Sonner Audio Allegro Unum Monitors | REVIEW

sonner audio allegro

These were the Sonner Audio monitors I was supposed to get a couple of years ago, the pair that left me dumbstruck when I first heard them at the 2019 Capital Audiofest. I’d never heard of this company before I detoured into that room on that fateful day, so I didn’t know what to expect. First, the tonality was superb and realistic and natural and musically informative. Second, there’s killer bass for such a small monitor. The Sonner Audio Allegro Unum certainly wasn’t cheap, but it didn’t sound like it, either. They were special, I quickly decided. I’ve been thinking about these compact beauties ever since.

I thought I’d review them soon after that show because we said things like, “Can I review these?” and “Yes.” But a lot of plans were made before the epidemic. In addition, Gunny Suryan kept selling the Sonner Audio Allegro Unums he had in stock–to which I say, don’t turn your back on a sale for li’l ol’ me–and a new version of the dedicated stands were also being developed. So the Unum review would be postponed, just a bit.

Words and Photos by Marc Phillips

By last year, Gunny finally asked me if I’d settle for reviewing the much larger and yet less-expensive Sonner Audio Legato Duo, and we agreed that I would drive them back after the Pacific Audio Fest in Seattle. (Hijinks ensued after I learned the boxes for the Duos were enormous and only one would fit in my Mazda at a time.)  I was shocked, however, when all of the gear I asked to review–from several different manufacturers–was at my house just a couple of days after I made it home, It usually takes weeks and months to arrange reviews like this. The Sonner Audio Legato Duos, however, evidently brought a small friend along to my home–I noticed two extra boxes on the pallet.

lucy loves this speaker

By now you’ve probably guessed what was in those two extra boxes. Yes, it was a pair of the Sonner Audio Allegro Unums. They had stowed away on the pallet with the much larger speakers, and when the moment was right they jumped out and said “howdy!” I checked with Gunny to see if he had made a mistake. He laughed, and I think he might have shouted “Surprise!” But it was simpler and cheaper for Gunny to ship everything from the show directly to me, a mere 160 miles away. That’s when Gunny told me about the stands, and he told me to give the Unum a listen if I wanted, and to hold onto them until the stands were ready.

You know what I did. I placed them on the solid granite Acora Acoustics SRS-G speaker stands and gave them a premature audition, which sounds kind of naughty. I’d been waiting for the Borresen Z1 Cryo monitors to arrive, and had all the Aavik and Ansuz gear already in place. The Sonner Audio Allegro Unum speakers, I discovered, were an incredible warm-up act, but I had to proceed with other reviews so I boxed them up and set them aside.

Time passed, and I started to feel guilty for not playing the Sonner Audio Allegro Unums. Look at them, all packed up and nowhere to play. So yeah, I listened to them without the dedicated stands. In fact, I placed them on those Acora Acoustics solid granite stands and I thought they sounded spectacular. I wanted to write the review without the new stands and then just add something later when they arrived. In the meantime, I spent several weeks with the superb Legato Duos, gave them a big thumbs up, and sent them away.

marc phillips system

Inside the Sonner Audio Allegro Unum

I thought that the larger Sonner Audio Legato Duo speakers ($9,500/pr USD) were fantastic values, by the way. Just a lot of speaker for the money, any way you look at it. Before you tumble into a bigger-is-better mindset, know that the small two-way bookshelf Sonner Audio Allegro Unums are actually Gunny’s flagship speaker, positioned and priced higher than the big Legato Duos at $12,000/pr USD.

The Sonner Audio Allegro Unum is a two-way ported design with a 1″ ring dome tweeter and a customized 6″ magnesium cone mid-woofer. The curvy cabinet enclosure is made from one piece, and the front baffle is made from aluminum.

