Fyne Audio SUPERTRAX - Page 7

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important fact which is not intuitive,
and it means a super tweeter will affect
the overall sound across the frequency
domain, not just at high frequencies.
So, for a super tweeter to work
correctly in the time domain, it has
to be positioned backwards on the
cabinet, to match the acoustic source
of the main driver. Positioning the super
tweeter at the front of the cabinet, as
is often seen is not ideal, although it
could be argued that with a discrete
non-point source loudspeaker this is of
little importance, as the design concept
is already compromised as outlined
above.
We can now appreciate how adding
a super tweeter improves system
performance, not just with wide band
materialsuchashi-resdigitalles,vinyl
and tape, but with limited bandwidth
material such as 22kHz CD Red Book
standard.
WHY AN OMNIDIRECTIONAL SUPER
TWEETER?
As we stated initially, the concept of
a super tweeter is by no means new
and over recent years, commercial
examples have come to market by
manufacturers over the year. These
are designed to sit on top of the
main loudspeaker cabinet and radiate
energy directly at the listener, either
from a directly radiating dome, a
ribbon transducer or similar device.
Such devices will have a very narrow
dispersion at these ultrasonic
frequencies, which means they will
beam like a torch.
We noted earlier that the relationship
in amplitude of fundamental frequency
and harmonics needs to be accurately
preserved both on axis and at points off
axis. In a typical room, a high proportion
of sounds perceived by the human ear
arereectionsgeneratedbytheoffaxis
response of the speaker. The even off
axis response of a point source IsoFlare
driver,meansthatthereectedenergy
has the same harmonic structure as
the direct on axis energy. Therefore,
any enhancements by means of a
super tweeter are best served by
an omnidirectional device with even
response at any angle, placed at the
acoustic centre of the main driver,
rather than a forward facing one, that
beams energy directly at the listener.
The SuperTrax makes use of an
upwardsringsupertweeter,designed
to be placed on the main loudspeaker
cabinet, above which is mounted
a contoured acoustic diffuser. The
acoustic diffuser makes use of a
Tractrixprole.TheTractrixproleis
known to maintain a 90 degree angle
at each intersection of the expanding
wavefront. The plane acoustic
wavefront generated by the dome is
translated into a spherical wavefront
into the room, where it meets the
diffuser. Fyne Audio made use of
theTractrixproleintheirpatented
BassTrax™ loading system, where the
principles are similar.