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THIEL CS3.7 loudspeaker review

A bold design yields remarkably transparent sound

Based in Lexington, Kentucky, THIEL Audio has been building high-performance loudspeakers since 1977. Audiophiles around the world know and respect THIEL for their unswerving pursuit of accurate sound reproduction. Their small family of speakers combines rigorous engineering and meticulous craftsmanship inside and out.

THIEL CS3.7

THIEL CS3.7

The CS3.7, a 3-way full-range floorstanding speaker that replaces the CS3.6, one of the most highly regarded and best-selling high-end loudspeakers of the past 15 years. It was my good fortune to spend two weeks evaluating the CS3.7s in my 2-channel home system. I wish I could have kept them for two months.

Getting started

The CS3.7s replaced a combo of ACI's Sapphire III stand-mounted monitors and Titan powered subwoofer, which I've owned for over 10 years. Standing a few inches under four feet tall and tipping the scales at 91 pounds apiece, the CS3.7s are much larger than the Sapphires. Still, I think few people shopping for true full-range speakers would find their size imposing in a medium-sized or larger room. This particular pair wore a beautiful natural cherry finish.

Placement can make or break any speaker's performance, so I started off playing it safe by positioning the CS3.7s exactly where my Sapphires had resided in my basement listening room. That put them about 8 feet apart, 8 feet from the "sweet spot" in the center of the sofa, and a couple of feet out from the front and side walls. The speakers were "toed in" a bit (angled inward toward the sweet spot). Since the floor is carpeted, I installed the four heavy-duty screw-in floor spikes supplied with each speaker.

This pair of CS3.7s were among the very first produced, with serial numbers 005 and 006. THIEL recommended giving them a minimum of 100 hours of "break-in" before doing any serious listening. Makers of high-quality loudspeakers generally recommend a break-in period ranging from 50 to 400 hours to allow the driver diaphragms to limber up for optimum performance. After connecting them to my system (see details here), I dropped a CD in the tray and set the player on infinite repeat. Since my time with the CS3.7s was limited, I only gave them 20 hours of break-in before first sitting down to listen.

Initial listening impressions

I've been interested in THIEL speakers for years, partly because they consistently receive rave reviews, but also because I've always considered myself a disciple of the "lean and clean" school of music reproduction as opposed to "lush and romantic." I've tried to assemble a system that digs out musical details and presents them with depth and dimensionality. Euphonic sound that "warms" or "pretties up" the music isn't for me; I want to hear everything, warts and all. And that's exactly what the CS3.7s delivered.

Rather than dragging out test CDs or old favorites, I began by playing some discs that had been in heavy rotation during the previous few months. The CS3.7s' sound immediately struck me as detailed, clean, and extraordinarily revealing, with very low distortion. On track after track I heard details that I'd never noticed before.

This open, transparent quality gave me the sense that I was hearing the recording and not the speaker. The CS3.7s didn't impose any perceptible sonic signature on the music the way some speakers do. High-quality discs sounded spectacular, but the limitations of some so-so recordings were more clearly on display than when heard through my Sapphires. An example is the 4-Track Recording Session CD by the Zimbabwean dance band The Green Arrows. This is not a polished recording to begin with, but the stinging electric guitar leads seemed a tad edgier through the THIELs. Of course, the speakers had barely begun the break-in process.

The speakers' sound continued to improve almost on a daily basis. I'm sure part of that perception resulted simply from me getting used to the THIELs' presentation. Several friends and colleagues came over on a few evenings — everyone I mentioned the CS3.7s to wanted to check them out. You'll find more about those sessions toward the end of this article, but before relaying any more listening impressions, I want to touch on the technological and design aspects that distinguish these speakers.

The inside story

THIEL Audio is named after the company's co-founder and chief product developer, Jim Thiel. Jim visited Crutchfield to lend a hand with the training sessions for our Sales and Tech Advisors, and he offered a mini-seminar on loudspeaker design. Although THIEL speakers are classified as "box" speakers, Jim's out-of-the-box thinking is the key to their exceptional performance.

The THIEL approach to speaker design and construction focuses considerable effort and expense on increasing each component's strength and stiffness while reducing its susceptibility to vibrations. That applies to the cabinet, drivers — everything.

THIEL Audio CS3.7 Loudspeaker Seen from above, the CS3.7's front baffle is sloped to provide time coherence between the woofer and the mid/tweeter array.

Rounded cabinet contours, an aluminum cap piece, and a machined-aluminum front baffle are among the design features that set the CS3.7 apart from previous THIEL speakers. The super-rigid cabinet sides are formed from 15 layers of hardwood laminated together into a curved shape under high pressure. The sloping front baffle provides time coherence between the woofer and the mid/tweeter array, which preserves music's timing information, ensuring that all of the music's spatial cues are reproduced naturally.

