Review: Acapella High BassoNobile MKII Loudspeakers

Review: Acapella High BassoNobile MKII is a real investment. But one that is worthwhile as For many, this could mean the end of their search.

Sixty-two high, weighs 130 kilograms – but no, this trumpet of a sound transducer is not the flagship of Acapella Audio Arts , but only the medium format. If at all: There are only three smaller, but eight larger models in the Duisburg-based manufacturer’s line-up, which apparently has a weakness for full-blown loudspeakers. Well, for most of us this “medium-sized” Acapella High BassoNobile MKII should appear quite respectable.


Acapella has been building extraordinary loudspeakers for more than four decades and during this time has devised the spherical and hyperspherical horn as well as, not to forget, its own horn-supported ion tweeter in its range. But not only is the company’s history long – if you want to find out more, please refer to our Acapella company report – the speakers from Duisburg are also real cross-country skiers. This is also the case with the BassoNobile, which was first presented to the public in 2012 and now, after nine years, has been fundamentally revised. At that time, other providers are already with MK V, if not with completely different models.


The basic concept of the BassoNobile has of course remained true to: It is a closed two-way loudspeaker . Both are unusual, given that you usually have to deal with three- or four-way constructions in this weight and price range (32,600 euros) – and closed cases are also rather the exception. Although they are said to have better impulse behavior, this is at the expense of the sound pressure output in the bass, which is why many developers rely on bass reflex after allput. Shyness in the bass is not to be expected here, because the Acapella High BassoNobile MKII is, as I said, not that small. I’ve owned refrigerators that were a lot more delicate. With so much volume in the hindquarters, real deep bass is also possible with a closed passive loudspeaker.

Pro Kanal arbeiten zwei 10-Zoll-Treiber in der Acapella High BassoNobile MKII. Beide Woofer stecken in ihrer eigenen, geschlossenen Kammer

The basic concept of the BassoNobile also includes this special mid / high-frequency horn, which is on the one hand hyperspherical in shape and on the other basically functions as a full-range driver . A total of five octaves – from 800 to over 25,000 Hertz – is responsible for the asymmetrical construction, which is just under 44 centimeters in diameter. This means that the presence and brilliance area , in which the human hearing is particularly sensitive, is seamlessly covered from one point. That gives hope for good things.

But what is the term “hyperspherical” all about? It describes the geometry of the horn funnel, i.e. how the horn opens in the course from the neck to the mouth. “Our horn shape has a special spherical function which, in contrast to a spherical wave or exponential function, starts from a spherical point at infinity,” says head of development Richard Rudolph. From an opening angle of 180 degrees, however, this horn shape is expanded by a second spherical function. The horn bulges slightly backwards – therefore hyper spherical.

Für das hypersphärische, asymmetrische Horn hält Acapella ein Patent

But that’s not all: “With our patented asymmetrical structure, the sound runs through the horn mouth at lower frequencies much more homogeneously and enables a phase-neutral connection,” Rudolph is convinced. With classic horn shapes, the sound wave breaks off at a certain cut-off frequency and creates a phase jump. That is the reason why they are much more difficult to connect to the lower layers. The opening angle of the horn, which goes beyond 180 degrees, its asymmetrical shape and the special positioning on the baffle with the “broad side” facing outwards are intended to optimize the impulse and phase behavior of the entire loudspeaker.

Das hypersphärische Acapella-Horn, seitlich betrachtet: Es wird aus glasfaserverstärktem Kunststoff gefertigt, im Innern steckten zudem resonanzdämmende Materialen

What’s new?

Not only the shape of the horn is special, the drive is also special. In the case of mid-range / high-frequency horns, a compression driver with a corresponding chamber is usually flanged to the neck of the horn. It’s different with Acapella. You’ve heard almost all compression drivers on the market, says Rudolph, but there wasn’t anyone who seemed suitable for the job. Problem areas are regularly the “breaking open” of the membrane from a certain frequency as well as the compression itself, which is not as free from side effects as it is actually necessary.

Blick ins Horn: Statt eines Kompressionstreibers setzt Acapella auf einen Hochtöner mit 1-Zoll-Gewebekalotte

That is why Acapella generally uses a “normal” tweeter with a 1-inch fabric dome, and this also applies to the High BassoNobile MKII – without a chamber in front. It is a new development that is supposed to enable even more distortion-free reproduction. In addition, the driver, flange and horn were matched to one another in extensive listening and measuring sessions, says Rudolph. The horn driver and woofer – both manufactured exclusively for Acapella – were developed by the Norwegian chassis specialist Seas and optimized by Acapella to the respective requirements.

