hat’s the way it usually begins. No secret connection, no covert deals or “options”. Last February I received the following e-mail:

Hello,

Since recently I have been running a company that builds audiophile speakers. I would like to get in touch with you in order to discuss the possibility of reviewing my products in your magazine “High Fidelity”.

Web page (under construction as for now): www.impulsaudio.pl.

Greetings,
Sławomir Chimczak
InpulsAudio

Mr. Chimczak’s offer has been accepted and the review scheduled for August – I suggested this date due to a rather copious workload with reviews commissioned earlier. Not without importance was the fact that this issue was supposed to be a Polish Edition. The review would be an introduction of the company to the market and as such it needed a proper setting.

A short story of…
InpulsAudio

The company was set up by two friends: Sławomir Chimczak (37), Physics graduate at University of A. Mickiewicz in Poznań and Jarosław Szymender (39) – Electronics and Telecomunication graduate at Poznań University of Technology.

Mr. Sławek Chimczak speaks:
The idea to build speakers was born as early as 2006. Since then we have tried various construction methods, tested various drivers etc. We were encouraged by positive opinions from friendly audiophile shops (i.e. about the Alize version I or a 3-way closed box speaker). In the meantime we did several designs for our friends, such as “the 2-way” or “the Stratus version I”. Our desire is to provide well designed products both aesthetically as well as technically. We are trying to maintain a reasonably low price.


At the beginning we focused on refining the production process and finding proper subcontractors, which turned out to be more difficult than we imagined. At the same time we were working on creating an interesting speaker design both acoustically as well as aesthetically (enclosure, crossover and finish). We are striving to offer the best price without trying to cut the production cost by using cheap drivers or low quality crossover components.
We subcontract MDF cutting, CNC routing and spray painting processes. The rest, including cabinet assembly, dampening, soldering and crossovers is handmade by our own efforts. As for the cabinet assembly – we glue the panels ourselves and use bracing and tilted panels. All holes are CNC-ed and natural veneer is used for the finishing touch (venge, walnut, anegre and other colors upon customer request).
Even though we promised three models at the beginning of the year, we have been able to complete only one – the Stratus. The next design, the Alize (2-way ported monitor sporting a 15cm TangBand 1367B and Vifa DX25) should be available in September together with its floorstanding sibling (priced 2500 and 2900 PLN, accordingly). Later on we are thinking of introducing a 2.5-way speaker in a closed enclosure. All of our products are designed from scratch. We choose the drivers, design the enclosures and crossovers ourselves.

The speakers arrived in August, brought from Poznań (where ImpulsAudio is located) by Mr. Chimczak himself so we had a moment for pictures and conversation. As it was mentioned above, the company consists of two people, Mr. Sławomir Chimczak and Mr. Jarosław Szymender – the former is responsible for logistics, speaker aesthetics and contact with the shops and the press while his colleague is in charge of speaker design. They both take part in the production process and speaker testing.
Packaging was up to the standard – well thought through, no bang up job whatsoever. The only thing missing were the bags for the speakers. The cabinets have a classic polish to them, looking a bit old-school but elegant at the same time, which is due to the used materials like veneer and pin mounted grille, the shape of terminals and bass port.
Two models were offered for the review – a 2-way ported monitor sporting the 15cm TangBand W5-1367B and the Vifa DX25TG for 2400 PLN/pair and a 2-way ported floorstander with the 18cm Dayton RS180S and the Seas27TBFC/G, estimated to be selling for 3600 PLN. The life as it is teaches us that the prices can alter depending on the component prices from the providers. According to the information sent in February, the third design that was supposed to be ready in July would be 2.5-way in a closed enclosure.
I opted for the floorstander which was ready at that time and it was a good choice as the other two are being finished only now. During that time the estimated price of the Stratus speakers went slightly up from 3600 to 3900 PLN due to the already mentioned change in component prices and extra costs.

The Stratus is a design with the Dayton midwoofer (handling bass and midrange) and the Seas tweeter (treble) – both sporting aluminum cones. This is evident from the first glance in the case of metal dome, the Dayton is not so obvious, though, as its cone and the fixed phase cone are black anodized. The tweeter is mounted in an asymmetrical offset position which supposedly decreases the impact of diffraction on the tweeter characteristic. The solution is known from such speakers as ProAc which are widely recognized as the ambassador of that design. Below the drivers, in the middle of the speaker we have the bass port, which is a plastic tube with a streamlined mouth.
The cabinet panels are made of MDF finished with natural veneer. We can choose from three types of wood. The boxes are braced inside with frames drilled for the cables. This is a neat idea as I recall the Stereophile measurements which suggested that loose cables inside the speaker vibrate strongly enough to introduce measurable distortion. The speakers are fitted with double terminals in a plastic port – I can’t resist the impression that single terminals would be plenty enough. Four brass spikes are mounted to the bottom of the speaker. They are supposed to harmonize with the company logo made in a similar way medals are struck. The crossover uses good quality resistors and capacitors. The grille is attached to the front baffle with classic pins.

