ULTRA AUDIO -- Archived Article

June 1, 2003

Acapella Audio Arts High Violon Loudspeakers



Masterpieces in sound

I first heard of the Acapella line of top-end speakers from Vince Scalzitti of Tri-Cell Enterprises, their North American distributor. Over beers, he described the experience of being ushered into the Acapella sanctum at Frankfurt's annual High End show:

"They do things differently over there," he said. "You don’t see the product until you’ve been introduced to everybody in several languages with a lot of bowing and handshaking. Then they hand you a glass of cognac, everyone stops talking, a pair of big double doors open, and you are ushered to a plush upholstered chair in the sweet spot. When the Acapellas started playing I was covered in sound, picking it off my sleeves and jacket…."

Needless to say, I was immediately intrigued.

Though reviews on these speakers are rare, and meeting someone who has actually heard a pair is even rarer, the company’s promotional material states that it has been in business since 1978. Designer Alfred Rudolph of Germany apparently solved the non-trivial technical problems associated with the ion tweeter at that time, and, together with partner Hermann Winters, has been selling speakers incorporating this tweeter ever since.

Speaker layout

The Violon is a very unusual three-way. It consists of a top-mounted midrange horn about 20" in diameter, a center-mounted ion tweeter enclosed in a small horn that appears to be made of brass, and a 10" bass driver in a large acoustic-suspension non-ported enclosure. The High Violin is 30 pounds heavier than the standard Violin, due to the presence of additional reinforcement in the bass cabinet. A "sub active" version is also available with an additional woofer for deeper bass. Internal wiring is Acapella’s proprietary ceramic-coated silver.

The finish on the review pair was white lacquer for the cabinet with metallic royal-blue automotive finish on the horn. A removable grille, also white, covers the rectangular portion of the speaker and contains a hole through which the tweeter horn protrudes. The news on the WAF (wife acceptance factor) is not very good, at least for this color combination in our leather-and-hardwood living room. My wife gave them a flat zero, and that’s before she found out how much they cost ($29,000 USD -- definitely not the bargain basement). Two other qualified wives who visited us during the three-month tenure of the High Violins also volunteered WAFs of zeros, I’m afraid. This is not to say that these speakers are unattractive. They have a colorful geometric look reminiscent of the ‘60s, and would be a striking centerpiece in a New York warehouse loft or any large, dramatic space with some architectural flair.

The Violons are also big, standing about 5’4" and approximately 14" wide. Weight is a solid 230 pounds. I mounted them on a pair of (non-standard) conical spikes on coin-type floor protectors. Both positioning and operation were straightforward. The removable tweeter unit fits into a shelf within each cabinet. A pair of signal wires emerge from the back of the tweeter and are connected to the horn driver by means of three-way binding posts with big plastic color-coded nuts -- finally, a pair of binding posts you can actually tighten by hand without tearing the skin off your fingers. The midrange unit is jumpered in similar fashion to the bass unit. I operated my pair in a biwire configuration without the jumpers. The tweeters have a control on the back that allows independent adjustment of the tweeter volume, which has a major effect on the centering of the stereo image -- play with it, set it, and forget it.

Room placement

My 12’ x 14’ room was clearly too small for these speakers and did not offer all the positioning options that I would have liked. The Violons were placed on either side of a big-screen TV (how humiliating for them!), about six feet apart with minimal toe-in and only a foot or so from the long wall. These units are much too tall for true near-field listening (within six feet). I was able to achieve satisfactory blending of the drivers, however, by pushing the listening couch against the back wall, which put me eight or nine feet away from the front baffles. Since this pair had been previously used for demonstration purposes, no break-in period was needed.

Associated equipment

Associated equipment consisted of the new BC24 hybrid tube/solid-state power amplifier from Blue Circle; a number of other amps that paraded through my listening room over the review period; the AVTAC Pasiphae transformer-based voltage selector and router (VSR); the Sony 777ES SACD/CD player acting as a transport via a dCS Delius DAC and Purcell upsampler; MIT Digital Reference cable; MIT350 interconnects; Cardas Neutral Reference speaker cables; and Transparent Super power cords. My usual speakers are the JMlab Electra 915.1.

The ion tweeter

Electricity is a fascinating thing. Apply a constant voltage to a wire and you get electrons flowing obediently through it as direct current. Apply a varying voltage and you have alternating current. In that case, the electrons move back and forth without really going anywhere, but the self-reinforcing electrical and magnetic fields that result from this motion begin to take on the properties of electromagnetic radiation. At low frequencies, the fields remain more or less within the wire. At higher frequencies, they begin to ride along the wire’s surface, resulting in the so-called skin effect -- attenuation of the high frequencies due to the lack of cross-sectional area of wire available in the skin. At still higher frequencies, electromagnetic radiation will detach and escape from the wire altogether, as it does in a radio transmitter.

