August 2010

201008_curvi_frontIn October, while wandering the Sound and Vision Expo in Manchester, in the UK, I came across a unique local company called Curvi-Hifi, a new hi-fi competitor that does not make your typical loudspeaker. Instead, they’ve gone a completely different route, one suggested by their name: they make curvy speakers. The curved shape instantly made me think of Bowers & Wilkins’ flagship Nautilus speaker. But unlike B&W, who took the path of complex configuration, Curvi-Hifi chose a simpler way. Curvi-Hifi’s first speaker is unlike anything on the market today.

Form and function

Curvi-Hifi’s Model 1 Version 2 ($8000 USD per pair) took company designer Christopher Liauw five years to develop. Its unique single-driver design features sophisticated tapered-line (aka transmission-line) bass loading. And one look at the Model 1’s curving shape will tell you that Curvi-Hifi takes its name literally. Its free-flowing contour is as unique as they come, and mimics to some degree the human form: someone sitting on the ground with his knees drawn up to his chest. This shape reportedly helps reduce internal reflections by dissipating the driver’s back-wave energy away from the driver. Those reflections could otherwise muddy the overall sound by being reflecting back into the driver, and through it to the listener. Curvi-Hifi makes a good point that such instruments as the trombone and tuba don’t have sharp internal edges (though some manufacturers do make tapered-line speakers with sharp internal corners).

Tapered-line speakers are also known for producing bass levels that far exceed their size. This applies to the Model 1 Version 2, which measures only 39.4"H x 6.5"W x 17.7"D. Its narrow front baffle, in particular, helps to avoid excessive diffraction, but the tapered line itself is 7.9’ long, and strategically damped to extend the speaker’s bass response down to 35Hz. The enclosures are made of birch plywood, hand-assembled so that the grain of each ply is perpendicular to the direction of vibrations from the driver. This supposedly helps rapidly dissipate energy and spread it out over a wide range of frequencies, thus minimizing structural resonances. This process is reportedly very labor intensive despite use of a CNC router.

The 4”-wide, wide-bandwidth midrange driver was designed by Ted Jordan, who has spent decades perfecting single-driver designs with full-range response. This one, with a cone of pressed aluminum, is said by Jordan to have high excursion capabilities. The key to its full-range response is the cone’s flare. According to Liauw, “The flare allows the driver surface to flex in a controlled (arguably quantized) manner that enables the effective radiating area of the driver to reduce with increasing frequency; the driver acts as a classic pistonic driver at bass frequencies, however at treble frequencies the controlled flexure results in only the central part of the driver emitting sound.” Liauw claims that this driver can produce frequencies up to 25kHz without help from a tweeter.

A single-driver speaker benefits by needing only a simple electrical network, as Liauw explained: “There is no electrical crossover in the Curvi -- the change in radiating area of the drive singlet is dependent on controlled flexure of the driver. There is, however, a filter that compensates for diffraction losses of upper bass output around the cabinet -- without this there would be a 6dB step-down in the frequency response in the upper bass region giving a rather thin and overly forward presentation. A lot of the development cost went into specification of this filter (Christien Ellis of CE Electroacoustics was of vital assistance here). It has to be stressed, however, that the network is very simple and is made up of the best quality components including a heatsink-mounted Vishay thick-film resistor that is hugely over-specified (in terms of power handling) for the application. This results in negligible thermal stress and a very transparent sound. At frequencies above around middle C, this resistor is practically the only element between the amplifier and the drive unit, and at frequencies below around middle C, a 1.25mm-thick copper wire inductor is practically the only element between the amplifier and the drive singlet.” In other words, not much gets in the way of the signal being fed the speaker by the amplifier.

When I received the Model 1 V2s, I was impressed by their fit’n’finish and the quality of their clear finish of satin acrylic lacquer, but their overall appearance is in the love-it-or-hate-it category. In addition to the above mentioned acoustic benefits, Liauw also aimed to boost wife-acceptance factor and change the commonly encountered loudspeaker aesthetic. Modest in size, each speaker weighs 53 pounds and can be moved about by a single person. All internal wiring is solid-core copper, connected to a pair of 4mm gold-plated sockets. You can’t use spades or bare wire -- you have to use banana plugs.

