Country of Origin



Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (i5, 256GB SSD, 40GB RAM, Sonoma 14), 4TB external SSD with Thunderbolt 3, Audirvana Studio, Qobuz Sublime, Singxer SU-6 USB bridge, LHY Audio SW-8 & SW-6 switch, Laiv Audio Harmony and Sonnet Pasithea; Active filter: Lifesaver Audio Gradient Box 2; Power amplifiers: Kinki Studio EX-B7 monos & Gold Note monoa on subwoofer; Headamp: Kinki Studio THR-1; Phones: HifiMan Susvara, Meze 109 Pro; Loudspeakers: Qualio IQ [on loan] Cables: Kinki Studio Earth, Furutech; 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 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: FiiO R7 into Soundaware D300Ref SD transport to Cen.Grand DSDAC 1.0 Deluxe; Preamp/filter: Lifesaver Audio Gradient Box 2; Amplifier: Kinki Studio EX-M7; Headamp: Cen.Grand Silver Fox 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; DAC: iFi Pro iDSD Signature; Head/speaker amp: Enleum AMP-23R; Speakers: Acelec Model One
Headphones: Final D-8000 & Sonorous X, Audeze LCD-XC, Raal-Requisite SR1a on Schiit Jotunheim R
Upstairs headfi system: FiiO R7; Headphones: Meze 109 Pro, Fiio FT3

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: £3K/ea.

Analog version left, digital version middle and right.

Like a hole in my head. "I need xyz about as much" is how the saying goes. How about a hole in the wall? Before you envisage a rat or termite infestation, human intruders, flooding or other distinct undesirables, add the word 'virtual'. If we could create a virtual 1½ x 1½ metre hole in the wall behind each of our loudspeakers, what would happen? We'd depressurize the area. From that we'd expect reduced room modes and cleaner time domain performance due to fewer late-arriving slow-decaying bass reflections. Swiss pro-audio company PSI Audio in conjunction with two local universities have created exactly such a hole-producing thing. Its effect claims to be up to 45 times larger than its actual 64cm x 21cm columnar size of easily managed 11.1kg. Its pressure-absorbing bandwidth is 15 to 160Hz. It needs no calibration since a built-in microphone measures our acoustic conditions in real time. Its digital circuitry is groomed for minimal latency. Its twin 5½" drivers create compensatory negative pressure though PSI are quick to stress that theirs isn't a basic anti-phase effect. They explain that the device lowers the acoustic impedance of the air fronting it. It's most effective in the room corners behind the speakers because that's where pressurization from playing music tends to be highest. Plug in a power cord. Set the depressurizing action's magnitude manually with up/down gain switches; or remotely by free smartphone app.

In short, the PSI Audio AVAA C214—I'll henceforth call it Eva to eliminate caps—purports to seriously shrink the cubic volume which passive bass traps must be to get as effective across like bandwidth. Where space and décor considerations outlaw classic passive bass traps, the far tidier active Swiss invention particularly with a plant on top should slip in without much resistance. We're also assured that Eva won't change our music signal. It's not in the signal path after all. Instead it bleeds off the follow-on pressure which wavelengths long enough to wrap around our speaker cabinets cause between them and the front wall. Hence my lead-in. Without explaining the 'how' of the invention, calling the 'what' of the effect a virtual hole in the wall seems most à propos. To experience this desirable black hole sucking in high standing pressures that only contribute negatively to our sound, I had to get in line. Review units were in heavy demand. Yet the company's sales & marketing manager Fabrice Del-Prete located a journeying pair just then staring holes into walls in Hamlet's country. To boom or not to boom? He earmarked the units for an Irish pitstop before moving onto the next demo.

To rewind, I know of three main addresses to in-room bass issues. The physically most intrusive is the classic passive bass trap. Completely invisible is digital room correction software to notch out response peaks in the amplitude domain. Visible but far smaller than passive traps are super-dipole aka cardioid aka Ripol subwoofers or equivalent bass systems in speakers. Due to lateral out-of-phase cancellation and asymmetrical front/rear radiation (lower output toward the front wall than the listener), such systems shape directional bass. They put far fewer bass energies into a room than typical woofers which below ~200Hz radiate omnidirectional. At minimum six hard boundaries of walls, ceiling and floor now become secondary sound sources. The casual term for this is room gain. Each reflection adds output. As sound becomes more directional with rising frequencies, room gain diminishes. So does reverb. My pick of the three bass problem solvers for the main system has been cardioid radiation. I use no classic acoustic treatments other than the Swiss sound|kaos sub.

Due to its built-in highly desirable acoustic cancellation pattern, it must bring big cone surface to bear which in my case means dual force-cancelling 15" woofers. Those don't behave like typical pressure generators. Instead they're called velocity converters. There's a simple remote bypass switch on my active pure analog hi/lo-pass xover. I have it set to 100Hz/4th-order to cover 35Hz/70Hz modes. Bypass demonstrates the huge difference from the seat. In full-range speaker mode hence with omni bass, I hear instant fat room boom. Pear-shaped is quite literal. In the time domain I hear offensive ringing. Its overhang or drone even overlays the lower midband. Whilst digital EQ can surgically cut out response peaks, it can't do zilch about time-domain ringing. Though post-EQ bass will exhibit more linear loudness, it still bounces off all hard boundaries just as it did before. 80% of typical omni bass still continues to arrive at our ears noticeably delayed behind its direct portion. I call this ghosting. It follows a bass transient's impact like a cloud of exploding dirt accompanies a mortar hit.

Since Eva claims to absorb bass rather than just diminish its amplitude where an EQ could get far more specific on peaks and dips, we expect her primary improvement in the time domain¹. We envisage superior stoppage. Bass won't linger as much past its recorded sell-by date. But lingering bass is endemic to 99% of all speakers. So its users have adjusted to its bloomy texture by calling it powerful, warm, big or fat. They could react to a reduction of these attributes as less or lighter or leaner bass like a negative. They're not really keyed into such bass' timing mess, its loss of articulation, its blurriness from overlap that lasts far longer than it should. If so, noticing the benefits of Eva beyond likely reduced bass amplitude could take just a bit of an ear/brain readjust? I certainly expected to focus on her impact on time fidelity. It's something which ownership of a Ripol sub has made me very sensitive to and critical of. What only users of effective traditional bass traps could tell us who additionally must be willing to temporarily remove them all is how close two Eva might come. Can two small active bass traps absorb as much as an array of big passive types? I won't have a clue. In our digs, passive traps big enough to actually work are beyond the pale².

¹ Corrective software can already improve the time domain performance of our speakers with digital delay. This can for example time-align a vertical baffle's tweeter with its woofer. Equivalent smart bass management can do it for a corner-placed subwoofer with digital latency which additionally sits extra meters from the seat than our speakers. By inputting the distance differential, the software applies the correct time delay to sync up its speaker high-pass with the sub. Such software simply lacks Eva's real-time monitoring via microphone; and its actual absorption rather than just delay effect. The same is true for room correction software which applies strategic attenuation of frequency peaks but can't cause physical absorption of low frequencies to eliminate their reflective time delay.

² This expression dates back to 13th century Ireland to describe people living in parts that were outside British control. Called the Pale, these areas originally were parts of the counties of Meath, Louth, Kildare and Dublin. "Once you passed the Pale, you were beyond the authority and safety of English law so subject to all the savageries of rural Ireland. Beyond the pale thus became a colloquial phrase meaning outside the limits of acceptable behaviour or judgment."

… to be continued…