Our downstairs sub is a specially folded open baffle and purely passive. I power it with a Goldmund/Job 225 amplifier. The sub's cardioid dispersion eliminates sidewall reflections, even reduces front-wall gain. This very effectively minimizes room resonances across its bandwidth. I filter it and the speakers with an 80Hz active analog xover. Its 4th-order slopes define by their -6dB spec. That extends Ripol's 'free' room treatment across 2+ octaves. Because there's zero latency, the sub can sit between the speakers equidistant to the seat. As proper 3-ways, their dipole 6" Satori mids hand off very lazily on a 1st-order slope at 600Hz. As such they see no bass to begin with. For them dynamic liberation factors not. It very much does upstairs however where 4" isobarically loaded widebanders do the biz in puny aluminium cabs. Filtering those really takes them off the leash to run with the big dogs – as long as a sub fills out their pathetic bottoms that is¹.

¹ In my book, a core 2.1 appeal is that our mains can shrink. In fact my current upstairs speakers were an experiment in just how far such shrinkage can be taken. These Korean minis are exactly as wide as a CD. Actively high-passed, their small drivers strut and swagger rather than stress and compress. I have numerous far pricier bigger speakers that could replace them. Why I don't is for two reasons. One, this 2.1 combination sounds better, goes lower and does so far cleaner. Two, I'll invariably favor smaller kit if—I don't live palatially or run eviction SPL—sound quality is on par. If superior? Well, hello! I recommended these to Rob Fritz at AudioArt Cables in San Diego who looked for small but excellent monitors. He and wife fell in love and will soon represent more MonAcoustic speaker models.

Time for the main course: filet filtration done two ways so with little and large speakers and dual 9.5" and dual 15" subs. "Would Sir care for some extra gain? How about remote control and a big legible display?" "All of it, James. I'll take the lot. Why don't you take the rest of the day and tomorrow off? I shall be busy for a while. Drive the Bentley. I won't need it."

Filtered outputs on Aavik's flagship preamp.

Back in the real world, it's a virtual guarantee. A number of plucky punters will solicit Aavik to stick this filter into a small box with display and remote. I'll back their request just because. As a fully committed 2.1 listener, I do belabor the limited choices our kind currently suffers to bolt on proper point.1 smarts to existing otherwise complete 2.0 systems. Not everyone should be ready to ditch their current preamp when all they want is the C-280's filter module. Converting this already stiff €4K PCB with two sets of RCA to a standalone component with three sets of RCA and its own power supply obviously won't come in for less. But even at twice that—certain readers just went from stiff to rigor mortis postremus—it'd still be half of what the filter-kitted C-280 demands. Who doesn't love 50% off?  Could this be a popular product? That's for Audio Group Denmark and their fearless dealers to divine.

Back in my less aspirated world, I'd ordered an icOn sub xover to expand my fixed 80Hz upstairs filter to 7 frequency choices from 40-120Hz as I already enjoy downstairs. With remote-controlled analog master volume to work with fixed-gain converters like Denafrips' Terminator Plus with 12th Anniversary firmware, it'd mirror Aavik's basic functionality just with fewer inputs and only partial remote control.

Filter module installed in I-880.

Imaginative punters staring lustfully into their crystal balls see the faint outlines of one or more Børresen subwoofer. Surely the firm won't leave that side of the filter business solely to the competition? Given Michael Børresen's inventiveness, the big question should be, what type of sub? Clearly not yet another ported or sealed box affair. Or will he really mix it up there to come up with something different?