Albums auditioned during the review

---

• Daft Punk, Random Access Memories, Columbia Records/Sony Music Japan SICP-3817, CD (2013)
• Eva Cassidy, Songbird, Blix Street Records/JVC VICJ-010-0045, XRCD24 (1998/2010).
• Laurie Anderson, Homeland, Nonesuch 524055-2, CD + DVD (2010);
• OMD, English Electric, 100%/Sony Music Japan SICP-3810, CD (2013);
• Pink Floyd, Is Anybody Out There? The Wall Live, EMI 5235622, „Limited Edition”, 2 x CD (2000).
• Project by Jarre for VIP room, Geometry of Love, Aero Prod 606932, CD (2003).
• Warne Marsh Quartet, Music For Pracing, Mode/Muzak MZCS-1111, „Mode Paper Sleeve Collection vol.1”, CD (1957/2006).

Japanese editions of CDs and SACDs are available from CD Japan

In a way, auditioning audio equipment is similar to interviewing. You have a set of prepared questions and you try to get an answer to all of them. If, however, the person you interview turns out to be particularly interesting and changes from an interviewee into an equal partner, then the interview turns into a conversation and flows unguided. That was what happened with the Stratus speakers for which I had a collection of records which I had used earlier to audition another set of speakers presented in the current edition of “High Fidelity”. After listening to the first few, I started picking others from the shelf guided by a need to check this and that and this again. As if the sound signature “forced” the listening program.

That was perhaps because some things were clear from the very beginning but other needed to be verified and looked upon from a distance. For example, we know at once that these are highly resolving speakers with a great definition. These two are the key characteristics that underpin everything else. The presentation is clear and transparent, with a well-defined attack that does not “float”. The whole sound seems to be fast and precise. I cannot point my finger at any coloration in the sense of frequency response bumps and dips, but you can hear that the overall tonal balance was shifted higher than in the Harbeth speakers.
Going back home, after delivering the speakers, Mr. Chimczak shared a short information which turned out to be important. Originally the speaker was designed for the use of nearly identical (if not identical) Seas tweeter, but from another series. That modification resulted in a slight but noticeable change of frequency characteristic. The whole range covered by the tweeter is a little bit stronger than before. The measured frequency characteristic is within 2.5dB. I do think that it would be a good idea, though, to compensate for the tweeter range. This can be done in two ways: either the company corrects the crossover or the end user has to take care and choose the rest of the system appropriately. Either way is good and will bring desired results. As it can be deducted from the information provided by the manufacturer the speakers will have the crossover adjusted.

I believe that all the factors mentioned above have been decisive in the repertoire selected. I mostly listened to the vocal records from the 1950s and 1960s, and jazz. Then electronica and old rock music. Older records surprised me with the lack of “patina” that is so often present. I am aware that they are quite old, but the unification of their sound done by inexpensive products is often so significant that it changes perception of their presentation. The ImpulsAudio speakers offer the sound that is similar to that of the analog master tape, not vinyl. The difference between those two analog media is huge and does not rest in details but in the structure of sound itself. Which version is true? Honestly, vinyl is more pleasant than the tape it came from but the tape is closer to the true sound. The same happens with the Stratus speakers which also do a great job at differentiating the recordings. For instance, the first 12 songs from Here Comes Carole Creveling recorded in 1955 sound transparent and their slightly emphasized range over 2 kHz is audible. This does not ruin the proportions nor does it irritate but gives the whole presentation a certain character. The last two songs were recorded a year later and evidently transferred from vinyl records. The voice of Carole Creveling is darker and warmer. The speakers from Poznań had no problem with showing those differences. They did not stopped, however, at the simple observation here but allowed the listener to understand the source of those changes. It was the result of their resolution and definition.
A lively and open character of the sound best suits this type of recordings but jazz from that era is also its forte. Joe Pass, Warne Marsh Quartet, Chet Baker, The Modern Jazz Quartet – the list can go on – are records with poignancy, passion and energy that often were lost due to smoothness and warmth. The drivers in the Stratus are nothing of the kind, the attack and speed are their trademarks.

