Thiel Coherent Source CS2.7 User manual

ELECTRONICALLY REpRINTEd fROm ApRIL 2013
IssuE 232
The Legacy
Continues
Thiel’s
innovaTive
Cs2.7
HOTTEST
NEW GEAR
of the
A
T
C
E
S
SPECIAL AFFORDABLE
SPEAKER ISSUE!
7 Models from $398
5 TOP SPEAKER
DESIGNERS
Reveal Their Secrets
OPPO’S AMAZING
Do-It-All Blu-ray Player
MUSIC FROM
Led Zeppelin
Buddy Holly
Bob Dylan
Chet Baker
+
New High-Res
Downloads
2
4
P
A
G
E
S

ThIEL Cs2.7
LOudspEAkER
Anthony H. Cordesman
Photography Joel Salcido
a Major
sTep
forward
Posted with permission from NextScreen, LLC. All rights reserved. © 2013. Any unauthorized duplication of this article is strictly prohibited.
For more information on use of this content, contact Wright’s Media at 877-652-5295.

has a long track record of producing some of the best speakers around, but
this time it has taken a major step forward.
The Thiel CS2.7 is a remarkable transducer at any price and a superb value
even at its cost of $7999 a pair. To be quite frank, I expected far more sonic
compromises relative to Thiel’s top-of-the-line CS3.7. In practice, however,
the CS2.7 is one of the most neutral, detailed, and transparent speakers I’ve
heard, and its only real compromises lie in the deepest bass—a sonic area
largely of interest to synthesizer and organ fans.
I also have to say that a photo will not do it justice. If you want to seduce
your wife into accepting a oorstanding speaker—and paying nearly eight
grand for it—the Amberwood version of this speaker is as suitable for
exhibition at MOMA as it is for the listening room, combining a sculptured
prole, a visual impact that manages to be striking without being dominating,
and a size whose shape and height is well suited for real-world listening
rooms without appearing to tower over the rest of the furniture.
But then, as a loyal reader of TAS, you have to at least pretend you could
care less about looks. It should all be about the sound (although a little
“glitter factor” in technology and design can be allowed to creep in).
Sonic Coherence, Treble and Midrange, and the “Coaxial Coincident Driver”
Let me begin with sonic coherence and the soundstage. The Thiel CS2.7
comes close to mimicking a point source. Like other current Thiel designs,
it uses the same coincident tweeter/midrange driver pioneered in the CS3.7
(see sidebar). As a result, almost all of the music and soundstage information
emerge from a single driver. Whether this is necessarily better than closely
spaced separate drivers is far from clear. There are many other speakers
including my reference Vandersteen Model 5 Carbons that achieve excellent
coherence with separate tweeters and midranges.
Nevertheless, what Thiel calls a “Coaxial Coincident Driver” not only
produces a remarkably integrated sound without tying the imaging and
soundstage to a location near the speaker or a given driver; it also has the
kind of unity and transparency that full-range ribbons and electrostatics are
praised for.
If you need a written description for techie (read “dork”) status in bragging
sessions with fellow audiophiles, Thiel states that, “the midrange and tweeter
diaphragms are formed of anodized aluminum. The unique ribbed geometry
of the midrange is engineered to deliver immense rigidity and clarity. An
uncharacteristically large diameter voice coil further braces the midrange
against the out-of-phase bending common in virtually all other loudspeaker
drivers. Tremendous control and high output capability is afforded by the
massive neodymium magnets powering the drivers. A very large ring magnet
THIEL drives the midrange, while ve neodymium magnets
drive the tweeter. As with all Thiel designed and built
drivers, this element utilizes a short-coil/long-gap
and copper stabilized motor system to ensure ultra-
low distortion and utter faithfulness to your music.”
Decades of listening to high-end speakers have
taught me that no single design approach is “best” or
“right.” It has also taught me, however, that the nest
speakers do largely live up to their hype.
In this case, the highs and midrange are truly
revealing without any tricks emphasizing the upper
midrange or presence areas, without creating any
apparent peaks in the highs, and without some sweet
spot in loudness or dynamic detail. This comes
across clearly with massed strings and demanding
solo passages with clarinet, trumpet, and ute—
instruments that can all sound hard or lose some
of their musical realism with the wrong driver and
speaker.
As is the case with the CS3.7 and all of today’s best
speakers, the CS2.7 is not forgiving, but it also does
not harden classical music or acoustic instruments.
It is exceptionally revealing of the detail in small
(very well recorded) jazz groups and demanding
rock recordings. It also gets voice consistently
right, avoiding any coloration of male voice in the
midrange and articial exaggeration of the upper
range of soprano voice or exaggeration of sibilants.
The Sound Stage, the Drivers, and the Cabinet
The radiation patterns of the Coaxial Coincident
Driver are also exceptionally well chosen, provided,
as the instruction manual states, that you keep the
speakers a reasonable distance away from sidewall
reections. The soundstage has very good coherence
from left to right, without gaps in the middle or
seeming to cut off to the left or right of the speakers.
The sound is consistent at any reasonable listening
height and loses very little upper-octave data and
imaging detail when you are standing. You can use an
unusually wide spread between the speakers without

