KEF Audio Uni-Q User Manual
Uni-Q®Loudspeakers - The Range
People who know sound, know KEF.
It’s a name that commands such respect because we’ve never
been a ‘me too’ manufacturer. Ever since the early days of hi-fi,
our approach has been driven by a passionate belief in the power
of new materials, new technologies and design ingenuity to
heighten the enjoyment of recorded sound.
This is as true today as it was back in ’61, when KEF was founded
by Raymond Cooke, which is why KEF speakers have ranked
among the finest in the world in every decade since.
In that time, KEF has pioneered many landmark innovations.
New diaphragm materials. Neoprene damping. The use of
computer modelling in research and quality control.
Digital testing to unprecedented tolerances. Total system design
methods. Conjugate load network techniques. And arguably
the greatest breakthrough of all: the Uni-Q array,
based on technology originally developed for the NASA space
programme and protected by world wide patents. No other
manufacturer has done more to advance the principles of
loudspeaker engineering, and none is better placed to exploit the
potential of the latest digital formats.
Separating out the midrange and high frequency drivers
into their own pods has long been a KEF tradition dating
all the way back to 1977 with the worlds first speaker
to do this, the Model 105. This technology lives on today in the
Model 207 flagship.
KEF - THE FACTS AND THE FEELING
‘Fresh ideas are what we breathe - but only obsession with detail can make them work’
Raymond Cooke MBE 1925 - 1996
Founder of KEF
KEF Production Facility at Maidstone
Model 105 1977-79 Model 105/4 1980-82 Model 105/2 1982-87 Model 107 1986-89 Model 107/2 1990-96 Model 207 2001
POD TECHNOLOGY
1
KEF LOUDSPEAKERS
What to look for when choosing your speakers
Of all the elements in your audio system, changing your speakers
can make the biggest difference in sound quality. As a rule of
thumb, the speakers in a basic two-channel hi-fi system often
account for about a third of the total system cost.
Speaker quality has a lot to do with size and the number of drive
units; but ultimately what matters is how well they reproduce
your kind of music or film soundtrack in your room at the volume
you most enjoy. Although technical specifications are helpful,
you can only find which model best suits your personal
preferences by hearing them in action. These are some of the
things you should be looking for...
Drive units
Hi-fi drivers are dedicated to different parts of the frequency spectrum.
Bass units reproduce sound between 20 to 500Hz, midrange drivers
(carrying most of the identifying tones of music or speech)
usually from 200Hz to 4kHz, and HF drivers (tweeters),
from 2kHz to above 20kHz. Long-throw drivers allow
a large amount of cone movement, and therefore
generate higher sound pressure levels. A strong
chassis such as cast aluminium provides a rigid
platform for the moving coil/cone assembly and avoids
the energy being drained from the cone into the cabinet
itself. Some form of mechanical decoupling between the chassis
and the cabinet can greatly reduce the transmission of this vibrational energy to
the cabinet walls.
Cone materials vary.Tweeters are usually made from metallic or fabric materials
- the former tend to be very revealing and detailed; the latter, a more
reserved sound.
Components
Crossovers act as the brains of a speaker,
allocating the various frequency ranges to the
appropriate drivers, with filters to stabilise
impedance loads and shape frequency response.
The quality of the components (such as polypropylene capacitors
and air-cored inductors) directly affects acoustic fidelity.
Setting up
High performance speakers usually have dual sets of connectors
(binding posts) and crossovers with separate sections for low and
high frequencies. This is to accommodate bi-wiring (using two
sets of cables to improve resolution) and bi-amping (in which
each set of connectors is wired to a separate amplifier for
optimum response across the frequency range). KEF’s new
Reference Series even features 3 pairs of connectors for
tri-wiring or tri-amping. Most speakers sound better after a few
hours use. All you have to do then is sit back and enjoy.
Imaging
Stereo imaging is the illusion of a realistic 3D presence that seems not to come
from the speakers themselves, but a virtual sound stage in which different
instruments or sound effects are localised. With conventional speakers
(as opposed to KEF Uni-Q), this illusion only occurs in a relatively small area -
the ‘sweet spot’.
To test speaker dispersion characteristics, move around the listening area.
Does the sound fade as you move away from the main axis of the speaker?
Do central images stay centrally located at some frequencies but not others?
Measuring performance
The smoother a speaker’s frequency response, the more faithful its reproduction
of the audio signal.Transient response is also important, reflecting the speaker’s
ability to respond quickly to any sudden change in the signal without blurring
(smearing) the sound. How loudly a speaker plays depends on its sensitivity,
maximum output capability and power handling.Low sensitivity speakers require
larger amounts of amplifier power to reach a given loudness level.