The mid-woofer is one of the features that separate the Allegro line from the Legato line. As Gunny describes:

“The Allegro’s mid woofer cone is made from a Magnesium Aluminum alloy. The stiffness of this alloy allows a large and rapid pistonic cone movement without deforming/flexing its shape. This cone has a high density of 1.9 gram/cm3 which enables vibration acceleration (stop and go cone movement) to occur in a split second. As a result, detailed sound and a fast transient can be heard effortlessly.

“One unique property of this Magnesium Aluminum alloy is its self-damping sound characteristic. Warm, coherent, open and detailed sound is the outcome from using this unique material. This mid woofer is designed with a large magnet and a long voice coil to support a large excursion cone movement. To prevent break up during the cone movement the driver includes a reinforced rubber surround with a radial pattern. The large cone excursion can also create non linearity issue and air turbulence behind the cone. A heavy copper ring is mounted in the magnet poles to reduce any non-linearity and intermodulation distortion. To minimize cone backward air flow and cavity resonant the speaker frame is constructed from molded metal with a large opening above and below the spider.”

binding posts

Numbers-wise, the Sonner Audio Allegro Unum is a fairly accommodating speaker. It has a nominal impedance of 8 ohms and is very easy to drive–the recommended minimum power from an amplifier is just 3 watts per channel. I paired the Unums with a 200wpc class D amplifier (the Aavik U-280) and a 28wpc class A push-pull tube amplifier (the Audio Note UK Cobra) and, quite frankly, the Unum embraced each of them in very similar ways.

The crossover point of the Sonner Audio Allegro Unum, by the way, is at 2kHz, part of Sonner’s “Symmetrical Panoramic Design” crossover design:

“Sonner has developed a proprietary crossover technology that is called Panoramic Crossover Technology (PCT). This crossover is designed specifically to control each speaker driver’s frequency response, impedance variation and phase behavior. Low or flat impedance variation is Sonner’s key design element, which makes our speakers easy to be driven by different type of amplifiers. The crossover’s electrical and acoustic phase is determined using computer modeling in conjunction with the cabinet time alignment angle structure.

“All crossover components are point-to-point connected without using the interference of a Printed Circuit Board in order to achieve the highest purity of recorded sound. Once the final crossover is assembled, every single crossover is measured using a software. This software allows us to compare the measurement results to the theoretical crossover design. After passing this quality control review, the crossover is encapsulated/potted in an Epoxy compound. The purpose of potting crossover is to reduce microscopic vibration from crossover components and downstream speaker drivers.”

The Sonner Audio Allegro Unum is available in gloss black and gloss white. If that doesn’t seem like enough choices for you, then I should introduce you to one of Gunny’s features you’ll find up and down his product lines–the removable leather-covered baffle, known as the acoustic panel. The openings in this panel were designed to “complement time alignment of the cabinet and Sonner’s proprietary Panoramic Crossover Technology. The main objective of the design is to control sound dispersion and improve coherent sound as if the sound comes from a single point source.”

You can customize your baffle colors for your Sonner Audio Allegro Unum, everything from Blue Lagoon to Buckskin to Chestnut to Orange Spice to Red Poppy to White Pearl. I really loved the combination of black on black on my review pair, especially in contrast to the silver on the drivers, but I can also imagine sitting down at home with a complete set of all the baffles, trying each one until these speakers magically pull the room together.

allegro unum versus legato duo


It’s sort of funny. I’ve spent much of 2023 listening to two nearly complete systems–one from Audio Group Denmark and one from Audio Note UK. The Sonner Audio Allegro Unums were evaluated during two distinct time periods–one with one brand, and one with the other. To make things a bit clearer, I should remind you that plenty of time–too much time, really–passed in between. I only mention this because I know some will draw a comparison between the two systems, and I’m not sure I can offer that. Good thing I’m such a good note taker, as someone else recently observed at a high-end audio show.

