Gravitas 12

Reviewer: Frederic Beudot
Digital Source: Aurender A10 streamer + Denafrips Pontus DAC, LHY SW6 ethernet switch, Jay's Audio CDT2 Mk2
Analog Source: VPI Scout 1.1,  Zu-DL103 MkII, Genesis Phono Gold
Amplifier: Triode Labs 2A3i, Enleum AMP-23R
Speakers: Ocellia Calliope .21 Twin Signature, Rogers LS 3/5a, Zu Essence, KEF LS50 Wireless II
Cables: Zu Varial, Ocellia RCA cables, Zu Event mkII speaker cables
Power Cords: Zu Mother, Ocellia power cables, Absolute Fidelity power cables
Powerline conditioning: Isotek Nova
Sundry accessories: Isolpads under electronics, GIK Audio room treatment
Room size: 18'x14'x10' 
Review component retail: TBA

Publisher's intro: My discovery of cardioid bass changed the way I do playback. I reviewed a few speakers and subwoofers from Bastanis/Zugspitz, Cygnus, EcoBox, ModalAkustik and Voxativ all of which were based on an expired Axel Ridthaler patent for 'super-dipole' bass trademarked Ripol. My search eventually ended with the big 2×15" sound|kaos sub now called Gravitas 15. When Frederic Beudot on staff discovered a Mongolian throat-singing Rock group that dished out low bass beyond his widebander's reach or power, I proposed that he investigate Martin Gateley's smaller twin 12-inch sub because its 'folded open baffle' mirrors the MO of his Ocellia Calliope .21 Twin Signature widebanders. Having myself spilled copious virtual ink on the Ripol subject already, it was long overdue that another voice and opinion added itself to the topic. To jump start Frederic on the hidden tech behind a rather simple-looking geometry, the above graphs from the concept's inventor demonstrate three unique aspects. 1/ asymmetrical radiation quite different from a classic open-baffle dipole. 2/ very significant lowering of the woofers' resonant frequency. 3/ much reduced cubic volume compared to a sealed box. Of particular interest is the first aspect which not only sports dipole's lateral cancellation aka figure 8 radiation but adds reduced output toward the front wall relative to the direct output aimed at the listener. This causes far reduced room gain with its reflective delays and room-mode triggers. Finally, a Ripol's MO isn't that of a pressure generator but velocity converter.

Ripol is based on a Siegfried Linkwitz idea. The Ridthaler/Hoos patent sold in 2004 and expired in 2014. These graphs show how the same woofer loaded into a sealed box, standard open baffle and folded Ripol baffle radiates differently; plus how the latter nearly halves its woofer's resonant frequency versus the sealed box.

It's why Aleksandar Radisavljevic of Raal ribbon fame who designed the open-baffle EcoBox opted for Ripol bass; why Bastanis and Voxativ pursued it to match their high-efficiency widebanders; why Martin went that way for sound|kaos. Why would one (want to) combine very fast well-damped mid and high frequencies with classic omnipolar so room-resonant box bass? It's beyond me why unlike the AMT whose expired Oskar Heil patent spawned endless tweeter clones, the equally expired Axel Ridthaler patent has met with such oversight. Where I'm concerned, Ripol loading stores the least amount of energy, causes the highest self damping for the quickest least ringy response and is most independent of room acoustics of all the conventional bass systems we might use in a standard-sized listening room. It's directional not omni bass. Let's find out what Frederic thinks about it. – Ed

A Ripol's basic geometry: one front slot for in-phase output, two rear slots for out-of-phase output create the desired asymmetrical radiation pattern. The cabinet cheeks cradle the woofer magnets for the most compact dimensions. The sound|kaos woofers are from Denmark's Audio Technology.

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… to be continued…