The Music of the Spheres
Further thoughts on the Anthony Gallo Acoustics Nucleus Solo Loudspeakers
Little remains to be said about the Nucleus Solo's enclosure, other than to re-emphasize that its design goes a long way to eliminating the deleterious effects of both internal standing waves and external cabinet diffraction. As a result, the Nucleus throws a naturally wide, deep soundstage, and draws images with sharp focus. There's no denying that the Nucleus Solo makes a unique visual statement, with its spherical bass enclosure and cylindrical tweeter perched atop, yet it is a form-follows-function design rather than an overt attempt to differentiate the product from the multitude of others at its price point. To a considerable degree, the Nucleus Solo is a superb loudspeaker because of the shape of its enclosure rather than in spite of it.
The Nucleus' driver complement is rather special indeed, comprised of the terrific Dynaudio 17W75 XL woofer and the Gallo-designed Cylindrical Diaphragm Transducer (CDT). Despite what you may have heard elsewhere, the Dynaudio driver is modified by its manufacturer for use in the Nucleus Solo, and works wonders in the 0.5 ft3 spherical enclosure provided by Gallo Acoustics (cleverly dubbed the Bassball, and recently granted U.S. patent number 5828766), resulting in bass that is both deep and highly articulate. Whether pounding out the bass drum kicks on Doug McCleod's Come to Find (Audioquest), or communicating the growling intensity of the double bass lines from Respighi's Pines of Rome (Chesky/RCA LSC), the Nucleus Solo never left me wanting for low frequency spills and thrills. If the Solo's -3dB point of 32Hz doesn't prove sufficient for those audiophiles with large rooms or pesky downstairs neighbors, the Nucleus Reference's additional 6Hz of low-frequency headroom and 6dB/channel of additional output should satisfy.
The wide-dispersion CDT tweeter (with a horizontal radiation pattern spanning a whopping 330 degrees) is a superb high-frequency transducer, truly the jewel in the Nucleus' crown. The CDT communicates all of the air and sheen of high massed violins, with none of the grit and glare typical of metal dome designs. High-pitched percussive instruments, like bells, triangles, celesta, and glockenspiel, are naturally resonant with neither their initial impact nor their trailing overtones given short shrift. While listening to any number of well-recorded jazz and classical recordings, I became increasingly aware of a sense of purity and authenticity to the reproduction of trumpet, saxophone, snare drum, hi-hat and cymbal, that I had yet to experience from traditional tweeter designs. The CDT's purity and transparency do come at a price, however, laying to bear flaws in upstream components without hesitation. The entry-level Audioquest PT/Benz-Micro MC Gold tonearm/cartridge combination, which, if not exactly at the pinnacle of analogue audio reproduction, acquitted themselves well in the presence of less revealing transducers, were exposed as having a rather peaky upper midrange and slightly sharp treble by the Nucleus Solos. In similar fashion, the Solos immediately communicated the vast improvements in midrange and treble refinement afforded by the latest incarnations of the VPI JMW-10 tonearm and Benz-Micro L0.4 moving-coil cartridge.
The CDT represents a significant achievement in the areas of macro and micro dynamics, showing many competing designs to be flawed in comparison. On a macro scale, the CDT startled with its powerful, yet refined, presentation. Where others compressed macro-dynamics and became course and hard, the CDT remained composed and unfettered. At the opposing end of the scale, subtle dynamic shadings, such as the slight shifts in pressure between drum stick and snare drum head heard on Nardis from Patricia Barber's Café Blue, were resolved with breathtaking clarity and precision.
During the many months I've lived with the Nucleus Solos, I have found the blend between their disparate drivers to be virtually seamless - quite remarkable considering that no electrical crossover is involved in the transition from woofer to tweeter. Rather than myriad capacitors, inductors and the like, the fluid progression between the Solo's high and low frequency drivers is a result of the naturally capacitive properties of the CDT, resulting in a complete attenuation of signals below 2kHz, and the modified Dynaudio woofer's roll-off above the 2kHz point. The complete absence of phase shift inducing passive components in the signal path implies that but a single pair of high-quality wires (supplied by Nirvana, I'm told) exists between the Solo's binding posts and the drivers themselves - a truly minimalist design, this, resulting in commensurate gains in clarity, resolution, and coherence (to hear the full measure of the Solos' continuity, one need only listen to the imperceptible hand-off between drivers during transitions from left hand to right hand piano lines).
The CDT's wide dispersion mandates careful placement of the Nucleus Solo with respect to room boundaries. The informative manual supplied by the manufacturer provides setup guidelines applicable to a variety of listening spaces. In addition, absorptive felt strips are provided for those extreme situations in which the CDT's off-axis output must be reduced in order to avoid injurious reflections from adjacent surfaces. While the Nucleus Solos do appreciate some breathing room both beside and behind them, they work exceedingly well in listening rooms of greatly varying dimension, including our Associate Editor's fairly large listening space (which benefits from substantial distance between the Solos and the side walls) and my considerably smaller, yet heavily treated, one.
The Nucleus' curvaceous, spiked Barcelona stand, affixed to the spherical enclosure with large threaded thumbscrews, anchors the enclosure to either hardwood floor or carpet with surprising solidity. There is still room for improvement here, however, as the slight flexibility of the 1" cold rolled steel used in the Barcelona's construction allows for some movement of the spherical enclosure when relatively little force is applied to its front or rear. I have little doubt that large woofer excursions (of which the long-throw Dynaudio driver is possible) could provide the requisite force to induce small-amplitude sympathetic motion of the Nucleus' enclosure, perhaps resulting in subtle time and phase anomalies (an extreme non-programmatic example of such was provided by an under-damped Audioquest tonearm, which caused rather violent woofer pumping and Linda Blair-like convulsions of the Nucleus' enclosure).
Coercing the high-efficiency (90 dB) Nucleus Solos to give of their best requires relatively little power. The breathtaking 45 Watt/Channel Atma-Sphere M-60 Mk.II Reference tube power amplifiers (reviewed by Anthony Kershaw elsewhere in this issue) proved a stunning match for the Nucleus Solos, erecting an expansive, three-dimensional soundstage of realistic scale and proportion in place of the listening room's confining boundaries. The output transformerless Atma-Spheres not only communicated micro-dynamic subtleties with unparalleled precision, but presented orchestral crescendos with great power and little effort. The deepest and most articulate reproduction of music's nether regions, however, demanded the likes of solid-state power, in this case the 175 Watt/Channel SimAudio Celeste Moon W-5, whose grain-free, anything-but-traditional-solid-state sound proved an ideal match for the microscopically revealing Solos.
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