Reviewer: Srajan Ebaen
Financial interests: click here
Sources: 27" iMac with 5K Retina display, 4GHz quad-core engine with 4.4GHz turbo boost, 3TB Fusion Drive, 16GB SDRAM, OSX Yosemite, PureMusic 3.01, Tidal & Qobuz lossless streaming, COS Engineering D1 & H1, AURALiC Vega, Aqua Hifi Formula, Fore Audio DAISy 1, Apple iPod Classic 160GB (AIFF), Astell& Kern AK100 modified by Red Wine Audio, Cambridge Audio iD100, Pro-Ject Dock Box S Digital, Pure i20, Questyle QP1R
Preamplifier: Nagra Jazz, Wyred4Sound STP-SE MkII, Vinnie Rossi LIO (AVC module), COS Engineering D1
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F5, F6, F7; Bakoon AMP-12R; Crayon Audio CFA-1.2; Goldmund Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics One SE Up NC500MB; LinnenberG Audio Liszt
Loudspeakers: Audio Physic Codex; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & Submission; German Physiks HRS-120; Eversound Essence
Cables: Complete loom of Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink;Black Cat Cable redlevel Lupo; Titan Audio Eros power cords
Power delivery: Vibex Granada/Alhambra on all components, 5m cords to amp/s + sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands [on loan]
Sundry accessories: Acoustic System resonators
Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room, hence no wall behind the listening chairs
Review component retail: TBA

July 26th: "See my new design draft for Furioso Mini. Maybe there still will be some small adjustments but it is very close to final." That was Rainer Weber, contract engineer for Germany's Kaiser Acoustics. The v3 designation shows that this is not how today's story began. At Munich HighEnd 2018—in the next photo bracketing Chiara—this first model of Kaiser's new line had looked exactly like my review samples which subsequently shipped. But those were recalled a few days after. By that time Kaiser had collected sufficient post-show feedback from dealers and distributors who lobbied not for sonic changes but a slightly smaller more svelte form factor. Now compare as above so below. You'll appreciate how v3 grew a faceted face and dual not single folds/kinks on the side walls; how the opposing passive radiators relocated upward to now sit slightly higher than the frontal mid/woofer. Finally, internal volume shrunk by about 6 litres to reduce overall size. Quite the stem-cell rejuvenation to show design morphs in action. As consumers, we rarely are privy to progressive iterations. We see final production, not what led up to it. For once a bump on the review road—I had already penned an extensive 3-page preview with first listening impressions which had to get scrapped—provided a chance to compare the last two stages of an industrial design process.

It's reminder also on hifi shows not just being about cast-in-stone product launches. Routinely launches gauge reaction. They test the waters. They reserve the right to subsequent changes. Furioso Mini v2 had already collected major thumbs up at shows in Prague, Mumbai and Munich for astonishing sonics. Certain markets simply wanted more sugar in their eye candy. Because smart companies listen to their customers, Kaiser went back to the drawing board and Rainer dipped his pen into the sexier ink pot to make it so.

But already Mini v2 became a disruptor when it forced the Furioso flagship back to the same drawing board, this time on performance. Huh? A day after the Prague show, Rainer's FaceBook post explained it. "Mini is home from Prague. The next step is to update Furioso Grande with a ribbon tweeter." That's because the big new floorstander had bowed at a France dealer demo with a costly Beryllium dome. Meanwhile a Mumbai show visitor with Tidal speakers using a 30mm diamond tweeter had called v2 "one of the best stand mounts I heard in a while." On March 26th, Rainer Weber sent me a link to's subsequent coverage of the Mumbai show which shared that assessment: "... the setup of Kaiser Audio's Furioso Mini... paired with Octave's V40SE integrated valve amplifier with Black Box and AVM's CS8.2 used as a CD player... evolved from Friday onward. On Sunday, it became quite apparent that we would have no choice but to give it the 'cost no object' Sound of The Show... for truly magnificent and jaw-dropping resolution, attack, decay and timing. We were hoping that we could have some true competition to a Nexus Audio setup but yet again the man behind Nexus Audio came, saw and conquered the show." To reiterate the surprising upshot, Mini's Russian ribbon tweeter had shown the Grande's ScanSpeak Beryllium dome a clean set of Prada heels. But there was more disruption.

By early April, Rainer's update laid it out: "Furioso Mini is a really good speaker; perhaps too good but I won't reduce performance for the sake of fitting the portfolio. I am a designer and try to do my best at any given budget. However, at present the Mini betters Furioso Grande also in the bass [Grande v1 drawings below]. Grande can displace more quantity but not more quality or refinement. So I will make a new smaller Grande with dual 24cm SB Satori woofers. It needs to be better than Mini. It will be a challenge but I can't imagine anyone buying a more expensive bigger speaker and not getting more performance. So this time, no Furioso Grande in Munich. For now Mini is much better." Smaller speaker, better bass? That definitely mandated a revisit.

