Interview Miro Krajnc SoulSonic Speakers

Exclusive interview with the Soul man

Tell us a bit about your background.

My father was into music a lot, he played a few instruments and had quite a large collection of reel-to-reel tapes and phonograph records and I was into music ever since I can remember as well. When I was young I would order many records from the USA, I was mostly into progressive Bluegrass back then (banjo players like Trischka, Fleck and Cloud or guitarists like Tony Rice and Mark O`Connor), but eventually I started listening to other forms of music as well, classical and jazz, or some acoustic guitar fingerpickers like Kottke, Hedges, DeGrassi or (Slovenian guitarist) Bojan Drobež, all of them are among my favorite musicians too. I really enjoy Tango music as well. My son Timi plays in one such band, honoring the music of the late Astor Piazzolla.

My first "serious" system was built around a Kuzma Stabi/Stogi turntable, Yamaha integrated (I don`t remember the model, but it was later replaced by a Musical Fidelity B200 amplifier) and Sony APM 22 Esprit speakers.

While trying to find the source of hardness in the sound at higher SPLs, I checked the crossover parts in the Sony speakers and noticed that they had used some small ferrite core coils. At that time I had already read all the Speaker Builder and Klang & Ton magazines with great interest and decided to build myself new speakers from the ground up, using better crossover material and drivers, if possible. The first speaker I actually built was a WHD B410 subwoofer, in accordance with the Stereoplay plans, but after that I went on to build some freestanding two way speakers. I purchased some books about loudspeakers (Martin Colloms, Vance Dickason, etc), CAD software like CALSOD and AudioCAD and one of the first affordable measurements systems, Liberty Instruments' IMP. Equipped with all these goods I began experimenting like mad. Apart from the WHD sub, I never built anything according to someone else's plans, I wanted to make everything in my own way.

Through the years, I have analyzed thousands of commercial and DIY loudspeaker systems, observed the measurements, listened to the loudspeakers and tried to find some correlation between all of them. I really came to my conclusions and preferences after listening, but the theory supported my listening impressions.

I have tried to understand the engineering principles behind the most popular high end speakers and have learned from many renowned loudspeaker designers and their differing philosophies.

I tried all the prevailing approaches regarding crossovers (series, parallel, steep, shallow XO orders), low frequency loading techniques (closed box, bass reflex, passive radiator, various bandpasses, various transmission lines, horns, aperiodic damping, open baffle), monopole, dipole, bipole and omnipolar radiation patterns, various driver materials like aluminum, magnesium, titanium, Beryllium, carbon fiber, glass fiber, Kevlar, polypropylene, various paper mixes (my favorite cone material), planar magnetics, ribbons, AMT , plasma (ionic) drivers, you name it.

I spent a lot of time trying to nail down the culprit of all those nasty box resonances, but the turning point came when I experienced the sound of the Apogee Diva, the legendary planar magnetic/ribbon dipole speaker.

I knew the sound of the many great boxed speakers of that time, but this was something entirely different - I was actually shocked by their sonic realism.

Later, I heard some great line source (Magnepan) as well as plane source (ESLs) speakers and was convinced this was the way to go. These types of speakers seemed always much more capable of "pulling my strings" than anything else.

Of course, the dome and cone speaker driver industry kept telling me that the planars are old fashioned, bulky and inefficient, which is partly true, but all these arguments would melt away in seconds, as soon as I listened to the speakers themselves.

To this day, the most memorable experiences I have had with any speaker types are those of the Apogee Diva, Acoustat Monitor 4, Martin Logan Request and the bigger Soundlabs. For a few years I was hooked by the sound of spherical horns and spent a lot of time building and developing them, but eventually became discouraged by not being able to avoid certain problems of this approach.

Years ago I thought I knew something, but in recent years I`ve begun to think of myself as a person who has more smart questions than stupid answers. At least with speakers and recording techniques it seems we`re all still in the dark ages, rather than highly advanced ones, but the progress is evident, of course.

Why SoulSonic Speakers?

Well, for the past twenty-some years I was actually searching for a loudspeaker principle that would bring me the closest to the original event, that would, technically, be as good as it gets, that would reveal all the quality differences in the recordings, but still wouldn`t force me to prefer my music selections based on the sound quality rather than music quality. In short, it would have to enhance my listening pleasure with almost all recordings – which is quite difficult to find these days.