Assembly was straightforward. All I had to do was secure each speaker to its hefty plinth with four screws. Curvi provided high-quality spikes, which screwed into each plinth. At 83dB (2.83V) sensitivity, together with a minimum impedance of 5 ohms at 20Hz (average impedance 8 ohms), the Model 1 does not present a particularly difficult load in terms of current demand, but it does require relatively high-voltage drive. Amplifiers of fairly generous power are therefore necessary to drive these speakers to their full potential. Single-ended-triode amplifiers with power output below 30Wpc will not be suitable for the Curvi if reasonable sound levels are required.


For this review, my reference system consisted of an Oppo BDP-83 universal Blu-ray player hooked up to a Peachtree Audio Nova integrated amplifier. The unbalanced interconnects were made by Artisan Silver Cables and Monster Cable. I also used a Hewlett-Packard Pavilion notebook computer to stream digital files via Kimber USB cords from a 500GB Western Digital external hard drive to the Peachtree’s internal DAC. The amplifier was hooked up to the Curvi Model 1 V2s via Monster MCX-2s speaker cables. Power was run through a Lindy six-outlet power conditioner.


201008_curvi_rearI didn’t have to wait long to sit down and enjoy the Curvi-Hifi Model 1 V2s; by the time they reached me, they’d already been broken-in. My initial impression was that Curvi’s simple approach to the electrical and acoustical design of the Model 1 V2s resulted in very pure sound. This made for a very involving experience with a natural musicality -- I felt as if more of the music was getting through to me unaltered by the speakers. This was unlike my experience of speakers that, by comparison, can make music sound processed; in other words, with the essence of the music removed.

A key technical benefit of the single-driver principle espoused by Curvi-Hifi is that there is no mismatch of the arrival times of the outputs of multiple drivers. Perhaps this is why the sound was so coherent, from the top to the bottom of the audioband. This coherence helped create a soundstage of considerable width and height. That stage’s depth was just OK in my room -- I’ve heard speakers that created more front-to-back layering. On the other hand, the Model 1 V2s’ imaging was exceptional. When I listened to pianist Radu Lupu, Uri Segal, and the English Chamber Orchestra perform the Andante of Mozart’s Piano Concerto 21, from Essential Mozart (CD, Decca 468517), each of the performers were portrayed in their own carved-out spaces on the soundstage, with air and space evident around each. The soundstage extended just slightly past the outside edges of the speakers, when the recording contained such information. These qualities always added to the realism of the performance, and when the recording called for a wide stage, the Model 1s were able to oblige.

Listening to “Time in a Bottle,” from Jim Croce’s Classic Hits (CD, Rhino/WEA 73890), I was presented with a clear, open midrange, and Croce’s voice was natural and warm. The Model 1 V2 leaned toward the warmer side of the tonal spectrum, though it was never too warm in a euphonic sense. It remained quite neutral overall, but had a warm sound in the mids that helped make voices sound more lifelike. Croce’s guitar sounded natural, with accurate timbre. The leading edges of notes were well defined, and the decaying sound of the notes seemed to go on forever -- again, if the recording contained such information.

I could hear a lot of microlevel detail through the Model 1 V2s -- low-level guitar notes were prominently displayed in the mix. This caught me a little off guard, and seemed quite a feat for a single-driver design; after all, microlevel detail is usually associated with dedicated tweeters. The Model 1’s single driver exceeded my expectations in regard to high-frequency response -- Croce’s subtle striking of his guitar’s strings was very much evident. However, the highs didn’t extend as far as with speakers that have extended, dedicated tweeters. Through the Curvi, very high frequencies sounded subdued in comparison to speakers that have greater HF extension. This didn’t dampen my enjoyment of the Model 1 V2s, but it did affect the speaker’s air and sparkle. The top end wasn’t as crisp as I’ve heard from some speakers with high-quality tweeters.

