Tannoy Kensington Owner's Manual - page 5
8
K
ensington
The
The Low Frequency Section
The low frequency section of the Dual Concentric™ driver has exceptional power handling and dynamic range. The low
frequency cone piston is produced from selected paper pulp. This is specially treated to absorb internal resonance modes
The twin roll fabric surround is also damped and shaped correctly to terminate the moving cone and provide optimum
compliance and linearity at large excursions. The cone piston is driven by a high power motor system consisting of a four-
layer coil suspended in a precision magnetic air gap. The coil is wound with a special high temperature adhesive system
and individually cured to ensure reliable operation at high peak power inputs. The shape of the low frequency cone is
arranged to provide optimum dispersion of audio frequencies at both the high and low ends of the spectrum. The cone
flare continues the high frequency horn profile to ensure a smooth transition at the crossover point.
The High Frequency Section
The high frequency driver consists of a wide dynamic range compression unit giving superb transient performance with
a smooth uncoloured response. The compression unit feeds acoustic power through a multiple phase compensating device
to the throat of a solid steel acoustic horn. This horn provides an acoustic impedance transformation to match the
compression unit radiation into the listening environment.
A magnesium alloy diaphragm, formed by a specially developed five-stage process, produces a piston with a very high
stiffness to mass ratio. Optimum molecular grain structure gives long-term durability. A very low mass precision aluminium
coil provides the driving force for the diaphragm, with fine multi-stranded copper lead out wires to ensure reliability. A
rear damped acoustic cavity controls the compression driver response and ensures further correct acoustic impedance
matching to the horn throat.
The response of the compression horn driver extends two full octaves below the crossover frequency to eliminate colourations
that can arise through operation over the fundamental resonance region.
The Magnetic Circuit
An Alcomax 3 high-energy magnet provides flux generation for both high frequency and low frequency driving motors.
Precision air gaps contain the magnetic flux surrounding each coil. The high frequency air gap has a unique shu8nt member
to apportion the total magnetic flux in the correct ratio between low and high frequency units. This gives an optimum
acoustic balance. Precision machined, low carbon steel pole pieces ensure unsaturated operation, linear flux fields and a
high heat sinking capability. High power inputs can therefore be handled with minimum change of impedance due to
temperature effects. A very robust, high quality, precision pressure die-cast chassis locates the whole magnet assembly
and positions the moving parts with high accuracy. This provides long-term reliability and yet does not interfere with the
acoustic radiation from the individual sections.
9
Alcomax Magnet
Alcomax 3 is an especially high-energy permanent magnet. The unusual iron/nickel alloy is doped with cobalt, aluminium
and other rare metals to produce a magnetic material with very special properties. Alcomax 3 has a high remanent magnetism
and energy product. In other words, it magnetises to a high level and retains that unusual degree of magnetisation. Alcomax
3 is also an electrical conduction. These properties give the Dual Concentric drive unit using an Alcomax 3 magnet an
exceptionally clean transient response and increased sensitivity.
The Crossover Network
During the design of the crossover network the acoustic, mechanical and electrical interactions of the high and low
frequency sections have been fully analysed. The crossover is therefore an integral part of the design of the system. The
crossover network provides complex equalisation in both amplitude and phase for each section and fully integrates the
response at the crossover point. All components are high precision, low-loss and thermally stable. Quality, low-loss
polypropylene capacitors are used. Air-cored inductors avoid saturation effects. A unique shunt element technique controls
the motional impedance of the drive units.
All components in the crossover network are hard wired to eliminate unwanted metal-to-metal contact and ensure freedom
from vibration. The components are laid out to minimise inter component coupling and are placed well away from the
driver magnetic field. Top quality silver-plated Van den Hul wiring is used throughout. High current switch blocks with
gold-plated screw terminals permit user adjustment of high frequency sound radiation to suit differing listening environments.
The complementary design of crossover and drive units means that the loudspeaker system as a whole behaves as a minimum
phase system over the audio band and therefore the acoustic sources of the high and low frequency sections are aligned
in time and space to ensure accurate reproduction of stereo images.
A Note on Auditory Perception
Our hearing mechanism locates natural sound sources with great accuracy by using the naturally occurring phase differences
(or arrival times) at middle frequencies, and intensity differences at higher frequencies, between each of our ears. Naturally
occurring sounds pass through the air to the ears at constant speed (345 metres/second or 1132 feet/second). All frequencies
travel at the same speed and therefore a frequency independent time delay is associated with the distances involved. (The
familiar time delay between a flash of lightning and the associated clap of thunder is an example). Human hearing relies
on the constant nature of the time delay with the intensity to locate natural sounds accurately. A pair of Tannoy Prestige
loudspeakers can uniquely reconstruct stereo images and provide excellent localisation of recorded sounds. The Tannoy
Dual Concentric™ driver principle ensures that the source of sound at high frequencies is one the same axis as the source
of sound at low frequencies.
The careful design of crossover network complements the drive unit to provide a coincident sound source at frequencies
where the human ear derives phase information for localisation. The loudspeaker system exhibits a time delay response
that is in essence independent of reproduced frequencies. In addition, the amplitude (or intensity) response is linear, smooth
and consistent. This provides the correct intensity information to recreate the original sound stage.