For these, too, Acapella relies on “classic” membrane material, namely a coated paper sandwich construction. Two woofers per loudspeaker each work in their own chamber, with the horn unit between them – and the crossover network directly behind the horn driver . Of course, it was also completely redesigned and got a little bigger: A second part of the crossover had to be moved to the base of the speaker for reasons of space. Both switch parts sit in their own closed chamber, away from the commotion that prevails in the bass department. Rudolph is covered with further details about the crossover design. I find out that everything was hand-soldered with Acapella pure silver conductors – and the same cables are also used to contact the chassis. This is one of the reasons why the loudspeaker has been given the first name “High”, which is reserved for the more complex versions of the loudspeaker models (the new BassoNobile is only available in the high version, however).

Das Terminal der Acapella High BassoNobile MKII: Der Hochton lässt sich pegelseitig in zwei Schritten bis maximal +/-0,5dB anpassen

New drivers, new crossovers – and what about the case? The Duisburg-based company continued to work on minimizing the resonance by means of struts, reflectors and damping inside as well as a “cascading support for the bass and tweeter”. The classic Acapella material mix serves the same goal: The three to five centimeters thick “boards” from which the loudspeaker housing is made are actually not at all – but multiplex-MDF-acrylic composites. The different sound propagation speeds of these materials should prevent resonances and thus the creation of phantom sound sources. Another advantage of the three millimeter thick acrylic outer skin is of a very practical nature: if a scratch should come in, it can be polished off better than with a thin layer of paint.

Speaking of the outer skin: high-gloss black and white are of course the classics, but other colors – and even veneers – are also possible, says Rudolph. The customer can determine the color of the horn quite freely.

Acapella High BassoNobile MKII: Sound impression & comparisons

What should I start the listening course with? The BassoNobile makes it easy for me: If a loudspeaker is called that, then of course with the bass. And it is indeed noble, as it combines virtues that rarely go together so perfectly. I have experienced something similar maybe two or three times. In terms of absolute depth and assertiveness, an Ascendo Live 15 (around 27,000 euros) was of course able to keep up, but it is active and aimed at a different target audience. When it comes to passive loudspeakers that serve “bass at eye level”, I quickly think of the Focal Maestro Utopia Evo , which costs 20,000 euros more. Let’s go through the bass checklist point by point.

Die Acapella High BassoNobile MKII im Hörraum

In terms of level, the Acapella High BassoNobile MKII in the basement plays well-balanced, even if a finger’s breadth would be more tasty than 100% neutral. So exactly right! Especially for my room, which is not exactly small with its 40 square meters and also takes some energy out where others often have a bass increase. With the result that neutrally tuned speakers such as the Blumenhofer Gran Gioia 2 × 10 (around 40,000 euros) crisp and tight, yes, maybe even too tight for some hearing tastes. The Acapella High BassoNobile, on the other hand, fits into my room like a fist in the eye, it looks perfectly balanced from the lowest to the upper bass. Conversely, it can of course be deduced from this: This loudspeaker also needs a little space to unfold. In rooms well below 25-30 square meters this is rather difficult, while areas twice and three times as large can be used with ease.

It is also clear that the Acapella descends half an octave to a whole octave lower than my Blumenhofer, who is more concerned with the former when it comes to the trade-off between efficiency and absolute depth – and indeed plays a little louder with the same power supply. The acapella’s low-pitched abilities of course do not primarily pay off with “shooting music”, but rather with the impression of the room. This can be heard, for example, with the baroque music album Stille Klagen, which was recorded in excellent quality in a church and is transported over the Acapella High BassoNobile MKII even more spaciously than I am already used to. But “shooting” is also possible. And how. One of my standard test tracks for this is “Fuck back” by Burnt Friedman & The Nu Dub Players . I was recently “beaten” in such a comprehensive and dynamic manner by the above-mentioned Ascendo. The Blumenhofer, on the other hand, distributes the piece’s synthetic impulses with a little more edge, the Acapella is slightly softer, but puts in more body.

But the High BassoNobile can and wants more. Above all, she understands a very differentiated representation of the musical happening – and that also in the tonal basement. Contoured, but never too dry or even emaciated, she sets up double basses completely naturally and freely in the room and makes the strings purr wonderfully real. This can be seen on Howe Gelbs “Piango” or “Sunrise” by Norah Jones, which is almost to death at hi-fi fairs . The special thing: This very successful combinationof substance and contour. Most loudspeakers tend either on the one hand (“nice and juicy, but a bit soft”) or on the other (“dusty dry, but very wiry”). The Acapella combines both in a congenial way. This is where the concept obviously pays off: a lot of driver space in closed, but large housings. High BassoNobile – the name really fits.