To put the Model 1 V2’s bass talent through its paces, I played “One,” from Metallica’s And Justice for All (CD, Elektra 60812). This is one of my all-time favorite songs, but its bass can overwhelm inferior speakers. This wasn’t the case with the Curvi, whose bass definition was spot on. There was solid weight, and enough power to make “One” come alive. I could hear good delineation of detail in the sound of the drums: As Lars Ulrich whacked his kit, I could easily concentrate on the tones of the snare and kick drums. The tonal character of each drum stroke was exceptionally accurate. Many speakers can produce generous bass, but only a small number can provide ample bass while delineating different bass notes. The Model 1 V2s were exceptionally good at this, and it anchored their reproduction of “One.” When Ulrich doubled-up on the kick drum and the song’s pace increased, I couldn’t help but drum along in my seat -- the bass definition was that good.

The Curvi didn’t reach the very lowest depths of a good subwoofer, but I believe its bass depth would be enough to satisfy most headbangers. Equally impressive was that the bass didn’t lose its composure when the song got faster and more complex. I could clearly hear Kirk Hammett’s guitar solo among the bombardment of the other two guitars and drums. This entire passage had weight, energy, sharp attack, and great rhythm, and the bass was always articulate.


It seemed only fair to compare the Model 1 with another transmission-line speaker, and recently I’d received for review a pair of PMC’s new Fact 8s. Unlike the Model 1, however, the Fact 8 is a two-way design with three drivers: two mid/bass cones and a soft-dome tweeter.

Perhaps not surprisingly, the two speakers sounded most similar in the bass; both had well-defined, articulate low ends that were as transparent as those of any speakers I’ve had in my listening room. I could clearly delineate the differences among different assortments of drums -- there was never a hint of “one-note bass,” and notes in the bottom end were reproduced with quickness and snap. There was a tonal correctness to the bass that I have rarely heard outside the upper echelon of high-end speakers.

I also heard similarities in the midranges of these two speakers. Both the Curvi and the PMC were pure and transparent across the midrange, though the PMC had a smidgen more openness overall in the midband. The Model 1 V2 lacked energy in the upper midrange and highs compared with the Fact 8. In the Curvi’s defense, it did extend higher than other single-driver designs I’ve heard, but the Fact 8 had better extension up top. The PMC’s treble was more open, with a better sense of transparency. Everything from trumpets and electric guitars to pianos and saxophones sounded crisper and cleaner through the Fact 8s.


I thoroughly enjoyed the time I spent with the Curvi-Hifi Model 1 Version 2. It is a musically engaging loudspeaker whose designer has taken a road less traveled, creating deep bass with only a single driver in a fairly compact and uniquely styled enclosure. For this, Christopher Liauw deserves a lot of credit.

The Model 1 Version 2 has a naturally warm, open midrange that remains transparent, and its transmission-line-loaded bass aided in creating some of the deepest, most expressive bass I have heard from a speaker of this size. The downside is that the Model 1 V2’s highs weren’t as airy as those of speakers with a dedicated tweeter. But what the Model 1 lacked in high-frequency extension it more than made up for in audioband-wide purity and coherence. Perhaps because these speakers lack a complex crossover network, I had an overall feeling that music was flowing through them unaltered.

The Curvi-Hifi Model 1 Version 2 is a must-listen for any audio enthusiast who values simple electro-acoustic and mechanical design as well as a free-flowing physical form that also happens to make excellent sound.

. . . Kevin Gallucci

Curvi-Hifi Model 1 Version 2 Loudspeakers
Price: $8000 USD per pair.
Warranty: Five years parts and labor.

Flat 58, Granby House
61 Granby Row
M1 7AR
United Kingdom
Phone: +44 (0)161-247-3325, +44 (0)777 276 6465


Ikon Audio Consultants
Phone:  +44 (0)1473 217 853, +44 (0)7956 476299