Some thoughts.
Ikea Starkvind is an EPA12 filter, comparable to MERV18, >99.5% filtration efficiency of particles 0.3 µm and up. This is way overkill. Most CR boxes are constructed with a much less restrictive MERV12 type filter, which is maybe 25% efficient at 0.3 µm. I mainly want to filter dust, pollen and mould spores, which are >3 µm, and I want to use PC fans so I want a non-restrictive filter so I can make use of the high air flow. Even for smaller particles, it would make sense to use a less restrictive filter with a lower filtration efficiency if it means it can move more air; 100 m³/h at 60% has a better clean air delivery rate (CADR) than 50 m³/h at 90% efficiency.
Judging by the measurements by Rob Wissman, the Ikea Starkvind is so restrictive that it needs more than twice the filter area for the same flow compared to the MERV12-13 Filtrete 2200 filter. So perhaps I should look at a different filter.
I looked at the different filter types available in the EU; the EN779 standard from 2012, and newer ISO 16890 standard. I think M6 (old standard) or ePM10 >60% (new standard) would be ideal, comparable to MERV11-12. However one class higher; F7 / ePM1 >50%, comparable to MERV13; is easier to find. That’s still 5 classes lower than the Ikea filter so should still offer much less resistance. Perhaps a class lower (M5 / ePM10 >50%) would still suffice.
A single 287x592x48 mm M5 panel probably offers about the same resistance as 4 Ikea Starkvind panels. I think that should work well with 5x Arctic P14 fans. Assuming fans performing at 60% max, and 50% PM10 efficiency, that’s about 185 m³/h CADR or about 3.6 clean ACH in the room. Or I could use 2x 292x292x48mm F7 panel with 4x Arctic P14, assuming again fans performing 60% max, and assuming 90% PM10 efficiency, that’s about 267 m³/h CADR or about 5.1 clean ACH. Enough space to expand to more fans and/or filters if needed.
Those seem like better filter choices than the Starkvind. Also, I received some feedback that I didn’t think of: I should probably reverse the flow so it doesn’t pull in dirty air right over my face when I’m sleeping. I guess inflow from the top, out from the front would be ideal. Back to the drawing board, I guess.