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Sonner Audio Legato Unum

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. 


A prime example of music that falls within Unum’s sonic wheelhouse was the duet between guitarist Pat Metheny and bassist Charlie Haden on “The Moon Is A Harsh Mistress.” Within an expansive and reverberant soundstage were loads of low-level detail, micro-dynamic energy, and timbral color. Obviously the subtraction of the Duo’s 6″ woofer impacted bass response, but the harmonics of Haden’s standup bass still managed to fan out and provide more than acceptable pitch accuracy and control.

Deep, head-banging bass from a foot-tall cabinet was obviously not Unum’s strong suit, but there was enough suggestion of room-pressurizing output in the 50–80Hz range to maintain the balance and character of a good jazz or symphonic performance and put an enthusiast’s critical ear at ease. Take Dave Brubeck’s “Take Five,” for example. In addition to the colorful, bouncy mids of the famed piano vamp, the standup bass and drums attained a pleasing spatiality with pitch accuracy, hints of warmth, and surprising decay. 

Vocals however were a strong suit—lively and well detailed, particularly with female singers. Ana Caram’s gentle vocal during “Fly Me To The Moon” [Blue Bossa] created a fair amount of warm air; her soft, rhythmic Bossa Nova guitar accompaniment was as placid as a tropical breeze. Male singers, like Johnny Cash singing Trent Reznor’s “Hurt,” missed some of their lower-midrange chestiness, but the Unum picked up on Cash’s vocal understatement and the catch of emotion in his throat—keys to a performance that is both electric and haunting

Speed and transient attack were very good; the cabinet seemed virtually resonance-free. The Unum possessed a tactile spontaneity that drew my ear to the plectrum of Joni Mitchell’s dulcimer or the rosin on cellist Yo-Yo Ma’s bow, or the tick of a classical guitarist’s fingernails playing upon the strings. That resolution paired with a general lack of port overhang or spurious resonances seemed to propel a recording’s energy into the room as if materializing from a time machine.

Unum’s soundstage, replication of scale, and dimensionality were solid considering its humble size. Images were cleanly spaced and stable. Orchestral section-layering was indicated, but ultimately stage depth was limited. To my ears, Unum had a more focused signature, emphasizing a musician’s direct sound rather than extended ambient decay, a trait that registered with me as I listened to The San Francisco Opera’s live performance of “Somewhere” from West Side Story. The ability to send ambient information fanning across a stage to the furthest edges of the soundfield was not often fully realized—nor were the tactile and textural backing that supports and reinforces individual musical images and allows those images to fully inhabit the soundspace. 

In terms of unbridled output and dynamics, Unum’s physical size is a factor, so mind those 100dB P’s and Q’s.  While it can’t fully break the bonds of its own compact genetics, I’m not suggesting Unum needs to be coddled, either. Never shrinking from a challenge, cue up the heavy dance groove of Michael Jackson’s “Billie Jean” [Thriller], and you’ll likely be as surprised as I was by the amount of whomp, rhythm, focus, and drive coming from such a small speaker. Or, an even more extreme case, try listening to the gale-force depth and impact of the Kodo Drums during “Air” from the soundtrack to The Thin Red Line. Of course there’s some compression, and certainly there are limitations to how much kettle- or bass-drum air a compact can launch into the soundspace of a room, but the Unum surprised me time and again at its effectiveness in capturing the broad range of sonic color of this powerful material.   

The field of two-way compacts is an intensely crowded and competitive one.  To that end, the Sonner Audio Legato Unum was an engaging, civilized, and musically compelling experience—a well-honed package that makes a great case for elegance and poise in smaller room applications. Like its larger sibling, the Legato Duo, it’s the kind of speaker that just makes you want to cue up your favorite music, kick up your heels, and spend a lot more time listening. As it was with Legato Duo, making the acquaintance with Legato Unum was an absolute pleasure.

Specs & Pricing

Type: Two-way, ported-enclosure stand-mount
Drivers: 1″ ring-radiator tweeter; 5.5″ coated-paper cone mid/woofer
Sensitivity: 87.5dB
Frequency response: 43Hz–23kHz
Nominal Impedance: 8 ohms (minimum, 5 ohms)
Dimensions: 8.27″ x 12.6″ x 17.75″
Net Weight: 20 lbs.
Price: $4750/pr. (optional matching stand: $1120 per pair)

68 Daniel Webster Highway
Merrimack, NH 03054
(603) 881 3978 
[email protected]

By Neil Gader


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