Thiel CS3.7 Product Support Bulletin page 5

"The speaker literally 'melts' into the soundstage. You are never aware that the sound is coming
from two boxes in front of you . . ." —James Tanner, Bryston Electronics
The Woofer
also utilizes
an innovative diaphragm that is
basically flat and therefore reduces
the diffraction of the midrange energy
usually caused by the woofer's conical
cavity. The massive magnet powers a
very high output and low distortion
long magnetic gap, and distortion
is further reduced by the use of a
heavy copper pole ring and a copper
pole sleeve that reduces inductance
nonlinearity. The large 3 inch diameter
voice coil allows high power handling.
The very low frequencies are
augmented by a passive bass radiator
diaphragm which avoids the resonance
and noise problems of a ported
enclosure.
The Crossover
first order acoustic type that provides
the utmost in spatial and depth imaging
performance as well as overall realism.
This is the only type of crossover that
provides complete accuracy of amplitude,
phase, time, and energy, and therefore
the only type that does not distort the
musical waveform. Proper application of
this gradual-transition type of crossover
requires the use of more expensive
drivers with wider frequency ranges
than are required for use with common
quick-transition crossovers, but the benefits also include improved
uniformity of the speaker's output in all directions.
The crossover is meticulously engineered to achieve extreme tonal
neutrality and is constructed with extensive use of polypropylene
and custom polystyrene capacitors.
Most speaker distortion is produced because the voice coil
experiences changes in the magnetic strength as it moves forward
and back to produce sound — changes that are caused because the
ends of the coil become farther from the magnetic gap where the
magnetic field is strongest.
By contrast, in the THIEL long gap system, all of the short coil
is always within the long magnetic gap, and therefore the coil
does not experience changes in magnetic strength as it moves.
Because the magnetic field is constant throughout the coil's motion,
distortion is greatly reduced. These long gap/ short coil, copper
stabilized systems do require much larger magnets, but they
produce less than one-tenth the distortion of conventional drivers.
In addition, all THIEL drivers use a copper sleeve around the central
magnetic pole that reduces inductance distortion and the woofers
also use a thick copper ring that stabilizes the strength of the
magnetic field during long, high power excursions. These distortion
reducing methods result in noticeably greater purity of sound and
result in more effortless dynamic reproduction.
New geometry
diaphragm reduces
cavity diffraction and
extends bandwidth
Very large 5 lb. magnet
used to power the long
magnetic gap while
providing optimum
bass control
Thick copper pole ring stabilizes
the magnetic strength against
high power input to maintain
proper transient impact
is a true
Reducing Distortion
In THIEL's long gap design, the shorter coil remains within
a long uniform field as it moves through its entire range,
drastically lowering distortion.
www.thielaudio.com
Copper pole sleeve
reduces inductance
nonlinearity to
maintain purity
This graph shows the ideal response
to a step signal, which like music,
contains harmonics with phase and
time relationships.
This graph shows how the woofer
signal (red) and the tweeter signal
(blue) from the common 4th order
crossover add to produce a distorted
waveform (black).
This graph shows how the woofer
and tweeter signal from a 1st order
crossover combine to reproduce the
waveform of the input signal.
magnet
In a conventional magnet system, the coil
(red) is longer than the magnetic gap (yellow)
and therefore enters a weaker field (green)
whenever it travels from its rest position. This
changing field strength produces distortion.
copper sleeve
copper ring
Heavy die-cast
chassis
Very long,
magnetic gap
provides the
coil with a
large region
of uniform
magnet field
Large diameter, six layer
voice coil is much shorter
than the magnetic gap
so that it experiences
constant magnetic strength
during large excursions
Phase Coherence
Time
10%
Excursion
10%
Excursion
8 mm
8 mm
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