Two custom-designed "wave-shaped" 10" aluminum drivers occupy the bottom half of the speaker. The upper unit is a woofer while the lower one is a bass-enhancing passive radiator. The passive radiator's job is similar to that of the port in a conventional bass-reflex speaker — it allows low-frequency energy inside the cabinet to pass to the outside, but in a very controlled manner.

THIEL Audio CS3.7 Loudspeaker The mid/tweeter array consists of a 1" aluminum dome tweeter coaxially mounted with a 4-1/2" wave-shaped aluminum midrange.

The newly designed 4-1/2" aluminum midrange driver has ridges radiating from the center to the outer edge. The ridges increase strength and stiffness, extending the driver's operating range out to an astonishing 20 kHz. The midrange is actually crossed over to the tweeter at only 3 kHz, which means the driver has plenty of headroom for maximum accuracy. According to Jim Thiel, the midrange's extended response is a key factor in the CS3.7's exceptional midrange purity and delicacy.

THIEL Audio CS3.7 Loudspeaker THIEL's complex crossovers are the gradual-transition "first-order" type which provide complete accuracy of signal amplitude, phase, time, and energy.

The CS3.7s use an elaborate crossover network employing "first-order" filters. This type has a more gradual roll-off compared to other filter designs, and it requires higher-quality drivers that can cleanly and accurately reproduce an extended frequency range. First-order filters have less of a tendency to distort the musical waveform and are especially prized for their phase accuracy, which can result in better imaging than speakers employing crossovers with steeper slopes. (I've owned speakers with first-order filters for nearly 20 years, and can attest to their imaging and soundstaging prowess.)

While many high-end speakers provide dual sets of terminals for "bi-amping" or "bi-wiring," THIEL speakers do not. Jim Thiel's sophisticated crossover networks do much more than act as "traffic cops" directing the right frequencies to the right drivers. They help to optimize energy response and tonal neutrality, and Jim doesn't want any outside crossover or unnecessary cabling compromising his work.

Tweaking and "seasoning" the sound

My colleague Dave spent a lot of time at my place while the CS3.7s were in residence, helping me dial in the best sound. One evening about midway through the evaluation period, we got serious and used a measuring tape to precisely adjust the speakers' placement so they were exactly the same distance from the back and side walls, to within a fraction of an inch. After listening a little more, we also decided that the toe-in might not be optimal, so we shifted the speakers so they fired straight ahead.

Our adjustments reduced but didn't totally eliminate the sound's sometimes edgy tendencies. At that point, we were joined by another longtime audiophile and former Crutchfielder, Mike W. Mike was quite impressed by the CS3.7s, and was shocked when he learned they are a 3-way design. He described the sound as more seamless and coherent than he'd ever heard from a 3-way speaker. Mike knows quite a lot about speaker design and even built a few many years ago.

Mike is also a big fan of tube electronics and had brought along his Scott Nixon TubeDac, a physically tiny digital-to-analog converter. The TubeDac added just the right touch of warmth to CD playback, making discs that had sounded a little steely much more listenable. The sound didn't go all soft-focus, either. We were hearing tons of detail and a large 3-dimensional soundstage — the only area lacking compared to my DAC was deep bass extension. So, when Mike offered to let me borrow the TubeDac for the review period, he didn't have to ask twice.

Glimpses of greatness

A few days later, I hosted a listening session and invited the other home audio/video writers over to check out the CS3.7s. Not surprisingly, this was one of the best-attended sessions ever. As always, everyone brought some of his/her favorite music to share.

The more experienced listeners were struck, as I was, by the THIELs' seamless top-to-bottom response. I've put a fair amount of time and effort into optimizing the transition between my Sapphires and subwoofer, but the CS3.7s showed me that I still have a ways to go.

Imaging and soundstaging were consistently excellent. Sound extended well beyond the speaker cabinets when the program material called for it. Overall image height was a bit taller than with my speakers. The compact 2-way Sapphires do a superb "disappearing act" — floating a 3-dimensional image that seems completely independent of the speakers. This is a much more difficult trick for large floorstanding speakers to pull off, but the CS3.7s succeeded admirably. Where the THIELs really shone was on classical, jazz, and other acoustic-oriented music.

The THIELs' bass was always tight and musical, never overbearing or boomy. But it didn't match the extension and impact of my powered subwoofer (few full-range speakers can keep up with a good sub). For example, on Mickey Hart's Supralingua CD there are deep bass pulses where my subwoofer launches a pressure wave you feel as well as hear. The CS3.7s stayed tight as far down as they could go, but they'd eventually fade out while the sub just kept going.

Don't get me wrong — all of the listeners thought the bass sounded great and some thought I'd left my subwoofer on. Later, when I checked the CS3.7s' bass response using a test disc, I found that in my room the THIELs' output was rock-solid down to 40 Hz. By 35 Hz, it had rolled off audibly, and below 30 Hz there was very little going on. Listeners who prefer that full-body, subterranean bass impact should consider one of THIEL's Smart Sub powered subwoofers.