So, in essence, I was completely open minded and let myself be surprised by all these different loudspeaker technologies and I`ve put aside everything I knew from the theory, only the listening results would matter.

To me, a good approach should work with a minimum of input, which means, if you have a set of speakers that sound lousy with the entry level electronics and really require a massively expensive system to make it sing..., well, I think we`re talking fundamentally about the wrong approach.

Fundamentally, healthy speaker designs sound good on a wide range of electronics, ranging from cheap to very expensive and this is the case with my speakers, but of course they do show all the improvements with better electronics, make no mistake.

The way I see it, all components should be built with the aim of achieving the highest possible transparency, but in a linear manner, without emphasizing any portion of the spectrum and by preserving the dynamics as much as possible.

Taming the shrill sounding speaker with dark sounding amps and sources...that would be basically wrong in my humble opinion.

Of course I don`t think my speakers are perfect, far from it, we all still have a very long way to go, but they do have a high musical involvement factor, among other things.

Do you feel there is certain aspect of your speaker designs that sets it apart from the traditional planar dipoles?

One thing I wasn`t completely satisfied with was the bass performance of the majority of planar magnetic or ESL speakers, which mostly seemed somewhat softer and lacking in dynamics.

I have built a two meter tall planar magnetic woofer in the style of the biggest and oldest Apogee and although it sounded good, it was no match for the four 12 inch woofers in the dipole/open baffle mode. The efficiency was much lower, with less SPL potential as well. I wanted my speakers to be pretty robust, but was also concerned about the sound quality in the transition region between the ribbons and the woofer array. I tried many woofer types, but eventually settled on the AE dipole woofer range, which feature very well behaved paper cones, along with very cleverly designed underhung type voice coil topology, which reduces distortions and controls the diaphragm movements much better than with the mostly used overhung type.

I have set the crossover frequency in the range that gave the best compromise in terms of coherency as well as robustness – 500 Hz and I feel the overall sound quality confirms that.

Another thing that sets my speakers apart from the others is in the way I have dealt with the »Allison dip« effect which is very problematic in small rooms. For this purpose I have developed a special crossover technique that corrects this (upper bass) problem.

What is the story behind your decision to use the ribbon, for the mid high range?

Ribbon is one of the oldest and simplest driver working principles and it dates back to 1924 when Walter H. Schottky and Erwin Gerlach co-invented the first ribbon microphone. By turning the signal path in the opposite direction, the first ribbon tweeter appeared. This early invention was the basis for all later planar transducers like planar magnetic, air motion transformer and other Heil types that are now being developed. So, in effect, I owe much more to this early invention than to the later commercial products that evolved around it.

As much as I loved the sound of the old tall ribbons (and newer ones), I still felt there was room for improvements. For one thing, I was really concerned about the diffraction issues of the deep cavities found in the existing ribbon designs. My ribbon construction is a very shallow, low diffraction type, with great dispersion characteristics in the horizontal plane. Additionally, I have developed a simplified type of ribbon clamping that makes ribbon replacement a very easy task.

Dou think your current speaker range has only advantages, with no shortcomings compared to other speaker types?

Well, the most obvious disadvantage would be of course their size and the required minimum distance from the back wall to show all their potential. I think they`re not suitable for any rooms with less than 25 square meters available. The distance to side walls isn`t critical, but the wall behind the speakers is. To avoid too much early reflections that muddy and thin the sound, I would recommend about 2 meters (7 feet) or more distance from the back wall, measured from the centre of the speakers (if no ribbon absorbers are used). With even greater distance everything improves to an extent that is hard to believe without experiencing it. It would be a waste to put these speakers close to the acoustically untreated back wall and the best approach would be simply to follow the so-called Hong Kong setup, which was developed by Ivan Li (Limage) and such positioning enables the user to listen to the speakers from both sides, which could be considered a sort of bonus – just kidding. With this setup the speakers are very close to the side walls, but almost in the middle of the room, along the long walls.

