Soltanus Acoustics

Full range, Electrostatic loudspeakers
The Sound of Perfection

A lot of things can be said about wonderful technical solutions, miraculous measuring and the so called "big" manufacturers, etc. The truth is that we are able to tell only by heart whether some music system is making a noise or playing pure tones. Some say it can be proved by measuring... but we mostly don’t think so. Of course, the precise measuring is necessary, but only on a very basic level. We often meet with components that have wonderful measuring results, but something is missing: the real experience of live music. The explanation for this is that these components are adjusted in a deaf room, with pure ohmic load in strictly 20 degrees of Celsius, etc. The problem is that we can not reproduce these standard conditions because we do not listen to sine waves in perfect conditions.

There are some scientific efforts to improve high-tech musical instruments with pure "distortionless" sound. The question is: is it really music, or is it something else? 

We are speaking in terms of music instruments. For the reproduction of a real concert hall experience, the high-end equipment has to do the job similar to music instruments or even more. It is much harder because two loudspeakers have to reproduce all the concert hall instruments, in addition, at the same time. We have to admit, it is not an easy task. There is no perfect solution yet, and there might never be but we are heading for it.

Our opinion is that musical experience should be determining which technical solution is the most suitable for it and in a visually pleasurable way, of course. We believe that nobody likes to watch an expensive and awful black box in their living room. 

In our development and designing process, we use high-tech measurements, but only in a way a viticulturist uses a glass of wine during wine tasting. The essence of a glass of wine is the experience. It’s the same with loudspeakers. 

We wish a lot of pleasurable hours of listening to music for all of our customers.

What is a Soltanus electrostatic (ESL) loudspeaker?

It is a special breed of speakers offering extraordinary, compellingly realistic audio reproduction. The magical sound of Soltanus acoustics electrostats results from a uniquely fast, super light-weight diaphragm capable of instantaneous movement that creates sound with unflinching accuracy.

Additionally, a single electrostatic driver is capable of reproducing the entire frequency range where human hearing is most sensitive to (the entire human voice spectrum) the delicacy and richness of sound. This unique technology assures that what you hear is faithful to the original recording. Also, it eliminates the need for complex crossovers and multiple driver arrays (which cause distortion). Listen to any Soltanus acoustics electrostatic speaker and the difference will be immediately noticed.

How does a Soltanus electrostatic (ESL) speaker work?

Electrostatic speakers have three basic parts: the stators on the front and back (the black screens), a super-thin, visually transparent electrostatic diaphragm, and spacing spars that suspend the diaphragm in the middle. Your amplifier’s signal is applied to the stators to create an electrostatic field that moves the diaphragm and excites the air, creating the legendary ESL sound.

Technology: Electrostatic Advantages

The advantages of electrostatic loudspeakers include levels of distortion which are one to two orders of magnitude lower than conventional cone drivers in a box. The extremely light weighted diaphragm (8-28 times thinner than the human hair), which is driven across it’s whole surface. It has an exemplary frequency response (both in amplitude and phase) because the principle of generating force and pressure is almost free from resonances unlike the more common electrodynamic driver. Musical transparency is better than in electrodynamic speakers because the radiating surface has much less mass than most other drivers and is therefore far less capable of storing energy to be released later. For example, typical dynamic speaker drivers can have moving masses of tens or hundreds of grams whereas an electrostatic membrane only weights a few milligrams, which is several times less than the very lightest of electrodynamic tweeters. The concomitant air load, often insignificant in dynamic speakers, is usually tens of grams because of the large coupling surface. This contributes to damping of resonance buildup by the air itself to a significant, though not complete, degree. Electrostatics can also be executed as full-range designs, lacking the usual crossover filters and enclosures that could colour or distort the sound.

Since many electrostatic speakers are designed tall and thin without an enclosure, they act as a vertical dipole line source. This makes a rather different acoustic behavior in rooms compared to conventional electrodynamic loudspeakers. The line-source emulates the staging you heard in the concert hall. So the sound field is lifelike. Generally speaking, a large-panel dipole radiator is more demanding than the proper physical placement within a room when compared to a conventional box speaker. But, once it’s there, it is less likely to excite bad-sounding room resonances, and it’s direct-to-reflected sound ratio is higher by some 4–5 decibels. This in turn leads to a more accurate stereo reproduction of recordings that contain proper stereo information and venue ambience. Planar (flat) drivers tend to be very directional by giving them good imaging qualities, under condition that they have been carefully placed relative to the listener and the sound-reflecting surfaces in the room. Curved panels have been built, making the placement requirements a bit less stringent, but sacrificing imaging precision somewhat.

