Time & phase

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac late 2020 with Ventura 13.3, 40GB RAM, Audirvana Origin, Qobuz Sublime, Singxer SU-6 USB bridge, LHY Audio SW-8 network switch, Sonnet Pasithea DAC; Active filter: icOn Gradient Box at 80Hz/4th-order hi/lo-pass; Power amplifiers: Kinki Studio EX-B7 monos, Goldmund Job 225; Headamp: Cen.Grand Silver Fox; Phones: HifiMan Susvara; Loudspeakers: Qualio Audio IQ 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: Shanling M3 Ultra, Soundaware D300Ref; DAC: Cen.Grand DSDAC 1.0 Deluxe; Preamp/filter: Vinnie Rossi Signature L2 + icOn 4Pro + 4th-order/40Hz hi-low pass; Amplifier: Enleum AMP-23R; Loudspeakers: MonAcoustic SuperMon Mini, Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF + Akiko Audio Corelli; 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
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

A recent press release for Boenicke's new W22 flagship above contained a nugget: "… two sealed 15" woofers are delayed by the extra samples needed to fall precisely one cycle behind the mid/woofer". If you're unsure why that's something to brag about, consider active DSP-controlled bass. There's at least a small amount of latency from digital signal processing. It throws off phase coherence between mid and bass bands. "Being exactly one cycle late isn't audible; being off in phase very much is." It's how designer Sven Boenicke explained the difference. Wherein centers today's mini feature.

Because we can't go back in time, digital latency of active subwoofers compensates forward. We may compensate physically by placing the sub closer to our listening seat so that time alignment with the speakers locks back in. Or we can compensate by digitally delaying the speakers by the correct amount. If the sub is late, make the speakers late too until both even out. It's what certain subwoofers offer by routing our speaker signal through their plate-amp electronics. This accounts for their own latency; and/or that of dissimilar setup distances. The latter happens when a sub sits in a corner to maximize boundary gain. It's farther from our listening seat than the speakers. Now we dial in that extra distance in the plate-amp electronics and DSP adds the necessary delay to the high pass. Why would one late cycle in the bass be inaudible yet being less late though shifted in phase objectionable? Again, Sven Boenicke increases his digital latency by sufficient samples so that the delay completes a full phase rotation rather than stops short. It must be about syncing up excursions and rarefactions to have the push/pull of driver wave launches occur in unison. At least that's my read on it; and why 4th-order Linkwitz-Riley filters are popular. They offer 'perfect' phase summation even though they incur 360° phase rotation for a full-cycle delay. It also points at Wilson's micro adjustments for physical time alignment coupled to crossovers which aren't Vandersteen-type minimum-phase 1st-order. I admit that the more I think about the ramifications, the more my brain sends smoke signals of distress. All my weapons of math deduction are dismantled last-century issue. So let's pass my mind funk around. Here. Inhale deeply. See what you make of it. After all, most speaker buyers don't give a toss about time & phase. Should they though?