First to go were Martin's solid footers. Whilst downfiring subs are the worst offenders—their woofer orientation duplicates actual jackhammers—and despite stacked Ply's endless wood/glue layers, some of the very considerable forces generated by two closely face-to-face 15" woofers leeched into our parquet floor even though the inherent cancellation of two equal but opposing forces makes for a surprisingly still cabinet. Though not suspended as upstairs but with the sub floor now on a solid concrete slab, the big subwoofer still coupled to the floor for some structural amplification. With Jeffrey Jenkins' Carbide Footers enroute, I'd have proper vertical isolation plus the horizontal dissipation I already exploited with HifiStay's multi-layer rollerball footers. Those blocked the energy transfer quite effectively and far better than Martin's footers, just not entirely. I still had very mild 'knots' in the bass fabric that were structural not acoustic in nature. Those I expected the mega footers from Texas to cut entirely. As I put it in their review, "clean low frequencies without structural overhang warrant the right disruptive tech to insure that they just couple to the air and not to resonant objects as well. After all, we don't want our floor to behave like a piano's soundboard, our sub and/or speakers to become its exciters." Already without those disruptors adding vertical spring isolation with viscoelastics, the transformation of bass textures was wholesale. Even outside the room bass attenuated far more rapidly than the midrange. Upstairs there was no bass whilst the rest of the music remained audible: proof positive of a Ripol's very effective cancellation pattern doing its work as advertised.

Inside the room, bass had denuded of overhang from a probably 70% reduction of time-delayed room gain. Bass grip and the certainty of directness were clearly more powerful. Of course subjective bass density had reduced because the typical reflective blur surrounding it had seriously cut back. On extension I'd gained just a bit but the new clarity in the two lower octaves revealed more 'undertones'. Here I don't mean the literal opposite of overtones occurring below the fundamental. I mean hearing the true fundamental cleanly under the first harmonic an octave higher. Standard box subs of sufficient size will go lower and louder. But even heroic 550lbs constructions like Magico's dual 15-inch Q Sub can't help but play the whole room. Despite elite pedigree, unhealthy SPL potential and low anechoic distortion measurements, all box subs have us hear their bass more than once. That's a function of their 360° radiation pattern not overkill construction or extreme integrator expense à la $48'000 MXO with external PSU. Another benefit of Martin's natty pin-stripe sub was being able to play a lot louder without causing any congestion. If for simplified argument's sake we count our room's main reflective boundaries as six (four walls, ceiling and floor), reflections dominate direct bass by a factor of 6:1. The louder we play, the more reflective content leads. With a Ripol dispersion's acoustic short circuit, our ratio clearly diminishes significantly. Playing louder delays the reflective runaway. Clarity stays put far longer to invite high SPL. By the same math, we appreciate how much more power a folded open baffle consumes versus what arrives at our ear; and how much harder its drivers have to work to compensate for big losses in room gain. Relative to free loudness those losses are counterproductive. Relative to a cleaner time domain, they're essential. After experiencing the DSUB15 in person, I'm more convinced than ever that a big Ripol is the smart wo/man's solution for superior low bass without any room treatments whatsoever; or active bass traps à la PSI Audio's AVAA C20 from Switzerland.

At this juncture it's fair to remind ourselves. When I wrote this, sound|kaos hadn't yet readied their own filter/electronics. A purely passive cab with two woofers remained incomplete. It was useable only because I provided the low-pass—and high-pass which in my book is just as necessary—plus a first-rate 250-watt high-current class AB mono amp. Still, I'd not expect real sonic differences from Martin's eventual full package, just extra functionality with multiple filter settings and gain adjustments.

Until the Gradient Box arrived, I already had Pál Nagy's custom 80Hz/-6dB 4th-order LR filter box to compare to his 40Hz version I'd used thus far. Whilst my ideal value might ultimately slot between those two, I could start comparing what I assumed would be my lowest/highest filter values. With a mono sub, I really didn't think that I'd want to exceed 80Hz. I don't know how/why Magico arrived at 55Hz for their über-priced fixed analog crossover. Like mine, it runs 4th-order Linkwitz-Riley slopes. Perhaps Magico determined that 55 cycles are most universally useful?

The Gradient Box will offer separately settable hi/lo-pass values at 26, 40, 53, 60, 80, 92, 106, 120, 132, 145, 160, 171, 184 and 198Hz. The supply chains which the pandemic had clogged for vital electronics parts also delayed Pál's design so my sub renovation had to start with the woofers, not the bigger brain I'd eventually control them with [prototype and its designer at left].

Shaking paws at 80Hz did remove even more blur. That drained remnants of bass reverb still further as I worked my way through low-hanging fruit from Bombay Dub Orchestra, Burhan Öcal & Pete Namlook, Desert Dwellers, Kalya Scintilla, Mercan Dede and Bros. I heard no demerits, no loss of stereo imaging in the upper bass. In fact, by shedding room blur across the guiltiest two lowest octaves, image specificity in general improved. Regardless of handover frequency, a small thing I might still want is to elevate sub 30Hz response by just 3dB to apply a small boost. That too would come with the Gradient Box. Until then I had to be a good grasshopper and practice patience. Whatever subsequent mini tweaks I might learn of, I already thought the downstairs system completed just as I'd dreamt this addition would do. For the full postage of Ripol perks, I'll list far crisper timing, superior articulation from cleaner stops, elimination of bloomy ringing, no more ear pressurization from room loading, proper soundstage mapping into the sub bass, ability to play far louder without any environmental protests, no more bass leakage into adjoining rooms. For the neighboring bandwidth, I'll call it greater clarity. For the overall effect on the listener, I'd single out greater easefulness in general, higher bass intelligibility and speed in particular.

Closing this section, let's reiterate that with speakers already good to -3dB/33Hz, adding much extra bass extension in our rig was neither probability, need nor real desire. Given the DSUB 15's concept, this deal wasn't about more quantity but a very different quality. Those of the persuasion to proudly report that their aircon vents rattle and their guts get pummeled when the system plays bass won't see the appeal at all. A Ripol won't be for them. It's not about room pressurization or lock but the exact opposite. It asks that since our midrange and treble don't cause pressurization issues, why should the bass? To create an obvious seam of discontinuity with textures and time? If we're already cognizant of the issue to eye passive or active bass traps, it proposes a solution that decommissions their use. Why pay for a cure and think ourselves sophisticated if we could avoid the disease in the first place? Isn't that the very opposite of sophisticated?