Thiel SCS-3 Brochure

Supplemental
Technical Information
for model

THIEL SCS3

®

Coherent Source

This paper contains only information specific to the SCS3 speaker system.
It is intended to supplement the general technical information paper which
explains our engineering philosophy, goals and techniques.

Loudspeaker

THIEL SCS3 SPECIFICATIONS

Bandwidth (-3 dB)
Amplitude response
Phase response
Sensitivity
Impedance
Recommended Power
Size (W x D x H)
Weight

Driver Complement:
Woofer

6.5" (5.1" radiating area) with anodized aluminum cone, cast frame, 1.7"
dia voice coil. Underhung coil (short coil/ long gap) motor system. Linear
travel 3/16" pk-pk, 3 in3 linear displacement. 2.5 lb. magnet, 6 lb total magnet
structure plus 1.2 lb. shielding magnet. Copper pole sleeve. Made by
THIEL.

Tweeter

1" (1.2" radiating area) with anodized aluminum dome. Aluminum coil.
Underhung coil (short coil/long gap) motor system. Linear travel 1/8" pk-pk.
Powered by 5 neodymium magnets weighing 1.7 oz. Copper pole sleeve.
Ferrofluid. Coincident with midrange.

48 Hz - 20 KHz ±2 dB

46 Hz - 22 kHz

minimum ±10°

87 dB @ 2.8 v-1m

4Ω, 3Ω minimum

30-200 watts

7.5 x 10 x 19 inches
30 lb

7/00

Time coherent topology

10K

Frequency

1K

10

5
0

-5

-10

-15

-20

-25

-30

10020

20K

Amplitude — dB

On-axis, octave averaged, 30° octave averaged

An important design goal for the SCS3 which is not shared
with our floor-standing products is placement flexibility. The
requirement that the speaker provide time coherence while
placed either vertically or horizontally and at any height
necessitates that the speaker be symmetrical both horizontally
and vertically and, therefore, that it use either coincident or
D’Appolito driver configuration. The SCS3 uses coincident/
coaxial mounting of a very high output 1" tweeter and a high
output 61/2" woofer.

Typical Shelf Speaker

Placed on Side

THIEL SCS3

Frequency response

The graphs below show the frequency response of the SCS3.
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.

The second graph shows the on-axis, octave-averaged
response. This curve is representative of the speaker’s tonal
balance and shows that the SCS3 is very accurately balanced,
any over or under emphasis below 12 KHz is less than 0.5 dB.

The third graph shows the 30° off-axis, octave averaged
response and illustrates that the speaker’s overall energy
response is well balanced, with no large depressions in any area
of the spectrum. This high degree of uniformity is in part the
result of the SCS3’s first order crossover system.

Off-axis Listeners

(top view)

Two-way speaker positioned on its side
causes the sound from the drivers to reach
the off-axis listener at different times.

Coaxial tweeter response

To maintain time coherence the tweeter must be aligned with
the woofer. There is usually a significant problem with the
response of tweeters which are mounted coaxially in a woofer.
Energy from the tweeter is reflected from the woofer’s
diaphragm and causes destructive interference.

25
20
15
10

5
0

Amplitude — dB

-5

-10

25
20
15
10

5
0

Amplitude — dB

-5

-10

25
20
15
10

5
0

Amplitude — dB

-5

-10

The SCS3’s woofer diaphragm shape has been designed to
greatly reduce negative effects on the tweeter’s response as can
be seen in the third graph. By shaping the diaphragm as a short
tube opening into a shallow flare reflections are almost entirely
eliminated. In addition, the woofer’s surround is mounted to the
rear of the diaphragm such that the tweeter does not really “see”
it as a diffraction-causing obstruction. Since the shape of the
woofer’s diaphragm has been optimized for the tweeter’s
response rather than to minimize its own resonances, it would
not exhibit response as good as it otherwise would. To remedy
this problem the woofer diaphragm is reinforced with very light
and stiff molded polystyrene on its back side.

10020

10020

10020

Frequency

Frequency

Frequency

Off-axis Listeners

Coincident driver mounting results in all
listeners hearing the sound from the
drivers at the same time.

10K

20K

10K

20K

20K

10K

1K

1K

1K

This
graph shows
the response
of the
SCS3’s
tweeter in an
infinite
baffle and
the second
shows the
tweeter’s
response
when
coaxially
mounted in
a typical
woofer.
Irregularities
can be seen
above 4KHz
caused by
diffraction
effects.

Step response

This graph shows the SCS3’s response to a step signal.
Notice that the overall triangular shape is very well preserved
with the output remaining smoothly positive until 2.6 ms when it
finally crosses zero due to the fact that the bass response extends
to 46 Hz rather than DC. The irregularities seen in the first few
hundred microseconds are due to the tweeter diaphragm
resonance at the ultrasonic frequency of about 23 KHz.
Waveform accuracy this good can only be achieved with first
order crossovers and time coherent driver positioning.

Output

0.5 1.0

1.5 2.0 2.5

Time – msec

Time response

The energy-time response of the SCS3 shows that the
speaker’s output quickly decays to -40 dB in 1.5 milliseconds,
indicating very clean inter-transient silence. Such performance is
the result of metal diaphragms that have 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

Shielding magnet

Wide roll rubber

suspension

Tall shouldered

aluminum diaphragm

Kapton

coil former

Copper

pole sleeve

Short

aluminum coil

Very long

magnetic gap

Neodymium

focusing magnet

Large radial ring

neodymium magnet

Copper pole sleeve

Short voice coil

THIEL SCS3 Woofer

(shielding cup not shown)

Cast aluminum chassis

Large magnet

Long magnetic gap

Polystyrene diaphragm
reinforcement

Aluminum diaphragm

THIEL SCS3 tweeter

The SCS3’s tweeter is a unique and sophisticated device that
incorporates many unusual features that provide extremely
uniform response, enhance output ability and reduce distortion.

• Very long, linear mechanical excursion is provided by a
unusual wide roll suspension that is molded of rubber rather than
thermoformed of plastic so that it possesses low memory,
reducing a subtle form of distortion termed hysteresis.

• In order to eliminate another subtle form of distortion
caused by electrical currents (Eddy currents) in the voice coil
former, Kapton is used for the former material. Since this
material does not provide the mechanical stiffening of the
diaphragm usually provided by an aluminum former, a
diaphragm with a long shoulder is used that possesses its own
stiffness.

• A copper sleeve is used around the pole to stabilize the
strength of the magnetic field which reduces distortion,
particularly at higher output levels, and to reduce the coil
inductance which reduces distortion caused by the nonlinear
magnetic characteristics of the steel pole and extends the high
frequency response.

• An aluminum coil is used to maximize efficiency.

• Very high output ability and very low distortion is provided
by a long, 5 mm magnetic gap which allows linear excursions of
3 mm pk-pk.

• To power the long magnetic gap to field strengths
necessary for high efficiency, an unusual arrangement of a large,
ring-shaped, radially magnetized neodymium magnet is used in
conjunction with an additional disc-shaped neodymium magnet
above the gap. The combined magnet weight of 48 grams is
more than 4 times the magnet size usual in neodymium-powered
tweeters.

THIEL SCS3 tweeter

THIEL • 1026 Nandino boulevard • Lexington, Kentucky 40511 • USA

Telephone: [phone] • Fax: [phone] • E-mail: [email protected] • Web: www.ThielAudio.com