Thiel CS6 Loudspeaker
While I have auditioned other Thiel designs since then, the larger speakers worked optimally in rooms bigger than mine, and the smaller speakers didn't achieve such a good across-the-board balance. Then, at HI-FI '96 in New York, I spent some time auditioning pre-production samples of the Thiel CS6 in the Innovative Audio room. Yes, this speaker was significantly more expensive than the CS2 2, but it both promised very much more and offered the chance to sound well balanced in smaller rooms like mine. Accordingly, once the CS6 was in production, I asked Thiel for a pair of review samples.
Designer Jim Thiel gives much of the background to the design of this speaker in my interview with him elsewhere in this issue. To summarize, the CS6 is a reasonably large (50" tall) floorstanding speaker combining a 10" aluminum-cone woofer with a 12" passive radiator and a coaxial midrange/treble unit. Unlike earlier Thiel designs, all three of the CS6's drive-units are made in-house, and much attention has been paid to reducing drive-unit nonlinearity. The coaxial unit is particularly noteworthy, as it places a 1" aluminum-dome tweeter on the center pole-piece of the 4" midrange unit. This unit's cone appears to have a very shallow flare, but it is actually a composite: a cast Styrofoam piece sandwiched by anodized aluminum cones with different profiles. This gives the diaphragm both an optimal shape for the tweeter to "see," and the combination of stiffness and damping it needs to move cone resonances out of harm's way.
As in all Thiel "Coherent Source" designs, the crossover is acoustic first-order, and the front baffle, which is cast from concrete, slopes back to bring the acoustic centers of the drive-units into time alignment on the intended listening axis. The speaker can only be single-wired, via a pair of terminal posts on the speaker's base. Also like all Thiel speakers, the CS6 is beautifully finished, with "book-matched" veneers used on each pair. (The veneers are from farmed hardwoods.) A metal frame supports a black grillecloth; when this is in position, there are no acoustic obstructions in the radiation paths of the drive-units. Spikes are supplied to couple the speaker to the floor beneath its owner's carpet.
The speakers I reviewed were the second pair of CS6es we received. As is Stereophile's policy, we allowed the manufacturer to visit when we set up the first pair, so that they could ensure that we were listening to representative samples. The first pair were set up first in the Stereophile listening room, then in Larry Archibald's room. In both rooms, designer Jim Thiel felt something was not right about the sound and asked if he could submit a second pair. We agreed, provided—as is also our policy—that the questionable performance of the first pair would still be mentioned in the review. My formal review auditioning exclusively concerned the second samples (footnote 1).
My first auditioning of the new samples took place in the Stereophile room. The CS6's balance was warm, smooth, and grain-free, coupled with excellent low-bass response, pinpoint imaging, good soundstage depth, and superb retrieval of recorded detail. Other than ultimate loudness capability, I felt the CS6 to be better balanced overall than the original version of the Thiel CS7, which I had auditioned in the same room a couple of years before (footnote 2). These samples did not sound vividly etched in the mid-treble as had the first pair, yet they offered the same transparent view into the music.
Footnote 1: Readers who have doubts about this policy should note that we are very concerned that we review samples that are representative of what people can actually audition at dealers. We are careful not to offer comments on sound quality to visiting manufacturers, but we do pay attention to what they say. If they are comfortable about the way their products sound in the reviewer's room, then we assume that the product is sounding the way it is meant to sound.
Footnote 2: Wes Phillips reported on these samples of the CS7 in January 1996 (Vol.19 No.1), while Tom Norton reviewed an earlier pair of CS7s in October '95 (Vol.18 No.10).