ACE
The holy grail of loudspeaker design has always
been to generate big bass from small boxes. The
trouble is, the laws of physics make this almost
impossible to achieve, as bass extension relates
directly to efficiency and cabinet size.
Continuing a 40-year tradition of genuine design
innovation, KEF engineers have now developed a
way of overcoming this apparently insoluble limi-
tation. It’s called Acoustic Compliance
Enhancement (ACE), and it works like this. In con-
ventional speakers, cone motion is restricted by the
acoustic pressure in the enclosure as the air is
alternately compressed and expanded by the
cone moving in and out. The smaller the enclo-
sure, the greater the pressure that acts on the
cone. By dramatically reducing this pressure, ACE
allows the cone to move as freely as it would in a
much larger cabinet, generating bass extension
out of all proportion to its actual size.
This is achieved by introducing granules
of activated carbon into the enclosure
- a material containing millions of pores
ranging in size from visible fissures to holes
a few molecules across. One of its
characteristics is a capacity for physical adsorp-
tion, the gravity-like molecular force in which a
substance (usually a gas) accumulates in a thin
film on the surface of a solid. In the ACE loud-
speaker when the cone moves inwards the air
pressure increases, triggering adsorption of air
molecules from the free air into the carbon. This
removal of air
molecules from the free air causes the internal
pressure to decrease. When the cone moves
outwards the opposite happens and the
carbon gives out air molecules. The ACE material
is constantly acting to reduce the pressure vari-
ations in the enclosure in a
controlled and linear fashion.
It’s an innovation that makes an amazing
difference for the listener. By enhancing
compliance by anything from 150% to 300%,
ACE-enabled loudspeakers perform like units up
to three times their size. In trials of
identical Uni-Q arrays fitted to an ACE
enclosure 40% smaller than the test cabinet,
not only did the listeners agree that bass was
undiminished - they unanimously preferred the
bass attack of the ACE version. And that’s
the acid test of any radical breakthrough in
audio design: subjectively as well as objectively,
ACE enriches the listening experience.
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Effect of ACE on a 10 litre closed
box loudspeaker
Based on those developed for the legendary
Reference Series, the Uni-Q arrays in the new
KHT range are the most sophisticated yet, with
new metal dome HF drivers that reproduce the
human voice with breathtaking accuracy. In
purely practical terms, the larger sound image
gives you far greater flexibility in placing your
speakers where they look best. For home theatre,
it means that you experience even the subtlest
3D soundtrack effects with the same clarity and
realism wherever you sit.
Uni-Q
Excellent dispersion characteristics common
with all Uni-Q based products showing wider
listening area
Conventional loudspeaker dispersion showing
narrow ‘sweet spot’
Technology
KEF’s patented Uni-Q driver configuration dis-
perses the sound image over a much larger area
than a conventional speaker, instead of being
restricted to a small ‘sweet spot’.
This outstanding off-axis response is made pos-
sible by using aerospace materials to
engineer a high performance tweeter that’s
small enough to mount in the exact acoustic
centre of the bass/midrange cone so that both
act as a single point source – an ideal that so
far, only KEF has achieved.
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