April
2021

Country of Origin

Poland

Lotus 10

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (i5, 256GB SSD, 40GB RAM, Sonoma 14), 4TB external SSD with Thunderbolt 3, Audirvana Studio, Qobuz Sublime, Singxer SU-6 USB bridge, LHY Audio SW-8 & SW-6 switch, Laiv Audio Harmony; Active filter: Lifesaver Audio Gradient Box 2; Power amplifiers: Kinki Studio EX-B7 monos & Gold Note monos on subwoofer; Headamp: Enleum AMP-23R; Phones: Raal 1995 Immanis, HifiMan Susvara; Loudspeakers: Qualio IQ [on loan] Cables: Kinki Studio Earth, Furutech; Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps, Furutech DPS-4.1 between wall and conditioners; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc amp stands; Sundry accessories: Acoustic System resonators, LessLoss Firewall for loudspeakers, Furutech NCF Signal Boosters; Room: 6 x 8m with open door behind listening seat
2nd system: Source: FiiO R7 into Soundaware D300Ref SD transport to Cen.Grand DSDAC 1.0 Deluxe; Preamp/filter: Lifesaver Audio Gradient Box 2; Amplifier: Kinki Studio EX-M7; Headamp: Cen.Grand Silver Fox; Loudspeakers: MonAcoustic SuperMon Mini + Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF, Akiko Audio Corelli; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan]; Sundry accessories: Audioquest Fog Lifters; Furutech NFC Clear Lines; Room: ~3.5 x 8m
Desktop system: Source: HP Z230 work station Win10/64; USB bridge: Singxer SU-2; DAC: Sonnet Pasithea; Headamp: Kinki Studio THR-1; Speaker amp: Crayon CFA-1.2; Speakers: Acelec Model One
Headphones: Final D-8000 & Sonorous X, Audeze LCD-XC, Raal-Requisite SR1a on Schiit Jotunheim R
Upstairs headfi system: FiiO R7, COS Engineering D1, Cen.Grand Silver Fox; Headphones: Raal 1995 Magna, Meze 109 Pro, Fiio FT3

2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m

Review component retail: €21'000/pr

June 2021. The other 15. Attentive readers might know that Poland's Cube Audio are working on a massive 15" widebander and a new 15cm version. Wrote their Grzegorz on September 15th—there was a definite number's game afoot—"I'm still working on the 15" but for the last three months did very little with it. We had multiple production process enhancements and more but I needed a break from R&D. I will revisit the project by probably next week. We already developed a new motor with a 2" voice coil and 5kg of neodymium magnets. This motor has 2.2 Tesla of flux in a very wide gap that allows us to use a very thick Faraday ring. The driver arrives linearly at 20kHz (!) but I'm still not too happy with the overall sonic balance in that reasonably sized cabinet I want. More experiments are needed."

Time for a mini history lesson. When in the 13th century the Knights Templars settled in western Poland, they built the Saint Stanislaus chapel in Chwarszczany village. "According to at least one local legend, it's here that the Holy Grail, the cup that Jesus Christ drank from at the last supper and which later held his blood, could still be hidden." So says a CNN Travel article on the matter. Local archeologists suspect a hidden tunnel into the structure so there's still hope for the legend.

In the annals of speaker builders, one holy grail has been the point-source single driver covering the entire audible bandwidth. Cube's big 15" is still searching for it, just not in Chwarszczany but Poznán. By April 6th, 2022, "we're busy prototyping and optimizing production. But soon we should have the other model with the small 5" widebander and 7.8" woofer." That's what I wrote two years ago but didn't publish. In the interim this team launched sister brand Qualio Audio with already two models, the IQ and Quantum.

Now we fast forward to May 15th 2024 to skip over more R&D and suspended experiments. Cube had just returned from the Munich show where they'd bowed the new Jazzon 2 and today's flagship, the Lotus 10. That revisits their earlier widebander+woofer concept, skips over an interim execution of sidefiring woofer and applies dual 10-inch front-firing drivers to the task. One is a next-gen multi-whizzer widebander with redesigned magnetics, new diaphragm geometry and voice-coil former. That runs wide open. The other is a low-passed custom woofer of the same membrane and surround material. That makes this a 1½-way; with an unexpected difference. A 4-position adjustment on the main driver has position 3 a pass-thru whilst 0, 1 and 2 each apply 1.5dB of resistive cut to pad down sensitivity from 95dB to 89dB depending on setting. The box measures 30x53x105cm WxDxH and weighs a substantial 50kg. Claimed bandwidth is 25Hz-25kHz, nominal impedance 6Ω. So Cube's Grail dream of a 15" widebander lost by just an inch. Lotus 10 applies 14 inches of compound surface to the bass register divvied out over two cones so twice the motor, half the excursion. One obvious domestic benefit is the resultant narrower box.

Digging one inch deeper into the novel adjustment, "these are switched resistors that operate in parallel with two other filter elements in the woofer path. Only the resistor value changes, the low-pass filter topology does not. Filter frequency is 300Hz and the slope of the incoming woofer is an effective 6dB per octave." And, "the holy Grail hunt isn't over yet" completed that email with a smiley emoji. So in position 3, the link from our amp to the widebander's voice coil is a classic direct connection. In the other positions, a single resistor inserts to pad down the widebander's sensitivity which increases the woofer's relative output. Whilst the control sits on the widebander, it's actually a passive 'tone control' which adjusts our bass balance to room, ancillaries and taste. Onto the name Lotus, it's an obvious continuation of Nenuphar, the previous flagship whose name means waterlily and whose dimensions are virtually identical. As the photo indicates, IsoAcoustic Gaia 3 isolation footers are part of this package.

… to be continued…