BLOG #27. StereoPravda SPearphone SB-7 Reviewed by Russian Salon Audio Video Magazine

The Russian Salon AV just published a review of our SB-7s:

http://www.salonav.com/arch/2017/05/vnutrikanalnye-naushniki-stereopravda-spearphone_sb-7.htm

The English translation follows.

Stereopravda SPearphone SB-7 in ear monitors

Author: Ruslan Tarasov  May 15th 2017

What we have got before our eyes is a real art object. Its designer assures us that these earphones open some new horizons in front of audiophiles, so they carry out an important cultural mission to broaden his musical outlook. I would definitely vote for this – its “educational mission” has always been the real essence of true High End Audio.

…NOTHING BUT A TRUTH

Even very experienced High End Audio devotees could hardly see a real guide into the musical world in SPearphone SB-7 ear monitors. They’d rather resemble a twisted rope with curiously asymmetrical transducers finished with the silicon sound isolation tips. I would suggest skipping the price of this piece of artisanship at this moment to avoid a premature reaction. Let’s take it as a conceptual creation made with “cost is no object” in mind to achieve unique sonic results and to prove new ideas.

A short history of these state-of-the-art ear monitors would be helpful. A long time ago Mikhail Kucherenko, one of very first High End Audio head honchos in Russia who’s had a lot of experience in home audio had bought a pair of Etymotic Research ER-4S ear monitors, an obscure product at the time. Being immediately impressed with their outstanding sound quality, after using them for a few years Mikhail decided to look at what’s inside, took their drivers off and started to experiment with some alternative ways of inserting the drivers in his ear canals. This way, in fact doing “scientific” experiments on himself, Mikhail had found some new techniques for improving the earphones’ sound quality that he gradually started to apply to his own In-The-Ear-Monitors (IEMs) designs afterwards.

Basically, all the main solutions he has come to is what is already well known to the hearing aid industry. But the goals pursued in that field are completely different: the audiologists investigate the reasons of hearing loss while the engineers search for the ways of bringing the patients back to the world of speech. By the way, this field became recently so advanced that some of the hearing aids models allow the hearing deficient patients an ability to not only hear what’s being said in front of them but to enjoy music.

“SB” letters in SB-7 moniker mean “the second bend” – this is the second turn of a typical ear canal right before the eardrum.

Nevertheless, there is a drastic difference between the hearing aids industry effort and the StereoPravda’s effort. Even if the SPearphone SB-7 designer has gone through a similar path, his experiments with hundreds of various driver combinations, cables and other components that took him over ten years of experiments served a different purpose: to apply his acute audiophile hearing abilities to seek out an outstanding sonic solution for ordinary people who are very passionate about music.

No surprise then that his creation does look quite peculiar – nothing like typical “ear plugs” earphones or hearing aid devices, and a far cry from the look of “custom IEMs” so popular among professional musicians.

The main idea of Mikhail Kucherenko’s ear phones construction in encoded in their name. “SB” letters mean “second bend” – this is how the second turn of the ear canal right before the eardrum is called in anatomical terms. Behind the ear drum there is a cavity with receptors sensitive to the sound vibrations. After multiple experiments Mikhail came to conclusion that the drivers should be placed as close to the “second bend” as possible, actually, in “direct view” (or, if you will, “in direct hearing”) of the eardrums.

But this is where the problem is. How deep the multi-way bundle of drivers could be inserted into the ear channel even if we’re talking about the most miniature and the most current drivers of Balanced Armature-type? Physically, it’s not easy to cram a lot of drivers in the space of a typical ear canal. So, what to do? To sacrifice a number of sound bands? That’s not a very good decision either, for virtually all the BA-drivers available today are quite narrow-band and, in addition, are not very linear – they are able to provide a flat frequency response through the whole audible range only via a carefully matched combination. From the onset of this project the technology of custom ear mold IEMs (CIEMs), in which most of the drivers are positioned in the individual ear mold usually outside the ear canal and “shoot” in all the various directions inside it, were dismissed due to the contradiction of the project’s “ear drum vicinity” principle. Another reason for the CIEMs idea’s dismissal was an obvious sound colorations as a result of the sound propagation via long curved sound bores drilled in the CIEMs mold material.