Why do Soltanus acoustics ESLs also have woofers?

Electrostatic speakers can not reproduce deep bass sounds (below 100Hz) as effectively as a cone woofer. Soltanus acoustics’ solution is a hybrid design that provides the best of both worlds—a high quality cone woofer to reproduce low bass and a single electrostatic driver to reproduce sounds in the frequencies where human hearing is most sensitive to nuance.

Thanks to long research and development, when you listen to Soltanus acoustics hybrid system you notice that the harmony between ESLs and active subwoofers is perfect.

The Soltanus acoustics subwoofers are built solidly with high-density materials to minimise cabinet resonance and provide a foundation for the high-output woofers and high-current 250-watt RMS, 300-watt peak amplifiers. Additionally, the built-in active control unit can offer you a flat acoustic response (both in amplitude and phase) in every environment in a variety of positions, relative to ESLs.

Soltanus acoustics woofers offer a continuously variable low-pass crossover between 40 and 1000 Hz implemented with a precision-designed filter for optimum attenuation slope and minimum group delay. This enables seamless integration with any Soltanus acoustics main speakers as well as with speakers from other manufacturers.

The variable phase controller is essential for clean, detailed and location-less bass, which can be precisely adjusted independently from the woofers position in your room. Another reason for developing this controlling unit is that every loudspeaker has it’s own phase response, velocity, and of course distance from the listener. All frequencies have to reach to the ear at the exact time for correct reproduction. This phenomenon is mostly expressed when using a woofer with an electrostatic loudspeaker. Leaving this out of consideration is the reason of believing that a dynamic woofer can not be integrated with an electrostatic system.

At very low frequencies, all rooms exhibit a phenomenon known as room gain, which produces a mild bass boost. The smaller the room, the higher the frequency at which this starts. These low frequency level controls enables you to compensate for excessive room gain by cutting output in the 20- to 80-Hz range or, if you prefer, to accentuate the feeling of deep-bass energy by augmenting lowest frequencies.

Although ports are a convenient and cost-effective way of increasing low-frequency output, they rely on resonant energy in a way that impairs bass quality. That is the reason we do not use them. A good sealed system will exhibit less transient-blurring group delay while maintaining smooth, consistent response regardless of output level or voice-coil temperature. Listen carefully to the sound of a bass drum, and you'll hear the difference.

Easy Set-Up and Integration with Any System

Audio and video products available today represent a confusing myriad of connection options and setting configurations. Understanding this complexity, Soltanus acoustics designed subwoofers with an input architecture that is easily integrated in both stereo and home theatre systems.

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SA 06 SF VIR
NZ$ 15,795.00 (incl. GST)
I have a friend that purchased a pair of these. I have been listening to these for about 3 weeks now. I currently own a system with Martin Logan CLS's so I am familiar with electrostatics. The...
Soltanus Acoustics proudly presents the world’s first Crossoverless, Multipanel, (ESL)...
Something really special, the ESL Virtuoso of Soltanus Acoustics, found its way into our...
A system that took me completely by surprise was built around a pair of Soltanus Acoustics ESL...

All Products

SA 06 SF VIR
NZ$ 15,795.00 pr (incl. GST)
I have a friend that purchased a pair of these. I have been listening to these for about 3 weeks now. I currently own a system with Martin Logan CLS's so I am familiar with electrostatics. The...
Soltanus Acoustics proudly presents the world’s first Crossoverless, Multipanel, (ESL)...
Something really special, the ESL Virtuoso of Soltanus Acoustics, found its way into our...
A system that took me completely by surprise was built around a pair of Soltanus Acoustics ESL...

Reviews

The Virtuoso delivers each overtone so precisely, giving us impression that we are right in front of the sound source, the speaker carves out the important mid range, at lower levels & Intimacy is increased to the utmost.
Tobias Hecklau - AUDIO TEST

SUMMARY: With ESL VIRTUOSO, Serbian maker, Soltanus Acoustic success in extending the benefits of electrostatic speakers - like unique,clarity and transparency up to and including the bass region. They are a high-tech at discount rates. Musical fine spirits for those with sufficient space in the listening room, these special speakers are highly recommended. -

EXCELLENT 90% rating

Something really special, the ESL Virtuoso of Soltanus Acoustics, found its way into our auditioning laboratory. According to the maker, the ESL Virtuoso is the world’s fi rst multi-panel electrostatic unit that requires no crossover, thus the full-range design was in order. In Montreal, the Serbian team and the lead designer Zoltan Mikovity were awarded the “Best of Salon Son & Image 2015” award. 