My general feeling has been that if an audio component makes recordings sound more different than alike, it's probably doing something right. The CS3.7s did this to a greater extent than any speakers I've lived with. I mentioned earlier that I was frequently hearing details I'd never noticed before. A good example is the SACD version of Bela Fleck's classic, Drive. Over the CS3.7s I heard the sound of picks striking strings as these amazing players traded blistering bluegrass solos. Just as a singer's intake of breath becomes part of his/her phrasing, the sound of the picks added to the drive of the music.

This remarkable transparency cuts both ways, however. Because they're so revealing, the CS3.7s are very sensitive to equipment, room, and recordings. If you try to use these speakers with ordinary sources or amplification, you may miss much of what these thoroughbreds can do. It's similar to the way new owners of high-definition TVs are sometimes disappointed by the way standard satellite or cable TV fare looks on their big, razor-sharp screen.

Different room, different story

There were times during the evaluation period when I wondered if the CS3.7s were simply too much speaker for my room. The dimensions are 13.5 feet wide, 24 feet long, and a hair under 8 feet tall. My suspicions were confirmed upon hearing the CS3.7s in Crutchfield's large acoustically treated training room, which is quite a bit longer and wider than my listening room, with a much higher ceiling. Sound during the training sessions was much bigger and more relaxed, and bass extension was far superior.

Room issues aside, it was a pretty fair comparison because we used PS Audio electronics to drive the THIELS during the training sessions, and I use PS Audio gear at home. Several folks who attended the training said it was absolutely the best sound they'd ever heard in that room. I've attended hundreds of sessions down there and I completely agree.

What I learned

Thiel's new CS3.7s are hugely impressive speakers. Matched with high-quality source components and amplification, these speakers can deliver a deeply immersive listening experience. Their sound is unbelievably transparent and revealing; you hear deeper into the mix.

I ended up respecting the CS3.7s more than loving them, but I honestly feel it's due more to the limitations of my setup and room than to the THIELs themselves. Because the CS3.7s are several inches taller than my speakers, and were positioned firing straight ahead rather than toed in, they interacted more with the room than my Sapphires, in ways that hurt the sound.

I understand now why reviewers for high-end audio journals like Stereophile and The Absolute Sound typically keep speakers under review for several months. At this level, we've gone beyond simply doing the basic job of a loudspeaker and have moved into rarefied territory where a component performs more like a precision instrument. Which is precisely the performance many demanding audiophiles are searching for.

After spending just two weeks with CS3.7s, I'm convinced that I failed to take their full measure. The sound continued to improve right up to when I had to box 'em up and bring 'em back. I'm confident they would sound better in a month, and better still after six months. And I know I could have coaxed even better sound from them given more time to experiment with ancillary components.

Anyone shopping for speakers in this price range should make every effort to hear the THIEL CS3.7s.

More listening impressions

"There were numerous moments that blew me away, but the most striking moment came during Charles Mingus' song "Wednesday Night Prayer Meeting" off the Blues and Roots disc. It was so real — with my eyes closed all of a sudden it sounded like the saxophone was right there in the room with us. That piece is packed with movement and sounds of all kinds, and the THIELs revealed ridiculously subtle details, every nuance of every attack and decay — all the stuff that makes for a sublime listening experience." — Mike

On the Liz Carroll/John Doyle cut, I was especially struck by the moments where the guitar and fiddle halt briefly before continuing with renewed vigor. The THIELs, driven by the powerful PS Audio amp, nailed that effect by stopping and starting on a dime. In concert, that tactic heightens the emotional impact, but listening at home, it rarely packs the same punch. Last night was different — I felt the same jolt of intensity that I felt during a live session by the same musicians. — Julie

There were a couple of points where I was really impressed. The Buena Vista Social Club track ("Chan Chan") sounded really warm and detailed — I definitely heard things I'd never heard before, especially during the instrumental part towards then end. I could pick out little riffs from individual instruments I hadn't noticed before. Hot Chip's "The Warning" sounded so spot on — the rhythm was tight and precise, and the highs were absolutely crystal clear. — Amanda

Associated equipment

  • PS Audio PCA-2 stereo preamp
  • PS Audio GCA-500 stereo power amp
  • Denon DVD-3910 DVD player (SACD playback and CD transport)
  • Electronic Visionary Systems Millennium 2 DAC
  • Scott Nixon TubeDac (borrowed)
  • Music Hall MMF-7 turntable
  • Monolithic Audio phono preamp
  • PS Audio speaker cables; PS Audio and Ven Haus Audio interconnects and power cables
  • Panamax 5500 line conditioner

Music selections

  • Bach: Goldberg Variations (Transcriptions for Strings)
  • Mickey Hart Supralingua
  • Liz Carroll & John Doyle In Play
  • Charles Mingus Blues and Roots
  • The Decembrists The Crane Wife
  • Freyda & Acoustic Atta Tude Midnight at Cabell Hall
  • Radio Tarifa Temporal
  • The Ginn Sisters Blood Oranges
  • Hot Chip The Warning

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