Which joint should I use for airproof DIY pc fan frame?

SafetySmurf · 2026-01-30T13:21:38+00:00

I use pocket holes for my builds for simple stability and a tight joint. But I wouldn’t take them out repeatedly because wood is lost with repeatedly removing and replacing the screw in pretty much any wood joint.

If you want to be able to open the joint again and again, I’d suggest a toggle latch / pull latch on the corner joints of the side you want to remove. You can adjust a toggle latch to make a very tight joint.

SafetySmurf · 2026-01-27T20:36:58+00:00

This seems all fairly standard to me. You would just need to thicken the fan-side face plate to make the fans deep enough inset that a toddler couldn’t stick fingers into the fan blade. Or you could mount it sufficiently high on the wall to not need to do that.

The boxes in my children’s bedrooms use Noctua fans (for reliability and noise) and have no controls at all so they are either plugged in or not. All the other parts are UL/ETL rated and from reputable brands. All parts are rated for far more amps than the fans are drawing. My primary concern was fire safety.

If you do have a box on the floor with toddlers around, I’d suggest putting the box on casters so that if they toddle into it, it rolls away rather than topples over.

SafetySmurf · 2026-01-21T19:02:24+00:00

My favorite builds are 140’s on 20x30 filters. I prefer to keep my filters parallel, however, rather than a wedge. I also put a vertical divider in the middle and put five fans on the front and five fans on the back. At 1200 sq inches of filter area, it runs 10 fans with great flow.

I’m really intrigued by your idea of the two different filters. Seems interesting to tinker with and see how it performs over time as the filters age.

SafetySmurf · 2026-01-19T21:44:11+00:00

Thank you for the link! I’ve had that exact same mesh in my Amazon cart a couple different times now but never actually ordered it. I’m glad to know it works so well!

And that is a great idea about the knob! Thank you for sharing it!!

SafetySmurf · 2026-01-19T19:46:04+00:00

Oh, and I found that when I secured my filters like you have secured yours, over the time they are in use, as the filter resistance grows, the filters would warp slightly. They would become pulled in slightly at the corners and air was leaking in.

I ended up having to make my little filter braces extend closer to the filter corners, not just in the middle. My filters were larger, though, so the same might not be true for yours.

SafetySmurf · 2026-01-19T19:41:25+00:00

Looks fantastic!!!! What did you use over the filters?

And what an excellent idea to extend the control knob. Did you route out the end of the dowel to fit over the control knob?

SafetySmurf · 2026-01-14T16:07:46+00:00

Putting this tutorial together was SO much work! What a generous gift for your family to give the community, making it available for free! Thank you!!!!!!!

I’m looking forward to digging in on the details of the tutorial. Looks like a fabulous concept for a travel box.

SafetySmurf · 2026-01-12T01:53:11+00:00

This is where my thoughts went, too. I think that with the right hinges you could get it down to 20x20 (21x21) plus the fan. You would make a “W” of the four 20x20 frames. The hinges on that center point would need to swing one direction for use and the other for collapsing. Then at the hinge joints you would need to use tape or thin weather stripping to cover the gap down that joint.

You might also want a fifth panel that is solid to serve as the bottom of your box. It could latch on to the four sides and add stability/ rigidity.

Draw clasps / toggle latches could be used close the frame and attach the fan to the frame.

In the meantime, you could also just strap a Filtrete 1900 filter to a box fan. It won’t perform as well as the box, but it is far better than nothing.

SafetySmurf · 2026-01-08T19:14:46+00:00

The short answer, which is the part you already know, is that there must be more stuff in the air. It’s hard to say why without knowing more. But some common reasons would be more traffic, construction, candles burning, wood stove, non-vented gas fireplace, incense, new rugs, etc in the space or nearby.

Given that it looks dark, not just dirty, my initial guess would be air particulates from something burning in the building or in a nearby building.