So, a unique idea of a co-axial “nude” construction came to Mikhail’s mind. All BA-drivers’ radiation patterns in his designs are placed in parallel to the ear canal’s “main” sound propagation axis. A slight tilt of the silicon tips takes in account of the typical ear canal shape (typically ear canal starts going inside the head and then turns above in the vicinity of the eardrum). The small “brick’s” edges prominent under the SB-7’s tight polymer skin that to me initially do not, really, seem to coincide with a typical human anatomy, are the famous BA-“receivers” from the American manufacturer called Knowles, Inc. Mikhail decided their exact combination and their exact configuration after his long and arduous auditioning using his set of sonic criteria.

All BA-drivers used in SB-7 operate “full range” with an only exception of one built-in standard Knowls’ crossover built in only one prefabricated dual driver used.

All seven BA-drivers used in SB-7 operate “full range” with an only exception of one built-in standard Knowls’ crossover built in only one prefabricated dual driver used. So, there are no crossovers to be used in SB-7, only “matching” Vishay resistors, in series with each one of two driver assemblies. The two sections are wired differentially with two balanced cable lines.

In the “Bass” assembly, two separate dynamic BA-transducers are installed in the back next to the input wire, and its own sound tube loads each one. In “Mid-High” section located closer to the silicon tip there are five drivers. The one located in front of the earphone is without any sound tube at all and operates full range, down to the deep bass. The four drivers in the middle of the “Mid-High” section have one sound tube per each pair.

As we can see, the “Bass” and “Mid-High” section separation is only relative, and the reasons for the separation are the properties of the BA-drivers used and the implementation of the earphone’s physical configuration. The sections are matched with each other by the “matching” resistors in series with the drivers, and the individual (pair of) drivers’ acoustical loads. Mikhail prefers to call these driver sections as the “secondary” one and the “key” one respectably.

It should be noted that the SB-7 earphones can be used as a two way active system – to implement an active mode they should be connected to the StereoPravda DACCA dedicated audio processor via two separate mini XLR connectors.

A strange feeling of something being subtracted from the overall sound, and all of a sudden that results in a gain in resolution: an acoustic instrument started to play with even more colorful realism.

I can predict the first question, and there is no doubt that it is going to sound something like, “Can that thing be inserted in your ear canal?” I would answer it directly: it can, but not in every ear canal.  The listeners with narrow ear canals, especially, the younger ones, are deprived of enjoying SPearphone SB-7 virtues. My usually unstoppable kids didn’t even try to sneak this exotic stuff off the table to listen to them (and let their friends to do so either).

Are these earphones really uncomfortable? Yes and no. Your first feelings can be pretty painful. And in the beginning it was hard for me to withstand the deeply inserted earphones for more than half an hour. But after the third or the fourth session of their insertion the physical discomfort gets substantially smaller – the cartilage tissue of ear canal gets used to the foreign object inside (a similar experience should be familiar to every earphone user). Then the mental comfort finally sets in and you forget about anything inside your ears.

How stable are they positioned in your ears? Provided the cable is properly “dressed” around the ear and the clip is fastened to the cloths, their intended positioning within the ear canal will be pretty reliable.  Of course, the acoustic isolation they provide will not be of “a death grip” variety which individually made customs ear molds can provide, but it’s still better compared to the majority of typical “earplugs” IEMs. And after your ears would adapt to the SB-7’s shape at the proper insertion depth, their positioning inside your ear canals will improve so that the earphones would sit reliably and isolate your ears from the outer world quite well, even during a walk on the street.

An inevitable question about the cable would be: why is it so thick? The thing is, a group of matching resistors is located inside the input connector case instead of the earphones themselves, and that’s why just two standard pairs of wire are not enough. In order to obtain a separate connection for each pair of drivers sections the special cable was developed. It’s based on a 32-conductors Stereolab audiophile phono interconnect, more than appropriate for its sonic qualities, and which later was modified to meet the mechanical demands of portable use (in the context of reliability). By the way, Chris Sommovigo, a widely recognized cable authority and a former head of Stereovox and Stereolab, designed the cable and custom manufactures it for the SB-7s. And it took him as many as ten generations of the product development to match all the cable’s properties to the intended use. So the cable (not user-replaceable, which is taken for granted, of course) is just as unique as the earphones are.

