Triple bypass

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, LHY Audio SW-8 network switch, 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: sound|kaos Vox3awf + sound|kaos DSUB 15 on Carbide Audio footers, Audio Physic Codex, Qualio IQ; Cables: Complete loom of Allnic Audio ZL; Power delivery: Vibex Granada/Alhambra on all source components, Furutech passive 6 on amps, Furutech DPS-4.1 between wall and conditioner; 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 clock-slaved to Denafrips Terminator +; Preamp/filter: icOn 4Pro + 80Hz active filter; Amplifier: Crayon CFA-1.2; Loudspeakers: MonAcoustics SuperMon Mini, 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 Signature;  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; Active DSP speakers: Fram Midi 120
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m
Review component retail: varying

Use mouse-over for loupe enlarger; or right-click to open in full-size new window. To the right of the subwoofer its Goldmund/Job 225 amp and the Gradient Box, to its left the Kinki EX-B7 speaker amps.

In the context of heart surgery, bypass is a scary word. Triple is just awful. In hifi a bypass is a painless elimination of a component or cable to isolate its sonic effect. Think with/out comparison. Today is about a triple bypass I recently had, no invasive surgery implied. The first bypass came with Pál Nagy's Gradient Box, a smart subwoofer xover. It allows proper division of sat/sub labor via user-adjustable hi/lo-pass outputs on RCA or XLR. If set to 80Hz as I do, a full-range signal enters it off a variable source or preamp. Then a +80Hz signal outputs to the speaker amp/s, a -80Hz signal to the sub amp. The slope is always a mirror-imaged 4th-order Linkwitz-Riley. A remote-triggered 'bypass' command kills the sub and removes the filter on the speakers. In an instant it restores them to full-range performance sans sub so with zero rewiring or getting out of the seat. Rinse and repeat ad infinitum. For a reviewer that flip flop is super convenient. But it can do a lot more.

With a cardioid aka Ripol sub like ours, 'bypass' goes farther than just bandwidth and tonal balance comparisons. Say that the speaker is essentially full-range. Say that we have our sub volume set for a linear response. With/out sub should show little to no difference in frequency response unless we play rare music with significant signal below our speaker's reach. But there's more. Starting below 200Hz, any ported/sealed box speaker radiates omni to involve our four-or-more walls, floor, ceiling plus all hard furnishings as reflective surfaces. In the amplitude domain those reflections add up to room gain. It's free extra loudness which our room adds to the speaker's direct output. In the time domain room gain is always late because reflections travel longer than line-of-sight sounds. A cardioid bass system's anti-phase cancellation eliminates sidewall gain, reduces floor/ceiling gain and even minimizes front-wall gain. That cleans up time fidelity very noticeably. It strips away much of the fuzz, blur, bloom and even boom which trails and envelops bass transients. Obviously the bandwidth of this improvement limits to the cardioid bass system's range. Above where that cuts off up to ~200Hz, radiation still is omni. But if the active cardioid coverage is wide enough, it'll include two or three of our most offensive room modes. Suddenly their boom is gone. It's free room treatment without any bass traps.

In my hardware context, that's the secondary effect of the Gradient Box's bypass switch. It works as a narrow-band instant room subtractor/adder. That exposes time fidelity changes. Though good to say 30Hz to reproduce 99% of musically relevant data, all such box speakers still suffer from room gain's blur in the time domain. Switching the Ripol sub in shows that in a hurry. With it, omni fuzz, bloom and boom disappear. My third recent bypass came from Qualio's new IQ speaker. Operating dipole +600Hz up—a shallow 1st-order filter there still lowers that number—there's no box loading across the majority bandwidth. By using the same Ripol sub and Gradient Box filters, I leave my first two most room-critical octaves clean. Now I can easily compare any of our box speakers to the IQ. That demonstrates how box loading compromises speed, openness and tonefulness across music's heartland of the midrange. It's not as instantaneous as hitting the actual 'bypass' button on the Gradient Box remote. But it's easily doable in ten minutes of speaker swaps. It's what I did over the holidays for some hifi education. My takeaway was unsettling. Not only is box sound a thing at least in the sandbox I play in—perhaps a heroically built Rockport speaker can eliminate it?—losing it then getting used to its absence makes a return to it quite unattractive. That's not meant to diss box speakers. I've lived with them all my audiophile life. Getting rid of the box with top-shelf drivers like Qualio's simply does something which I find very attractive.

In closing, today's header referred to 1/ bypassing/re-entering a sub and active crossover with one switch; 2/ bypassing a box speaker's 20-80Hz room interactions with one switch; 3/ bypassing box loading with open-baffle operation without changing the bass. Who knew that a triple bypass could be so much fun and educational? I can highly recommend it. Let's hope we can all stay well clear of the other kind…