MusikBass

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz, Tidal, Denafrips Terminator+ clock-synced to Soundaware D300Ref SD transport/USB reclocker; Preamp: Vinnie Rossi L2 Signature with WE VT52/300B or Elrog 50/300B; Power amps: LinnenberG Liszt monos; Headamps: Questyle CMA-800r monos; Phones: HifiMan Susvara; Loudspeakers: Audio Physic Codex; Cube Audio Nenuphar; Aurai Audio M1 [on loan]; Cables: Complete loom of Allnic Audio ZL; Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps, LessLoss C-MARC Entropic cords between wall and conditioners; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands; Sundry accessories: Acoustic System resonators, LessLoss Firewall for loudspeakers, Furutech NCF Signal Boosters; Room: 4 x 6m with high gabled beam ceiling opening into 4 x 8m kitchen and 5 x 8m living room so no wall behind the listening chairs
2nd system: Source: Soundaware D100Pro SD transport; DAC/pre: Denafrips Terminator or COS Engineering D1; Amplifier: Bakoon AMP-13R or Crayon CFA-1.2; Loudspeakers: Acelec Model 1 w. Franck Tchang magnesium super tweeters, sound|kaos Vox 3awf, Zu Submission subwoofer; Power delivery: Furutech GTO 2D NCF; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan];  Sundry accessories: Audioquest Fog Lifters; Furutech NFC Clear Lines; Room: ~4x6m
Desktop system: Source: HP Z230 work station Win7/64; USB bridge: Audiobyte Hydra X+; Headamp: Kinki Studio Vision THR-1; Phones: Audeze LCD-XC on Forza Audio Lab cable; Powered speakers: Fram Audio Midi 120
Upstairs headfi system: Source: Soundaware A280 SD transport; Integrated amplifiers: Schiit Jotunheim R or Bakoon AMP-13R; Phones: Raal-Requisite SR1a, Audeze LCD-2, Final Sonorous X & D8000, HifiMan HE-1000
2-channel video system: Source: Oppo BDP-105; DAC: Kinki Studio; Preamp: Wyred4Sound STP-SE II; Power amp: Pass Labs XA-30.8; Loudspeakers: German Physiks HRS-120; Room: ~6x4m
Review component retail: €3'999 with external TruAudio S500-DSP mono amplifier

Directional bass? Low bass propagates omnipolar. That means equally in all directions so we hear it more than once. First we hear the direct sound which hits our ears without bounce. Next we hear—whatever comes first—the ricochet off the side or front walls, ceiling or floor. Finally we hear the last reflections from the farthest boundaries. Depending on involved time delay, our ears either sum all this data into one, albeit with blurred edges and ringing; or our brain processes the late signal as a ghost aka room-induced reverb/echo. What if bass could be made more directional and without the massive DSP Kii's Three exploits?

Enter Axel Ridtahler's so-called RiPol loading, a patented dipole-evolved H-frame scheme which controls dispersion pattern, increases radiation resistance and lowers its drivers' resonant frequency, an effect maximized with smaller cabinetry. Unlike the spherical radiation of the sealed subwoofer at left or the symmetrical fig. 8 pattern of a classic dipole in the middle, a RiPol radiates as an asymmetrical quasi dipole. All three models for these measurements used the exact same 40cm woofer. Note the change of resonant frequency between sealed box and RiPol loading, the far smaller cubic volume of the latter and its superior dispersion control across all frequencies of its bandwidth.

How does it work? Two woofers in very close proximity fire at each other. Their positive-going output vents through the front slot created by their mounting geometry. Their negative-going output vents out back through the two other slots of the triple-chamber frame. Destructive interference between in-phase front and out-of-phase rear radiation creates much reduced output at the sides, i.e. at 90° of the radiation axis. This avoids room modes and with it, bass that doesn't stop decaying. That's free and invisible room treatment. The loading of two face-to-face woofers in a minimal enclosure increases their useful bandwidth and raises radiation resistance to lower their resonant frequency for superior cone braking power. As per the patent, out-of-band chamber resonances above 180Hz should be actively filtered out. 

Inside slot open, outside slots sealed shows '+' radiation emitting out the front (left) | inside slot sealed, outside slots open shows '-' radiation firing out the back

Open-baffle makers Ecobox and Bastanis as well as widebander experts Voxativ have embraced RiPol loading for some of their speaker models. There's no typical box resonance and the concept's reduced real estate with extra extension makes it easier to integrate visually.

At Munich HighEnd 2019's newcomer exhibit, Michael Wydra had premiered his German ModalAkustik company. In collaboration with Axel Ridtahler, it proposes a ~€3'000 compact 2 x 12" RiPol passive sub in black or white that's optionally packaged with the €999 TruAudio 500w mono amplifier with volume, low-pass from 20Hz-250Hz in 2Hz increments, filter slope up to 8th order 48dB/octave and rumble filter all selectable/changeable by remote. When I wrote this as an October 2019 industry feature, sales were purely domestic still. So Michael was naturally hesitant to pursue an English review which could attract inquiries he wasn't yet prepared to fill. A good year later, I inquired again. That's because his concept was far too smart and handsome to let the Germans have to themselves. I'm a German expat. Saying so makes it nothing but transferred patriotism aka self interest.