Profile
employs our recent aluminum-magnesium alloy inverted
dome diaphragm in its most sophisticated version.
The objective is not so much to improve the already
excellent high-band performance, but to focus on
the lower range, with increased linearity and decreased
distortion.
The
Profile tweeter replaces the TRC model of the preceding
Electra line, which used a dome from the Tioxid
5 family (titanium dome covered with a 5µm
film of titanium oxide). The knowledge acquired
from mastering the pure Beryllium dome demonstrates
that we have indeed pushed the evolution of the
technology to its limits, especially in matters
of damping. The alloy of aluminummagnesium is an
excellent solution; with similar characteristics
of rigidity and linearity, damping is far superior.
Indeed, the nature of the material permits the design
of a less concave form than in the past and which
is much more favorable acoustically. It also allows
the removal of the phase piece, which is occasionally
the source of compression and distortion. This being
said, the Profile tweeter joins the Utopia Beryllium
TBU from which it borrows other essential characteristics.
The
inverted dome tweeter
The traditionally designed tweeter with convex membrane
requires the use of a coil glued to the peripheral
edge of the dome. There are no other possible choices.
This, however, is far from favorable, as the mechanical
coupling is less than perfect. There is a true lever
effect between the center of the dome and the far
removed coil. Tests and simulations show that the
center of the dome is no longer reactive at high
frequencies, and stays frozen. Only the peripheral
edge of the dome in direct contact with the coil
(the most rigid) is reactive. Dynamic behavior is
compromised, which translates as a decreased output
and an affected directionality.
An inverted dome acts much like a woofer, in smaller
dimensions. The coil rests on the inner part of
the dome, distributing the impulse more uniformly
over the entire surface of the dome. This improved
mechanical coupling also permits a lower resonant
frequency, an important consideration when determining
the cutoff frequency between the tweeter and the
midrange, with a minimum of distortion. Last, but
not least, compared to a conventional dome of equal
diameter, the inverted dome’s coil has half
the mass, an enormous conservation of energy. This
is an essential parameter in dynamic behavior.
The
Profile tweeter
The Profile tweeter is a more elaborate version
of the aluminum-magnesium dome from TNC of the Chorus
series, which itself is a very successful model.
Other characteristics of the design are groundbreaking.
The very compact magnetic circuit uses Neodymium
N48M, the most powerful element in its temperature
class (100°). The flux density rises to 1.7
Tesla, compared to 1.5 Tesla of the TRC. Neodymium
is a material that has enormous benefits, but does
have one defect: the magnet tends to demagnetize
under extreme heat, which is the case in certain
circumstances).
This particularity required precautions to avoid
raised temperature, proportional to the intensity
of the current circulating in the coil. The excellent
performance of the inverted dome allowed us to find
the solution: the coil has an impedance of 6 Ohms
with a comparable, if not higher sensitivity than
a tweeter equipped with a coil of 3 or 4 Ohms, thereby
giving the same acoustic output at only half the
current. Also of note: heat dispersion is so low
that no Ferro fluid is required, which would hinder
the movement and performance of the tweeter (loss
of detail and dynamics due to a sticky fluid). As
in the Utopia Be TBU, this tweeter uses the same
Poron® suspension. It is a cellular urethane
foam that, aside from its remarkable damping qualities
(used in silent-bloc, anti-vibration installations…),
it is perfectly stable over time, keeping its mechanical
qualities regardless of the demands placed upon
it.
The use of Poron® also inhibits the suspension
from acting upon the dome. Compared to the TNC,
the levels of distortion are lowered by a factor
of 1 to 10 at 1 kHz and almost as much at 2 kHz.
This immediately translates to a very clear high
band, which is more transparent in the remarkably
low cutoff area at 2.6 kHz, where the ear is extremely
sensitive. Even more important, in optimizing the
magnet and its loading into the baffle cavity, we
employ an advanced Thiell and Small configuration
which benefits from a better linearity. This allows
a much better union with the midrange thanks to
a better-distributed energy. The result is a delicate
and ethereal finesse, without coloration, or a sonic
character at a given frequency. The absence of subjective
distortion, even at high levels and at the crossover
frequency, is another quality of this design.
