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IntroductionIntroduction and Overview
The KEF Reference Series 209 subwoofer is a ‘state
of the art’ subwoofer for use in the very best home
theatre and stereo systems. Every component is
critically designed to give optimum acoustic
performance in a compact, elegant enclosure.
The key components in the 209 subwoofer are the
drive unit, the amplifier and the enclosure – all three
of these contain innovations that make this model a
class leader.
The 18” (450mm) drive unit is designed to give
60mm (peak to peak) of linear excursion.
The magnetic field, which powers the motion, is
constant over that region.
The magnet system is a
radically different design
from that found in
conventional loudspeaker
drivers, it has been
designed by KEF from the
ground up using advanced
computer modelling techniques to predict the
behaviour and orientation of the internal magnetic
field. Unlike conventional drivers the Reference 209
magnet system uses a series of 24 neodymium
magnets radially arranged around the voice coil of
the driver. This unusual topology allows the unit to
have a remarkably long range of motion while
maintaining a very strong magnetic field around the
voice coil. Together with a double suspension and
massive roll surround this allows high levels of bass
to be reproduced with very low distortion - giving
a sense of power and clarity not normally found in
high end subwoofers.
The amplifier section is custom designed to get the
very best out of the new drive unit. A 1000W class
D power amplifier with switched mode power
supply allows top end performance in a neat and
tidy package. In addition, the front end
incorporates Digital Signal Processing (DSP) which
is used to provide comprehensive equalization
options and an innovative room acoustic
correction system (see page 9 for an overview and
page 23 for operation guide).
The enclosure is beautiful on the outside and highly
technical on the inside. Attached to the inner
surface are 30 ‘ACE’ modules - tubes of activated
carbon which increase the effective internal
acoustic volume by a factor of 2. ACE technology
(see page 8) is KEF’s solution to the oldest catch 22
in loudspeaker design – that to get good bass
extension with good efficiency you need a large
enclosure. The Reference Series 209 subwoofer
gives the kind of bass extension normally found in
subwoofers twice the size.
This subwoofer is specifically
designed with bass speed and
articulation in mind, because of
this we chose to make the
subwoofer a closed box design.
A closed box design does not
rely on the resonance of port or
passive radiator for output.
All sound radiation is from the
18” driver the motion of which
is carefully controlled and
damped by the amplifier and
large magnet system, there are
no port resonances to continue
ringing after a sudden bass event.
Additionally it is not possible to
recreate extreme low bass
output with a ported system,
which cannot radiate below the
port tuning frequency.
All this technology is neatly packaged in an
elegant enclosure with straightforward connection
options and an easy to use remote controlled
user interface.
You can run the Reference Series 209 subwoofer
with the default ‘switch on’ settings or experiment
with the DSP based equalisation options to fine
tune it to your particular system setup.
Line level or high level speaker inputs are available
to allow flexibility in set-ups. In addition, line level
connections are possible as either single ended
(phono) or balanced (XLR).
For ease of use and installation the subwoofer is
equipped with an IR remote control allowing for
easy adjustment of subwoofer level, cut off
frequency and phase from your listening position.
A microphone is also included to allow the
subwoofer to measure the sound produced within
your room and compensate for abnormalities using
integrated room correction algorithms.
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