July
2021

Country of Origin

Switzerland

DSUB 15

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 Gaia reclocker, Avatar CD transport, Soundaware D100Pro SD card transport; Preamp: icOn 4Pro SE; Power amplifiers: Kinki Studio EX-B7 monos; Headamp: Kinki Studio; Phones: HifiMan Susvara; Loudspeakers: Aurai Audio Lieutenant, Audio Physic Codex Cube Audio Nenuphar Cables: Complete loom of Allnic Audio ZL; 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 Krion and glass 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: Soundaware D300Ref SD transport; DAC: Denafrips Terminator; Preamp/filter: icOn 4Pro + 4th-order/80Hz hi-low pass;
Amplifier: Crayon CFA-1.2; Loudspeakers: sound|kaos Vox 3awf, Zu Submission; 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: ~3.5 x 8m
Desktop system: Source: HP Z230 work station Win7/64; USB bridge: Audiobyte Hydra X+; Headamp: COS Engineering H1; Headphones: Final D-8000; Powered speakers: Fram Audio Midi 150
Upstairs headfi/speaker system: Source: Soundaware A280 SD transport; Integrated amplifiers: Schiit Jotunheim R, Bakoon AMP-13R; Phones: Raal-Requisite SR1a; Loudspeakers: Acelec Model 1, Power delivery: Furutech GTO 2D NCF
2-channel video system: Source: Oppo BDP-105; DAC: Kinki Studio; Preamp: Vinnie Rossi L2; Power amp: Pass Labs XA-30.8; Loudspeakers: German Physiks HRS-120; Power delivery: Furutech eTP-8, Room: ~6x4m

Review component retail: TBA

Sublime? Let's rumble the audio myth of slow omni bass. If a woofer is tasked to move maximally 80 x per second, a tweeter x 35'000, it's easy to see why woofers are thought slow. Whilst with the nekkid eye we'll never see a tweeter move, we might watch a woofer shudder or try to jump its hoop. Hello big excursions to move sufficient air for desired loudness. The fact that a woofer's action can be visible but never a tweeter's probably pools into the 'slow bass' notion as well. But there's more. Imagine sound like three-dimensional snooker but when the strike ball hits, its target fractures on impact. Now it doesn't pursue a linear path bouncing off table rail cushions until motional energy exhausts itself. It pursues simultaneous paths to hit all your walls, floor, ceiling and objects in the room. That's because in nature, sound propagates in all directions. It also would with speakers were those a perfect theoretical point source so infinitesimally small to radiate spherically. But most speakers are boxes. Their drivers aim in only the forward direction. For sound to wrap around a box and go omni, wavelengths must exceed its baffle width. In box speakers, treble and midrange behave directional so radiate into so-called half space (forward and in increasingly attenuated fashion sideways). The long wavelengths of the bass wrap around the box to behave omni-directional or as full-space radiators.

Frontal radiation exits the single front slot, rear radiation the dual rear slots.

That means we hear bass at least twice. First we hear the direct sound which aims straight at us. A bit later, we hear the sound which went rearward, reflected off the front wall, then came back at us. In-between we hear sound that reflected off other boundaries so parks its delay between direct and latest arrival. Hello. Anything which arrives late is slow. There's no two ways about it. The larger our room dimensions, the greater the lengths to which rear-firing ricochet sounds must go before they arrive at our ear. Though our ear/brain attempts to sum the direct and reflected portions of a sound into one event, it doesn't take genius to see that 'attempt' needn't equal total success never mind zero brain effort. It's perhaps easiest to say that the bigger the delay we're asked to digest, the more our bass is drawn with a very thick very soft pencil and the hand guiding it has the jitters. Lines are broad, their edges fuzzy and the smallest details which would rely on a maximally hard maximally pointy tip are blurry or wiped out entirely.

Phase shift too is a delay albeit by contrast very small. If bass arrives at our ear not only late but also out of phase with midrange/treble sounds and its own higher harmonics, attacks will smear, be out of sync thus soft. Critical listeners sense that such bass isn't particularly snappy or articulate but instead warm and bloomy. It's why Wilson's top speakers pursue adjustable physical time alignment despite not practicing 1st-order filters. Even sound delayed by one or more full cycles will register its attack more sharply when its excursion overlaps parallel excursions elsewhere in the bandwidth rather than becomes a rarefaction. It's all push at the same time, not partial push and pull for conflicted messaging in time. So there is something to slow rumbling bass.

An obvious if impractical antidote is the infinite baffle. Now a subwoofer mounts inside the front wall. Its flush woofer emanations have nowhere to wrap because the entire wall has turned into the sub's front baffle. Of course coupling a low-bass generator to a wall cavity transfers sound to the other side of the wall for neighborly miff. It also kills time alignment with the main speakers unless those were in-walls too or delay digitally. Here Bruno Putzeys' Kii III active monitor already proposed another way. The orientation of its multiple woofers plus heavy DSP creates strategic out-of-phase cancellation for cardioid dispersion. That means full output to the front, much reduced output to the rear. Having reviewed it, I can vouch for its efficacy. You can stand behind that speaker and barely hear any bass. An even more obscure solution is Alex Ridthaler's RiPol whose earlier patent expired. That's a specific dipole variant which creates destructive interference aka out-of-phase cancellation at the sides—so no sidewall engagement—plus reduced output at the rear plus lowers its woofers' resonance frequency plus works as a velocity converter not pressure generator. For the details, read my origin story.

Here it suffices to say that the DSUB 15 from sound|kaos auteur Martin Gateley goes beyond just adding low bass. It transforms the usual omni-directional bandwidth across which you set it to be far more directional. In one fell swoop it eliminates typical room snookers in the bass, pressurization issues and box talk. It does so without DSP or any latency. That's what makes it fundamentally different from not just box subs but even standard dipoles. As with the latter though, the price to pay is scaled-up surface area to compensate for out-of-phase cancellation. With the Swiss sub, that means dual 15" woofers so the 353.5 inch² cone surface of a single 21" woofer. Raw air movement is clearly generous. That RiPol loading works as advertised I already knew from reviewing Voxativ's Pi bass, later Modal Akustik's Musik Bass, both designed with advice from Alex Ridthaler. Due to its dual 10" woofers shown on the next page, that pretty white sub below began its acoustic roll-off at 35Hz to be 6dB down at 18Hz. The bigger sound|kaos is designed to go lower.