Sonner Audio is a relative newcomer to the high-end scene. Nonetheless, the Boston-based loudspeaker company has turned out to be a fast learner, a fact that I discovered during my evaluation of its mid-priced offering, the Legato Duo, a rakish 2.5-way floorstander (Issue 293). The speaker I encountered had a warm inviting sound signature, an articulate presence range, and a weightier bass footprint than I expected. I concluded it was a welcome addition to the high-end neighborhood—an opinion I stand by today.
Currently, Sonner offers two product lines—the upscale two-model Allegro Reference series and the lower-cost three-model Legato Series. Given my positive experience with the brand and my fondness for compact loudspeakers, when Sonner offered up the smallest member of its Legato series, the Unum, for review, my interest was instantly piqued.
The Unum certainly fits the profile of a classic two-way compact. At just a tick over a foot in height, it utilizes a bass-reflex enclosure with a rear-firing port. The elegant, raked-back cabinet doesn’t use traditional-box back and side panels; rather its seamless, curvilinear looks are more along the lines of Sonus faber’s renowned “lute-shape” enclosures. To accomplish this, Sonner’s enclosures are machined CNC-style into a single curvilinear monocoque, which is intended to reduce internal standing waves and minimize energy storage.
Like its bigger brother, the Duo, the Unum employs a 1" ring-radiator tweeter and a 5.5" coated-paper cone mid/woofer. The crossover point is specified at 2.5kHz. (Missing, of course is the separate 6" aluminum woofer of the Duo.) Relatively easy to drive with an 87dB sensitivity, the 8-ohm Unum thrives with excellent amplification like the Aesthetix Mimas 150Wpc integrated I used throughout this evaluation. Visually Unum was easy on the eye; the natural semi-matte finish was elegant and restrained. Sonner has also reinvented the traditional and shall we say dull grille cloth and come up with a fashionable leather trim panel that is part of the time alignment design and the tweeter’s acoustic lens. This magnetically attached trim panel leaves the drivers open to admiring eyes (and fingers), but can be covered with a grille that mounts over the leather trim. The leather trim can be personalized in veneer or color-customized, even custom-engraved.
A couple of set-up notes; Given Unum’s short baffle and the tight arrangement of its transducers, adjusting speaker height is important—to align the listener’s ear with the center point of the drivers. Sonner recommends a stand height of 26–27.5", and I couldn’t agree more. Such a stand permits fuller and more open sound, even and accurate balance, and precise imaging. Additionally, as a speaker of restricted bass extension, the Unum also requires careful distancing from the rear wall in order to fortify the 50–100Hz range. In my smallish room, I found a distance of roughly eighteen inches from the wall to the back of the speaker to be a satisfying solution for bass reinforcement. The take-away? Size, room, and setup always matter—all the more so for small two-ways.
In sonic performance, the Legato Unum scored handily in regions that remain the province of well-executed two ways—a segment I consider “specialist” by nature. Namely, its near-single-driver coherence, spotless pinpoint imaging, and ability to convincingly disappear were all in evidence. In fact, many of the same virtues that I encountered with the floorstanding Legato Duo have carried over to the Unum, particularly in the area of vocal intelligibility and image stability.
Unum was a portrait of an open, forward-leaning, midrange-weighted compact. Never dull, its presence range (a key region between 2–4kHz, where human hearing is at its most sensitive) was lively rather than recessive. Predictably, its overall balance was, indeed, a lighter one—a trait fully consonant with its size and drivers—but its mids were notably full-bodied. Even cello, a difficult instrument for any compact to master, was reproduced with much of the harmonic and transient complexity and resonance of the real article. This performance was all the more impressive coming from a five-inch mid/bass driver. The treble range, courtesy of the fine ring-radiator tweeter, was non-fatiguing, and possessed satisfying bloom and air. Noteworthy in this regard was the high-octane trumpet solo during the Manhattan Jazz Quintet’s cover of “Autumn Leaves.” This solo can leave lesser tweeters dangerously overexposed, but the Unum skated through smoothly and convincingly.