@Wintrmute: The extended version simulates and measures flatter for ~70% of the drivers tested, usually it also finds a nicer shaped impedance plot. The other 30% prefers the non-extended form for flattest output, matching driver specifics to design specifics (mainly Qes and Vas).
Have you changed the position of the driver yet? Magnet inside the horn or inside the chamber is a similar driver specific orientation. I wouldn't recommend it specifically for the Kappalite nor would I change it to the Extended version but it's easier done then adding the extra panel.
It sounds like your missing out on a relatively small change, that misses the drivers preferred orientation, combined with a lot of trouble to get there. Especially since you say you're happy with the current result!
I suppose you don't have a router, which you could use to round off the edges (rounding bit 8 mm radius). What I would do however is sand it with an eccentric sander. First with 80 grid on the surfaces, which you could also use to create small (2 or 3 mm radius) rounded over corners, then go up to 180 (or 240) grid before lacquer. Sanding gently by hand between layers with something like 400-800 grid.
There's a few out there. It's either done as side-by-side or mouth-to-mouth. The latter which has the added benefit that the panel at the mouth opposite of the driver (that is generally enduring most stress) is now in a much more balanced position as the 2 drivers opposing forces largely cancel each other out.. This also means you can leave some of the panel bracings out. See the second attachment for Cubo 218 (at 120 cm height), to give an idea of the overall scheme, of things.
I have just completed the build of a Cubo15 with Kappa 15LFA, but only now realised that there is a angled piece at 87 degrees where we had it at 90 degrees. Will this effect the performance much or is it okay? It's for festival purposes, so we use it outside filtered at around 40 Hz and a LPF at around 80-90 Hz with a 12 dB/octave slope.
We are currently building another Cubo15, so we have not tried it yet, but everything else is build to specs.
Thanks for a awesome design (I have heard it before and it's a crazy good bass bin!)
Which driver is the best one for Cubo 15 extended of the recommended ones? Any body have plans of a nice 12"/1" top to 2-4 cubo 15? And if I wanna go 3-way what should I build? I have trouble to find the sn12b but I can find the 12pe32.