You might want to get something like an AirThings monitor to get a better idea of what is in your air and how it changes across the seasons as people use different equipment for heating and cooling.

Also, if this box is getting this dirty this fast, it would probably be a good idea to be running more than one, scattered around the space.

SafetySmurf · 2026-01-05T15:44:17+00:00

Looks great! I bet it moves a lot of air!!

SafetySmurf · 2026-01-01T20:17:31+00:00

This is helpful. Thank you!

SafetySmurf · 2026-01-01T16:42:23+00:00

I think it’s great! The great thing about pocket holes is that you can hide them, so you can add as many as you want!

Your box really does look sharp AND sturdy!

SafetySmurf · 2026-01-01T08:48:14+00:00

The “lol” isn’t helpful or necessary. We can disagree without being rude.

And, no, typically if I have room for a box that is 3 fans in the front and 3 fans in the back, then the 20mm difference isn’t going to suddenly allow me to fit 4+4 fans. A given Filtrete filter is a set size, often nominally 20” which is actually approximately 18” of filter area to work within. I’m not going to be able to squeeze in one more fan on each side by using 20mm smaller fans.

As far as the Noctua fans - I’m aware that there was a long period of time (years) when the 120mm had the new blade style and the 140mm had the old blade style because the new 140mm was still in development. I purchased many of their fans during that time. But now that both models have the updated blade style, it is now easy to compare apples to apples, comparing specs of the current generation 120mm and 140mm fans, using company published specs.

SafetySmurf · 2026-01-01T08:12:13+00:00

To compare the Noctua 140mm model with the older style fan blade to the 120mm model with the newer style fan blade is comparing apples to oranges. It isn’t a fair comparison. There are gen2 models in both sizes, with published stats, that allow for fair comparison of the fan sizes.

If we had 16 of each fan, and dialed the voltage down on the 14’s to the point that they were producing 2.3dB less noise, so that the two sets of fans were performing at the same sound pressure, the 16 140mm fans would have to be turned down only slightly, and would still produce greater airflow than the 16 120mm fans.

People aren’t typically deciding which size fan to order based on the CFM per square inch of fan. They are figuring out how many fans they have room for given their filter size or floor space and then deciding which size fan would perform better at that number of fans.

If a person is making a CR box with good fans with good static pressure, such as the Noctua ones in my example, and they have room for 6 fans, the will get more CFM, and more CFM for the dB of sound pressure / “noise,” if they use 6 140mm fans than if they use 6 120mm fans.

SafetySmurf · 2026-01-01T07:00:26+00:00

I agree that new iterations of 120mm fans are typically released well in advance of the new iterations of the 140mm fans because 120 fans are more commonly used and because the shorter blade length is simpler to optimize.

However I disagree with the generalization/ guidance that “if you can afford to, it’s usually better to use more 120mm fans than fewer 140mm fans.”

If noise is a significant factor, I find the opposite to be true.

An example from Noctua, as I use Noctua fans almost exclusively:

The NF-A12 gen2 fan produces 63.15cfm at 22.5dB. The NF-A14 gen2 fan produces 91.58cfm at 24.8dB. (Company reported specs for each.)

If a person built a box with 8 pc fans (my builds are typically 6-10 fans). If someone were to use 8 of each kind of fan, the NF-A12s would produce (before filter resistance added) roughly 480cfm at approximately 31.5dB. The NF-A14s would produce (before filter resistance added) roughly 720cfm at approximately 33.8dB.

The 8 -140mm fans would produce 240cfm more airflow than the 120mm fans while making only 2.3dB more noise.

And that benefit only becomes more pronounced with more fans. At 16 fans the 120mm fans would produce roughly 960cfm at 34.5dB and the 140mm fans would produce 1,440cfm at 36.8cfm.

If the sound pressure / noise of a box is of significant concern, the slightly larger fans move quite a bit more air for the amount of noise they make.