Reading this description one might be concerned that the sound could be a bit hollow and light. If that was the case I would ask for the speakers to be taken back and suggested another year of testing. This is not the case with the Stratus speakers. Their sound is full bodied and the bass is well controlled. Although, when in English Electric by OMD or Jarre’s Geometry Of Love something gives a real punch at the very bottom, the sound becomes undifferentiated and loses its definition there; there is no booming sound, though. The impulse dies out quickly and does not slow down the sound. The sound is simply more rounded, has less body and more splash. There are very few speakers within this price range that can handle the problem so well – their bass either does not extend that low or it is colored. Not so with the Stratus. I mention undifferentiated lowest bass only out of duty, because what happens in the upper regions has an excellent definition and by contrast every distortion, however small, is clearly visible. As I say, though, other speakers do much worse in that respect.
The whole sound is saturated but not warm. It is not dense in the sense that there is no strong and clear “plankton” between the instruments. Something else happens. Instead of cutting the instruments out of background, which can be sometimes a result of emphasizing the attack and generally the higher midrange, the phantom images are big and three-dimensional and occupy quite a lot of space. Where we usually have “air”, here we have the sound that is energetic and tangible. It is different from that offered by warm speakers where the lower midrange plays the main role by exposing the background noise and this way suggesting the room acoustic. We have much more sounds from the Stratus, more information about the instruments and the recording than from warmer, smoother speakers.
To have it all, one needs to remember about the thing I already mentioned: it is worthwhile to select a proper amplifier and a player that will not emphasize what is the strongest in the Stratus – the higher midrange. Well balanced components from NAD, Music Hall or, and that is probably the best idea, Arcam (FMJ A19) should prove the best choice. This suggestion, of course, is relevant to the speakers I reviewed. If the manufacturer holds to its word and corrects impedance, the last paragraph will be no longer applicable. Yet because the text is about the pair of speakers I auditioned and not about the manufacturer declarations, I am not removing it.

Summary

I know several versions of Eva Cassidy’s album Songbird, both vinyl and digital. I own three of them myself: a classic aluminum CD, an XRCD24 made by JVC and vinyl prepared by S&P Records. Each one of them is different. Contrary to intuition, the warmest sound we get from the CD version and the most detailed and open from the vinyl. The warmth of CD is a part of something bigger – of certain veiling and closing the sound. The vinyl and the XRCD24 improve resolution to the next level but at the same time they show more details and high frequencies – the quality of recordings of this compilation is much easier to see, not only differences between tracks but also a rather poor quality of them all (the worst are overexposed sibilance and the lack of body in vocals). The Stratuses do not curtain anything and present all of this in an honest, direct way. They will also show the flip side – the fact that most of the recordings are live ones, even though the audience cannot be heard (it was faded out in three recordings from Live At Blues Alley), or demo versions. That adds to their credibility and diligence.
They are nicely and accurately made, old-school looking but nice speakers with a highly resolving sound and with an excellent definition. The sound is not thin with strong good bass. The soundstage is not imposing, but is very natural and we notice it only when it was the intention of the sound engineer. The range over 2kHz seems to be a tad stronger which calls for attention when choosing the rest of the system. However, that could be straightened before the speakers are launched to the market.

If somebody is looking for a classic looking speaker with audiophile aspirations, the Stratus will be the answer. This is a middle sized 2-way port-loaded floorstander. It sports the Dayton RS180S driver for the mid-bass range and the Seas 27BFC/G tweeter – both with aluminum cones. In front of the tweeter dome there is a protective metal grille. The mid-bass driver has a solid cast chassis and fixed phase cone that also helps to cool the voice coil down. The smaller driver is offset to the side of the cabinet which is supposed to minimalize the diffraction impact on the driver frequency characteristic.

The cabinet panels are made of 22 mm MDF. The interior is divided into two chambers: at the top for the tweeter and at the bottom for the crossover. Access to the crossover is possible from the bottom of the speaker after unscrewing the panel. The top chamber has a tilted panel to reduce standing waves. There is extra bracing between the bass driver and the bass port and below the port as well. The crossover is behind yet another 6.5cm panel. Damping material is 1cm felt and 3cm wool. The felt is on the panels surrounding the bass driver while the wool fills the tweeter chamber and the bottom and upper part of the cabinet. Most of interior is empty, though. Internal cabling comes from Jantzen – 2.5mm OFC 5N copper wire soldered to the drivers. The speaker terminal has two sets of binding posts to enable bi-wiring and bi-amping. It is provided with the golden jumpers which are worth replacing with something really solid. The speaker rests on four adjustable spikes and pads.

The port is tuned at 38 Hz. Both drivers are crossed over at 1650Hz using 2nd order filters. Crossover components are mounted on a thick MDF board which is in turn attached to the bottom of the cabinet. The components are soldered point-to-point without a PCB. It is evident that there are two separated circuits, one for each driver. The tweeter crossover inductor is mounted perpendicular to the woofer inductor and additionally rotated by 45 degrees in another plane. The crossover mounting screws are made of non-magnetic metal. All inductors are air-coils (the woofer inductor uses 1.4 mm wire). Metal resistors are used as well as Jantzen Z-Standard capacitors in the tweeter section and Jantzen Cross-Cap in the woofer. The crossover was designed with 3.5dB reduced baffle step compensation, hence the relatively low speaker sensitivity.