The ESL Virtuoso belongs to the rare species of the full range electrostatic that can play frequencies over the entire range of human hearing. These devices are very rare because the electrostatic operating principle has difficulty playing the bass range and are therefore usually combined with conventional (electro-dynamic) woofers. The Virtuoso however, is designed as a full-range solution, which brings a further advantage - there are no disturbing frequency dips or overlays in the transition frequencies. 

Electrostatics 

The speakers consist of two charged stators surrounding the conductive membrane. Music signal applied to the stators produces an electrical field, which attracts or repels the membrane. As a result, it stimulates the air to vibrate, thus producing sound waves. Since the membrane is 8 to 28 times thinner than human hair, it operates extremely fast and can perform even the smallest movements correctly. This enables a direct and accurate representation of the played material.

However, the membrane often has difficulty reproducing large amplitudes undistorted. Due to the all-around open construction, low frequencies can be diminished causing an acoustic short-circuit. The problems in the bass range can only be compensated by a sufficiently large radiating surface, which was obviously attempted in Virtuoso. The loudspeaker measures no less than 153 centimetres (cm) in height and incredible 68cm in width, it reaches a membrane area of about one square meter. 

With a depth of 33 cm at the base and 5 cm at the upper end, typical of electrostatics, it is quite thin. Nevertheless, it comes in at 26 kg, a decent weight for this speaker genre, and it should be installed with the help of a second person. The design can be best described as classic and clean, which was a good decision because of the lush proportions of the speaker. The front and rear sides are covered with black fabric, the side rails come optional in black or wood veneer finish. The speaker stands on a massive metal base, equipped with three spikes. 

On the rear side of the speaker, above its power socket we could admire some adjustment possibilities. There are terminals for amps with a damping factor of less than 25 and for amps with higher value. For amps with a damping factor of less than 25, there is a rotary switch for adapting the Virtuoso to them. This nice feature, unfortunately, often falls flat because the damping factor of many amps is not specified in their respective data sheet. In that case, the best is to try and trust your own ears. Unlike many other electrostatics, Virtuoso is not picky when it comes to amplifier and I understand dazzling results can be achieved with tube amplifiers. Another rotary knob called “Tweeter bias” is for raising or lowering of the highs to adapt to the room or personal taste.

Sound and placement 

For the speakers to deliver their full potential, it is recommended to break them in for about 200 hours (this is eight days and eight hours). The manufacturer provides a burn-in CD for this. According to the manual, it is recommended to let the speaker continuously run for about 24 hours as it could sound a bit thin otherwise. Also, fully broken-in speakers should be given a ten minute warm-up period, in which the stators can charge. You should also invest enough time in the placement. Since the Virtuoso is firing as much to the back as it does to the front, this could lead to undesired interference between the direct sound and the wall-reflected signal. In addition, it is well known that electrostatics have smaller sweet spot than electro-dynamic loudspeaker, which, in our experience, also applies to the Virtuoso. (Warning: do not sit too close to the speakers set).

Sound Test 

When the right placement is found, one is rewarded with a special impression of the finest quality. The phantom mids are also modelled out like any other sound events, which are spread across the entire stereo width. It is striking - the distinction between the individual instruments works particularly well. This is a great advantage of electrostatics, which can be explained by the great fidelity in general. The special feature of the Virtuoso is razor sharp lower frequency range, which cannot be said for most other electrostatics. 

There are songs with electronic bass and bass drum that are difficult to disentangle. We have never been able, until now, to hear these two instruments delineated so clearly in Lenny Kravitz song “Are you gonna go my way”. There were also discoveries of previously unheard subtleties in many other well-known pieces. It’s like re-discovering your favourite music all over again and this time properly! ESL Virtuoso delivers hugely in the midrange and treble range. 

For example, we have rarely heard pianos and harpsichords so vividly, freshly and naturally. Modern mixed (recorded) singing which is provided for generating psychoacoustic closeness with artificial overtones, from our test samples, appears incredibly close, almost as if the singer was a few centimetres in front of us. This is a result of the precise reproduction of small and micro vibrations, that a conventional, electro-dynamic speaker cannot reproduce, due to its relatively heavy membrane. 