All this being said, recently, I have started to work on a ribbon absorber that would absorb almost all of the back wave radiation and thus make it possible to place my speakers pretty close to the back wall, without the negative sonic effects. I think this addition will make them much less sensitive to placement in general – which is another advantage.

SoulSonic speakers aren`t efficiency champions, but even in this regard they are above the majority of planar speakers, at least a few dB, I would say.

Other advantages? Everything else, ha ha...

Seriously, in terms of sonic realism, they`re quite good, I think.

Tell us something about the outstanding aesthetics of SoulSonic speakers.

I was inspired by some historical designs, but I wanted to create something different, something that would fit into all environments and that would act as a work of modern art, which is quite different to the bulky boxes that enjoy zero WAF or PAF (people acceptance factor).

The visual design was, of course, also dictated by their working principle, with a few nice touches.

The first prototypes weren`t all that elegant, but eventually I polished the details and the results speak for themselves, I think.

As soon as I decided to use cone woofers and knowing that I need a certain baffle to prevent too early dipole cancellation, I decided to make the speakers a little less bulky by utilizing the trapezoidal glass baffle. The trapezoidal shape ensures smooth transition of the damaging dipole short circuit over a wider range of frequencies.

Since the AE woofers are very heavy (10kg each) and have their wooden spine to support them, the thought of using the glass as an acoustic baffle seemed very attractive.

I don't like square shaped objects, but I do like smooth curvatures and all this shows up in my speakers. Usually, people tend to hide their speakers or integrate them in the walls, but my speakers actually don`t need any excuses for being put right in the middle of the room...OK, just kidding.

Regarding the visual aesthetics in general, I believe nowadays a product should be as good as it gets in every aspect. I know the majority of audiophiles are only concerned about the sound performance which is of course the main factor in regard to musical enjoyment, but if the product could be made refreshingly good looking and (!) good sounding at the same time – why not? Does it have to be ugly to suggest serious performance ?

I would like to help change that old prejudice that if a piece of audio gear looks beautiful, then the manufacturer must be covering some serious performance flaws compensating it with the visual aesthetics.

I mean, these things aren`t mutually exclusive, there is an increasing number of components that prove my point, Absoluta from Italy, being one perfect example. Their amps look and sound marvelous. There are many more examples.

Tell us something about the IMPULSE and WAVE speakers.

The IMPULSE was the first model I came up with. It was the result of my quest after the speaker that would satisfy me personally in every possible regard.

Perhaps at this point I should mention my listening preferences: I love the sound to be immediate, alive, dynamic, spectrally balanced, with tall soundstage and great transparency. I hate the pin-point imaging of the small point source type bookshelf speakers in absolute terms, of course. When listening to live, unamplified music, the pin-point imaging is certainly not something I`m after. To enjoy live musical events in terms of audiophile vocabulary would be missing the entire point of the musical message. However, what I do like is the natural 3D image shape of the live events.

OK, one little dirty secret, on my main computer I listen to a pair of small bookshelf speakers that were built by my son Timi, because it`s convenient and I don`t want to fire up my main system just to check some youtube links that were sent to me – please keep it a secret, though :).

In absolute terms, I prefer the sound of bigger speakers, simply because they are more able to move the necessary amounts of air that live music events demonstrate to us so effectively.

In this regard I consider even my speakers too small. I mean, the musical instruments have large surface areas that barely move and trying to mimic their sound by means of small domes and cones is...well , you figure it out.

With small speakers you get high surface loudness, which is unnatural and with large speakers we are moving towards low surface loudness, which shouldn`t be neglected if we aim for a dynamic reproduction of music.

Moving on, the dipole speaker approach has one specific characteristic that I really favor over the monopole approach and that is the »sound velocity« radiation characteristic as opposed to the »sound pressure« characteristic of boxed (monopole) speakers. In simple terms, the dipoles don`t pressurize the room and ears in the same way as boxed speakers do. Their sound is much more connected with the listener through the air than through the floor and walls for instance, if you get my point?

I think this the major difference compared to all other boxed speakers and not the »enhanced ambience« that is supposedly created by the sound bouncing of the walls, coming from the rear of the dipole speakers, like some people think.