Die Acapella High BassoNobile MKII - mit und ohne Frontbespannung

Such a foundation is naturally easy to build on – whereby the rest of the tonal house is also quickly described: balanced-neutral, it continues through the mids to the highs, which are only served an iota milder. All in all, the Acapella High BassoNobile MKII has a very balanced effect, with a slightly sonorous impact. Their tonal coordination is somewhat reminiscent of that of the Dynaudio Confidence 50 (26,000 euros), only that the Dane doesn’t get that far down in the bass, and therefore doesn’t play quite as broadly. It also has a somewhat milder gait in the upper octaves. If you like, you can adjust the high frequency of the Acapella High BassoNobile MKII a little with the jumper cables on the terminal, but there are no worlds here. Logically, the maximum possible “deflections” are only +/- 0.5 dB. I found it most conclusive in the zero position anyway.

The real stuff

The coherent tonality is important, but it does not or only partially explains this special “touch”, the magic that can emanate from the Acapella High BassoNobile MKII. Balanced, a little warmer, full-range – others can do that too.

The magic in the midrange and treble band arises rather from the great resolving power of this broadband horn, which serves five octaves from one point completely seamlessly. And please don’t get it wrong: The resolution here is so high that it never sounds like “presented on a silver platter”. No, that would be a helpful circle class, as it is slightly emphasized and thus more of a dissolution surrogate than the real material. And so all the background noises when making music – reaching around on stringed instruments, quiet breathing while singing, chair creaking / rustling in the orchestra, etc. – are clearly conveyed, but it happens as if passing by, naturally casual, never nerdy.

Such “noises” seem to me to be less decisive, however, the high-resolution gait of the Acapella really pays off, especially in other places. In particular , when it comes to the timbre and the atmosphere in the room, it really comes through. And those in turn are essential reasons why classical music sounds so – sorry – damn great with the High BassoNobile.
Representing string instruments in a lifelike manner is a fine art, because it has to have a rich overtone spectrum can be played back correctly. It is less about gross things like more or less level in the treble, it is more important to represent the individual spectral partials, which are relatively quiet in relation to the fundamental tone, very cleanly and in the correct ratio to one another, so that this “simply real impression” is then “summarized”. arises.

Die Acapella High BassoNobile MKII von vorne

It may be that an almost full horn with compression driver in the high frequency is conceptually not primarily designed for something like this, but one shouldn’t generalize either, a Blumenhofer Gran Gioia 2 × 10 with a classic program sounds much too good for that. Still, I have to admit: The Acapella’s hyper-spherical broadband horn actually plays in a different league. Violins and cellos appear comparatively less pale and porous with her, she works out the timbre of the instruments more completely. Another benefit is that the strings and string sections are modeled even more tangibly. In fact, this trait reminds me of the Dynaudio Confidence 50, but the Acapella dissolves a bit better.

And then there is this ominous “room atmosphere”, as can be seen in the example of the aforementioned album Stille Klagen . I don’t know exactly how it does it, but by the Acapella High BassoNobile MKII I mean hearing the air move in the church … I know, I know, this is nonsense. But it just works that way. To put it more technically, there will probably be some kind of subtle, quiet reverb tails, which our test subject traced very accurately and for longer than I would otherwise be allowed to experience. The stage design breathes and lives with every note, you feel as if you are inside the church. Ghostly! Somebody should tell me again that it doesn’t matter that much about breaking up.

Stage talent

And speaking of the stage: the quality of the spatial representation is absolutely astonishing for a loudspeaker of this size. Such giants often stand in their own way, while well-made high-quality compacts play out their conceptual advantages here and succeed with a picture-book graduation of the musicians. And yes, compared to the best monitors, there is still room for improvement in terms of imaging precision. But on the one hand, you have to attach greater importance to such a high level of localization, because some people consider this to be “hyperrealism”, i.e. artificial. On the other hand, the comparison is silly anyway – you don’t stand in the booth twice if you think that the dynamic range and bass performance of a compact machine are enough, right? No, you don’t do that. So the Acapella has to be compared to large loudspeakers – and that’s when I think of the Focal Maestro Utopia Evo mentioned at the beginning. That is the same weight, if not price range (52,000 euros).

Das Horn der Acapella High BassoNobile MKII

The Frenchwoman is slightly ahead of the pure edge sharpness of the image, but it seems to me that the Acapella sound structure is a little more organic and rounded. Ultimately, it’s a matter of taste. When it comes to the width and depth of the stage and the ability to “breathe” dynamically, the High BassoNobile MKII is no worse. In addition, like the Focal, she knows how to give each voice and each instrument its own sphere, a certain aura. With this “air” around it, the musicians appear more naturally embedded in the entire stage than if they were standing “naked” in the room. Unfortunately, this auditory impression is a bit difficult to describe … hm, if we were dealing with a tube amplifier, I would speak of “Bloom”. Was this helpful to you? With the focal test I have called it the “space within a space” effect. Well, whatever you want to call it, in any case it ensures that the stage is not simply presented accurately and expansively, but rather looks very natural overall and with all the precision less “as if gridded” or sterile.


