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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, Vinnie Rossi LIO (AVC module), COS Engineering D1, Wyred4Sound STP-SE Stage II
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F5, F6, F7; Crayon Audio CFA-1.2; Goldmund Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics One SE Up NC500MB monos; Linnenberg Allego monos
Loudspeakers: Audio Physic Codex; Albedo Audio Aptica; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & Submission; German Physiks HRS-120; Eversound Essence
Cables: Complete loom of Zu Event; Ocellia OCC loom: 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
Power delivery: Vibex Granada/Alhambra and Three 11R
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: Rectangular 5.5 x 15m open floor plan with two-storey gabled ceiling, wood-sleeved steel trusses and stone-over-concrete flooring
Review component retail: €6'000/pr
Voxativ from Germany have built a sterling reputation for proprietary widebanders by way of raw drivers; and for finished loudspeakers including dipole high-efficiency subwoofers. Now Cube Audio from that other Germany of Eastern Europe—Poland to be precise—position themselves similarly. They presently offer two different wideband drivers and two short floorstanders to show them to best effect. Not content to run off-the-shelf AER, Alpair, Eminence, Enviée, Feastrex, Fertin, Fostex, Lowther, PHY, Seas Exotic or Supravox, Cube's Grzegorz Rulka, physicist and engineer, reportedly invested 2 years and 200 prototypes to mint their own 8" units called the Fa8 and Fc8 [€490/€790 each respectively]. The following table shows their Thiele/Small parameters. Rulka's collaborator is Marek Kostrzyński who otherwise works for Pylon Audio, one of Poland's most successful speaker houses. For Cube, Marek assisted on their previous F155 and F180 drivers already, making the current units formal next gens.

Fa8 Fc8
Fs  = 43Hz Fs  = 42Hz 
Re  = 6Ω Re  = 6Ω
Le  = 0.095mH Le  = 0.094mH
Qt  = 0.41 Qt  = 0.38
Qes = 0.42 Qes = 0.39
Qms = 14.2 Qms = 14.3
Cms = 0.758mm/N Cms = 0.81mm/N
Vas = 59 liters Vas = 55 liters
Sd= 230 cm² Sd= 230 cm²
Bl  = 8.5Tm Bl  = 8.6Tm
Xmax = ±2mm Xmax = ±3mm
Xdamage =  ±6mm Xdamage = ±6mm
Sensitivity = 92dB Sensitivity = 92dB

Common to the Fa8 and Fc8 are hybrid neodymium/ferrite motors, underhung voice coils, ultralinear low-loss spiders and bicone paper membranes coated in organic resin to be impervious to moisture. The 'a' gets an aluminium faraday ring, the 'c' a copper/aluminium version to eliminate eddy currents and to lower voice-coil inductance for reduced distortion. These underhung voice coils operate within and never leave the 9mm long gap with its 1.9 Tesla strong magnetic field using 0.01mm tolerances. From the sensitivity specs we see that like Enviée, Cube don't push for triple digits. From the photos, we already saw that they eliminate typical baskets to get by with the sheerest structural minimum. This lowers reflections and compression effects to improve air flow and dynamic response.

Cubing the square. In its open-bottom internally tapered quarter-wave cabinet with acoustic foam liner, the all Polish Bliss C stands just 1 metre tall and shadows your floor with a 40x25cm footprint. Weight is a solid 26kg. The published response curves at 0°/30°/60° suggest that the most linear treble will be had at about 15 degrees off-axis. Experiments with gentle toe-in from straight out are advisable. Steep toe-in would seem not to be but that also depends on room damping and your amp's HF performance. A rolled-off valve amp could benefit from a slight rise. Back to the drivers. Their specs read far more alike than not. Then there's the lower suspension. This clearly is not the typical resin-impregnated pleated cloth. A spider's job is to centre the voice coil and add a restorative force to the stroke. With its mass, the latter function also damps and absorbs some of the incoming signal voltage. Traditional spiders thus are lossy affairs. It's why certain Fertin drivers even replace the rubber surround with three tensioned carbon stalks. Cube do not. They combine a classic quite wide foam surround with a spider made of a non-conventional material which requires CNC machining.

This prompted the following questions for Grzegorz and team:
1/ can you explain how the F8a and F8c specs translate into behavioural and audible differences when the specs seem very similar?
2/ can you explain how the drivers differ in makeup (the descriptions make it seem that primarily the faraday assembly is different)?
3/ can you explain how your ‘machined spider’ works? By removing the usual pleated cloth, what is actually left to return the membrane to zero after each stroke?
4/ what were the reasons to not go after higher sensitivity (Voxativ for example go after 100dB)?
5/ what else makes your drivers unique?
6/ presumably the cabinet of the speaker is a quarter-wave Voight Pipe design?
7/ anything else about the speaker cabinet geometry our readers might like to know?

To which Grzegorz replied that they were "still working out the best way to answer your questions. We'd already wanted to create a few articles for our website regarding some of them so there is a big motivation now to do it right." I didn't see much of a challenge. As the designers of the drivers and cabs, they already had all the facts. They just had to explain them so potential buyers so they can differentiate between their options.

This setup of Norwegian importer Hagto Audio with Aqua Hifi DAC and DIMD integrated suggests a perfect match of speaker to room.