Written by Diego Estan Diego Estan
Category: Full-Length Equipment Reviews Full-Length Equipment Reviews
Created: 15 January 2022 15 January 2022

Note: measurements taken in the anechoic chamber at Canada's National Research Council can be found through this link.

Stenheim, a relatively new Swiss manufacturer of high-end loudspeakers, was a brand I had only heard of in passing prior to this review. The company was founded in 2010 and by 2011 had launched Alumine, its first line of speakers, which are, as the name suggests, built using non-resonant aluminum enclosures. Suffice it to say that, like most Swiss hi-fi companies, Stenheim’s offerings have never been inexpensive.

After Alumine, Stenheim added a more expensive series called Reference, currently with four models ranging in price from about 135,000 to 585,000 Swiss francs (CHF) per pair, or more, depending on options. (Since there is no North American distributor, we were provided the Stenheim product prices in Swiss francs, which we were told are converted to US dollars using the exchange rate current at the time of sale. At the time of writing, 1 Swiss franc traded at 1.08 US dollars.)


Today there are three main speakers in the Alumine line: the imposing 264-pound three-way Alumine Five floorstander, priced at 59,200 CHF per pair; the smaller three-way Alumine Three floorstander at 32,750 CHF per pair; and the subject of this review, the two-way Alumine Two bookshelf, which goes for 11,950 CHF per pair, or at the current US dollar exchange rate, about $12,913 per pair. For the Two, there are two stands available: a basic version for 1430 CHF per pair and a premium stand for 2850 CHF per pair. There’s also the Alumine Sub (starting at 26,900 CHF per pair), a subwoofer built around dual 13″ force-cancelling opposing drivers and a 1500W amp.

These model prices are for the speakers in standard colors: light gray or dark gray on the side, top, and bottom panels, with black front and back panels. For an additional charge per speaker pair, other colors are available for the top, bottom, and side panels, though the front and back remain black. And for an additional cost, SE versions of the Alumine Two and Five are available, priced at 15,170 CHF and 65,500 CHF per pair, respectively. These have premium crossover parts, wiring, and binding posts. However, since my Alumine Two review samples were the standard model in the light-gray finish, I was reviewing the least expensive speaker Stenheim makes, which is, even by audiophile standards, still very expensive. So is the Alumine Two worth that much?


I’ll get the bad news out of the way first: given the north-of-five-figure price tag for these speakers, I was expecting something more attractive. To my mind, the Two isn’t going to win any beauty pageants—with the timeless caveat, of course, that beauty is in the eye of the beholder. The Two has a plain-looking rectilinear cabinet, measuring 13″H × 9″W × 10.8″D. The front baffle sports a flared port, positioned in between and to one side of the two drivers. (A pair of Twos are mirror-imaged, with the intention that the speakers should be set up with the ports towards the outside.) I think the asymmetric positioning of the ports actually added to my impression of the speakers being aesthetically unappealing. But, again, that’s my opinion.

Now for the good news—my review pair appeared to have been built to the highest standards. At 37 pounds each, they felt very solid when I picked them up, and the joins between the panels, which are made of varying thicknesses of aluminum (from 0.4″ to 0.6″), were precise and exacting. Swiss precision is a well-known term, and this certainly applied to my review samples. To say this speaker passed the knuckle-rap test would be an understatement—it almost hurts your fingers to gently tap on any of the Alumine Two’s surfaces.


The Alumine Two sports a 6.5″ midrange-woofer with a high-strength cellulose-fiber cone, coated on both sides with damped resins. The tweeter is a 1″ fabric dome, loaded into a small machined-aluminum horn that’s been meticulously inlaid on the black front baffle. The crossover uses high-quality parts, such as air core inductors, polypropylene capacitors, and metal film resistors. On the rear panel, there’s a pair of high-quality five-way binding posts from WBT. Above the posts is a metal plate engraved with the brand and model names, the company’s “Swiss Made Audio Excellence” slogan, a few specifications, and, as you’d naturally expect on a speaker with a price tag this high, the words “Made in Switzerland.” No overseas outsourcing here to cut costs—nor should there be.

Stenheim rates the frequency response of the Two as 45Hz to 30kHz (no plus-or-minus deviation given, mind you), while they claim the sensitivity is a high 93dB (1W/m) and the impedance is a nominal 8 ohms, with a 6-ohm minimum. Recommended amplifier power is 10W to 200W.


