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FEATURES OF THE WOOFER UNIT
FEATURES OF THE WOOFER UNIT
Development of speaker systems vitally involves
the 3 elements of driver units, networks and
enclosures.
On development of NF-1, thorough investigation of
these 3 elements was made to have them well
balanced, so as to achieve total quality by attaining
incomparable performance from the same size
drivers.
Woofers which are responsible for reproduction of
base sound must meet the following 3 points which
are major sound quality-determining factors:
The introduction of HP diaphragms and newly
developed Biodyna composite material in the
vibratory system, being the key portion for
successful achievement of the above 3 factors, has
made theNF-1 woofer an ideal bass unit.
1) Configuration of HP diaphragms
In order to disperse stress, inflection points are
located at the top and bottom to form vertical
symmetry, and the height of curved surfaces is set
for optimal frequency
dispersion as dictated by
FEM modal analysis
results, with pentagonal
divisions which create
asymmetry to the center
as the basic option.
2) Properties required of diaphragm materials
Factors of importance with diaphragm materials
are:
1) Propagation speed
2) Modulus of flexural rigidity
3) Internal loss (tan
δ
)
For NF-1 diaphragms, we have set the following
target values, which we think the next generation
near-field monitors cannot be without.
To achieve these values, the materials described
below are introduced:
A) Base pulp: a mix of NBKP and banana fibers
Conventionally used NBKP wood pulp alone is
accompanied by sound distortion due to lack of
bonding strength at the pulp fiber level. This
distortion component present in reproduced sound
has been considered to be an integral element
with wood pulp, as seen in comments such as
'reminds listeners of paper'. Continual study for
usability of various
types of materials
such as carbon
fibers, PP, nylon,
polystyrene, metal,
etc. for vibratory
systems, made ever
since development
of wood pulp cones,
has failed to find
any material
compatible with
wood pulp which
has well balanced
tan
δ
and
propagation velocity. Meanwhile, Fostex has
succeeded in development of banana pulp
materials comprising long fine fibers with a high
level of bonding strength provided by the intrinsic
starchy component. This banana pulp provided
an opportunity for exploration into new
dimensions where distortion-free pulp cones can
be embodied without sacrificing the intrinsic
properties of pulp. Adoption of banana pulp and
NKP as the base pulp has made an excellent well-
balanced cone available for NF-1.
To be light in weight and high in
rigidity, with smoother response
To have a reasonably extended
high end and wider directivity
To achieve ideal performance
without need of any cross-over
provision
a.
b.
c.
Propagation speed:3000 m/sec., minimum.
Conventional pulp materials:2600 m
PP (polypropylene):1290 m
Modulus of flexural rigidity:6.0 (2 times
that of conventional materials, or greater)
Conventional pulp materials:2.81
PP (polypropylene):1.43 m
Internal loss (tan
δ
): 0.06, minimum.
Conventional pulp materials:0.033
PP (polypropylene):0.08
1)
2)
3)
Banana pulp fibers
HP diaphragms
