Do you recommend lining the walls at all? If so, should the rear wall be lined as well?
I lined mine with denim insulation and it ended up being more constrained than it should be around the port mouths - not quite as bad as the pic looks but not optimal. If I did it again I'd avoid at least the lower half of the rear wall.
I didn't model adding another 12 to this cab but I would suspect you'd run into trouble with port velocity pretty quickly.
I have one of the Kuda kits put together. Like all of Erich's kits it went together extremely quickly and easily. Right now it's just waiting on sanding before finishing. I have a gel stain + amber poly method that's worked well on BB before.
Some minor notes:
- I'm using an Infinity 1260w because I already have it, but the Dayton RSS315HF models well (exactly the same as the Infinity). An Ultimax in this cabinet could get a few more dB on the low end (with more watts) but would probably overwhelm the ports.
- Erich says it's tuned for 20hz. It comes with stock-length Precision Ports, i.e. a 12" connector for, according to PP, 18" effective length and a little over 22hz tune. WinISD seems to agree, but WinISD tends to be pessimistic on port length. That, of course, is before any cabinet stuffing. I've lined mine with denim insulation and will do a bead test once actually assembled. 2x3" ports model to 27m/s port velocity at power levels pushing the Infinity or RSS315HF to excursion limits, so I'm hoping the PP magic works. (The Ultimax model is hitting 40m/s which is way too much.)
The port length calculators do not take into account where the port is in the cabinet. Closer to the walls and/or closer to the back panel will lower the tuning versus what the calculators give. A very good example of this is with the VBSS cabinet where two 4" ports tune the 6cuft cabinet at 20hz due to placement of the ports.
Port velocity calculators do not account for the huge flares on the Precision Ports. There are well known companies using single 4" Precision Ports with Lab-15's and the two 3" ports in the Kuda-12 are bigger than the single 4" port. The Ultimax will have no issues and the port size is what Parts Express recommends.
One of the designers and I worked on the ported 18" cabinet that uses three 4" ports. Tuning ended up being 4-5hz lower than what the calculators figured. We maxed out an 18" Stereo Integrity HST-18 with it's 38+mm X-max and it had no port noise issues. Pretty sure we took videos of it and will upload them if I can find them.
I've had the flat packs here for a while but it took a little while to figure out packaging and shipping on the Kuda 18's due to their weight. The custom shipping boxes were ordered and should be here next week. The cabinet will have to be shipped in 2 boxes.