Thiel CS-3.6 Brochure

Technical Information

THIEL CS3.6

Coherent Source

®

Loudspeaker

This paper describes some of the technical performance aspects, design
considerations and features of the THIEL model CS3.6 loudspeaker system.
It is intended to supply information for those who are interested in such
matters. It is not intended to imply that good measured technical
performance is sufficient to guarantee good sonic performance.

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

Telephone: [phone] Fax: [phone] 7/92

DESIGN PHILOSOPHY

The CS3.6 is a precision instrument designed to very accurately translate electronic information into musical sound. All our efforts have

been directed toward achieving extremely faithful translation of all tonal, spatial and dynamic information supplied by the amplifier.

The CS3.6 is not intended to mask or mitigate shortcomings of the recording or other components in the music playback system.
We believe this approach is the only way to provide the potential of experiencing all the subtle aspects that help make reproduced music

a most enjoyable human experience.

CS3.6 DESIGN HIGHLIGHTS

• Extremely accurate frequency response:
29 Hz - 20 KHz ±1

• Coherent Source design: complete phase and time coherence

• Point source radiation pattern

• Very low energy storage

• Very high quality, innovative driver design

Crossover

The CS3.6 crossover incorporates 25 elements implemented
with 38 components. Most of the components are used to provide a
high degree of response shaping, correcting even small
imperfections that are usually ignored. Very high quality
components are used to ensure very low distortion levels. For
example, polypropylene capacitors are used extensively and all
capacitors are bypassed with custom–made polystyrene and foil
units. Also, all inductors are air-cored types wound with low
oxygen wire.

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/2 dB

Specifications:

Bandwidth (-3dB) 27 - 22 KHz
Frequency response 29 - 20 KHz ±1
Phase response minimum ±5°
Time response 150 µs -20 dB
Sensitivity 86 dB @ 2.8v-1m
Impedance 4Ω (2.5Ω minimum)
Recommended power 100 - 500 watts
Size 481/2 h x 121/2 w x 17 d inches
Weight 107 pounds

Driver Complement:

• 10" very long excursion woofer with advanced magnet system
and aluminum diaphragm operates up to 500 Hz.

• 4" mid-range with two–layer, air-core diaphragm and long­gap/short coil motor system operates from 500 to 3000 Hz.

• 1" high output metal dome tweeter operates above 3 KHz.

• 10" passive bass radiator

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/2 dB

PERFORMANCE GOALS

Since quality of musical performance is a very complex issue it is helpful to objectively identify the aspects involved. We believe

musical performance can be described, with not much oversimplification, as performance in four areas.

Tonal fidelity includes overall octave-to-octave balance, the fidelity of timbres, absence of vowel-like colorations, and bass extension.
Spatial fidelity includes how wide and deep the performing space seems, how convincingly instruments are placed from the center to

laterally beyond the speakers, how realistic the depth perspective is, how little the speakers’ positions seem to be the source of the sound,
and how large the listening area is.

Transient fidelity includes how convincingly realistic is the reproduction of the initial or ‘attack’ portions of sounds and how clearly

reproduced is musically subtle low–level information.

Dynamic fidelity includes how well the speaker maintains the contrasts between loud and soft and how unstrained and effortless is the

reproduction of loud passages.

FUNDAMENTAL DESIGN CONSIDERATIONS

In our opinion, natural spatial reproduction requires creating a realistic sound field within the listening room by mimicking the properties
of natural sound sources. These properties include wide area radiation and the absence of out-of-phase energy. To meet these requirements
the CS3.6 employs dynamic drivers. Dynamic drivers have the advantages of providing a point source radiation pattern with good dispersion
of sound over a wide area, great dynamic capability, good bass capability and a lack of rearward out-of-phase energy. Another advantage of
dynamic drivers is their small size which allows the multiple drivers to be arranged in one vertical line. This alignment avoids the problem
of line source designs which must place their different drivers side-by-side, causing the distances from each driver to the listener to change
with different listener positions.

The major potential disadvantages of dynamic speakers are diaphragm resonances (“cone break-up”), time errors, phase errors, cabinet
resonance, and cabinet diffraction. None of these problems is a fundamental limit and all can be minimized or eliminated by thorough and
innovative engineering, resulting in a speaker system without significant fundamental limitations.

TECHNICAL REQUIREMENTS

The task of engineering a speaker system requires the translation of the musical performance goals into technical goals. Although there
are also many minor design considerations, the following are what we believe to be the major technical requirements that contribute to each
of the musical goals.