The Alumine Twos came well packed in individual boxes with nothing else—not even grilles. It seems that Stenheim would like users to experience their speakers au naturel—unveiled and completely naked. I placed the Twos atop my 24″-high Focal Sopra No1 stands in my usual speaker locations: positioned so that they form a 9′ equilateral triangle in relation to my listening chair. I experimented with toe-in angle to see if my usual 15 degrees or so would be optimal—and it was. With a little less toe-in, image size and specificity suffered. The rear of each speaker cabinet was 22″ from the front wall.

My listening room is a relatively small (15′ × 12′), dedicated space that’s been treated with broadband absorption at the first-reflection points and on the long wall behind the speakers. There are also homemade bass traps in the front corners.


I connected the Twos to my McIntosh Laboratory MC302 amp (8-ohm taps) using generic 12-gauge oxygen-free copper speaker wires terminated with locking banana plugs that I soldered on. The MC302 was connected to my McIntosh C47 preamp using Monoprice balanced XLR cables. I used my Bluesound Node 2i as the source, which was connected to a Denafrips Terminator-Plus DAC with an AmazonBasics RCA-terminated digital cable via its S/PDIF coaxial input. I don’t own the Denafrips but had recently run it through its paces on the test bench (I perform all the electronics measurements for the SoundStage! Network), so I figured I should also put it to good use in this review.

The Denafrips was used in traditional oversampling (OS) mode with the Sharp filter engaged. I used the Node 2i as a Roon endpoint, using the Roon Remote app installed on my Microsoft Surface Pro 6 to control the Roon Core application installed on a dedicated Windows 10 laptop, which was connected via Ethernet to my network. Qobuz and my ripped (to FLAC) CD library stored on a Synology NAS served as music sources.


After letting the Alumine Twos break in for about 24 hours by playing music continuously through them, I sat down for a good listen. Again, I’ll give you the bad news first—immediately after playing a few well-known tracks, I found myself wondering, where’s the bass? Of all the two-way standmount speakers based on a 6.5″ midrange-woofer that I’ve had in my room, and there have been many—always placed in the same positions—the Alumine Twos were, to my ears, the most bass shy.

But to confirm what I was hearing with some objective data, I investigated by measuring the in-room averaged frequency response using my calibrated miniDSP UMIK-1 microphone and Room EQ Wizard software. First, I found that, relative to 2kHz, the Twos yielded a -3dB point at 38Hz in my room. As a matter of comparison, most of the two-way standmounts with 6.5″ midrange-woofers that I’ve measured in my room (always in the same positions) yielded -3dB points around 32–35Hz. More importantly, however, the Twos yielded effectively no bass boost due to room gain. Although most of the two-way standmounts I’ve measured yielded 5–10dB of extra output at 50Hz compared to 2kHz, the Twos were basically at 0dB.


Overall, the Alumine’s in-room response effectively looked like an ideal anechoic response—flat-ish from 40Hz to 10kHz. Research done at Canada’s National Research Council (NRC) and Harman International suggests that (and this is true to my experience) without a few decibels of domestic in-room bass boost (below 100–150Hz), most people find that a loudspeaker sounds thin and lacks bass impact and fullness—which is how the Alumine Twos sounded in my room.

As an example of this lack of bass, on Michael Bublé’s “Home,” from It’s Time (16-bit/44.1kHz FLAC, Reprise), the Alumines reproduced the lows with speedy recovery and nimbleness, but in the bass, they sounded several decibels shy of providing good tonal balance with the rest of the frequency range. With the volume turned up (about 90dB SPL peak, C-weighted at my listening position), I could not hear or feel an impact from the slow melodic bass track.

That said, one potential benefit of this lack of bass was the Alumines’ portrayal of Bublé’s voice. In my small room, where bass modes up to almost 300Hz are standard, on this track in particular, the singer’s voice can sound too thick or chesty through most speakers without the aid of room equalization. Yet the Alumine Twos’ reproduction of Bublé’s voice on this track sounded exceptionally clean and completely divorced itself from each speaker’s cabinet, flowing freely in space, with just the right degree of warmth and upper-bass body.

The sound of his voice was just the start of the good news with these speakers. After hours and hours of listening, I began to feel confident stating that above 100–150Hz or so (so, outside the bass region and approaching the midrange), the Alumine Twos were probably the best-sounding speakers I’ve ever had in my room! Their imaging precision was laser-like and their soundstage width and depth were beyond reproach. Their midrange sounded slightly forward and lively, and absolutely oozed with musical detail. The treble had just the right amount of output—neither too bright nor too dull—and sounded clear, airy, and delicate. My in-room measurement confirmed this treble response: I observed a textbook-perfect Harman curve from the midrange on up (about -1dB at 10kHz relative to 2kHz).