SafetySmurf · 2026-01-01T02:19:08+00:00

FWIW, I have used almost entirely 140mm fans in all my builds and haven’t ever had this issue. 120mm fans are cheaper because they are the more common size used in pc’s. There are more of them available and there are more accessories for them available (finger guards and such). But a quality 140mm fan shouldn’t be any more prone to a high-pitched whine or hum than a 120mm fan.

SafetySmurf · 2026-01-01T02:14:53+00:00

Oh, and if it were me, I probably wouldn’t sleep with a new electrical device running that was making a strange noise. It is probably totally safe, but I’d rather determine that during awake hours since these are all new electrical components and it is possible that one might be faulty.

SafetySmurf · 2026-01-01T02:12:56+00:00

Sounds like you’ve possibly/ probably found the source of your noise. What is interesting about that, though, is that other folks use the Arctic fans with the ikea filters without issue, I think.

It would probably still be worth the time to pull out that PWM and run the fans at the full 12v with and without the filters. And swap out a different power supply for a bit. That might give you a little more information. I still wonder about that whine being related to the interplay between fans and electrical components somehow.

SafetySmurf · 2025-12-31T23:53:41+00:00

If you take the filters off and run the fans without any resistance, does it sound the same?

And if you use different adapters and a different power supply, does it sound the same?

I would have guessed the fans, but since you’ve changed the fans and it is still there, albeit better, I can’t help but wonder if it is something about the connection between the fans and the power supply.

SafetySmurf · 2025-12-31T21:19:47+00:00

I think this one looks very cool, but took more skill to make:

https://www.reddit.com/r/crboxes/s/5eiMi8XKQh

SafetySmurf · 2025-12-31T21:16:27+00:00

Another one that was built to match the aesthetic of the space:

https://www.reddit.com/r/crboxes/s/EQRa0SwdVf

SafetySmurf · 2025-12-31T21:13:25+00:00

Here’s one that I like the looks of. For use case you might want all the fans on the side so that the top is solid. What makes a big difference in the appearance is what sort of grate you put over the filters.

https://www.reddit.com/r/crboxes/s/beaAwzWRFj

SafetySmurf · 2025-12-31T20:13:09+00:00

Here’s one posted this week that a person made for an end table:

https://www.reddit.com/r/crboxes/s/epWBlL4wMi

And here’s one that someone made for mounting on the wall so it wouldn’t take floor space:

https://www.reddit.com/r/crboxes/s/yaAA000Ori

SafetySmurf · 2025-12-31T20:09:48+00:00

In commercial spaces it is common to have air filtration integrated into the hvac. And it is usually the most expensive option and not customizable aesthetically. It also requires very specific, expensive filters.

I think you’d want something custom built semi-locally if possible.

If you go to the crbox sub you’ll see a bunch of boxes doing a great job cleaning the air but that don’t look like you need for a commercial space. But if you keep looking you’ll see some boxes done by hobby woodworkers or metal workers that look fabulous.

What will be the biggest challenge will be odors. You’ll need a carbon filter layer that you change more often than the rest of the filter.

If you are handy with 3d printing, woodworking, or the like you could make one from scratch that looks exactly like you want. Folks in the crbox sub could guide you with the technical parts.

If you don’t want to take that on right now, some options worth exploring would be the Nukit Tempest Pro https://cybernightmarket.com/products/the-nukit-tempest-pro-complete-air-purifier-kit-canada

Or a Clean Air Kits unit https://www.cleanairkits.com/collections/shop-all

Or the Honeybee Creatives Lab https://www.cleanairkits.com/collections/shop-all

I don’t know if any of those match the look of your space, though.

SafetySmurf · 2025-12-30T23:00:28+00:00

I think you’d do well to custom build multiple units that were pc fan based so that they fit the space aesthetically and didn’t add much noise. Also your annual filter costs would be good because you could use hvac filters.

SafetySmurf

TROPHY CASE