"The wood, the cello string wax, the strings themselves, the pluck – all of them sounded so naturally, and the only reason you can’t just touch them is because you can’t get inside your own head".

So, now, I’d like to tell you what happens after hitting the Play button. I’ll omit everything about adjusting the earphones to my own ear anatomy. After having got through this process the SB-7 sound simply disconnects you from outside world and takes you to the parallel music reality where literally everything is audible – from microscopic tonal strokes up to the huge sound waves rushing through the whole Universe!

My first attempts to analyze the quality of playback were quite futile. Dynamics, quality of bass, tone, sound dimensionality and other formal nuances were perceived as ideal. I noticed not even a slightest annoying factor which would interfere with my joy of music listening. And, neither a genre, or a place or an age of recording I ‘ve been playing really mattered – in newly discovered sonic reality everything seemed to be natural.

Nevertheless, there is some criticism abound the sound. It’s got to do with the quality of components in the signal path. If you connect the SPearphone SB-7 to a smartphone, sound degradation caused by hardware will become a real nightmare. The earphones possess with such a clarity that you can use them for the most precise equipment evaluation to identify some various interferences and noises, sound colorations and other technical hardware artifacts. Some pretentious (and in reality a dirty cheap) universal codec for HD Audio at the phone output of my mobile gadget that never called for severe criticism before now will fully reveal its ugliness. After several tests you start to clearly hear right away all the sonic differences between, say, WCD9320 and Cirrus Logic 4208 IC chips, recognizing the former by its sonic character that reminds of dry cracked soil, and the latter by a resemblance of greasy layers of a clown’s makeup. Of course, very different images might come to your mind, but they imprint your memory so hard that the sonic “signatures” that created these aural images will never be forgotten or confused… Though I must say, it’s not impossible to just to listen to the music “rationally” via this primitive gadget: these earphones are suitable enough to satisfy all the requirements of both their sensitivity, and the sound dynamics within the whole range of frequencies.

Switching to an “ordinary” digital music player – in this case it’s been a venerable HiFiMan HM-801 with an optional amplification module – and what a relief to my ears! All the above imperfections immediately disappear. They all have been replaced with a sound signature abound with great dynamics  as well as with very fine resolution and with an absolute liberation from any sonic constraint… Only after many initial hours of auditioning, you start to feel some of the system’s minute inconsistencies. The lowest bass is not completely developed. The midrange sounds a little “overheated”. The highs reproduction is very linear and clear – but with a trace of some strange “spicy” aftertaste.

I decided to find out the possible culprit of the above SPearphone SB-7’s peculiarities. I’ve got an interesting tool at my disposal: a white noise generator with adjustable band filters. You can identify all the most audible resonances in the output signal spectrum, one by one, by listening to the output, not by just measuring it with some test equipment. Usually such a procedure takes no longer than an hour, but with SPearphone SB-7 I’ve spent almost three hours “catching crickets” because their resonances are perceived to be so faint that even trained ear can hardly recognize them.

According to the measured data the precise settings for the parametric equalizer required for the proper sound “restoration” were created. They are shown on a screenshot below.

Of course, from a first sight the correction “comb” curve looks a bit frightening. But, trust me, the equalization curve for any other Balanced Armature earphones I’ve seen, including fairly expensive ones, does look much more extreme. It is usually totally riddled with a multitude of very steep “local” -8-12 dB dips (required for compensation of their very strong resonances) and also deformed by some compensation waves (to straighten out the broader dips and surges). But, as you can see, StereoPravda SB-7 in that respect is an exemplary of near perfect linearity. Some resonances are still there, but they are not substantial and evenly spread over an entire upper part of the audio spectrum.

Such a sonic result could hardly be achieved using just some test equipment and computer simulation techniques. Amazingly, Mikhail has achieved such an advanced result without any of those, relying solely on his subjective evaluations and thoughtful auditioning. And his main achievement is that in this very well tempered overall performance he has to bounce with many separate defining factors such as the cables’, the “matching” resistors’ and even connectors’ influence on the overall earphones’ sound . This is why I take what Kucherenko has done as an invaluable master’s example of artisanship, even with all the visible imperfections which are typical for a fully handmade product.