Bandwidth: (–3dB) 35Hz–20kHz
Frequency response: 35Hz–20 kHz +/-2.5dB
Phase accuracy: +/-10°
Sensitivity: [email protected]/1m
Impedance: 4 ohms (2.4 ohms minimum
@160Hz)
Recommended power: 100—400 watts
Dimensions: 11" x 41" x 16.7"
Weight: 77 lbs.
Price: $7999
ThIEL LOudspEAkERs
1026 Nandino Blvd.
Lexington, KY 40511
[phone]
spECs & pRICING
Comment on this article at www.theabsolutesound.com

ThIEL Cs2.7
LOudspEAkER
losing center ll or exaggerating the size of solo instruments or small musical
groups, and depth is about as good as your room, speaker placement, and
listening material permit. I would recommend a carpeted oor over a wood
oor for listening to the CS2.7s at reasonable distances, though it was no
more vulnerable to oor reections than other oorstanding speakers of its
size, and less so than many.
The cabinet shape and design obviously play a role here as well. The front
bafe is not as sculptured or physically “time-aligned” as some other speaker
designs, but the cabinet is tapered at the top, relatively narrow (11"), and
relatively deep (16.7").
The cabinet is also exceptionally well-braced inside, and replaces the one-
inch-thick MDF cabinet walls in previous CS2 Series models with much
stronger curved plywood. It uses a 3"-thick front bafe to mount the drivers
and three solid 1"-thick internal braces, the top one of which seals the
coaxial enclosure from the bass chamber. No parallel surfaces exist anywhere
inside the cabinet, limiting the development of standing waves. It is not as
mass-damped as some competing speakers. The CS2.7 weighs only (“only?”)
77 pounds. However, its structure and an excellent spiking system make it
exceptionally vibration-free even at volumes above 90dB.
This almost certainly contributes to its exceptional midrange coherence,
as does what is clearly an exceptional crossover design that blends the treble
and midrange in the Coaxial Coincident Driver near seamlessly with the
lower midrange and bass.
The Bass
If there is any trade-off in cost and size, it lies in the deep bass, but the trade-
off is much smaller than I expected. The CS2.7 has only an 8" woofer, but it
is supported by an oval passive radiator. Thiel also claims that this woofer has
“distortion that is 1/10th that of typical woofers of this size. The magnetic
system is a Thiel proprietary short-coil/long-gap design whereby the voice
coil never exits the ultra-strong and stable magnetic eld set up inside the gap,
thus helping the amplier exert complete control over woofer motion. The
motor structure is stabilized by sheathing the center pole with a copper sleeve,
and by including a copper shorting-ring at the base of the back plate. The
rst of these measures dramatically reduce the inductance of the voice coil
thereby ensuring that the frequency response of the driver is not modulated
by the motion of the coil over the pole. The copper shorting ring guarantees
that the voice coil’s magnetic eld (again, analogous to the signal from the
amp) always reacts against a rigid and xed magnetic eld as set up by the
magnet.”
Once again, I can’t validate any given set of technical or design claims, but
Thiel has long produced some exceptional woofers and passive radiators,
and the CS2.7 did meet its specication of relatively at power output down
to nearly 35Hz in the best location in my listening room when I measured its
response using a mix of pink noise, bass warble tones, an AudioTools RTA
and FFT routine, and an iTestMic.
The bass was not only extended, it was also very smooth with the right
room location, and very tight and detailed. As is usually the case, it also
initially sounded a bit limited until I ran it through the usual range of bass
spectaculars and test tones. Unlike many other speakers, the fact that the
CS2.7's bass does not have some inherent coloration or peak means that the
deeper bass really is deep, rarely produces massive power, and does not have
some form of “overhang” on deep bass transients.
This is not the ideal speaker to try to blast away with the opening organ
tone in Thus Spake Zarathustra, Saint-Saëns Symphony No. 3, or the kind of
electronic music and rock whose main musical virtue seems to be vibrating
your house or driving the neighbors in your apartment
building to manslaughter. You won’t get the same bass
with Kodo drums or the Telarc bass drum records as
you do with the CS3.7s or the subwoofer built into
my Vandersteen Model 5 Carbons, and you won’t get
the ultimate impact of an exaggerated deep bass line
in a vocal like the Jennifer Warnes’ recording of “Way
Down Deep” (The Hunter).
But for the other 97% of music you will get very
extended bass that will take you to the real-world
limits of the bottom octaves and do so with minimal
coloration. I’d also suggest that for most audiophiles
who are not total bass freaks, this can actually be
better than speakers that do have subwoofer-like bass.
The last 5 or 10Hz often come at a major cost in
room interactions the moment they actually appear.
This can sound dramatic for a while, but resonance,
room vibrations, etc. become a pain in the, er, ear
once you really start listening for extended periods.
(There is also enough extraneous deep bass on some
recordings to produce low-level room-effects almost
without you realizing or expecting it.)
In short, the CS2.7 has real bass for real music for
real people in real listening rooms. It may choose
overall accuracy from the top treble to deep bass over
exaggerated output in the deepest bass, but life is a
series of tradeoffs and this is a case where I feel Thiel
has made all of the right ones.
Compatibility and Interfaces
As for compatibility, the CS2.7 has no rear-panel
adjustments and no options for bi-amping or bi-
wiring—not that it seems to need such features. It
was not sensitive to any given speaker cable I had, but
clearly revealed the differences between the ranges of
AudioQuest and Kimber Cables I use as references.
It also produced the sound I expect from a range of
solid-state and tube ampliers, including my reference
Pass Labs XA160.5s and the Cary CAD 120S II, and
did not seem an unusually demanding load.
The CS2.7’s bass performance did, however,
benet from higher-current ampliers with higher
damping factors. I’d recommend a solid-state amp
with at least 100 watts and high current capability. As
for listening levels, the CS2.7 was clean with music
to levels of 110dB, although I did not explore its
possible use a rock monitor driven consistently to
levels of 120dB or more—levels that have no place
in high-end listening where anyone cares about his
hearing.
I recommend front ends, preampliers, and
ampliers that are neutral to warm, and avoid ones
that are a bit hard or bright. As least with classical and
other acoustic music, the CS2.7’s timbre is neutral but
does not have any added warmth or roll-off in the
upper midrange and highs.

