Page 1
Supplemental
Technical Information
for model
THIEL CS2.3
®
Coherent Source
This paper contains only information specific to the CS2.3 speaker system.
It is intended to supplement the general technical information paper which
explains our engineering philosophy, goals and techniques.
Loudspeaker
THIEL CS2.3 SPECIFICATIONS
Bandwidth (-3 dB)
Amplitude response
Phase response
Sensitivity
Impedance
Recommended Power
Size (W x D x H)
Weight
Driver Complement:
Woofer
8" (6.4" radiating area) with anodized aluminum cone, cast frame, 1.7" dia.
voice coil. Underhung coil (short coil/ long gap) motor system. Linear travel
0.4" pk-pk, 13 in3 linear displacement. 2.5 lb. magnet, 6 lb. total magnet
structure. Copper pole sleeve, copper magnet ring. Made by THIEL.
Midrange
4.5" (2.7" radiating area) with anodized aluminum diaphragm, cast frame, 1"
dia. voice coil. Underhung coil (short coil/long gap) motor system. Linear
travel 1/8" pk-pk. Magnet weight of .8 lb. powers midrange and tweeter.
Copper pole sleeve. Ferrofluid. Made by THIEL.
Tweeter
1" (1.2" radiating area) with anodized aluminum dome. Powered by
midrange motor. Coincident with midrange.
37 Hz - 20 KHz ±2 dB
35 Hz - 23 kHz
minimum ±5°
87 dB @ 2.8 v-1m
4Ω, 3Ω minimum
100-400 watts
11 x 15 x 41.5 inches
70 lb
4/98
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Frequency response
Mechanical crossover
midrange
cone
voice
coil
tweeter
dome
coupling
suspension
midrange
suspension
Moving system
10K
Frequency
1K
10
5
0
-5
-10
-15
-20
-25
10020
20K
Amplitude — dB
Combined output
Tweeter
Midrange
The graphs below show the frequency response of the CS2.3.
The upper graph shows the (normal) on-axis response and
illustrates the very high degree of accuracy; no frequency is
under or over emphasized more than 2 dB. You can also notice
the full strength bass extension to 35 Hz.
The second graph shows the on-axis, octave-averaged
response. This curve is representative of the speaker’s tonal
balance and shows that the CS2.3 is very accurately balanced
with no area of the spectrum over or under emphasized more
than 0.5 dB.
The third graph shows the off-axis, octave averaged response
and illustrates that the speaker’s overall energy response into the
room is well balanced, with no large depressions in any area of
the spectrum. This high degree of uniformity is the result of the
CS2.3’s first order crossover system.
On-axis
10
5
0
-5
-10
-15
Amplitude — dB
-20
-25
10020
On-axis, octave averaged
10
5
0
-5
-10
-15
Amplitude — dB
-20
-25
10020
30°, octave averaged
10
5
0
-5
-10
-15
Amplitude — dB
-20
-25
10020
Step response
This graph shows the CS2.3’s response to a step signal. You can
Frequency
Frequency
Frequency
1K
1K
1K
notice that the overall triangular shape is very well preserved
with the output remaining smoothly positive until 2 ms when it
finally crosses due to the fact that the bass response extends to 35
Hz rather than DC. The irregularities seen in the first 100 or so
microseconds are due to the tweeter diaphragm resonance at the
ultrasonic frequency of about 23 kHz. Waveshape accuracy this
good can only be achieved with first order crossovers and time
coherent driver positioning.
10K
10K
10K
20K
20K
20K
Time response
The energy-time response of the CS2.3 shows that the speaker’s
output quickly decays to -40 dB in less than one millisecond,
demonstrating very clean inter-transient silence. This
performance is the result of metal diaphragms with no
resonances within their operating frequency range and very
strong cabinet construction.
5
0
-5
-10
-15
-20
Output — dB
-25
-30
-35
0.5
1.0
1.5 2.0 2.5
Time – msec
Compound driver
The most unusual technical feature of the CS2.3 is its use of a
compound driver where the tweeter dome and the midrange cone
are both driven by a single voice coil. The advantages of this
unique driver are that perfectly time-coherent performance is
achieved without the cost and complexity of two magnet
structures or an electrical crossover network for the mid-totweeter transition. The design is implemented with a mechanical
crossover—a “coupling” suspension between the coil and the
midrange cone. By optimizing the compliance and damping of
the coupling suspension and the ratios of area and mass of the
two diaphragms, the driver exhibits extremely uniform response
from 100 Hz to 20 kHz.
Output
0.5 1.0
1.5 2.0 2.5
Time – msec
Page 3
THIEL CS2.3 WOOFER
Rigid aluminum
chassis improves
clarity
Very large magnet
to properly damp
high output motor
stabilizes magnetic
strength to improve low
frequency dynamics
Conventional overhung coil
Short gap
Long coil
THIEL underhung coil
Heavy copper ring
Aluminum diaphragm
eliminates resonance
coloration
Copper pole sleeve
reduces inductance
distortion
Short voice coil
and long magnetic
gap dramatically
reduce distortion
12
THIEL CS2.3 woofer distortion
10
8
Conventional motor
6
4
Short coil
Long gap
2
Total Harmonic Distortion – %
0
1
2345
peak excursion – ±mm
Page 4
CS2.3 DESIGN FEATURES
The baffle is sloped to properly
position the drivers for correct time
alignment and accurate reproduction
of transient musical information. The
rounded edges greatly reduce
unwanted diffraction for more “open”
reproduction.
A 3" thick baffle, 1" cabinet
walls, and internal bracing
greatly increase cabinet
stiffness. By reducing
unwanted vibration, both
clarity and imaging
performance are improved.
The synthesized first-order
crossover provides phase
accurate transitions between
drivers to preserve the
recording’s spatial information.
The network utilizes
polypropylene and custom-made
polystyrene capacitors, and low-
oxygen copper, air-core inductors
for very low distortion and
transparent reproduction.
The CS2.3’s uses a unique
compound midrange/tweeter where
to two units are driven by the same
voice coil. Perfect time coherent
performance is achieved without the
cost and complexity of two magnet
structures or an electrical network
for the mid-to tweeter transition.
The 8" woofer uses a very low
distortion short coil/long gap motor
system, powered by a 2.5 magnet.
The rigid aluminum diaphragm
eliminates resonance coloration, a
special copper pole sleeve
reduces inductance distoriton, and
a heavy copper ring maintains an
ultra-stable magnetic field.
The 9" passive radiator
eliminates bass port
resonances and noise.
THIEL • 1026 Nandino Boulevard • Lexington, Kentucky 40511 • USA
Telephone: 859-254-9427 • Fax: 859-254-0075 • E-mail: mail@thielaudio.com • Web: www.thielaudio.com
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