The Virtuoso delivers each overtone so precisely, giving us impression that we are right in front of the sound source. The psychological effect lies in the fact that such micro vibrations in nature are lost after only a few centimetres. As a result, the speaker carves out the important mid range („voices“) exemplary even if it is recorded („mixed at the recording studio“) at lower levels. Intimacy is increased to the utmost, particularly beautifully recognisable with Norah Jones’ Grammy winning “Don’t know why” song. 
By the way, it does not matter if you increase or reduce highs using the control dial. The change happens so skilfully and unobtrusively that the speakers never miss a beat. 
If I have anything to complain about, that would be that the level below 100 hertz drops significantly. This could perhaps affect pop and rock listeners, in which case we recommend the subtle use of a subwoofer. 
The Virtuoso doesn’t play as loud compared to electro-dynamic transducers, so please handle the speakers carefully - the ESL Virtuoso is more for sophisticated listener than for electronic DJs. With moderate volume, fans of genres such as classical, jazz and folk will get their money’s worth and will be able to enjoy their favourite music in unexpected quality. 

The best is yet to come: Serbian tech speaker does not cost EUR 20 000, nor EUR 10 000. The MSRP is listed at only EURO 9,950 and this price is not for a single unit, but for the pair. Although not inexpensive, they are well worth it 

Conclusion

With ESL VIRTUOSO, Serbian maker, Soltanus Acoustic success in extending the benefits of electrostatic speakers - like unique,clarity and transparency up to and including the bass region. They are a high-tech at discount rates. Musical fine spirits for those with sufficient space in the listening room, these special speakers are highly recommended.
EXCELLENT 90% rating.

........Tobias Hecklau

For us the ESL Virtuoso was a definitive must hear. But be warned. Chances are high that this will turn into a must have.
Marja & Henk

SUMMAY: We can be brief. If we had to start all over again assembling an audio system, the Soltanus ESL Virtuoso would be in the top 3 of our wish list. This speaker is well built, easy to place and its pricing for delivered musical quality very competitive. Its easy-going character makes it non-problematic to find a satisfactory amplifier match of either the tube or solid-state persuasion. Even damping factor is not critical with the supplied adjustments. Zoltan Mikovity’s design complies with virtually any amplification offered as long as it is sufficiently powerful for your desired levels. Know your damping factor and the Virtuoso will match it. Add some decent loudspeaker cables and musical satisfaction seems guaranteed, personal preferences aside. In the looks department, the Virtuoso scores just as other panels this size do. There’s a large black surface. Its curved top line, massive wooden side rails, super-smooth stretchy cover jersey and small footprint make the Virtuoso salonfähig and non-intrusive. For us the ESL Virtuoso was a definitive must hear. But be warned. Chances are high that this will turn into a must have.

EXTENDED REVIEW: Loudspeakerlandia can be divided into two major continents. On one thrives the dynamic driver, on the other hides the planar transducer. The dynamic driver is most populous by far. Due to its vast dynamic range, high power handling and sensitivity plus quite simple design and concomitantly lower manufacturing costs, almost 99% of all loudspeakers use cones ‘n’ domes. Flaws in a driver’s frequency response are relatively easily compensated for by limiting its bandwidth and commissioning other drivers designed specifically for a certain range; woofers, midranges and tweeters. Together with a filter system called the crossover, an array of drivers packed into a loudspeaker acts as one and in many cases it will still be considered a quasi point source. 

Next to acting thus, dynamic drivers all share another feature - a voice coil. Electric current from the amplifier is sent through it. Being suspended inside a magnetic field created by two permanent magnets whose lines of flux cross the gap between them, the voice coil floats in said gap. Physics dictate that the current flow through the circular coil in the flux field causes magnetic forces to operate along the coil’s axis: the coil moves forward and back. Attached to the coil—in fact to the so-called former on which the coil is wound—is a cone or dome generally called a diaphragm. The faster the current alters in the coil, the faster the diaphragm will move the air it pushes against and the higher the frequency of the air movements will be. Those air movements are detected by our ear-brain system to translate as sound. Some sounds are even discerned as, yes music by our cognitive mechanism.

By contrast, planar loudspeakers do not use coils floating in a magnetic field. In a ribbon loudspeaker, a strip of aluminium is suspended between two strong permanent magnets. The music as current is sent though the ribbon which creates a magnetic field around it. This field interacts with the field created by the two permanent magnets and makes the ribbon move back and forth. The ribbon can be small for high frequency use or large for lower frequencies. Just like with dynamic drivers, a ribbon-based planar loudspeaker excites the air which we (can) process in our heads into music.