High sensitivity speakers require relatively less and
can be used to compensate for low amplifier power.
When compensating for low sensitivity speakers
remember that a 10dB increase in sound pressure
level, which sounds twice as loud, requires 10 times
more power.
Always look for a wide dynamic range in a speaker -
the range of sound intensity that can be reproduced
without distortion. It’s expressed as a ratio in
decibels. In speech, this is rarely more than 40dB;
in orchestral works, it can be as much as 75dB.
Judge whether loud passages sound appropriately
louder than quiet ones. Can you hear subtle changes
when something else is playing loud? Does music
come to life at high volume, or blur?
Ask yourself also whether the sound picture is complete at the frequency
extremes. Or has bass, for example, been sacrificed to midrange clarity?
Accuracy is a matter of how closely the speaker reproduces live sounds.
How much detail can you hear? Do individual images sound separate from each
other, or are they like highlights in an acoustic soup?
Neutral balance gives the human voice a natural timbre, without distortion at
frequency extremes. Listen for colouration - do voices sound strange? Is there
too much sibilance? Can you differentiate the sound of similar but different
instruments? Or does a violin sound like a viola, a Stratocaster like a Les Paul?
SPL(dB)
110
100
90
80
70
60
20 200 2k 20k
FREQUENCY(Hz)
Ci Ref 2000
Ci Reference 2000
20 200 2k
FREQUENCY (Hz)
Ω
31.6
10
3.16
20k
22
The continuing evolution of KEF’s legendary Reference Series has
always been based on the concept of benchmark precision.
Every time a new generation of models is developed to
incorporate more sophisticated technologies, we build
prototypes that are as close to perfection as possible.
These then become the ‘Reference’ to which every
single production version must conform, each set
assembled by a skilled craftsman who matches their
performance to a tolerance of just 0.5dB.
As the latest incarnation of this approach,
the Reference Series is a quantum leap forward in
audiophile quality sound. In fact, its performance envelope
extends well beyond the range of human hearing.
This is not as futile as it may at first sound - whereas conventional
CDs carry no audio information beyond 20kHz, extended
bandwidth formats such as SACD and DVD Audio contain signals
up to 40kHz and more. Consider the analogy that even though
no-one drives at 200 mph, cars that are engineered to do so are
inherently better performers at lower speeds.
That’s why all new Reference series models come with a
state of the art 19mm (
3
/4”) titanium dome Hypertweeter
TM
for massively extended HF performance . Mounted in low
diffraction, chrome-plated steel enclosures time aligned
with the main array, they deliver flat response to 55kHz and
useful energy up to 80kHz. What you hear is a sweeter,
more natural sound.
Radical new Uni-Q driver arrays - the ultimate refinement
of KEF’s trademark technology - where the tweeter is
mounted at the acoustic centre of the midrange cone -
provide an immaculate single point source, the Holy Grail
of loudspeaker design. With the midrange cone and
surround integrated into a single Uni-Form moulding,
there are no discontinuities to distor t the HF energ y from
the 25mm (1”) elliptical profile titanium dome tweeter.
With only midrange frequencies to handle , movement of the
Uni-Q cone is so modest that virtually no distor tion is caused
by intermodulation with the tweeter. Like the bass drivers,
an open chassis design - minimises acoustic reflection
behind the cone.
The result is an even more spacious, better defined
sound stage over a very large area, with exceptional
off-axis response and none of the ‘sweet spot’
limitations of conventional speakers.
Bass extension is equally stunning, thanks to ultra-low
distortion motor systems and high tech reinforced
diaphragms. And with each bass driver radiating directly from its
own separate internal enclosure to avoid the distorting effects of
vertical standing waves that tall cabinets usually suffer from,
you experience noticeably clearer, more open bass.
As you would expect from a handmade KEF product,
build quality is as outstanding as the specification of each
individual component. Carefully graded and soldered by hand,
KEF’s own oxygen-free copper cable ensures the best possible
signal transmission, with terminals machined from solid
brass and plated in gold. High order crossovers with
advanced air-cored inductors and polypropylene capacitors
ensure faultlessly smooth integration.
For optimum performance in real rooms, all models
accommodate tri-wiring and are fitted with a boundary
control device to adjust bass response according to speaker
positioning and the acoustics of the listening area.
Magnetic shielding ensures trouble-free positioning in
home theatre applications.
Engineered from laminated birch ply using KEF’s own
internal bracing system, the new cur ved section cabinets
are elegantly profiled to minimise colouration and finished
in a choice of hand-matched hardwood veneers.
More than ever before, these are very special
speakers indeed.
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