When I caught up with Kaiser at Munich, Rainer explained how Mini's flat and high impedance was a result of working with Kondo's EL34 Overture during R&D. Internal Mini wiring plus wiring for its ribbon transformer's primary is Kondo's famous proprietary silver made available here to an outside firm for the first time in 40 years. A pre-show email from Rainer signed Director of NVH, Continental Automotive GmbH came with a PDF article showcasing his work at Powertrain-BU Engine Systems under the header "a man who literally hears quality. When it comes to the solving of acoustical problems, the principal expert for NVH is in demand across the continent".

It sketches out the backdrop against which Rainer develops Kaiser speakers: industrial well-funded measurement-centric research on how to lower automotive cabin and other noise. NVH is short for noise, vibration and harshness. That very neatly condenses focus and purpose into three short words. It explains Rainer's unique expertise and approach to enclosure design. He looks at it like a car cabin that's exposed to all manner of undesirable noise from its own engine and tyres; and how to reduce it. The result is that we hear less of the box, more of the music. That's especially germane with smaller speakers of full-range ambitions. The louder we play them with bassy music, the more they pressurize internally to escalate stress on the box, its drivers and also the filter components unless those seal into a sub chamber.

More on passive radiators or ABR, "they of course cost a lot more than a cabinet hole with an attached tube. By using four, the Furioso Mini's raw parts cost already eclipses equivalent ports by a factor of ten. That still reflects a lot higher in the final price. Also, a port not only works at its tuning frequency but as a kind of organ pipe with two open ends. So it exhibits a lambda/4 resonance often clearly audible in the midrange. A passive radiator doesn't. It does however create a useful additional null in the transfer function below the cabinet tuning. That causes less energy in a band where the room already acts a bit as a compression chamber. In the bass, you're correct thinking that one adds the cone surface of the radiator/s to that of the active mid/woofer. For the Furioso Mini, this sums to around 500cm², more than a 12-inch woofer. Due to this large surface, its acoustic coupling to the air is much superior to a small port. It's why an ABR usually enjoys more linear high-volume behaviour. To match a port's dynamic output to that of a radiator, you'd need big port area/volume. Then high SPL nonlinearities stop being an issue. Think of the old Onken enclosures. They used 90% port vs. cone area. Also, an ABR is very easily tuned in situ to a customer's room." Here we remember that a passive radiator's functional principle is mass. Increasing or decreasing it by changing variable weights on the cone alters its tuning.

The recalled pair out to pasture.

By September 20th, "for your eyes only" appeared in my inbox with this terse message accompanying a photo: "Test cabinets. Will send pics with drivers mounted this weekend. Looks rattenscharf. The new Mini." I'd not heard that German colloquialism in ages. Rattenscharf. Literally 'hot as a rat', it actually derives from Rattenschaf or 'rat sheep'. Due to favourable climatic conditions, sheep on the Falkland islands exhibit unusually frisky behaviour. Like rats, they copulate and give birth thrice a year. Clearly Rainer thought the Mini an unusually turned-on box. Shown here in his workshop next to a Chiara, I had to agree. These cosmetics were much improved.

By September 26th, "I am testing Silvercore autoformers to attenuate the ribbon. Sounds very good. But expensive."

Rainer was leaving no stone unturned. By October 6th, "making big progress. Went away from the Silvercores. Above 5kHz, they had less harmonic distortion than a resistive solution. However, despite high-passing the autoformer with just 1.1µF, I encountered high distortion below 1kHz. That probably was core saturation. A resistive solution performed much better and was x 30 cheaper.

"I still tested expensive Duelund cast copper capacitors but in this application, the less costly red Jantzen Superior Z caps were better. Next week I’ll get the final tankwood baffle. My prototype cabinet wasn't the very best. The actual enclosure will still improve bass and clarity. But already with the proto cab, the Mini outclassed Chiara." Talk about fratricide carefully engineered by the pater familias. Shakespeare would have been proud.

But Rainer wasn't done yet. On October 12th, the terse message was "ScanSpeak Ellipticor eats Viawave ribbon. HJ is changing the cabinet to fit new tweeter." HJ was obviously shorthand for Hans Jürgen Kaiser. And the ScanSpeak was a premium Danish silk-dome tweeter which just had had a Russian ribbon for breakfast. When I told Rainer how interesting it was that originally, the Mini had adopted the Viawave as an improvement over the ScanSpeak Beryllium tweeter in the first Furioso Grande, "yes, funny, isn’t? I was always a big fan of ribbons and I like their non- homogeneous radiation with less energy aimed at ceiling and floor. And I like natural tone colors. Ellipticor delivers. In regards to radiation, it is better also than a spherical dome. Do you remember the old Audax elliptical tweeter from 30 years ago, piezo with a gold surface?" I did. Pat McGinty whom I'd worked for used it in his Meadowlark Heron model. Furioso Mini was taking final form. What other wrinkles lay ahead before the book on it would close?
... to be continued in Q3/Q4 when production commences...

Kaiser Acoustics website