Another form of the planar loudspeaker is the electrostat. Compared to the electromagnetic principles of dynamic and ribbon drivers, the electrostatic driver is a completely different animal. It’s perhaps best to regard this type as one giant capacitor. An ultra-thin stretched membrane is attached between two rigid plates called stators. A very high voltage applied to the membrane often reaches 10kV. Once the audio signal is sent to the stators—the positive phase to one, the negative phase to the other—the signal creates an electrostatic field in relation to the incoming musical signal. That varying field now interacts with the static field of the membrane and makes the membrane move back and forth as it gets attracted and repelled by the stators. In moving this way, the air around the membrane is excited once again. 

The stators are perforated to avoid obstructions to the air flow. An electrostatic loudspeakers or ESL needs power from the grid to work. For the static part of an ESL aka its membrane, the polarizing voltage must be generated and the incoming musical signal stepped up from a few tens of volts to several thousands. The biggest difference with any other type of loudspeaker driver is that there is no physical contact with the moving ESL diaphragm. Only electrostatic forces make the ultra-thin film move. That film is lighter even than the air it moves. Being so thin, a dozen micron (12 x 10-6 meter) or less, also makes the diaphragm free of energy storage or self resonance. Colouration is no issue. Whilst we are at the benefits of ESLs, here are some more before we'll get to the liabilities (you didn’t think this was a free lunch, did you?).

By design,
An ESL is a very linear transducer. The voltages across its two stators are linear within the space between them. In electrodynamic drivers, the small space in which the coil moves inside the magnetic structure makes it hard to be linear just like the fields generated by the voice coil are not linear. The pushing and pulling action of the magnetic motor on the voice coil relies on the coil’s constantly changing position with regard to the magnet. With an ESL, the pushing and pulling of the membrane is linear across the complete diaphragm and the force applies evenly over the entire surface. Where dynamic drivers can and will suffer from break-ups as the cone is not always able to follow the coil movement exactly and oscillates, an ESL follows the input flawlessly (unless overloaded of course). Most dynamic drivers are housed in a cabinet which adds colourations and is always a compromise. ESLs don’t come with cabinets, hence don’t suffer their effects.

As already mentioned, the polarising voltage on the diaphragm must be applied by plugging the ESL into the wall. Placement in the room is another aspect that needs to be addressed carefully. An ESL is a dipole radiator which means the back of the loudspeaker emits just as much out-of phase energy as the front but very little sideways. Placement too close to the front wall does not work well but a spot in close proximity to a side wall is no problem. On that same placement topic, ESLs with a few exceptions show limited horizontal dispersion. This means their sweet spot is quite narrow. Likewise, vertical dispersion is critical when looking for the best placement. Experimenting with tilting the loudspeaker forward or back to match the listener’s ear height is essential.

ESLs are also demanding of the amplifier/s they are combined with. Sensitivity is not an ESL forte so a power amplifier capable of delivering sufficient voltage is necessary. That amplifier also needs to be able to handle a very reactive load. Impedance can dive dramatically as frequencies rise. Swinging down to 2Ω or 1Ω from a nominal 8Ω is no rarity. And in general an ESL does not play very loud, does not go very low and does not blow the creases out of your pants. That’s in general as we will see.    

Against this general background, we received an e-mail with a question: were we interested in reviewing a new crossoverless full-range electrostatic loudspeaker? Hola, wait a minute. Crossoverless and full range had to mean no added dynamic woofer, i.e. one huge room divider. Visions of immense Soundlab electrostatic speakers popped up. Admittedly our listening room is not small but really huge ESLs? Fortunately the e-mail pointed us at the website of the manufacturer, Soltanus Acoustics of Serbia. There were the dimensions: 153cm tall, 68cm wide with a depth of 5cm at the top and 33cm at the bottom. These dimensions were roughly the same as the Quad ESL 2905 we auditioned some time ago and still had fond memories of. Christened ESL Virtuoso, the review offer was tempting and we agreed to take it on. Arrangements with designer and owner Zoltan Mikovity in Subotica/Serbia were made who insisted to deliver them personally. At the agreed date and time, a white van with Serbian plates pulled up. After a night in a hotel, Zoltan and companion Milo who came along to help felt refreshed after their 1’500km long journey. In the early morning sun two flat wooden crates emerged from their van. With a modest weight of 26kg, the Virtuoso loudspeakers are easy to manhandle once released from their wooden confinements. Assembling them is down to attaching the Y-shaped steel bottom plate and affixing adjustable steel spikes in the front. The third spike is part of the steel plate and equipped with a long thread, enabling the Virtuoso to be raked forward and back for precise setup.

