Six weeks not moons after I wrote the intro, I asked Fabrice about ETA. "Your two AVAA C214 have been under test with the National Danish Television since March and they expect to wrap up in about 10 days I'm told. Then they'll come to you." Not just home-based audiophiles were curious about these active bass traps. Even professionals thought the concept worthy enough to look into more closely. Though I don't know what the Danes concluded, soon they were done and Fabrice asked for my delivery address. An enormous Schenker lorry dropped off two stumpy cartons. I carried both at once on my shoulders into the house. The included calibration card might tell those versed in acoustics a bit more about Eva's MO? The graph's horizontal line represents frequency from 20Hz-20kHz. Its vertical measurement unit is Pa-s/m for Pascal second per meter. That axis scales from 0 to 500. The typical response shows from 80 to 60Pa-s/m between 0-100Hz then diagonals up to 160Pa-s/m at 160Hz. The response called 'limit' parallels it at a higher 120Pa-s/m. The free-field response is a simple straight line from 0-500Hz; at a much higher 420Pa-s/m. The practical upshot seems to be that Eva requires boundary proximity to be effective. In the free field where pressure is lower she's far less productive.

Parked between a Qualio IQ speaker and sound|kaos cardioid sub for size, Eva cut a compact profile that'll be far easier to accommodate than the classic passive alternative.

IEC inlet and AC rocker face down, blue and red gain switches up. It couldn't be plainer. To play lustful Adam to our dark Eve—how would our ancestor have dealt with identical twins?—I went upstairs because its conventional rectangular room has identical corners behind the speakers. I reckoned that kicking off with a symmetrical layout would give the most obvious results. Once I knew what to listen for, I'd relocate downstairs where a fire place concealed behind a painting creates a 45° diagonal 'corner' behind the right speaker whilst the left's is a classic 90° job. That could require some fiddling to sort out optimum placement?

My easiest explanation of hearing Eva in action is to compare a sealed Audeze LCD-XC circumaural headphone with an open-backed Raal 1995 Immanis with frontal vent zones. One is a planarmagnetic with window-shutter magnets obscuring parts of the membrane front and back. Its solid wooden cup barricades the rear wave. The other is a triple-ribbon affair with no diaphragm shadowing or back-wave barrier. One suffers chamber resonances, reflections and energy storage to sound dark and muffled by contrast. The other sounds lit up all over and precise. The bass of one lingers whilst that of the other stops. Aside from different sonic textures and associated transparency, the first causes on-ear pressure effects by trapping energized air. Now hifi lingo segregates the audible range into bass, midrange and treble then subdivides each into low, mid and upper segments. That's ace if we want to zoom into particular frequency ranges then communicate our focus. It's asinine if we believe them to be independent entities. If they really stood aloof, changing one should have zero impact on the others. Yet actual experience proves otherwise. It's how super-tweeter experiments may have unexpected benefits far lower down whilst cleaning up the foundation invariably shines up higher bands.

Upstairs my Eva twins doubled as plant stands in the two front corners. Tiny green LED behind the grills confirmed 'on'. Another LED next to the gain switch changes color to confirm gain from -12dB to +6dB. Not just remaining blur from bass resonance cleaned up. Midband transparency still improved. There was no doubt. Even a classic sealed subwoofer's 360° dispersion can be made to play in a higher league of adroit stoppage when the main drone areas of a room's front-corner barriers are bled off. With forward subwoofer placement to compensate its 2.5ms digital latency for time alignment whilst putting my chair in a longitudinal anti node, I'd already sorted my bass rather well. Just so, the Swiss traps still cancelled out a small remaining resonant signature which—surprising regardless of understanding the connection—also improved my midband's lucidity. It's the old image of the undisturbed lazy brook. We cross it only to stir up silt and muddy its waters. Once on the other side, we turn to slowly watch the flotsam settle and the creek return to its pristine clarity. I'd crossed my bass river a long time ago. My waters were already quite unperturbed. Yet two Eva showed that more waiting was to be done. Further sediment could and did settle. Considering Eva's plant support, I had zero objections to her physical presence though would ultimately prefer white.

But then PSI Audio are a pro company. In that sector black simply wears a lot better. Now that I had the basics, it was time to play with the gain options whilst waiting on Fabrice's answer from the Munich show about recommended min/max distance from corner boundaries. I didn't have much room to manoeuvre but some. So I was curious whether closest proximity or some breathing room is preferred. "The closer in the corner the better so with the least possible clearance. You can even turn the trap upside down so with its LED down. If the pressure on the floor is really important, that could make an improvement." Armed with that advice, I rejigged my setup for closest corner proximity.