JAMO D 4 - Manual (Page 9)

9
In fact, the choice of “motor” materials makes use of magnetic oil for cooling and
resonance damping unnecessary!
All these features in combination allow the diaphragm to move effortless and the result is a
very natural, detailed, dynamic and open sound reproduction.
Mid-woofer/woofer
The woofer of the D 4 speakers features a brand new wood fibre cone.
This unique cone is made from wood fibre material, characterized by
very uneven fibres with different resonance properties. And thus, when
these fibres are pressed into shape to form a loudspeaker cone, the
different fibres will prevent each other from vibrating.
Furthermore the cone is coated twice in order to fine-tune rigidity and
internal damping.
First it is lacquered on both sides for increased stiffness – and as a side
benefit UV resistance is obtained - and secondly it is coated on the
backside with a tough hardening resin to maximise internal damping.
The result is a cone with very well controlled break up modes resulting in
extremely low distortion all over and a very open and detailed midrange
for optimum voice reproduction.
The basket is made of magnesium giving several benefits:
First of all it makes it possible to create a very open basket
– even behind the spider – thus ensuring high airflow at
low frequencies, avoiding reflections at high frequencies
and preventing under-/overpressure causing mechanical
losses.
Secondly, as magnesium is a non-magnetically material,
the magnetic force from the magnet does not spread out
in the basket, but stay concentrated where it is needed;
around the voice coil.
Finally, the very rigid material ensures that the heavy
magnets and the voice coil always are perfectly aligned
with the voice coil in the exact center of the magnet gap.
To ensure that the units are firmly attached – and airtight – it is mounted using 6 screws,
and the backside of the basket features two thin silicon stripes. Besides from ensuring air
tightness, the silicon stripes also prevent any potential vibrations that could arise between
the cabinet and the unit.