With just the thickness of the wall's base moulding for clearance, I now entered outrageous performance at the hands of "Oriental Bass" from Patrick Chartol's Istanbul album. It opens with a sweep into the abyss. Its end stop I'd not heard this defined and crisp before. That proved just the beginning. Throughout the track's sub-bass chicane beneath the meandering solo e-bass, I could now hear acoustic substance stripped off remaining structural gain. Again, structural gain is a euphemism for blurry resonance and messy timing. With that room reactivity gone, textural vagueness—hearing something down there without it being much more specific—had changed into clear pitch and stoppage. Getting this specific and texturally distinctive there at the lower edge of human hearing was a bit of a mindbender in my smaller room. This was back at textural continuousness à la Raal 1995 Immanis with its top-to-bottom seamlessness and driver control. There's no energy storage. There's no water effect where looking farther down, light diminishes and murkiness takes over. Looking into the LF at the very bottom, the upper-register clarity holds. It doesn't diminish. It doesn't get opaque. Sonic outlines don't wash out. In an untreated room, achieving such unbroken textural linearity with speakers down to 25Hz is virtually impossible.

Now my stereo 2.1 setup had it; with in-room power and scale which headfi's on-ear drivers obviously can't touch. But at the risk of getting repetitive, state-of-the-art headfi as an example of full-bandwidth resolution without smear really is my best pointer at what these active bass traps change to then approximate. On tracks like "Oriental Bass" played back at stout levels, Eva demonstrated what my setup without her still leaves under the table. It made me twice curious what she might do for downstairs if I deliberately screwed things up by running my Qualio IQ 3-way speakers unfiltered so full-range, cardioid sub disabled, port bungs removed. I knew full well that this would really let them ride my 35Hz and 70Hz room modes like a rodeo star. Could Eva really put a stop to that?

In a word, yes! Playing musical chairs four ways—full-range; full-range + Eva; filtered; filtered + Eva—demonstrated progression. Full range was clearly problematic. Full-range + Eva vs filtered was very similar and close to ideal. Filtered + Eva was realistic perfection. Me, myself and I had a selfie group hug for our applied Ripol smarts. Then the self-congratulatory smiles stopped with the admission that for less money so no passive sub, mono amps or active crossover, I'd get very similar if more 'invisible' results when particularly left Eva disappeared behind the plant. Going full hog was best but that last step small. And it required some compensatory gain boost on the low pass. Again, what were the audible gains? The vitamin C boost of consistent consistency. If you know your room/system dance and are honest, you'll easily pick out hot spots of loudness peaks and/or textural otherness. Narrow-band peaks for example could occur as a piano descends where monitoring with headphones confirmed that each tone was recorded at equal loudness. Think evenly spaced steps on a long stair down into the bassment. Wherever these steps betray irregularities in size or hardness, you've got a fidelity problem. Whether you choose to call it that or normal because you're used to it, I couldn't predict. Neither could I say how much it would bother you if you did call it a problem.

This segues straight into the final stretch. PSI Audio's AVAA C214 is a very effective problem solver. If you don't have the problem—or don't think you do—you won't need the solution. Simple as. Hard-earned experience across well more than 10 rooms throughout my reviewing career believes otherwise. Without room treatments or expert DSP, everyone has these problems. They're merely conditional upon how LF extended our speakers are to hit or miss our lowest room mode; and perhaps also how loud we play to exasperate or downplay severity. It's arguably conditional even upon having a headfi reference to teach us what the recorded tonal and textural balance of our music is before our room applies its gratuitous EQ in the first place.

No doubt £3K for a single Eva is chunky money. Plus, you'll want two for a standard rectangular room. The full Eva appeal should kick in after one has battled tonal inconsistencies for many years already because one's hearing grew ever more intolerant of lumpy frequency response and time-domain ringing. It's then that one fully appreciates the difficulties involved in solving these issues. Now chancing upon today's non-intrusive solution becomes worth its financial weight. It even has a social benefit. It cuts bass leakage into adjoining spaces to minimize irritation of others. As a reviewer, ownership of an Eva pair would open doors to speakers I presently can't entertain then liberate me to judge them without my current high-pass solution. Though brilliantly effective, that Ripol detour isn't something most people can duplicate. The same could be said for PSI's AVAA C214 of course. Still, our Swiss sisters ought to be an easier sell?

For the right listener—I'm looking at the attentive sort who's honest with himself—the AVAA C214 is like that square peg in a round hole. It doesn't look like it should work but does; not that I understand the 'how' any better now than I did going in. It will transpose the foundation of superior headphone fidelity into free-space speaker listening. The benefit isn't just a more even amplitude response. It's far reduced time-domain ringing. That creates superior intelligibility not just across the lower three octaves. Removing blur and mud down in the LF opens up the midrange which responds with a most enjoyable resolution increase. Hearing it in action seems like magic if we know our room's sonic signature and pay attention. Given the involvement of two Swiss university labs, the effect is backed up by serious engineering. Speaking more to that is for others who understand this science. My ears merely confirm that it does what it says on the tin. At present I know of nothing like it. For that and so elegantly solving an old problem with an add-on device that's not in the signal path but works in the acoustic domain whilst being physically tidy, Eva gets our award.

"Adam, you can come out of the dog house now and play your boombastic music again. We'll even join you. Yours, Eva & Eva"

PS: Four days after publishing the above, I learnt that at the just concluded Munich HighEnd show, PSI Audio introduced the AVAA C214 in white. First availability in limited quantities is predicted for this August. If you were still hazy on the acronym, it's Active Velocity Acoustic Absorber. And though the concept should be crystal by now, unlike a custom install of passive traps which might be mounted, a pair of Eva travels from one house or room to the next without a single screw loosened. Particularly for renters, a solution which so easily changes residence without customization requirements is truly ace.