Before Zoltan arrived, we had moved our resident Pnoe horns to make room for the Virtuoso. We agreed on setting them up 2.8m center to center and 1.7m into the room. The sweet spot with this initial setup was at 3.9m from the front line. Moving the speakers around was easy but a second person is needed to put protective footers under the spikes and shield a wooden floor. A modest toe-in aimed the center of the speakers at the sweet spot. Hooking up the ESL Virtuoso proved straightforward. At the lower back of each speaker sits a panel with an  IEC power inlet, two knobs and three (!) 5-way speaker binding posts. One binding post is for the return, the other two are for either a power amplifier with a damping factor 25 or less: or an amplifier with higher damping (lower output impedance). The two rotary knobs are to fine-tune the match with amplifiers of a low damping factor; and to adjust tweeter bias. Amplifier damping factors of 1-2, 3-4, 6-12 or 12-25 are selectable in combination with the binding post for a low damping factor. With the other selector, the tweeter’s bias can be tailored from -3 to +2 in accordance with the room’s absorptive/reflective behaviour.

All our amplifiers fit the high-damping figure to determine the matching connection. Zoltan wanted to make sure the speakers were in perfect condition so a preliminary connection with the review sample Abyssound ASX-2000 power amplifier was made using a pair of unbranded cables Zoltan had brought with him. Satisfied with the workings and initial setup, the two Serbs left. Because the Virtuoso were not fully broken in yet, we detached the AbysSound and connected a Devialet D-Premier with two lengths of Crystal Cable Crystal Speak. That’s because the Devialet has a built-in brown noise generator. Brown noise is ideal for burning in lower-frequency drivers since its energy distribution is mainly in the lowest frequencies. Each octave contains as much energy as the two octaves above it. The bandwidth between 20Hz and 40Hz (one octave) offers the same sound power as 40Hz to 160Hz (the next two octaves and so forth). We let the brown noise softly run for two days after which we played real music just for background levels and more softly overnight as an endless-repeat loop

Zoltan Mikovity started his audio life
With hornspeakers in a disco. It was at a friend’s place that he heard a Sonus faber Concertina run off a locally manufactured amplifier in combination with Kimber cables. That made him sell all his then collected audio gear and start the move into finer things. That obsession lasted 5 years until he could borrow a pair of DIY Martin Logan speakers whence the electrostatic virus infected him deeply. Next to listening to all manner of ESLs, Zoltan started to build his own speakers. Friends were his initial customers and his name and fame started to grow in the ESL burg of Serbia. He built and sold his speakers and repaired others until three years ago an investor arrived. This person owned a big system based on Vivid Audio speakers but was smitten by what Zoltan had built. With the help of this money angel, the Soltanus Acoustics company could launch to offer a whole range of electrostatic speakers. The Cricket model is a hybrid where sub 600Hz data are handled by a dynamic driver in its own ported part of the speaker. The Phoenix 150 and 180 are designed to work with an external (sub)woofer. Now this lineup is complete with the full-range Virtuoso.

Virtuoso’s frame is machined from very rigid MDF into which slide three transducer panels. This construction makes it easy to remove a panel without having to dismantle the entire speaker. The high-frequency panel measures 120x14cm and is designed to cover 200-20'000Hz. This is flanked on either side by a 140x16 cm bass panel capable of hitting 40Hz at -3dB. Each panel is constructed with perforated powder-coated flat steel sheet stators. Each stator hole isn’t merely a straight-edged laser cut but finished with nicely smooth edges. Once the holes are as smooth as possible, a plastic coat is applied. With the high voltages at work, any unevenness in this cover can result in micro arcing/sparking which would be audible as a hiss. With their static attraction to dust, some minute hiss with ESLs is unavoidable over time but hiss due to manufacturing problems is avoidable by design. Another trick Zoltan applied to improve his Virtuoso over competitors is to have the the high-voltage source running at 50kHz where others sticks to a non-switched 50Hz. Running at a faster pace, the capacitors involved in charging the stators have a 1000 times higher energy level which translates to a very fast dynamic character.