Another advantage is the line source characteristic of the ribbon mid/high frequency unit and although this is effective only above a certain frequency (speakers are all about compromises, remember?) and up to certain distances, it nevertheless helps to maintain a very desirable characteristic and that is the SPL from an infinitely long line source falls off at a rate of 3 dB per doubling of distance, while the SPL from an ideal point source radiator falls at the rate of 6 dB per doubling of distance. With line source ribbon, the nearfield extends up to three times of its longest dimension, while with a point source speaker this nearfield extends only to a couple of inches or centimeters, if you will. In practice this means that with a ribbon that is 2m tall, it will maintain its nearfield characteristic up to 6 meters ( the SPL will drop only 3dB for each doubling of the distance).

The net result of all this is no listening fatigue, even after prolonged, very loud listening sessions.

Speaking of WAVE, I realized many people will consider the IMPULSE too big for their taste or available space, hence the smaller WAVE was developed. Comparing them side by side, I would say WAVE has slightly less deep bass, less SPL capability and provides somewhat lower image height impression, but not much. The musical involvement factor is still very high though.

With bigger effective surface and overall dimensions, everything sounds more realistic through IMPULSE, but that`s understandable.

What type of material have you used for your speakers?

I have decided to offer two versions of my speakers, basic and Supreme. If we are talking about the speakers that were used for THE S.H.O.W. in Las Vegas, these were the Supreme versions with all silver wiring, silver WBT speaker terminals and Duelund capacitors. Impulse was equipped with the CAST Capacitors, while the WAVE was equipped with the VSF capacitors.

The basic versions will feature Obbligato caps which have an excellent price/performance ratio.

The basic versions will also have Peerless woofers, while the Supreme versions will use AE woofers. The latter will also have outboard crossover units and all speakers will be available in an active version too, upon request, of course.

Even the basic versions of WAVE and IMPULSE aren`t cheap to manufacture, let alone the Supreme ones and this reflects in the prices. I intend to develop two smaller speakers as well, but all will feauture the familiar design characteristics of the bigger models.

The upcoming IMPACT model is a step towards a lower price entry point. With it I will try to offer a dipole speaker that is somewhat more room friendly as it will radiate more into the forward direction and it will also provide a symmetrical, constant directivity horizontal dispersion characteristic. To my way of thinking it would also make for a great studio monitor. All SoulSonic speakers are so resolving and transparent that using them for studio monitoring purposes comes naturally to ones mind.

What happened at THE S.H.O.W. and CES?

Well, it was a great experience, to say the least. In the past I went to many Audio Shows and from my memory, the people would mostly listen, only sometimes expressing their impressions to the exhibitors. In my case, I was pleased to find out that the majority of visitors felt the need to express their highly positive remarks about our setup. Most of them said our sound was one of the best at THE S.H.O.W. and CES, while some felt it was the best of the whole event.

One visitor was very keen to find out how my speakers would perform with the WAVAC electronics and, with help from Mr. Takuji Sudo, I was able to get the amazing WAVAC preamp and 60W monoblocks for the entire show period (WAVAC Audio Lab PR-T1 preamp and MD-805mkII monos with external power supplies). The overall sound quality owes much to their electronics and I would like to use this opportunity to express my gratitude to the entire WAVAC crew and their US distributor, Mr. Jonathan Brown.

Most of the visitors felt SoulSonic Impulse represents a new breed of planar speakers, with enhanced dynamics and great bass reproduction, along with all of the qualities only a true ribbon can offer.

I got numerous enthusiastic remarks even from the competition, which is really satisfying.

Prior to SoulSonic speakers everything seemed predictable, on one side there were traditional dynamic boxed speakers capable of great bass impact and elevated SPLs and on the other side there were delicate sounding planar dipole speakers that, although very transparent, weren`t exactly the last word in bass performance and their SPL abilities seemed somewhat less potent.

With SoulSonic speakers all of a sudden it seemed you can have it all and that was indeed my intention.

You can read more about it at the SoulSonic website, there are many links and photos included.

What does the term HIGH END mean to you?

It means a quest for the highest quality sound reproduction possible, no more no less, – simple as it sounds. Of course, all we can do is only approach it as we will probably never fully reach it, but that`s the beauty of all creative processes – there will always be something to improve upon.

Your first customer?