The two systems were also very different from each other, and I’m not just talking about the gear itself. The Audio Note UK AN-J/D Hemp loudspeakers needed to be placed near the side walls along the short wall in order to achieve that magical bass response (AN claims 23 Hz) from a modestly-sized two-way. In other words, my entire listening room was rotated 90 degrees.

sonner audio allegro unum

During the first evaluation with the Audio Group Denmark gear, the Sonner Audio Allegro Unum monitors were placed exactly where I usually place two-way monitors–about 2.5′ off the back wall, slightly toed in. The only reservation I had about the sound of the Allegro at the time was a slightly narrow soundstage. Since the most common adjustment I make during speaker positioning is with the space between the speakers, I had no qualms about pushing the Sonners closer to the side walls. I heard a steady improvement, but I wasn’t getting those same 180 degree panoramic views I’ve achieved with bookshelf monitors such as the Borresen Z1 Cryos.

During Round 2 with the Sonner Audio Allegro Unums, I merely replaced the Audio Note AN-J/D Hemps, leaving the Sonners in almost the same side wall-adjacent spots. (We’re talking just a few inches, really.) That led to some center fill issues (the Audio Notes are impervious to these distances) so I brought them closer to each other, a couple of inches at a time, and once the Allegros were about a foot from the side walls we hit the jackpot and the Unums started singing just like the first time I heard them back at the 2019 CAF.

So what is that sound? For me, it’s a combination of the superb bass, going much lower than the size of the enclosures suggest (“they sound like much bigger speakers!”) and having that ideal amount of warmth. I talk about warmth all of the time, and it is some I find highly desirable and important, but the Sonners were able to deliver those two strengths in a tandem package, creating a cohesive sound that I find unique.

marc phillips system

Sonner Audio Allegro Unum Sound

Since I unpacked the Sonner Audio Allegro Unums around the same time I unpacked the Legato Duos I reviewed, I was able to compare the two directly and determine their priorities when it came to performance. (This reminded me a little bit of the comparison between the Qln Signature monitors and the Qln Prestige 5s–the smaller speaker is more expensive than the larger speaker.) The Legato Duos were able to deliver deeper bass and a bigger soundstage, but the Allegro Unums seemed to offer much more in the way of refinement–especially when it came to the natural and convincing midrange performance.

Much of that comes from the higher quality drivers and, as Gunny explains:

“There’s a superb crossover design that eliminates frequency breakup usually found in metal cone drivers without making the sound becoming sterile, top of the line crossover components (the size of the components are so big which make Sonner to build tweeter and mid-woofer crossover on separate module), and the additional care put into the enclosure, of course, such as utilizing aluminum front baffle to allow mid woofer deliver micro and macro transients without any unwanted resonant from front baffle.”

There are shimmering similarities between the two models, especially in the way Sonner Audio speakers always succeed when it comes to flagging the emotional content of a recording and delivering it, wrapped up in a pretty bow, and laid upon your lap. It didn’t take long for me to gravitate toward the Sonner Audio Allegro Unum as my favorite of the two, however–the fact that these bookshelf monitors were still capable of deep bass that approached the power of the larger Duo might have been the deciding factor. The Unums aren’t as big, nor as deep as the Duos, but they have more focus, and more detail.

ring radiator tweeter

The Legato Duos are still extraordinary values–what they do for less than $10K remains staggering. The Sonner Audio Allegro Unum, however, connects with me in the way that only high-quality, high-performance two-way monitors can. A lot of that has to do that added coherence between the drivers, the simplicity of the crossovers, and the ability to disappear easily into the room. Heck, most decent monitors do all that. I think what sets these apart from the others is the Sonner Audio design team’s  attention to voicing  by listening to different capacitors/resistors/inductors and internal wire to match well with the speaker drivers. As I mentioned in the Legato Duo review, the team is constantly changing the designs so they can discover sonic improvements. They’ll change the radii on one of the curved surfaces of his speaker enclosures, find something worthwhile to explore, then redesign everything else around that finding. Gunny has an electrical engineer on the team who worries about the fundamentals–Gunny is a supreme lover of music, and he just wants to deliver the finest version of it he can.