But what really set these speakers apart from other two-ways I’ve heard was their excellent transparency—they let the music flow through completely, leaving no sonic fingerprint of their own. The sonic result of this was fleshed-out 3D sounds floating in the air that were so completely devoid of the cabinets they were emanating from, it was downright eerie.

For example, when I played Natalie Merchant’s “Maggie Said,” from Edition Studio Masters (24/88.2 FLAC, Nonesuch/Qobuz), I was mesmerized by the purity, structure, and realism of Merchant’s voice as reproduced by the Twos. The track opens with Merchant’s slow, haunting singing dead center, high above the speaker plane, with only two acoustic guitars, one to the lower right, the other to the lower left. To say that it felt like her voice was floating freely, as if on a cloud yet, paradoxically, with the definition and structure of a chiseled slab of granite, would be an understatement—it was like she was there singing in my room. The level of transparency and realism that the Twos brought to my room is unparalleled by any other speaker I have experienced up to now.

As for tonal balance through the midrange, it was also perfect. It wasn’t nasal, bright, dark, chesty, or thin sounding—it was just right, in every way. The gentle plucking of the acoustic guitars on “Maggie Said” was also reproduced by the Stenheims in just the right way—once again, they sounded real, as if the musicians were there in the room with me. And there was just the right amount of attention-grabbing bite and sparkle to their sounds—but never too much. Each instrument and voice was so perfectly delineated in the mix, occupying its own volume in soundstage space and surrounded by a soft cushion of air. For example, within the soundstage projected by the Alumine Twos, Johanna Warren’s occasional soft supporting background vocal on this track was perfectly painted in its own acoustic space—just behind and to the right of Merchant’s lead vocal. The subtle cymbal brushes, behind and to the left of Merchant, were perfectly balanced in the mix, delivered with subtle, airy shimmery goodness. The same can be said for sibilance in the vocals, not just on this track, but on all of the others I tried. The sibilance inherent in the recordings was still apparent, but it was reproduced in a way that sounded exactly right—not so much that it was irritating, even at high volume levels, but with enough present to create an intoxicating sense of air around the voices.


I don’t think I need to go on because, aside from the Alumines’ lack of bass output and extension—which, I must reiterate, is an issue and did cause my overall musical satisfaction with these speakers to always fall short of where it needed to be—above the bass region, the Alumine Twos sounded, in a word, perfect. But then it was time for some direct comparisons against my reference speakers . . .

The super two-way standmount showdown

I made level-matched comparisons between the Alumine Twos and my own Focal Sopra No1 standmounts, which sell for $9990 a pair. Both speakers use a similar driver complement—the Sopra No1 has a 6.5″ midrange-woofer and a 1″ tweeter, though its tweeter has a beryllium dome. I used pink noise and an SPL meter and I found that the Alumine Twos were a full 2dB (A-weighted) more sensitive than the Sopra No1s in my room, so I compensated for the volume accordingly in each comparison as I switched back and forth.

Right from the start, one thing was immediately obvious and inescapable: the Alumine Twos lacked bass and the Sopra No1s accentuated bass, no matter what track I played. In fact, it was so obvious that it became distractingly obvious—this is because the No1s sounded almost like full-range speakers, with almost too much bass output, while the Alumines lacked appreciable bass output. And my in-room measurements confirmed these observations. As I explained above, while the Stenheims had effectively 0dB of bass boost (relative to 2kHz) in my room, the Focals yielded an admittedly over-generous 10dB of boost!

To complicate matters further, this significant disparity in bass output also muddied the waters in terms of my comparative perception of the midranges of both speakers—the lack of bass in the Alumine Twos gave me the impression of a cleaner, more detailed midrange when compared to the Sopra No1s’ midrange presentation. Therefore, this comparison, as I initially set it up, just wouldn’t do—I needed to level the playing field by letting my dual SVS SB-4000 subwoofers handle the bass region and having each set of speakers handle the midrange and treble.

To implement the subs, I used the electronics already in my system to set up both speakers in a 2.2-channel (two speaker, two subwoofer) bass-managed system, which is how I typically listen to the No1s anyway. Everything in the setup was the same, but both speakers were now high-pass filtered at 120Hz (24dB/octave) using my line-level passive Marchand Electronics custom crossover, handing off bass duties to my dual SVS SB-4000 subs, low-passed at 125Hz using their internal DSP-controlled crossovers (24dB/octave). I used the built-in parametric EQ function in my subs to correct for the three significant bass nulls in my room (63, 102, 130Hz), and applied my standard +6dB of bass boost (at 50Hz relative to 2kHz) for the subs, relative to both speakers. Since the Alumines were 2dB more sensitive than my Sopras in my room, I had to increase the volume by 2dB on my subs, in addition to reducing the volume on my preamp by 2dB every time I switched to listening to the Alumine Twos. After my first level-matched comparison, I knew I had gotten it right, as both systems had effectively identical bass performance—as they should, since below 120Hz the frequencies were being handed off to the subwoofers—leaving me undistracted and able to focus on the differences between these two fine speakers from the lower midrange up through the treble.


