AI Gemini tells us that the approximate baffle-step centre frequency of a 42cm wide plank is 276Hz. This represent the -3dB transition point between hemispherical forward or 2π/half-space radiation; and 4π/full-space omni dispersion. Given Supernova's dipole nature, this is also where the woofers' counter-phase cancellation starts. It advantageously sits above the 140-200Hz Schroeder frequency of a 4x6m room with 2.5m ceiling so 60m³ volume. The Schroeder frequency is where a room's acoustic behaviour changes from its modal zone below to the diffuse or reverberant zone above. In the modal zone, low frequencies create those distinct standing-wave peaks we call boom, bloom or ringing whose frequencies are based on our primary 4m, 6m and 2.5m room dimensions. Diminishing the amount of reflective acoustic energy we sink into the modal zone acts as partial room treatment. We mustn't absorb excess LF with colossal bass traps if we don't generate as much ricocheting bass mud in the first place. This is the signature benefit of dipole bass. Again, its road tax is loss of free room gain and the 6dB/octave acoustic roll-off below the baffle step to reduce efficiency and need large air motion from big cone surface. No free lunches. However, with Supernova our room's complete modal bandwidth falls inside its figure-8 cancellation pattern. That means maximally effective dipole room 'treatment'. It's how contrary to visual expectations, these mega woofers shouldn't overload a standard room as they predictably would when loaded by a sealed or ported box.

For a closer look at the modal mess our speakers make below the Schroeder frequency, jhbrandt can spit out all the details after we enter our three primary dimensions into its room-mode calculator as shown. Note how pretty much all of it happens below 200Hz. For a bigger view, click the image to open in a new window.

August 11th. During a phone call on another matter, I learnt that the project had completed. My samples would arrive before month's end. As suspected all along, Greg suffers from Oscar Wilde syndrome. "I'm a man of simple tastes. For me the best is good enough." Though at the onset of the OB project he had a certain sell target in mind, pursuing the ultimate from the platform's final drivers quickly tossed out budgetary limits. "If I know a certain capacitor to sound way better, I simply cannot use something inferior just because it's cheaper." Asked about final weight, I was told to expect ~50kg/ea. To be delivered on a half pallet because of the baffles' negligible depth, the plinths would arrive mounted on castors to roll right out. Once in their final resting place four feet above ground, the included sets of 3D-printed Vibron XL isolators could replace those. At ~90dB sensitivity, Grzegorz didn't pursue high efficiency only to compromise bass performance. For the same reason, his woofers cross in at ~150Hz not higher. As to the hot-swappable dress panels, they are painted MDF. This opens doors to custom colour jobs. Black or white are standard. I'd get my usual white. With the old rule that perception rules, Greg too was happy about Supernova.

"Because I sell direct, most clients don't really believe that Viper and Cobra can do exceptional bandwidth. They only see compact monitors and apply what they've heard from that genre in a store. To convince them that mine are very different would really want an active demo beyond my YouTube videos. Other than shows or my own studio, that would mean dealer sales so far higher prices. With Supernova, expectations based on sheer looks will match reality. That's unless one is already an open-baffle expert. Then one will still underestimate what these open-backed 15" woofers can finally do. In my room, I measure Supernova good for 22Hz!" Does this involve serious baffle-step compensation? "None. I have no midrange resistor/inductor in series with the woofers. My performance comes purely from harnessing the energy release in my crossover; strategic loading by the side rails; and exceptional woofers. But I do have a frequency response that tilts up linearly in the LF to give the desired in-room performance. Click on the next image for my first YouTube video of Supernova."

On another ascent up Mount Dipole Bass by way of Italy then China, here we see how the Diesis Audio importer Forthwise Audio of Hong Kong combined four of the brand's Bonham Tribute subs each with a 21"/53cm woofer with their Roma Triode open baffles which themselves use twin 15" woofers per side. Without subs, their quoted in-room response is 27Hz -3dB albeit against a colossal claimed sensitivity of 98.5dB/2.83V/m. So we're reminded. Filling a minor ballroom with dipole bass does require serious cone area to hit the limits of human extension. This begs a reminder invoice from Cap'n Obvious. A top-quality ported 10" woofer with room gain might hit a convincing 25Hz. On raw extension that accomplishes more with less. It's once we shift our attention to dynamics and feel that the air motion of open-backed twin 15ers registers; and becomes most obviously divergent from 25Hz headfi or unusually hung monitors of the active sort. It's the yap of small-woofer bass vs the real growl of the big dogs. It's hifi's occasion of no replacement for displacement. It's about physical stimulation beyond mere bandwidth satisfaction at the ears. Calling it bassy typically implies unnaturally goosed amplitude. But what if the feel of low frequencies not their quantity was simply more oceanic than pond-like? Would you still call that bassy; or the opposition anaemic? That's not a question for the Cap'n. That's your call.

… to be continued…