I told Ze'ev that in our décor, blue would actually look best but to keep things uncomplicated, green would obviously work just as well. If he didn't mind should my photos show up any cosmetic blems, that wasn't an issue either. Journeyman units do tend to get scuffed up.
8-inch Voxativ driver option.
"I looked at your reviews. You do publish good photos so I too would prefer blue. Let me check on all details early next week and get back with a plan." Two weeks passed then operations coordinator Cynthia Castro confirmed a split DPD shipment. Drivers and xovers would arrive straight from Pure Audio Project's German offices. The baffle parts would first ship in from the US to Germany then forward to Ireland. That was the plan. By agreeing to my request, Ze'ev would let me hear my first post-conversion full dipole to learn how close to Ripol benefits one can come well beyond just the low frequencies.
For vital Duet15 stats there's a rated 96dB in-room sensitivity and nominal 8Ω impedance, 29 – 32'000Hz bandwidth, weight of 15kg and dimensions of 54 x 99 x 27cm WxHxD. For an open baffle that's compact but of course a full-frontal 15" woofer does demand far more width than an extra skinny box speaker from Sven Boenicke.
Ze'ev's filter at left is a 2nd order 2-way with Mundorf parts on screw terminals. The matching resistors differ depending on widebander and allow the owner to fine-tune by +1 to -2dB. No filter frequency is published. There is alas mention of this particular woofer being good to 1kHz. If it indeed runs that high, the widebander above covers a quite limited bandwidth. It becomes a narrowbander for a change. As shown below, the Duet15 Prelude doesn't hide its assets. This segues back to Pure Audio Project where modularity rules. It allows the user to make easy changes and scratch that tweak itch whenever it gets unbearable. It just doesn't look as neat from the back as it does from the front. But if flat-pack king Ikea sold speakers, they'd probably look similar for easy shipping and assembly.
Basic math grooms expectations. We appreciate that due to its open mounting—no box to absorb/damp the rear wave—this 15" woofer moves as much in-room air as two box-loaded 15-inchers would; or for that matter a single such 21-incher. That's a very different proposal to a 6½" ScanSpeak Revelator or SB Acoustics Satori mid/woofer which in a classic upscale 2-way box monitor covers midrange and mid-30's bass if ported. From such extreme disparity of raw cone surface for today's speaker, we'd expect far more tone density and dynamics. Absence of box loading with its thru-cone bleed and omni bass radiation also predicts more speed and clarity particularly in the bass (less room interaction due to the acoustic short circuit on the baffle edges) but also across the bandwidth the Voxativ covers. Big, bold and spatially liberated should be highlights; pin-point imaging less so since we now add front-wall reflections across a far larger bandwidth than usual. Because big cones simply weigh more than small cones, we'd also expect less responsiveness at whisper levels despite Ze'ev's claimed 96dB in-room spec. The signature dipole radiation pattern of lateral nulls means virtual removal of our sidewalls as reflective surfaces. Our room will act as though it was wider. Even placement quite close to the sidewalls will have far less of an effect than with box speakers. In that sense it's fair to say that dipoles include some free room treatment.
The mounted Tang Band uses eight fixing bolts. The Voxativ gets the other four bores. Comparing between these drivers really is child's play. Just add/remove one resistor in the crossover, too.
Another functional difference to box loading is absence of compressed air as restoring force particularly on woofers. To minimize the loss of that force, dipole woofers tighten their suspension components of surround and spider. For jackhammer bass, box loading still tends to produce the harder attacks. That could be preferable for electronica with synth-derived bass. Meanwhile in-room bass reflections roughly halved mean that dipole bass tends to suffer far less overhang so stops more precisely. That leads to greater bass intelligibility—articulation, enunciation—and less overlay onto the midband. In short, the expected tradeoff between box/dipole so omni/more directional bass should be heavy/light mass, sharp/soft attacks, ringy/clean textures. All of that's basic Dipole 101. The real question was, how close or not would this particular implementation play to the lore?
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