Set up like this, I found both systems sounded remarkably close to one another in all the categories normally used to describe the sound of speakers. So I focused on the differences and found that the Alumine Twos edged out the Sopra No1s through the midrange with aural images that were slightly more chiseled and defined in space—the Twos had more solidity and definition. In terms of presence with vocals, both speakers were on par, delivering a slight lift in their frequency responses from about 500Hz to 2kHz (in-room), which made vocalists pop out of most mixes, giving a heightened illusion of real singers in the room. This is an attribute I covet in speakers and prefer over a dead-flat response through the midrange. For example, when I listened to Vanessa Fernandez’s voice on “Here but I’m Gone,” from Use Me (16/44.1 FLAC, Groove Note/Qobuz), it sounded equally present and palpable through both sets of speakers, floating freely above, between, and slightly behind the plane defined by the front panels of the speakers. But the Alumine Twos provided a slightly firmer 3D aural image, which made her voice sound more realistic. The Sopras did have a rebuttal, however, in that they made her voice sound slightly smoother, which was most obvious on hard vocal inflections. And at high volume levels, the Focal speakers were a tad easier to listen to compared to the Stenheims. Ultimately, though, I slightly preferred listening to the Alumine Twos over my own Sopra No1s for the realism they imparted.

When I compared both systems playing Michael Bublé’s “Home,” the same sort of differences emerged. The Sopras’ reproduction of Bublé’s voice was just a hair too thick and chesty sounding compared to the Alumines’ freer, airier portrayal. But, again, the Sopras did sound a tad richer, rounder, and smoother with his voice. Image specificity was first-rate with both speakers, but the Alumine Twos carved out slightly more precise aural images. The gentle guitar plucks, cymbal brushes off to the right of the stage, and Bublé’s voice in the center were in sharper relief on the stage through the Alumine Twos. Once again, I preferred the more precise rendition of the Alumine Twos over the smoother presentation of the Sopra No1s.

In terms of differences between the two speakers, I heard more of the same with Tracy Chapman’s voice on “Fast Car,” from her self-titled debut album (16/44.1 FLAC, Elektra). I also zeroed in on the reproduction of the cymbal crashes hard left and found that the Sopras had a slight edge over the Alumines, resolving more of the shimmery micro-details of the cymbal crashes during the long decays. The Stenheims punched back, however, with more realism, bite, and sparkle in their reproduction of the acoustic guitar on this track. We’re talking tiny differences here—the type I would never hear without quick, direct A/B comparisons. But they were differences nonetheless, and in this bass-managed 2.2-channel showdown, I gave the edge to the Alumines over my Sopras. I just wish the Alumine Twos had more bass output on their own.


Below about 100Hz or so, I found the Alumine Twos’ bass output to be seriously lacking in my room—especially given the speakers’ high asking price. So, if you expect and demand that your two-way standmount speakers have good bass output and extension, then, unless you have a very small room and are willing to place the Twos quite close to the wall to leverage some bass boost from the room, I must urge you to look elsewhere—either that or consider matching these speakers with one or two subs.

That recommendation for the sub(s) is something I hope you might take seriously, because the Alumine Twos’ midrange and treble reproduction was, without question, the finest I’ve ever heard in my room, providing spot-on tonal accuracy combined with transparency that was second to none—I could hear the recordings so clearly it was uncanny. Song after song, the solidity of the aural images and their 3D precision placements as they emerged from an empty space in my room consistently left me mesmerized. Those sounds, so sharply and expertly carved into tall, wide, deep soundstages, were so utterly devoid of even the subtlest cues that they were emanating from the utilitarian-looking square-ish boxes I knew were reproducing them, I found the sound of the Twos difficult if not impossible to find fault with. Except for the bass, that is.


In summary, when I combined these small speakers with my dual SVS SB-4000 subs, crossed over at 120Hz, I was, without question, in audio heaven because, excluding the use of Dirac Live room correction, they created the best sound I’ve ever heard in my room. So, yes, these Swiss-made speakers are expensive—but, when ideally implemented in a system, I can definitely see how the price for the Alumine Twos would be worth it for some.

. . . Diego Estan

Associated Equipment

Stenheim Alumine Two Loudspeakers
Price: 11,950 CHF per pair (approximately $12,913 USD per pair at time of writing).
Warranty: Five years, parts and labor.

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