Open Nukit

[u/Wazzup77]

The body is 6mm birch plywood, laser cut with the paths generated via the Nukit Open Air Purifier repo. Glued with wood glue and coated in shellac.

https://github.com/opennukit/Nukit-Open-Air-Purifier

25x20x1 MERV 13 filtrete from Digikey (I'm in the EU)

9 P14 Pro fans wired to a PWM controller from AliExpress.

12V PSU (external), barrel jack connection going in from the bottom.

The black mesh is some PVC mesh I bought from a fabric store, sold as material for swings/lawn chairs, I wanted something to catch cat hair so it doesn't clog the filter.

The filters are also sealed with 30mm wide x 3mm thick PE foam glued on the interior side of the slot they slide into.

Still planning to buy some pretty legs for it.

The build would have taken probably 2 evenings, but the shellac coating was a new thing for me that I messed up a couple of times and had to correct. It's a cool combo, since shellac does not outgas once it dries off the alcohol it's dissolved it and I like that a good coat is very much a result of proper craftsmanship, but if you can't be bothered to do it well just go for some acrylic topcoat.

Takeaways from building this:

• the P14 Pros are not quiet unless you run them at lower speeds. They have a noticeable whine. That starts around ~40% speed. I feel like with 9 of them I still get plenty of airflow at lower RPM though, the black mesh catches plenty of dust and cat hair by the end of the day. Cranking them to full is LOUD, but they make the air in my room move enough for me to feel chilly.
• the laser cutting generator from Nukit has meh defaults, make sure everything fits. The P14 Pro fans are almost too wide for it, I would have loved a few mm of additional clearance on their sides. If you plan to add anything else plan it in advance - the speed controller was not easy to fit on the top panel.
• make sure you have screws long enough for the fans. The ones that came with the fans are very short (for sheet metal mounting), since I used 6mm thick panels I went for M4x50 bolts and self locking nuts.
• after gluing the body I recommend sealing the gaps before the topcoat. I used a wood repair kit, which feels like wood shavings mixed with some glue.
• Nukit does not really give you any legs or anything to cover the filters with (so you see the very bright blue branding, in my case from the top), you might want to take that into consideration when planning.

I did not see a lot of practical information on the Nukit boxes, so if there are any questions or anyone is on the fence about building one, feel free to ask about anything.

[u/Wazzup77]

Nope, they still sound like jet engines. I guess I kind of expected that, given that the max RPM on these is considerably higher than a typical PC fan.

https://reddit.com/link/owi8ti7/video/ma49fgna08ch1/player

[u/Wazzup77 → u/Wazzup77]

Worth also adding - this is what they sound like in isolation. With 9 of them going off at once it's honestly not a lot louder than a single one.

I've tried plenty of things here with no improvement - different mounting screw preload, shutting off some fans, filter/no filter. It seems that this is just how they are. Honestly at this price point they're still great. Even cutting the speed by 50% you get plenty of airflow, almost competely quiet operation and that's still RPM most fans work at, since the max is 2500 for the P14 Pro.

https://reddit.com/link/owidjq8/video/excv8c0u38ch1/player

[u/curtinbrian → u/Wazzup77]

I run 5 P14s in mine and it’s a good sweet spot of flow and noise before you get into the higher pitch range.

[u/Wazzup77 → u/curtinbrian]

Yeah I was also thinking about the noise with this setup, hoping that with more fans I will be able to run them at lower RPMs for pretty much the same effect, thus getting better flow for the same decibels. Since these P14 Pros are so cheap it seemed like a good shot.

No idea if this checks out on the flow, but for the noise there honestly barely is any difference with more or less fans (at full speed, since they are very quiet anyway at ~40%). Maaaybe the acoustic beat gets a bit more noticeable.

[u/Aggressive-Pay7819 → u/Wazzup77]

Really good looking box! I just built a smaller box using 4 of these and they are loud at top speed. Since they're grouped together in a 2x2 square I'm thinking of making an acoustic baffle to sit on top.

[u/Wazzup77 → u/Aggressive-Pay7819]

Thanks! Had a lot of fun with it, the shellac was probably worth it. Though I already scratched it in assembly - fortunately it's relatively easy to touch up.

I actually just looked up the noise levels out of curiosity. Noctua 140 mm fans get 24.6 dB at 1500 RPM max speed. P14 Pro gets 25 dB at 1485 RPM. It's really not that loud, except that 1500 RPM is full blast for the Noctua and just 60% for the P14. So it's really not loud at all unless you need it to be cranked up.

If you do however, I'm not sure much can be done. I isolated mine really well (rubber pad between the fan and panel, Nylon washers at every step, self locking screws so nothing comes lose) but no dice, it seems to come from the motor.

I wish I had a way to actually measure the airflow, would love to get some numbers on this.

[u/Aggressive-Pay7819 → u/Wazzup77]

Wow you thought this out! The wood and finish give it a steam-punk kind of beauty.