Thiel CS1.5 loudspeaker Page 4
Soundstage width and depth are magnificent. Following the advice of Thiel's David Gordon, I placed the speakers about 9' apart, and found his suggestion spot on. Start with the speakers far apart, and see if you're unsatisfied with the soundstage width and the center fill. My advice is to place these speakers reasonably close to the back wall and as far apart as you can get them (without the distances from the side and rear walls being exactly the same). Toe them in about 10-15 degrees.
The sound is incredibly clear, clean, and crisp—almost like a good pair of electrostatics. Thiel speakers have a reputation for excellent clarity, but the clarity of the CS1.5s is astonishing—even by Thiel standards. Also, the resolution of low-level detail is—I hate to keep using words like this, because raving doesn't come naturally—well, breathtaking. The resolution is detailed and delicate.
Moreover, the positioning of instrumentalists and soloists laterally across the soundstage is both precise and palpable. With Broadway shows and opera recordings, I can hear precisely where the performers are located on stage—if a performer moves by a foot or two, I can hear it (assuming the information is on the recording).
I find that lateral positioning is often problematic with many loudspeakers—especially panel jobs. Even when I get a satisfying sense of spaciousness, I still get the feeling of left and right speakers. Set the CS1.5s up right, and they'll disappear.
I think the CS1.5 is such a success because it uses the new midrange drive-unit that Jim Thiel designed for the more expensive CS7 (footnote 3)—Jim liked this unit so much that he decided to use it as the CS1.5's woofer. He describes the woofer as a "cost-no-object" project, and it's easy to understand why.
This 6" driver has a cast magnesium chassis—rarely found in drivers used in $2000/pair speakers. To eliminate cone breakup and unwanted energy storage, the diaphragm is aluminum. The most important feature, though, is that the driver utilizes a short coil and a long gap between the coil and the magnet.
Most speaker drivers use a long voice-coil with a relatively short magnetic gap. The problem with this is that such drivers grow less linear as the drive level increases—crank 'em up and the speakers distort. The CS1.5's short voice-coil/wide gap design is more expensive because, for one thing, you need bigger, more powerful magnets. The magnetic field remains relatively linear over the full length of the voice-coil's excursion.
This is why the CS1.5 may be such a breakthrough speaker at its price point. The short coil/wide gap results in neutral timbre and superb resolution of detail. Combine this with an aluminum diaphragm, and you have performance which rivals that of any electrostatic.
The tweeter is a 1" metal dome, and the speaker has a passive radiator, which is said to eliminate bass-port resonances and noises, such as chuffing and farting. There's nothing emanating from this speaker's derrière. "Stop it, Sam." (Marina again, worried that Val will translate another of my articles and send it to the tube-amp factory in Minsk.)
Thiel recommends you run the CS1.5s with a minimum amplifier power of 50-150Wpc, but take this as a general guideline, not as something engraved in stone. I used several amps in the 50-100Wpc range before settling on my 20Wpc Audion Silver Nights, which drive the speakers quite well. The bass could be a little deeper and tighter, but not much. With the CS1.5, the Silver Nights give a wonderful sense of air and spaciousness, coupled with that truth of timbre that's so characteristic of triode amplifiers, especially those using the 300B output tube. (By the way, VAC has the new Renaissance 30 amplifier, which retails for $4990 and is rated at 30Wpc using two 300B tubes per side; this might be an excellent amp to use with the CS1.5s. These 300B jobs and their replacement tubes rarely come cheap.)
Jim Thiel wasn't surprised that I got good results from the Silver Nights. The CS1.5 is basically a 4 ohm speaker—use it off the 4 ohm tap of your tube amp. Jim describes the load as "very resistive," meaning that the resistance is virtually a flat 4 ohms, not rising above 5 ohms or dropping below 3 ohms. "Amplifiers love a resistive load," said Jim. "It effectively increases the power of the amp. This is why some people think amps sound better into a resistive load."
I'm not sure how the CS1.5 would do with tube amps that produce mushy bass. (You'd probably get mushy bass.) You might instead want to turn to a well-chosen solid-state model.
Footnote 3: Price not set at press time.