...was a passionate music lover from the Slovenian coast. He is a very experienced listener and he recognized instantly all the virtues of my speakers that I also believe are hard to overlook.

His former speakers Magnepan MG 20.1 were driven actively and so are now his IMPULSEs.

The current High End market situation?

In my humble opinion the situation will change for the better. Many speaker technologies will soon become obsolete and new technologies will emerge. It is my belief that the new, upcoming planar technologies will prevail as they simply offer too many improvements to remain overlooked. I wouldn`t want to go into details, but I know the facts that support my claims.

Is SoulSonic audiophile oriented company?

In the sense that our top priority is sound quality, yes, but SoulSonic speakers are so much more in many regards that they surely deserve wider recognition and markets. For one thing, unlike many high end speakers, they don`t blush if you feed them with high energy popular music that wasn`t recorded perfectly, they show all the imperfections but you can still enjoy and consume the music with the greatest pleasure, nevertheless – all this because they are able to bring out the very essence of the musical message, and this makes them universally useful.

This is a problem with many highly expensive speakers, they`re comfortable with high end recordings, but feed them with the average pop and rock and they fall apart.

Many people who otherwise have a good taste for many things in life, aren`t even aware there is such a thing as High End audio, but of course it takes some effort to reach them and this is probably the most underrated group of potential customers.

For one thing, I would also like to reach some classical musicians, conductors and fans, many of them listen through the kitchen radios which is OK for casual listening, but otherwise, I mean, come on?!

One anecdote: I hreached one Classical Festival Director once, asking if he can forward the link to my speakers to classical musicians and conductors as they would surely appreciate hearing their work in better quality in their homes. His response was that he doesn`t quite understand why professional musicians would need such speakers?! They actually don`t mind if the concert sound is great and the sound in their homes sucks(?) – probably a great attitude nevertheless, but obviously there is so much that needs to be done here.

In your view, what is the difference between audiophile and music lover?

If I answer this question straight, then the high end police are gonna come and arrest me, but since you dare to ask, it seems the question is valid.

Seriously, even the names suggest there is a difference between various »`philes«. Audiophiles seem to be after the sound, while musicphiles don`t care much about the quality of sound, but of course, any generalization would be unfair, as there are always exceptions to the rule. In this case I actually believe there are many audiophiles that are true music lovers – strange as it sounds. If you ask me, I might be »a mixed breed«, I`m most excited when great music and great sound are reunited, because then I get some true life inspiration and this I consider extremely important.

What is you view on tubes vs solid state?

Well, I really like the combination of the two. I have heard great and bad examples of both camps, but up until now none of my previous experiences suggested I should avoid any of the two types. Tubes in the preamp stages do seem to make a lot of systems sound very alive and also transparent, but I know the solid state approach can give extremely good results too.

At home I use a lot one magnificent hybrid amp built by Robi Krajnc (we`re not related), a friend of mine. This amp has one simple double triode in the preamp section and Darlington transistors in the output section and this combination seems to be extremely successful. The sound is very transparent, alive and involving and it puts many costly commercial amps to shame, no kidding.

Do you think the ultimate transparency, dynamics and musicality can be brought under one roof?

Yes, I think this is possible, these things aren`t mutually exclusive, although sometimes we witness systems that give such an impression.

I think a true achievement is if a component (or a system as a whole) is able to sound utterly transparent, refined and alive at the same time.

Is high quality more affordable today?

Yes, I do believe it is, never before have we witnessed so many affordable audio components to choose from.

What kind of people you see as potential buyers of the SoulSonic speakers?

I think those that are after the highest sound quality will represent the majority of customers.

I cannot say much about those that value aesthetics as well, since everyone has its own particular taste, which is understandable.

Will you strictly stay in the speaker production, or you're planning to expand with other components?

I have no other plans presently.

What holds the future for the SoulSonic?

I think the future is promising and will be very exciting. I cannot reveal all my upcoming plans regarding the speakers, but I think you will be surprised.

Would you like to tell something to our readers?

Enjoy the music as much as possible and try to be a part of solution for this planet, acting consciously in all aspects of your daily lives.

Matej Isak

Mono and Stereo ultra high end audio magazine
All rights reserved, November 2011