7
KEF T Series Technologies Explained
References
1. M. Dodd and J. Oclee-Brown, “A New Methodology for the Acoustic Design of Compression
Driver Phase Plugs with Concentric Annular Channels,” presented at The 123rd Convention
of the AES, preprint 7258, Oct 2007.
2. M. Dodd and J. Oclee-Brown, “A New Methodology for the Acoustic Design of Compression
Driver Phase Plugs with Radial Channels,” presented at The 125th Convention of the AES,
preprint 7532, Oct 2008.
TWINLAYEREDMFDRIVER
The T-Series Midrange Driver features a twin layered radiating
diaphragm. This technology (patent pending) allows the driver to
be slim and flat whilst still maintaining pistonic motion up to a
high frequency. The design has been optimised by finite element
analysis.
Slim Driver
The Slim System Design means the the Midrange Driver can be
only 27mm deep. The space required for the magnet assembly,
and that required to allow 4mm of diaphragm excursion
forwards and backwards, leaves only 5mm of depth for the
diaphragm. A simple flat diaphragm geometry has very little
inherent stiffness. Such a flat diaphragm would have structural
bending resonances at low frequencies, which would affect the
magnitude and directivity of the radiated sound field within the
working range of the driver. Over the midrange driver’s 95mm
diameter a conventional cone or dome geometry of this depth
would have very little curvature and thus again little inherent
stiffness. The twin layered diaphragm design has high stiffness in
spite of its restricted depth. There is no diaphragm resonance
below 2kHz which is its operating bandwidth.
Perfect Baffle
Discontinuities in the loudspeaker baffle cause reflections and
resonances of higher frequency sound waves. A deep cone
midrange driver can therefore colour the sound of a nearby
tweeter. The flat fronted T-Series Midrange Driver with smooth
surround has minimal effect on the tweeter. This is a step
towards creating the Perfect Baffle as seen in the KEF Concept
Blade.
Twin Layered Structure
The radiating diaphragm is a thin walled moulding. The material
is chosen to provide relatively high stiffness and damping with
the ability to be moulded into thin sections (down to 0.3mm).
Ribs extend perpendicular to the rear of the surface. These are
positioned both radially and circumferentially. The radial ribs
significantly stiffen the diaphragm to raise the frequency of its
fundamental (circularly symmetrical) resonance. The circular ribs
are located for attaching the voice coil former and suspension
and brace the diaphragm structure.The twin layered structure
has a thin layer of high elastic modulus material on the back of
the ribs. This increases the diaphragm stiffness further to push
the fundamental resonance above the working frequency
bandwidth of the midrange driver.
The technology has been developed using finite element analysis
(FEA) computer modelling. This allows very fine optimisation of
the design geometry and materials to produce a very high
performance loudspeaker driver.
Ventilation
Gaps in the circumferential ribs and holes in the rear layer allow
air flow through the structure. The straight radial ribs provide
uninterrupted air channels. This prevents high air pressure
fluctuations within the voice coil under the vibrating diaphragm.
TANGERINEWAVEGUIDE
The Tangerine Waveguide is a patented KEF Technology which is
now used in a number of products throughout the range. The
technology was developed from research work into compression
drivers which are used in high power systems for concerts.
[1]
Compression drivers are very susceptible to acoustic resonances
which occur in front of the tweeter dome. Whilst looking into
the behaviour of compression drivers in detail, it was realised
that the source of these acoustic resonances is also present in a
normal direct radiating tweeter. The Tangerine Waveguide is
designed to compensate for these problems thereby improving
the coupling between the tweeter dome and the air.
[2]
• A at diaphragm using conventional
technology resonates severely.
• A at diaphragm using new twin layered
technology behaves almost pistonically.
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General
Weight and Dimensions
