Thiel CS1.5 Floor standing speakers
The current trend in loudspeakers is to make them as small as possible, hide them in walls, or have a system that consists of small left and right satellites with a separate woofer or subwoofer. There are, however, practical limits to how small you can make a really good speaker and to how well you can hide one. Trying to get full-range performance from a small speaker always means a sacrifice in bass capability. Building a speaker into a wall virtually always means a major sacrifice in soundstage performance and often in frequency response as well. Using a separate woofer or subwoofer almost always means audible problems in the crossover region- unless the crossover frequency is well below 100 Hz.
Thiel takes a different approach in the CS1.5, a full-range floor-standing loudspeaker clearly designed to be kept several feet away from the side and rear walls. At the same time, it is relatively compact, measuring 8-1/2 inches wide, 11 inches deep, and 33 inches high. Its low visual profile and sloping front, together with the fact that it is deeper than it is wide, make it seem smaller than it is.
I'd much rather live with the visual image of a small floor-standing loudspeaker like this Thiel than with the more obtrusive look of a box speaker placed on many of the stands I've seen recently. And while the Thiel CS1.5 is, at $1,990 per pair, not inexpensive, a true price comparison with small shoebox-sized speakers must include the cost of stands. You will never get top performance by locating any loudspeaker worthy of the name on a piece of furniture or in a bookshelf.
The Thiel's cabinet is very well finished, with an attractive grille that does not have to be removed for best performance. The cabinet walls are an inch thick and have extensive internal bracing to reduce vibration. The baffle is sloped to provide proper phase alignment and transient information and, like that of most other high-quality speakers, has smooth, round edges to reduce energy diffraction and provide a more open sound.
The tweeter is a 1-inch metal dome with a large magnet, vented pole piece, and reinforced rear chamber for low resonant frequency and wide bandwidth. The 6-1/2-inch woofer uses a rigid aluminum diaphragm to eliminate cone break-up and energy storage; a short-coil, long-gap magnet to reduce distortion, and a copper pole piece to maintain a stable magnetic field. The woofer has two magnets with a total weight of more than 2.4 pounds; the second magnet has reversed polarity to reduce the stray magnetic field of the loudspeaker and allows the CS1.5 to be positioned nearer the TV in an audio/video system. There is a passive bass radiator to lower bass resonance and eliminate possible vent noise. The 18-element, first-order crossover is phase-accurate and uses polypropylene capacitors and low-oxygen, air-core inductors.
Frequency response is ±3 dB from 42 Hz to 22 kHz. Thiel's detailed frequency response curves exhibit exceptionally smooth performance from 50 Hz to 2 kHz and only minor irregularities up to beyond 20 kHz. The 30° off-axis response is very close to the main-axis response and is only about 5 dB down at 20 kHz. Time and step responses are also very good, revealing exceptionally fast, clean response, with excellent phase coherence.
The only caution I would give about the specs is that the speaker's rated 4-ohm impedance drops to as low as 3 ohms. I did not find that the CS1.5 posed any problems for well-designed power amplifiers, and it did not seem to be a difficult load. There are, however, a number of receivers and a few power amps that don't perform well with low-impedance speakers.
The first things that struck me about the sound of the Thiel were its smoothness and speed. The term "monitor" is much overworked, but it is perhaps the best term to apply to the CS1.5. There is very little coloration in the midrange and no roll-off or exaggeration in the treble. While there do seem to be some small irregularities in the response somewhere around 4 kHz, I did not hear any that significantly colored voice, piano, or guitar.
Furthermore, the Thiel has a great deal of transient detail and resolving power. It may not match the best ribbon speakers in this regard, but it is the equal of many electrostatics and is much better in reproducing subtle, low-level musical and sound-stage detail than most of the small to moderate-sized monitors that I have auditioned. The CS1.5 also is as fast and detailed in the upper bass and lower midrange as it is in the upper midrange and treble-outstanding performance in this price range.
The Thiel CS1.5 does not seem to favor one kind of music or recording over another. These speakers simply give you what is on your recordings, without coloring or romanticizing-a naturalness that is particularly welcome on voice and strings but also comes through quite clearly on solo piano and percussion sounds such as cymbal and snare drum.
This accuracy in frequency and detail is matched by good soundstage performance. The CS1.5 does not dramatize the soundstage or produce a large and open soundstage with every recording. Depth and width are natural rather than "exciting." If anything, the soundstage is just a bit smaller than normal. The apparent listening position is a bit forward, and there is a feeling of being slightly above the soundstage.
The CS1.5 does a very good job of making naturally recorded stereo music sound natural. Many smaller monitors impose a fixed soundstage on the music they reproduce; for good or bad, they become the concert hall and alter the music accordingly. The soundstage of the Thiel may initially seem understated by comparison, but what you hear is the recording and not the speaker. Imaging is equally natural. Some small stand-mounted monitors almost "etch" the imaging, providing a more defined image for each instrument than is actually on the recording. The CS1.5s do not artificially fix the image in place, and they do not alter its size.
The Thiel's bass, however, is not deep or powerful by high-end standards. This may present problems in large rooms or where bass power is a key consideration. The CS1.5 certainly has as much or more bass than most speakers its size, and it does produce considerable power to below 50 Hz, if not much below 45 Hz. It has exceptional bass detail within its range, and its bass response rolls off very smoothly, without the boost or hump that many small and medium-sized monitors exhibit just above their bass cutoff frequency.
Coupled to the speaker's flat and extended treble, this lack of added bass warmth or boost can make the CS1.5 seem a bit lean and lacking in bass energy. This is likely if you place the cabinet 3 feet from a rear wall and 5 feet from a side wall, as called for in Thiel's instructions. Try the CS1.5s in a medium-sized room, and place them closer to the rear wall for a touch of room reinforcement. Also, use the spiked feet and avoid an amplifier that is dry or lean.
The CS1.5 is capable of excellent dynamics and a surprising amount of output, bettering many speakers in these respects. Fine for classical, jazz, and most rock, it's a speaker for those who enjoy music and accuracy more than sheer power.
The Thiel CS1.5 is an excellent example of how far medium-sized monitors have come in the last few years. It may not have the deep bass or dynamic range of its more expensive siblings-and if I had the money, I would prefer the Thiel CS3.6. That speaker, though, costs almost twice as much. What the CS1.5 does provide is an excellent soundstage and upper bass, midrange, and treble I'd associate with speakers costing a great deal more. With the right placement, the CS1.5 is an outstanding buy, one that makes true high-end sound affordable.