Now I’d like to mention the results of mating the SB-7s with other dedicated headphone amplifiers. The equalization curve used for the earphones’ operation with HiFiMan-801 player enhances the SB-7s’ sonic signature with a bit of “plasticity” and nobility cleaning their upper and midrange bands from that “ringing” residue masking important music information. Hey, does it sound weird? Kind of, all of a sudden, if we would subtract a bit of overall sound would this result in an increase in the resolution?!

Nevertheless, after my “restoration” curve was applied to the “raw” playback chain, every acoustic instrument did start to sound with even more colorful realism.

But with the hybrid Schiit Vali 2 amplifier fed from Schiit Modi Multibit DAC the same trick didn’t not work out. The sound of this set up is significantly more “strict” and dense in midrange, while crystal clear highs seem to be a little unnatural. So, it’s obvious that this setup requires its own special equalization curve suitable for its tube amplification stage. And looks like these new curves will be definitely worth the effort, as even without equalization this pair of miniature components does obviously outperform the portable HiFiMan-801 in rendering of small detail accuracy, articulation and dynamic contrasts.

After that, I plugged the earphones to the Burson Conductor Virtuoso V2 combo. Sending the signal from my notebook computer to the built-in DAC via USB leads to a pretty good result: precise microdynamic patterns, more sweeping and articulated bass, pleasant and sweet midrange. The upper frequency range is pretty sweet, but I wouldn’t call it fully natural. My original equalization curve only spoils the sound. For some reason it impairs the microdynamics as well – with the EQ the system is degraded to lower class.

But everything changed when the same Burson receives the analog signal from the aforementioned Schiit Modi Multibit. The midrange resolution became just too fantastic! The wood, the cello string wax, the strings themselves, the pluck – all of them sounded so natural, and the only reason you couldn’t touch them is because you couldn’t get inside your head. Some lack of the lowest overtones is noticeable, but the high frequency band was impeccable in details and dynamics, and the equalization curve did deliver what it should have– it made the perception of acoustical nature of instruments more acute.

Finally, using the same DAC a tube heavyweight AudioValve Eartube headphone amplifier was added into the playback chain. The SB-7s’ sound quality with it is so hard to complain. The sound is precise and harmonious. There is not a slightest feeling of the music signal being amplified or converted in any way – the music purely flows to the ears. The sound is completely liberated, almost free of any colorations (even if they were still there, they had some pleasing to the ear origin) and abound with the richness of musical content, even at the extreme frequency ranges or strong dynamic bursts that enhanced your belief in what you’ve been listening to. Only in pauses you are able to realize that you’ve been listening to a simple digital “HiRez” recording, not to the live music itself, when through the subtle background noise you could capture a barely hearable “breath” of a big and expensive tube amplifier being shamelessly revealed by theses earphones.


THE COMPONENTS USED FOR THE STEREOPRAVDA SPEARPHONE SB-7’s REVIEW
Sources
    Digital player / DAC: HiFiMan HM-801
    Smartphone: Nokia Lumia 930
    Notebook: Apple MacBook Air A1465
DAC: Schiit Modi Multibit
Phone amplifier: Schiit Vali 2
Burson Conductor Virtuoso V2
AudioValve Eartube
Cables
    analog interconnect RealCable CA1801 (modified)
    digital: USB / mini USB InAkustik Reference High Speed USB 2.0

Stereopravda SPearphone SB-7
Manufacturer: OOO “StereoPravda”
www.stereopravda.com

Type of drivers: armature (with balanced yoke) Knoles, virtually two way
Impedance: 17 Ohms
Sensitivity: not known
Frequency range: 5 – 52 000 Hz
Sound isolation: not known
Cable: 32 braid in textile wrapper, 1 meter, 3.5 mm mini Jack connector
Weight: 23 gr.
Price: 150 000 rubles

24.05.2017 // Author:  (Bigmisha) // Number of views:  1848