ThIEL Cs2.7
LOudspEAkER
The Coaxial Coincident Driver that is at the heart of the
CS2.7 is the identical unit used in the more expensive
CS3.7. It mounts an aluminum dome tweeter at the center
of a midrange diaphragm, ensuring that the output of
the drivers arrive at the listener’s ears at the same time,
no matter what the listening distance or height. Moreover,
there’s no electrical crossover between the midrange and
tweeter; the tweeter is high-pass filtered mechanically by the
suspension surrounding it. Removing crossover components
from the tweeter signal path has obvious advantages.
Jim Thiel told me several years ago at a CES how he had
conceptualized such a driver and its advantages. When
combined with first-order crossovers, the system would
be time and phase coherent at any listening angle, height,
or distance. Jim thought about the driver for more than
a year, putting off building a prototype because he
believed that he’d need to dedicate six months to a
year to perfecting the driver. He had other, more
pressing, design commitments that required
his attention.
One Saturday, he was overcome with
curiosity and made what he thought would be
the first of dozens and dozens of prototypes.
A couple of hours later, he had, to his great
astonishment, a working prototype that
performed nearly flawlessly. That driver
became the cornerstone of the Thiel line.
What’s remarkable is that Jim had worked
out, purely in his head, every last detail
of the driver’s construction needed to
make it perform as intended. The trial
and error took place in his imagination.
The ribbed aluminum midrange
diaphragm is equally innovative. Jim had been working
with different materials and cone shapes in an effort to
produce the stiffest material with the lowest mass. His
efforts paid off with about a 10% increase in stiffness and a
10% reduction in mass. Most loudspeaker designers would
have been thrilled by this advance and moved the driver
into production. But Jim told me that he asked himself
“Why settle for a 10% increase in stiffness? Why not try for
something with ten times the stiffness?” This inspiration
resulted in the radically different ribbed aluminum
midrange diaphragm of the coincident driver, as well as
the flat ribbed woofers in the CS3.7, which, according to
Thiel, are ten-times stiffer than conventional diaphragms.
—Robert harley
ThE ThIEL COAxIAL COINCIdENT dRIvER
I did, incidentally, get information from Thiel after
I completed the rst draft of this review that the 2.7s
take some 300 hours to break-in. This is one hell of a
long practical break-in time. I also found that break-
in did not make a dramatic difference or affect the
issue of timbre I’ve just discussed. The speakers did
seem to get even more transparent and have a slightly
higher degree of midrange warmth with break-in, but
there is no way to exactly compare a speaker with
the 200 hours I’d put on it when I began this review
versus the same speaker at 300 hours when I nished.
Acoustic memory simply is not that accurate.
I would strongly recommend you actually read the
instruction manual. It has unusually good speaker-
placement instructions, and it’s worth spending
serious time experimenting with placement. The Thiel
CS2.7 is not particularly placement-sensitive if kept at
a reasonable distance from room boundaries, but it is far too good to simply
plunk down casually without a long series of efforts to nd the best mix of
soundstage, bass, overall timbre, and detail in a given room. I’d also suggest
that if you do hear any initial coloration, you have a placement and not a
speaker problem.
Finally, the Thiel 2.7 works as well with digital room-compensation
systems as any speaker around, and worked very well with the very affordable
DSPeaker Anti-Mode 2.0 Dual Core unit [reviewed by Robert E. Greene in Issue
230]. But don’t push the Thiel 2.7s much below 30Hz, by using too much
bass boost in the lowest frequencies, or equalize them much above 200Hz,
unless you really need to. The speakers already have really good bass for
transducers their size, and trying to turn them into an electronic jukebox is
not going to improve their sound.
Summing Up
One hell of a speaker—and one your wife or partner is likely to be happy
to live with.