the

findings from previous projects. The use of the same

plating of both pin and contact minimises the potential

for galvanic corrosion.

Fig. 6 Speaker Connectors

The Ovator S-600 In Use

Installing and setting-up the Ovator S-600 is simple. It is
fitted when packed with a pair of castor trolleys and,
with its carton upright and opened at the front, it can
simply be wheeled into position. Once in position the
caster trolleys can be removed and the Ovator S-600
placed on its pre-fitted floor spikes. Spike adjustment
and levelling is simplified significantly by the rear spikes’
top adjustment and locking access.

The Ovator S-600 is a wide bandwidth, neutrally
balanced and uncoloured speaker capable of very high
volume levels without significant compression or
distortion. Its exceptional time domain behaviour and
extremely low noise-floor mean that fine musical detail
is reproduced naturally with coherence and clarity. It is
designed primarily for “free-space” positioning within
the listening room. However, thanks to its consistent
and wide dispersion it is relatively insensitive to
positioning. Its listening sweet-spot is also considerably
wider than typical conventional speakers.