If you apply radiofrequencies (around 30MHz) to a conductor at very high voltages, the electromagnetic fields may interact so vigorously with the surrounding air while trying to escape that the air is ionized and heated to the point at which it becomes a luminous plasma. The plasma extends for a short distance around sharp edges or points in the conductor and glows magenta/pink. This phenomenon is at the heart of the ion (or plasma) tweeter and is called a corona discharge. The plasma "flame" is often incorrectly referred to as a spark or an arc. Both of these require two conductors separated by a gap rather than a single conductor with a sharp edge, and tend to make a lot of noise. In the case of the arc, a relatively huge quantity of power would be required. The coronal-discharge phenomenon is a much more subtle effect, more closely related to St. Elmo’s fire than to your local welding shop.

Possibly the most exotic of the exotic driver technologies, the ion tweeter is the stuff of audiophile fantasy. The size of the plasma can be varied virtually instantaneously by varying the voltage applied to the conductor so that the resulting rapid change in volume vibrates the surrounding air. Since the process is driven by an electromagnetic field, the actuator (which is the field itself) has essentially no mass. Hence, near-infinite acceleration is possible, allowing near-perfect tracking of the high frequencies.

Acapella’s Spharon ion tweeter is, as far as I know, the only current production ion tweeter available in the world, though ion-tweeter kits seem to have something of a following in the do-it-yourself (DIY) community. The Spharon is enclosed in a Faraday-cage-type chassis with its own power supply and AC cord that can easily be removed from the Violons. The Spharons are also available separately (for $6900) for use in speaker projects. Acapella’s tweeter uses a sophisticated tube-based oscillator that can be set to detect the presence of a musical signal and automatically ignite itself with a series of audible clicks. When not in use for several minutes, the tweeter also turns itself off. By contrast, the DIY versions require that you wave an insulated screwdriver close to the electrode tip to get it going -- no thanks.

OK, but what about the poison gas?

Well, there is that, yes. Electrical discharges of all kinds, such as those at the brushes of an electric motor, produce ozone, which is a moderately poisonous gas. The ion tweeter is no exception; but the amounts are quite small. Occasionally, I could just barely detect the characteristic odor of this gas if I stuck my nose around the back of the loudspeaker. I felt safe on the whole. I would consider this mechanism of death-by-stereo quite unlikely.

Down to the sound

The High Violons have a specified 91dB sensitivity and 100W continuous power handling, which on the face of it would appear to make them suitable candidates for the widest possible range of amplification, from 8W triodes to 250W transistosaurs. 40W or more are recommended, however, and I soon found out why. My beloved and heavily modified KR Enterprise 300bsi sounded very nice through the Acapellas, but was unable to drive them to my preferred critical-listening level (which is admittedly, fairly loud) with its 25W, and tended to sound weak in the bass. The overall effect was, well, gutless. True 8W triodes? Forget it. The Antique Sound Labs unit I tried suffered from a bad case of flatulence trying to shift those woofers and tended to clip in the highs as well.

Though I won't question the veracity of the sensitivity figures, the impedance of the drive units may also have an important effect. Hermann Winters indicates that the ion tweeter impedance is 600 ohms, which is a very high figure owing to the active nature of the tweeter electronics. It should be easy to drive. The minimum impedance of the whole speaker is said to be 3 ohms. Hermann suggests that the High Violons can be nicely driven at modest volume by low-powered tube electronics if the 2-ohm tap on the output transformer of the amplifier is used. I believe it, though I did not try this out myself.

The 80W tube/solid-state hybrid BC24 power amp was happily on hand for another review, so I yoked it up to the Violons. The BC24 is a $2400 amp, which is a fraction of the cost of the speakers. I had heard it through my JMlab Electras and not been particularly bowled over. My first impression through the Acapellas, however, was "Wow!" After loading up the BC24 with expensive NOS tubes from Siemens, things only got better.

Apart from the somewhat surprising finding that a Canadian sub-$3000 power amp and a pair of super-exotic thirty-gee transducers from Germany seemed made for each other, the first thing that struck me about the speakers was the tweeter. The corona discharge popped on with a few clicks and a little whining sound (they tend to hiss and spit a little at the start, but then settle down to essentially dead quiet). Almost as soon as the plasma flames were lit, they started putting out the cleanest, clearest, purest treble I have ever laid ears on.