The Sonner Audio Allegro Unum, the flagship of the line, is the ultimate expression of Gunny’s love of music–at least for now. I predict a Allegro Duo in the future, because it makes sense to me. I haven’t mentioned this yet to Gunny–let’s see what he says.

sonner audio allegro unum

Listening Sessions

Julian Gerstin’s Littoral Zone has been a favorite of mine over the last couple of years. It’s one of those multi-percussion ensembles that show off layers and layers of exotic instrumentation, and while there is an occasional melody supplied by the odd horn or flute, the magic here is finding the music among the rhythm, and how individual noises eventually create tones that fill in all the spaces. On lesser speakers, it sounds like a fascinating yet slightly disjointed collection of drums, shakers, bells, rasps and pieces of wood, but the Sonner Audio Allegro Unums connected those dots with aplomb and quickly found the moods and the feelings hidden within.

I’ve been spending time with that newly remastered version of Pink Floyd’s Animals, trying to determine if I like it or not. To me, the new version seems a little too clean, and perhaps a little too different from the original pressing, like they threw in some alternate takes. (I do like how the remaster eliminates the tracking distortion at the ends of each side–the original pressings have grooves right up to the label.) The Sonner Audio Allegro Unums allowed me to highlight the differences in the new version with ease since they are so detailed, but at the same time I relaxed a little more this time, and accepted what I was hearing merely because it was supremely musical.

This is where I discovered the incredible imaging of the Unums. On “Dogs,” of course, there are dogs barking. On the remastered version, some of those dogs sound far more real than before, and my dog Lucy noticed. She started barking. She started sniffing. She noticed the pinpoint placement of the dogs and she looked right at that spot. I heard so much familiar music take a step toward a more natural and realistic tonality when the Sonner Audio Allegro Unums were in the system.

sonner audio allegro unum

Sonner Audio Allegro Unum Conclusions

If I enjoyed the Sonner Audio Legato Duos as much as I said I did in the review, and I gave it a Reviewers Choice Award, then it stands to reason that I would give the Allegro Unums the same award. And I will. But since I spent a lot of time with both speakers, and they’re both very close in price, I should point out why you should pick one speaker over the other.

The Sonner Audio Legato Duo is a LOT of speaker for the money, as I’ve mentioned. You match them with superior amplification and source material, they will sound like a far more expensive speaker. They’re also beautiful and distinctive with their backward rake–it’s a look that will capture your attention every time you walk into the room.

The Sonner Audio Allegro Unum isn’t the obvious crowd pleaser that its brother is. It will appeal to slight more discerning tastes. It doesn’t go as low in the bass, but it’s not far off. It’s beautifully made, but it might not be as noticeable in your room.

The reason why the Sonner Audio Allegro Unum is my choice between the two goes back to the strengths of an excellent two-way monitor design–mainly, coherence between the drivers. The Unums were focused and precise, which made the Legato Duos sound a tad diffuse and soft in comparison. In other words, a prospective owner will need to compare the two to determine those preferences. But here’s the good news–both speakers have plenty of Gunny in them, and they sound more similar than not. And Gunny’s all about the music, the way it connects with the listener, the way it makes our lives more tolerable. Whichever Sonner you choose, you will have chosen well.

pta reviewers choice

rear port

sonner audio allegro unum



  1. Acora SRB, Borresen Z1, and this speaker. Can you say which is better (to you of course, since you reviewed all three in your room)? Or… are they all so close that one must go and listen to all three – honestly that would be hard for me, and most, to do, which is why I’m interested in your thoughts. Love your reviews, and thanks in advance.

    • Hard to say, since all three speakers were auditioned in different systems. That’s the issue with doing comparisons via memory–it’s not reliable. That said, all three are stellar mini-monitors and it’s going to be a matter of personal preference for the prospective owner.

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