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A different mono or stereo

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, Singxer SU-6 USB bridge, Sonnet Pasithea DAC; Active filter: icOn 80Hz/4th-order hi/lo-pass; Power amplifiers: Kinki Studio EX-B7 mono, Enleum AMP-23R; Headamp: Kinki Studio; Phones: HifiMan Susvara; Loudspeakers: Aurai Audio Lieutenant w. sound|kaos DSUB 15 on Carbide Audio footers, 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 D1300Ref SD transport clock-slaved to Denafrips Terminator +; DAC: Denafrips Terminator+; Preamp/filter: icOn 4Pro + 4th-order/40Hz hi-low pass; Amplifier: Goldmund Job 225; Loudspeakers: sound|kaos Vox 3awf, Dynaudio S18 sub; 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 Win10/64; USB bridge: Singxer SU-2; Headamp/DAC: iFi iDSD Pro Signatur;  Headphones: Final D-8000; Active speakers: DMAX SC5
Upstairs headfi/speaker system: Source: smsl Dp5 transport; DAC: Auralic Vega; Integrated amplifier: Schiit Jotunheim R; Phones: Raal-Requisite SR1a
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note I-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m

Mono or stereo? With the big cardioid sound|kaos DSUB 15, I find that a higher division of hi/lo-pass labor between mains and sub—4th-order Linkwitz-Riley so the sub is already up 6dB at 80Hz while the mains are down 6dB—doesn't betray 'mono' bass when using one sub centerstage. Au contraire. Spreading free room treatment of Ripol's asymmetrical dispersion across a good two octaves cleans up bass reflections and their time blur audibly more than the 40Hz transition I also tried. Plus now it cancels my second higher room mode.

When this passive sub first landed, it came with a Vovox mono cable. That sums its twin 15" Audio Technology dipole woofers. I tried to run their sum off one channel of a Kinki Studio integrated. Really bad idea. I was instantly greeted by vicious ground-loop hum that just wouldn't budge. Replacing the stereo machine with Kinki's 250-watt mono amp banished the hum to Kingdom Come.

I've been running my sub off the mono amp ever since. And yes, it did remove the integrated's super-convenient remote volume from the equation. As long as the sensitivity rating of my speakers and the voltage gain of their Enleum amp didn't mean the sub had to play more quietly than its direct feed to balance, I could trim the speakers with the AMP-23R's attenuator should the sub need to get louder. The master volume embeds in a Sonnet Pasithea DAC with 16Ω output impedance.

Recently the sound|kaos Vox3awf monitors joined their stablemate sub downstairs. Gain matching locked in close enough. I lucked out. If I had to increase bass gain with another speaker, up to 17dB of spare gain in a Wyred4Sound's STP 2SE preamp could front the sub amp. Ideally volume control embeds in the latter. I prefer fewer boxes, cords and cables. So that desirous thought ticked on like a forgotten time bomb for nearly a year. Finally it went off. Duh. With two woofers on hand, couldn't Martin simply reconfigure my cable so Kinki's integrated could step in for good and free up the mono for potential mains duty?

He most certainly could. "I have a 4-core 1.6m Vovox which I just need to terminate on the amp end. Do you want spades or bananas? I'll keep the two cable leads apart in case you want to try more widely spaced mono amps to drive your sub. The stereo cable will halve the amp power as the drivers are 8Ω in parallel so the amp sees a 4Ω load. I'm going to try another set of drivers over the weekend. Those are Chinese Lii 15" unit with dual voice coils. With a switching array, I could overcome the 4/8Ω issue. It's a very nice driver."

With my new cable, I can now report on what if any difference I hear between mono bass and this different kind of stereo bass. It's still only one subwoofer. But its two drivers now work as a stereo not summed-to-mono pair. If I prefer my original solution, I can always go back. Nothing ventured, nothing learnt.

Kinki mono dedicated to sub duty.