I warn you now that there are going to be a few superlatives in this review; parental guidance is advised. That tweeter, in case I didn’t make myself understood the first time, is entirely extraordinary. The consonant sounds of "bah" and "pah" are really the same sound, but produced a few milliseconds earlier in the case of "pah." The ion tweeter similarly closes the microsecond difference between a tweeter with realistic speed of attack and one with a convincingly real speed of attack. Instead of developing a rapid transient on, say, the sound of a drum stick striking a cymbal, the sound just appears in the air full grown with all the details that your brain tells you should be there.

Not only is it revealing, delicate, timbrally accurate (yes, I’m talking about the timbre of a tweeter), and ungodly fast, this tweeter’s best trick is that it somehow manages to sound realistically energetic without being the least bit bright. I recall shopping in a large grocery store recently, and suddenly realizing that the background music echoing around the ceiling was coming from a live musician. Apart from the fact that the musician was making some mistakes on a well-known tune, the main clue to the presence of live music was the unfettered quality of the treble. The Acapella tweeters preserve the boundless quality of live treble energy in a way that is unlike any other device I’ve heard. Move out of the sweet spot, go into another room, and the tweeter can still be heard with live-music-like clarity. The lifelike nature of this tweeter is unquestionably the dominant sonic characteristic of these speakers, and cannot be overstated.

If anything, this tweeter is so good that it upstages the other drivers to some extent. Nevertheless, the horn midrange and woofer also performed exceptionally in that they seemed to be able to keep up in terms of speed with the tweeter, which was particularly impressive with regard to the 10" bass driver. In my room, there was little to no horn coloration coming from the midrange. Interestingly, despite the location of the tweeter in the middle of the cabinet, the frequency spectrum seemed to arrange itself in the usual order: highest sounds on top, vocals in the middle, and bass at the bottom. Bass was very agile with a satisfying "thwacking" quality, though without quite as much detail in the rendering as I get through my JMlabs, and the soundstage was very, very solid.

The wall of sound

The presentation was solid enough, in fact, to be described as a wall of sound. I’m not sure about "picking sounds off my jacket," but I will agree that the palpability and openness of the presentation gave it a tactile quality. A recording by the great jazz guitarist Lenny Breau called Cabin Fever [Guitarchives 2], made during a drying-out period for the artist in a secluded cabin on Vancouver Island, illustrates the immense palpability of which the Acapellas are capable. This is a terrifically authentic-sounding recording with no post-production chicanery between you and the artist. Word is that the cabin in which it was made had no electricity, so a portable generator had to be used -- I’m talking authentic here.

Lenny’s solo acoustic guitar on "What is this Thing Called Love?" lunges out of the speakers with all its raw nylon-string sounds and guitar-body resonance eerily intact. Timbral accuracy and image solidity were such that I had the impression I could see into the guitar well enough to make out the label on the inside. About halfway through, Lenny steps out of the changes and goes double time with a kind of cadenza founded on a driving, repetitive bass line. Largely because of the speed of the Acapellas -- which is somewhere between that of a Lamborghini Countach and the Saturn V rocket -- the rhythmic energy of this section rocked so hard it left me gasping for breath. This is solo acoustic guitar recorded in a cabin with no electricity, remember.

The guitar image was grandly scaled without seeming overblown. That is, its apparent size was larger than it would have been if Lenny with his guitar had been sitting nine feet away from me at the speaker position, but no larger than if he were sitting a foot away and my ears were in the same position as the microphones during the recording. The presentation was not forward, in that the images remained at or behind the speaker plane, but there was an undeniably tactile impression of sounds leaping out from the speakers. This aspect of the High Violon sound is just plain fun and rather addictive.

By comparison, the same amp through my JMlab 915.1 speakers produced a whitish sheen where the nylon details should have been, threw a soundstage on a smaller scale, and lacked the punch, speed, separation and general excitement of the Acapella’s presentation. In no way could the JMlabs come close to that "real live" quality I associate with the ion tweeters. I had thought that my speakers were fast, and that the speed of my system was primarily limited by the amplifier. I was wrong. The Acapellas are not just high octane, they are a different mode of transportation. Remembering that the 915.1s cost roughly $3000 when new, this is hardly a fair comparison, of course. As an aside, the JMlabs acquitted themselves much better when driven by my KR; but that’s not comparing apples to apples.

I tried both the solid-state Chord SPM 400 and the Sugden Masterclass pure-class-A solid-state monoblocks through the Acapellas. Each had their strengths. The Chord was well-mannered, coherent, and very detailed in the highs, while the Sugden had a bit of the impressive richness in the midrange that I associate with pure class A, and was the better match. In the end, neither could manage the arresting realism of the BC24. This was notable given that both these amps are much more expensive than the Blue Circle. I suspect that the tube gain stage in the BC24 is its secret.