Having run in the speakers sufficient, it was time for some serious listening. Input was the Qobuz Desktop app via a La Rosita Beta DAC down to the Music First passive preamp and subsequent Hypex nCore 1200 monos. The ESL Virtuoso were grid-fed by Crystal Cable power cables whilst Nanotec SP#777 Great speaker cables carried the music signal. With a dispersion of 35°, these ESLs were really focusing and the sweet spot was fairly narrow but by no means claustrophobic. On the other hand, dynamic loudspeakers lose almost 50% of their direct output over the first meter as their wave front spreads out. An ESL acts as a line source to produce a cylindrical wave form without the same losses over distance. The result is great clarity full of resolution. Soltanus have chosen flat panels unlike the curved ones Martin Logan popularised. Curved panels disperse sound more widely but lack the directness of flat panels.

Now listening critically, the harmonic coherence of the Virtuoso was the second thing evident after its directness. First we played Farat by Anna Maria Jopek, a live album loaded with emotion and craftsmanship. Next to the unique vocal timbre of Mrs. Jopek, the sax of Henryk Miskeiewisz and piano of Leszek Możdżer really stood out in their naturalness. Played over the Virtuoso, the stage was deep and wide, the band arched behind the singer. Each member of the band could be identified individually but wasn’t isolated. Another live album that oozed involvement was Montrealby guitarist Jesse Cook. His repertoire of mainly rumba flamenco may be a bit cheesy but the atmosphere captured from this concert makes up for everything. With the Serbian speakers it was hard to resist getting sucked into the performance. We also noticed another effect, namely that the sound did not change as we moved farther away from it. Leaving the sweet spot to walk to the back of the room some 10 meters away did not cause the stage image to alter in depth. Only width shrank over being closer. 

For a third sample of a live performance, we chose Christy Moore with Live at Vicar Street. Playing this felt like a private concert and no emotion was spared. Deeply touching lyrics and sparse instrumental use led to get up and be jolly in Lisdoonvarna. With its extreme focus, the Virtuoso didn’t make for casual listening. The listener will be involved. There’s no escaping that. Studio-recorded Jazz was next on our list by way of Road to Ithaca by the Shai Maestro Trio and James Farm by Joshua Redman and friends. The first album by the trio led by the pianist known from his work with Avishai Cohen meanders between Jazz and poppy melodies. Notes are prudent and accented and offer nice insights into the instrument’s timbres. The ESL Virtuoso followed without any objections even at realistic volumes. Though the specifications limit lower extension to 40Hz -3dB, we never felt the urge to call upon our Zu subwoofer to add in the bottom octave. The balance between lower end and upper limit was satisfactory and the transition so smooth, no multi-driver dynamic loudspeaker would be capable of it. On James Farm, the saxophone of Joshua Redman added another sonic spectrum to the piano-drums-bass trio. Again the Virtuoso showed that even at elevated volumes, any preoccupation with ESLs being handicapped was a myth where this Soltanus was concerned.

To see if and howamplifier choices would influence the sonic outcomes, we swapped the class D monos for our Trafomatic Kaivalya EL84 tube monos. They tick the box for higher damping factor but only put out 25wpc. That’s 25 tube watts*. Zoltan rates his Virtuoso at 86dB which meant the Kaivalyas had to work to earn credits. We had to open up the volume control beyond its 12 o’clock marker on the passive Music First but there was room left for more. We started with the more than warm baritone growl of Leonard Cohen on his latest Popular Problems disc. This album is a nice step forward in the range started by the Rick Rubin productions of old soldiers like Johnny Cash and Neil Diamond. Under the production lead of Patrick Leonard more known from glossy Pop work with Madonna, the Cohen songs are simple in melody, the arrangements equally unelaborate to leave all the more room for the bitterness and vicious humour in Cohen’s lyrics. We love it. So did the Virtuoso in combination with our tube amps. For small ensembles and grouchy voices, this marriage was absolutely successful. Large-scale classical obviously benefited from greater power reserves. That is what we tried with the Devialet D-Premier, its maximum power set to 120wpc down from the default 240wpc. Our now defunct model remains a great integrated work horse despite its once shiny finish starting to sadly deteriorate. We played for instance the Naxos edition of the Stokowski/Mussorgsky Pictures at an Exhibition under conductor Jose Serebrier. With more horsepower, the large orchestra came to life and made clear how this ESL was more than capable of handling such a complex musical input without distortion or other problems. We remembered that when playing the Quad ESL 2905, the protection system had kicked in at several occasions when we asked too much. No such interruptions with the Virtuoso. It played on and filled our room with satisfying SPL.

Where the ESL Virtuoso got picky was with cables. Too thin a conductor and the sound collapses. With the impedance of the loudspeaker swinging over a wide range plus lowish sensitivity, its cables must conduct current. Skimp and dynamics will collapse whilst the general sound pales and grows smaller and thinner. With the right cables, that’s avoided of course. Another point of interest was the supplied AC cord. Clean power is crucial. When supplied, the results are rewarding. Differences between a $1.50 power cable and a decent aftermarket cord are a no-brainer. 