Tonal fidelity:

• Accurate frequency response so as to not over or under

emphasize any portion of the sound spectrum

• Absence of resonances in the drivers or cabinet so as not to

introduce tonal colorations

Spatial fidelity:

• Point-source, uni-polar radiation

• Time response accuracy to preserve natural spatial cues

• Lack of cabinet diffraction

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Transient fidelity:

• Phase coherence to provide realistic reproduction of attack

transients

• Very low energy storage to provide clarity of musical detail

Dynamic fidelity:

• High output capability

• Low distortion

DESIGN GOALS

The technical requirements result in the following major technical design goals:

1. Very uniform frequency response

2. Time response accuracy

3. Phase response accuracy

4. Low energy storage

5. Low distortion

FREQUENCY RESPONSE

In our opinion the human ear is sensitive enough to the balance between component harmonics of musical sounds to detect frequency
balance errors of as little as 0.2 dB if they are over a range of an octave or more. Therefore we believe that extremely accurate frequency
response is an absolute requirement for a truly good speaker. Our design goal was to achieve accuracy in the design prototype of ±.75 dB
with a production tolerance of ±.75 dB. The result is a tolerance in every production speaker of only ±1.5 dB and a tolerance from speaker
to speaker of only ±1.5 dB at all frequencies.

Even more important than the maximum amount of response error at any frequency is the octave averaged, octave-to-octave balance
which has a very high correlation with the perceived tonal balance. Our design goal was to achieve octave-averaged response within ±0.5
dB from 200 Hz to 10 KHz. Any deviation more than 0.5 dB is confined to only a narrow frequency range and therefore will have less
effect on the perceived balance.

Achieving these goals requires the use of drivers with exceptionally uniform responses, drivers with very high consistency (so that few
units need be rejected), drastic reduction of usual cabinet diffraction which causes response errors, and an unusual degree of compensation
in the electrical network of even minor driver response anomalies.

Driver Response

The major cause of non-uniform driver response is diaphragm resonance. These resonances are also the major energy storage
mechanism.

In the case of the CS3.6 tweeter, a metal diaphragm is used that is stiff and light enough so the lowest diaphragm resonance occurs
above the range of hearing at 26 KHz. Therefore, there are no resonances in the audible range to cause energy storage or response
irregularities.

The CS3.6 mid driver uses a very effective new method of greatly reducing diaphragm resonance (patent applied). The diaphragm is
constructed of two cones, each with a different shape, which are joined at the rim and at the neck with only air between them. The resulting
three-dimensional structure is drastically stronger than a conventional diaphragm of equal weight. This increased strength causes the

frequency of lowest diaphragm resonance to be

Figure 1 Conventional diaphragm with vibration Figure 4 New double diaphragm

Figure 2 Frequency response of conventional

diaphragm

Frequency response magnitude - dB

45
40
35
30
25
20
15
10

1

log Frequency - KHz

Figure 3 Frequency-time response of conventional
diaphragm

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substantially higher and low level vibrations to be
substantially less.

Figure 1 illustrates a conventional diaphragm

and the vibrations that normally cause irregular
frequency response. Figure 2 shows the response
of a CS3.6 mid driver built with a conventional
diaphragm. Apparent in the response is a
depression in the 1 to 2 KHz region followed by
a hump from 2 to 3 KHz, a dip at 4 KHz and a
final peak at 4.7 KHz. These irregularities are
due to diaphragm resonances. Figure 3 is the
frequency response of this driver through time
and illustrates how the resonances cause the
driver’s output to ring. It can be seen that the
driver’s output up to 5 KHz requires 1 milli­second (ms) before reducing to the -20 dB floor.

Figure 4 illustrates the new diaphragm.

Figure 5 shows that the response is much more

uniform than the conventional driver and shows
far fewer irregularities. Figure 6 shows that
diaphragm resonances are virtually eliminated
below 7 KHz. Even the one resonance at 7 KHz
is mild. Below 6 KHz the driver’s output is
exceptionally clean, reaching the -20 dB floor in
less than 0.5 ms.

The CS3.6’s woofer is the first in a THIEL
product to employ a metal diaphragm. The
anodized aluminum material provides much
higher stiffness and compressive strength than
conventional diaphragm materials. The primary

Figure 5 Frequency response of new diaphragm

Frequency response magnitude - dB

45
40
35
30
25
20
15
10

1

log Frequency - KHz

Figure 6 Frequency-time response of new diaphragm

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2