In comparing a number of different amps, a curious feature of the Acapellas emerged. All the amps seemed to benefit from the Violon’s obvious strengths without having their weaknesses emphasized. That is, they all sounded pretty darned Acapella-good. Normally, a speaker that makes several different amps sound similarly good would be said to have a lack of transparency to changes in upstream components; but this case may be an exception. If an amp had poor treble control, you heard that. Upstream changes such as tube rolling or cable switching were also clearly audible, yet a parade of amps ended up sounding much better through these loudspeakers than I would have expected. I can only conclude that the Violons somehow selectively accentuate the good stuff and leave the bad on the tarmac.

Swedish record company Opus 3 has put out a very satisfying sampler called Showcase [Opus 3 21000] featuring a collection of beautifully recorded, primarily acoustic tracks. Gospel blues number "I Want Jesus to Walk With Me," by Eric Bibb stands out as exceptionally detailed and musical. Through the Acapella-Blue Circle combination it was pure delight. Richness, palpability, fullness, rhythmic drive, imaging, and the Violon’s trademark dazzling high-frequencies all stood out. Having started with solo guitar recorded in a small cottage, I was unprepared for the size and depth of the soundstage on the Bibb recording. The word is huge, both left to right, and front to back. Reviewers often talk about the illusion of the back wall disappearing when the soundstage is deep. The Acapellas do this beautifully, and impart such a solid feel to the illusory back wall that I was found myself tempted to think it wasn’t an illusion at all.

As with all Opus 3 recordings, there is no compression of dynamics. On this track in particular, the peaks in the vocals are perhaps ten decibels louder than the baseline lyrics. Bibb’s plaintive cries during these peaks burst forth with so little apparent effort and so much clean sound pressure that they rattled the china and had me "this close" to believing I was listening to the real thing.

I don’t claim to be synesthetic, but I would describe the overall tonal color of my 915.1s as being illuminated by a bright incandescent light. The Bibb piece (and all other music) played through my speakers has a touch of warmth as a consequence. The High Violons, on the other hand, project images as if suffused with a very bright blue-white light. The effect is wonderfully absorbing and impressive.

Operating to this point by direct drive from the Delius to the amp, I then put the AVTAC Pasiphae into the chain. The Pasiphae is a new kind of passive preamplifier that uses transformer-attenuators to control volume instead of resistors (review to follow). This component took the performance to a new level, adding timbral details, bass fullness, wider soundstage, and even more speed to the presentation. The dixieland version of "Comes Love," performed by the Swedish Jazz Kings, had me actually riveted -- and until that moment I was no fan of the Swedish Jazz Kings. I would have thought Swedish Jazz an oxymoron. But there they were, somber white men with tubas and banjos, rocking my world. In the past, the inevitably imperfect rendering of such harmonically complex sounds as that of the banjo has put me off dixieland music. Here, for the first time, was the full glory of honkytonk piano riding on a realistic V/I tuba foundation. I listened entranced to the whole track, then played it again.

More evidence of the remarkably lifelike abilities of the Violons, and another transformative experience, was to be had on this disc from the Erik Westberg Vocal Ensemble’s "Sanctus." This is a monastic homage to the Deity performed by a full choir. With the Pasiphae on line, I had chills. Every voice, the approximate age of the person behind the voice, and the degree of closeness to God of each was rendered sensible. The softer and warmer focus of my Electras on this piece was pleasant and involving, but the overall effect was not nearly as arresting as it was through the Violons. With the Acapellas on line, my living room was suddenly and violently knocked down and an entire cathedral built at full scale, complete with cavernous resonance, heavy masonry, and white-robed supplicants. I had an actual twinge of guilt that my sinful self should be spying on such an intimate moment of religious observance. The system was that good.

In fact, the dCS-Pasiphae-BC24-Violon combination that I now have in my small living room is without much doubt the very best system I have ever heard. Not that I’ve heard a wide selection of systems in this price range. Nevertheless, given the unique design features of the Acapellas, it seems reasonable to suppose that at least some of what this system does, no other may do as well. Excitingly, I would also suggest that this already amazing level of performance could be further improved. As good as the BC24 is, I heard greater liquidity, more tonal vividness, and perhaps even better separation of sounds when playing the KR through the Violons -- but alas, with insufficient power. For a better match with the KR, I guess I’ll just have to win the lottery, buy a bigger house, and get the Acapella Spharon Excalibur, which is almost eight feet tall and boasts 100dB efficiency.