In conclusion,
We can be brief. If we had to start all over again assembling an audio system, the Soltanus ESL Virtuoso would be in the top 3 of our wish list. This speaker is well built, easy to place and its pricing for delivered musical quality very competitive. Its easy-going character makes it non-problematic to find a satisfactory amplifier match of either the tube or solid-state persuasion. Even damping factor is not critical with the supplied adjustments. Zoltan Mikovity’s design complies with virtually any amplification offered as long as it is sufficiently powerful for your desired levels. Know your damping factor and the Virtuoso will match it. Add some decent loudspeaker cables and musical satisfaction seems guaranteed, personal preferences aside. In the looks department, the Virtuoso scores just as other panels this size do. There’s a large black surface. Its curved top line, massive wooden side rails, super-smooth stretchy cover jersey and small footprint make the Virtuoso salonfähig and non-intrusive. For us the ESL Virtuoso was a definitive must hear. But be warned. Chances are high that this will turn into a must have.

Condition of component received: Perfect, hand delivered in wooden crates. 
Reusability of packing: Yes. 
Website comments:  Informative in English.
Completeness of delivery:  Perfect.
Pricing: You’re kidding?
Human interactions:  Very kind, professional and obliging.
…….Marja & Henk

 

Manufacturer’s reply: 
I sincerely want to thank Marja and Henk and the staff of 6moons for their extraordinary effort in assessing the merits of the ESL Virtuoso. Because a designer and manufacturer is like a father of a child, as would be the case with any positive review, I consider this a great encouragement to come up with more and better efforts for our customers in the future. All of us at Soltanus Acoustics are indebted to you. Given the completeness and accuracy of your well-versed review of our Virtuoso and my agreeing with you in an overall sense, I only have a few comments to share. 

Your comment about pricing put a smile on my face. I’ve had that exact smile since we established the price. I know full well where the Virtuoso belongs sonically yet couldn’t be happier for being able to place it price wise where we did. Our customers though are the ultimate judge. Another very important fact about Virtuoso which I thank you for mentioning is that its crossoverless design may actually make this speaker the first ESL in the world. I’m not aware of another such product. 

I’d like to thank two dear friends for pushing my right buttons to break with long-held ESL design beliefs. Without their persistence, the Virtuoso wouldn’t have been born. Jody and Dragan, from the bottom of my heart: thank you. I extend another heartfelt thank you to my partner and friend Zoltan Tamas, for sharing the same vision and his unconditional support of all of our projects, with Virtuoso being the most challenging thus far. In closing, I’d like to wish 6moons continued success in the future. Your willingness as well as your ability to seek out a ‘new kid on the block’ is well recognised in our industry and very much appreciated. -
.......
Zoltan Mikovity, chief designer, Soltanus Acoustics

Awards

Soltanus Acoustics Virtuoso - included in "The Best of Salon Son & Image 2015"
A system that took me completely by surprise was built around a pair of Soltanus Acoustics ESL Virtuoso speakers. The ESL Virtuoso is a two-way, full-range electrostatic that can be run without a crossover, so long as your amplifier’s damping factor (recommend 25+) is high enough. Designer Zoltan Mikovity assured me that most amps qualify, but if yours doesn’t, there’s a knob on the back of each speaker that will engage the crossover, and an alternate binding post to connect one of the speaker cables to. The ESL Virtuoso has a claimed bandwidth of 40Hz-20kHz, +/-3dB -- thats airly wide.

At the front end of the chain was an Auralic Vega digital processor, feeding digital signals to an Aurum Acoustics Integris CDP player-preamplifier. 

This system clarity was superb, and its midrange presentation was to die for -- voices sounded dazzling. The level of transparency was also first-rate -- the piano in “Within,” from Daft Punk’s Random Access Memories (Columbia), hovered precisely in space with crystalline clarity, while Rebecca Pidgeon’s voice in “Grandmother,” from her The Raven (Chesky), was so clean, pure, and effortless, it was as if she were there in the room.

Mikovity told me that his inspiration for the ESL Virtuoso was the Quad ESL-57, many of which he’d repaired back home in Serbia, where Soltanus Acoustics is based. Of course, he wanted to create something better -- and I have no doubt that, with the ESL Virtuoso, he has.

. . . Doug Schneider