Revel Performa F228Be Loudspeakers
Australian Hi-Fi 29
distortion going on, and there’s no crossover
anywhere near the crucial vocal range. (The
electrical crossover frequencies are specified
at 260Hz and 2.1kHz). The beauty of using
two bass drivers is that you split the load, so
the power-handling is higher and the excur-
sion is minimised, so distortion drops away.
It’s not very cost-effective, mind you, because
it costs more to manufacture two small
drivers than a single large driver, but I guess
at the price Revel is asking for the F228Be,
that particular cost isn’t going to be an overly
large portion of the overall price.
The two bass drivers used in the F228Be
are, however, works of art in themselves. The
cones are made from a material Revel calls
‘Deep Ceramic Composite’ (DCC) alumini-
um, while the frames are fully cast. Rated by
Revel with an overall diameter of 203mm,
the cone itself is only 158mm across, and the
Thiele/Small diameter is 170mm, for an ef-
fective cone area (Sd) of 227cm². This means
that if Revel had used a single bass driver, it
would have had to have been around 270mm
overall to deliver the same ‘punch’ as the two
drivers on the F228Be. As for that DCC mate-
rial, Mark Glazer, Revel’s Principal Engineer,
says the cones are made using a plasma elec-
trolytic oxidation process that uses a plasma
discharge to create a ceramic coating on both
sides of an aluminium core. The two ceramic
layers provide constrained layer damping
that pushes the cone’s breakup modes outside
the pass band, allowing the driver to main-
tain ideal pistonic motion through its entire
operating range.
To ensure proper voicing during the cross
from the two bass drivers to the midrange
driver, the midrange driver’s cone and chassis
are made from exactly the same materials as
the bass drivers. In fact the overall construc-
tion is identical... the midrange driver just
has a smaller diameter cone, at 130mm.
(Again, this is a nominal measurement. The
cone itself is just 105mm across, and the
Thiele/Small diameter is 112mm.) Obviously
the most distinctive aspect of the cone mate-
rial Revel is using is that it’s white... almost
chalk-white, in fact, which is presumably the
‘raw’ colour of the ceramic material used.
I can’t say that I am a huge fan of this
colour—and my wife certainly wasn’t!—but
once you’ve attached the supplied grille,
which is black cloth stretched over a fairly
flimsy but perfectly adequate plastic frame,
you’ll only be able to see the drivers under
some lighting conditions. The surrounds
of the bass drivers and midrange driver are
made from Santoprene, which is a thermo-
plastic vulcanizate
made from rubber
particles encapsulat-
ed in polypropylene.
Santoprene combines
the longevity of rubber
with the flexibility of
foam without any of
the drawbacks of either
material and as a result
is now one of the very
best materials available
from which to make loudspeaker surrounds.
As you’ve probably already guessed
from the model name, the 25mm diameter
dome of the F228Be’s tweeter is made from
Beryllium (chemical symbol: Be). The magnet
used to drive the beryllium dome is massive,
comprised of two 85mm diameter ceramic
magnets. Beryllium is becoming the go-to
material of choice for tweeter domes,
not least because it’s half the weight
of either titanium or aluminium, yet
four times as stiff, but also because
it’s also more self-damped then ei-
ther of these metals. (For the record,
Beryllium is also a metal, albeit a
‘rare earth’ metal.)
The Beryllium dome not only
makes it the odd driver out in terms
of construction material, but also
makes it the odd driver out in terms
of colour, as it’s basically black. Revel
has largely ameliorated this visual
discontinuity by fronting the dome
with a waveguide that’s made from
exactly the same material used to
make the cones on the midrange
and bass drivers. According to Kevin
Voecks, this waveguide ensures that
the tweeter’s dispersion character-
istics match that of the midrange
transducer in the crossover region,
and also ensures wider dispersion
at higher frequencies. ‘This gives
the loudspeaker very smooth sound
far off-axis,’ says Voecks, ‘providing
consistent sound over an exceptional-
ly wide listening area, which is an
important contributor to overall sound
quality.’ I have to say that I’m not
sure that calling it a ‘5th-generation acoustic
lens waveguide’, as Revel does, is a great idea,Beryllium is becoming the go-to
material of choice for tweeter
domes, not only for its weight,
but for its self-damping ability
partly because it seems incredible that in
these days of finite element analysis it could
take five generations to arrive at a design for
a tweeter waveguide... but also partly because
I cringe to think that at some time in the
distant future the company could be offering
a ‘457th-generation acoustic lens waveguide.’
As you can see from the photographs
accompanying this review, the Revel F228Be
is a bass-reflex design, with a single circular
port located on the front baffle, immediately
below the bottom-most bass driver. This port
is 70mm in diameter for most of its length,
flaring to 80mm at either end, and is 160mm
in length. The inner and outer flares are done
using plastic mouldings, with a short section
of cardboard tubing linking the two. Unlike
with some other models it offers, Revel does
not supply foam plugs that can be used to
block or otherwise alter the output of the
ports, but I guess that if you’d like to experi-
ment for yourself, foam is cheap...
Around the back of the Revel F228Be
you’ll find four large, gold-plated speaker
posts linked by large gold-plated buss-bars.
Leave the buss-bars in place if you’re not
bi-wiring or bi-amping, but remove the bars
if you are.