How does the Acapella High BassoNobile MKII fare in the dynamic field? After all, we are dealing with a horn loudspeaker. First: very good. Second: Somehow it doesn’t sound like horn at all.

To try again with the giant focal: impulses came a little sharper, fresher via this French non-horn . And it is the same – albeit more clearly – with my Blumenhofer horn . When the drumstick hits the skin, the plectrum plucks the string or the piano hammer strikes it, it initially seems a bit harder on both of them. But what follows immediately afterwards is traced more accurately by the acapella in a finely dynamic manner. The difference can also be clearly seen in acoustic guitars, for example on Julie Byrne’s album Not Even Happiness : When the fingertip slides over the string, the High BassoNobile brings it across immediately, but a shade softer and milder than I’m used to – afterwards the string purrs and vibrates more subtle, more delicate, richer in overtones. The instrument seems more physically lined anyway. So, remember: Microdynamics in a class of its own, but not as sharp as possible, as many automatically assume with horns.

Acapella High BassoNobile MKII - Basstreiber

In terms of coarse dynamics, there is no stopping it. And not only when the brass volleys start sharply or when the pianist really puts in a lot of effort. You can also listen to large symphonies at concert level and let yourself be blown away by tutti passages including kettledrum inferno and all the zip and zapp. It’s crazy how confidently the Acapella gets that across. And it’s amazing how cleanly she implements such level orgies and jumps. Yes, you need a really big loudspeaker for something like that!

I have seldom been as impressed with a loudspeaker as I was with the Acapella High BassoNobile MKII – such a balanced, highly audiophile overall package is rare. You can tell the BassoNobile that years of (listening) experience and refinements have gone into it.

Of course, such a large loudspeaker needs enough space to unfold, but those who can afford it usually don’t lack that. The driving electronics should be of high quality, but do not have to be extremely strong. More important than pure power are good resolution and timbre fidelity so that the existing potential can also be accessed.

Anyone who can provide, pay and drive the Acapella appropriately can experience such a broad-band, dynamic, high-resolution and spatially convincing sound that the desire for more should not arise for a long time. If at all again. For many, the High BassoNobile MKII could mean the end of their search. It’s a real investment. But one that is worthwhile.

Profile Acapella High BassoNobile MKII:

  • Real full-range loudspeaker with balanced, slightly sonorous tonality. A bit more powerful in the bass, a bit more subtle in the treble.
  • The bass range convinces with substance, enormous depth and an immediately dynamic note. It is contoured and grippy, but does not overdo it with the dryness either, so that acoustic instruments with a larger proportion of low frequencies come across very convincingly.
  • Not least because of the broadband horn, the mids and tweeters work like a unit, there are no transitions or breaks.
  • One of the greatest strengths of this loudspeaker: Thanks to the splendid resolution, the tonal color is very authentic – not just opaque, but very differentiated and, well: “simply real”. In general, quiet signal components are reproduced in an exemplary manner, be it room reflections / reverberation, the fading of notes or background noises when making music.
  • The acapella plays very dynamically, fine as well as coarse. You can drive the highest level with it and always have reserves up – quiet listening also works better with it than with many other speakers. The transient reproduction looks real and immediate, but there are loudspeakers that convey impulses harder and more sharply.
  • Another strength is the convincing spatial representation. Not least because of the real deep bass capabilities, huge stage spaces can be staged. The acapella introduces the musicians how far behind the baseline, just as the recording requires. The width, depth and height of the stage area are convincingly measured.
  • What is astonishing for such a large loudspeaker is the very free, precise and three-dimensional representation of voices and instruments. The edges could be even sharper, but the Duisburgers seem to consciously speak for a more rounded, organic image – especially since the sounds are also given a certain aura / air around them, which makes everything seem very natural.
  • The High BassoNobile is a large loudspeaker, so it needs space. Even if specific size specifications are always to be taken with caution: I think that from 25-30 square meters up you are better on the way than below. Especially since a certain listening distance to the loudspeaker makes sense, from 3.5 meters a good guideline seems to be a good guideline. Amazingly, however, the Acapella can be positioned quite close to the back wall, in the test it was less than 60 centimeters – neither the bass puffed up nor did it affect the representation of the virtual stage.


  • Model: Acapella High BassoNobile MKII
  • Concept: closed 2-way loudspeaker with hyper-spherical broadband horn
  • Price: 32,600 euros
  • Dimensions & weight: 162 x 52 x 71 cm (HxWxD, with horn), approx. 130 kg / piece
  • Versions: body high-gloss white and black, horn according to customer requirements; Special designs are possible
  • Nominal impedance: 4 ohms
  • Efficiency: 93 dB / W / m
  • Guarantee: 5 years