Flies in the ointment

The degree of driver integration and coherence which has been achieved by Herr Rudolph is nothing short of a technological tour de force. How, for example, did he rein in the tendency of horn drivers to offer a presentation that is forward of the speakers? How were the expected horn colorations controlled? And how did he get such speed out of a big woofer? The three drivers work together superbly, as evidenced by the solidity and realism of the images they project, but they are still three radically different drivers in terms of technology. If you listen for it, you can certainly detect the different signatures of the tweeter, horn mid, and woofer.

Comparing the BC24-Violon combo with my KR-JMlab pairing is instructive. The JMlabs have greater driver coherence, though they cannot match the Acapellas with regard to either speed or high-frequency energy and fidelity. The Electras also have a more relaxed feel, whereas I would describe the Violons as more high maintenance for the listener. Credible realism and unfettered treble energy just seem to demand that one pay attention.

The presentation of pop music is another issue, though I admit that this may be more of a source issue than a speaker issue. Through this uber-system, every bit of high-frequency emphasis, the digital reverb, every twist of the compression knob, in short, every artificial "enhancement" in the production process is audible. Dave Mathews' Crash, for example, [RCA 66904] sounded somewhat alarming, revealing a host of artificial effects I never knew were there. It is fair to say, though, that this presentation was also more emotionally involving than the version I am used to through my regular system. The Violons do not "rock" in the traditional sense of imparting added rhythmic energy to pop tracks through midbass and treble emphasis. They do, however, rock like I’ve never believed possible in terms of extracting excitement from well-recorded music.

Finally, the midbass area is not quite as filled-out as it should be, though this may well be a room artifact. Room interactions can easily be the dominant factor in bass performance, and the Violons were certainly not designed to be shoehorned into my little living room.

When all is said and done, these are minor quibbles, which are the only kind one can make of a truly great speaker.

A last listen

Rebecca Pidgeon has a strong following among audiophiles for her stunningly clear and high vocals on a number of deliciously clean-sounding and folksy Chesky recordings. Not mainstream stuff perhaps, but perhaps the mainstream isn’t ready for it. The title track of The Raven [Chesky 115] is one of my all time favorites. Through the High Violons, the glorious swooping sadness of Pidgeon’s voice radiated from a huge glowing orb between the speakers that reached out in all directions into the room. Background strings were dead-perfect timbrally, separated, delicate, living and breathing. I had the impression of being enveloped and touched on all sides by the blue-white radiance of the sound. It may not be surprising that a selection containing so much information in the treble was so exquisitely rendered through the Violons, but I hesitate to dismiss the experience. My notes from that session say "I can die now."

But aren’t these speakers too expensive?

I’ll grant you that a pair of speakers that cost as much as a minivan may seem like too much money for most audiophiles. On the other hand, here at Ultra Audio we have a no rubbernecking policy. If you can’t afford it, move on to the next review. Just kidding, I can’t afford them either. I’ll go to bat for Alfred and Hermann here, though I’ve never met them. I contacted a do-it-yourselfer who has sourced the parts to build his own horn speakers. He estimates the build cost for the Violons to be more than fair when you apply the standard markup for a high-end company to stay in business, and even more fair when you consider that Acapella seems to have got it right.


The Acapella High Violon speakers embody a design that is going on 25 years old and yet still represents a cutting-edge masterpiece in sound. These speakers are exceptional, bordering on revolutionary. Unique among production speakers, the ion-tweeter device is just unbelievable for realism, energy and clarity, and the other drivers match the tweeter for speed. The High Violons are capable of seemingly preternatural realism, grand scale, and a unique tactile quality that is absorbing and addictive.

Like Icarus, the higher they fly, the harder they fall. After my time with the High Violons, I’ve now had the unhappy experience of listening to some highly regarded conventional tweeters that sound like wet cardboard. In comparison with my own JMlab Electras, and, indeed, most other speakers systems I’ve heard, the Violons offer a giant step forward in realism, scale, treble refinement, and palpability. Get ‘em if you can, they’ll challenge and delight you every step of the way.

…Ross Mantle

Acapella Audio Arts High Violon Loudspeakers
Price: $29,000 USD per pair.
Warranty: Five years parts and labor.

Acapella Audio Arts
Hermann Winters KG
Koloniestr. 203
47057 Duisburg

Website: www.acapella.de

North American distributor:
Tri-Cell Enterprises Inc.
176 Monsheen Dr.
Woodbridge, Ontario
Phone: (905) 265-7870 or (905) 265-7869
Fax: (905) 265-7868

Website : www.tricell-ent.com  


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