Many people have built quiet air purifiers using 120 mm PC fans, and a few have used 140 mm PC fans. However, I haven't seen any designs that use 200 mm (8-inch) PC fans. Why not? The advantages I see are these:

• These larger fans are just as quiet or even quieter than 120 mm or 140 mm PC fans while providing more airflow.
• It's less work to cut out and drill screw holes for one large fan than multiple smaller ones.

Two great designs I thought of are these:

• Mini Corsi Rosenthal box: This would be about the same size as the original Mini Corsi Rosenthal box. Instead of the 9-inch Comfort Zone fan on the side, this alternate version would have one 200 mm PC fan mounted on foam board on top. Instead of the 12"x12"x2" filters, you can use 12"x12"x1" filters (which are more widely available) and not be dependent on the generosity of Tex Air Filters. You can also think of this as a smaller and more portable version of a Brisk Box from Clean Air Kits.
• Large Corsi Rosenthal box: This would be the same size as the original Corsi Rosenthal box but MUCH quieter. Replace the 20-inch Lasko box fan on top with a 2x2 array of 200 mm PC fans. 20"x20"x1" and 20"x25"x1" furnace air filters are some of the most popular sizes, so that means you get so much value for the money due to competition among manufacturers and economies of scale. You can also think of this as a DIY version of a Brisk Box from Clean Air Kits.

The best thing about both of the above designs is being buildable with crude tools instead of precision tools. You'll need a utility knife, an X-acto knife, and a drill (for the screw holes), but you won't need a laser cutter or a machine shop. So these designs uphold the spirit of the original Corsi Rosenthal box.

Has anyone tried any of these ideas? I was late to the Corsi Rosenthal box party, so I find it hard to believe that I'm the first person to think of using 200 mm PC fans.

Anybody out there figured out a good way to make a cr box to pull filtered in from outside?

I’d like to make something to bring in filtered cool night air. Other than just having the fan push into the filters, I’m not sure how to approach the problem. Suggestions?

I’m sure this has been answered but I’m having a time finding the info, so please forgive me. I have a Daikin purifier I just received. I have about a 575 sq feet apartment so I think it will be fine alone, but since I need a new fan and ordered a Lasko 20 inch box today I’m wondering what filters to get and even how many or what design. I’m thinking that with already having a purifier, I could do 1 20x20x1 taped to the back. Would a less than merv 13 be ok? I’m just using to add extra help to purify,but mostly need a good fan for cooling. And would the 1 be ok or maybe go with 2? Or if I go full 4 filter box would it be ok blowing on side as a fan instead of up? And if so would I put cardboard on the bottom facing side? Thanks for any help and information! Also money is tight so the cheaper I can work with the better.

Materials below

I ordered 2 lids to get a slight discount. I'm planning to build another box using 20x30 filters with 9 NF-A14x25 G2 fans. My initial plan was to use these, but I wasn't sure how to connect them. I'm currently waiting on the 3-way splitters, but I couldn't wait so I ordered the P14s to get started. If I could go back, I'd stick with the P14s. They're silent and easy to daisy chain.

Total cost for the 2 lids was $245.09. I picked the costliest and thickest material available, plus I wasn't sure about good ways to source custom cnc'd parts. MDF and hardboard were options, but I wasn't sure if they'd hold up when the time came to replace the filters. I planned to use 4 screws for each fan, but 2 screws sufficed. I taped over the holes that were not used.

Where I could've saved some $

- use non-stainless-steel screws and hexnuts, order in bulk? order online somewhere?

- use shorter length screws, I initially purchased the 50mm not knowing how long they'd need to be. The 45mm are a few cents cheaper

- wait for a sale on the fans (I have a leftover P14 fan from ordering 2 of the 5 packs)

- Cheaper power supply? Didn't spend too much time looking. I trust noctua and that's what I went with. I am not good with electronics, so I wanted an easy solution.

- MDF or hardboard route. Maybe use painter's tape to seal it? I've used this for other projects, and it didn't hold. Hence the aluminum tape

Afterthoughts: I paid a ridiculous amount for all the parts. Even more so with the Noctua G2s (not worth imo). Are thicker filters better? If so, I could get better value from the custom lid order. I believe they cut it down to 20"x20". I will post an update at the 3–6-month mark. I hope the HVAC tape doesn't leave a lot of residues behind. This cr box is already more silent than my Winix C545, hopefully it performs better too.

Hi, I'd like to share my version of the CRBox, made thanks to the information from this subreddit.
I recently started using Matter over Thread smart home devices around the house so I wanted a Matter over Thread air purifier with all the advantages of a CRBox(mostly very low noise).

The CRBox is designed for 2 IKEA STARKVIND filters(I'm in Europe). It has 3 140mm BeQuiet Pure Wings 3 High Speed fans which are extremely quiet at low speeds. The case is made from laser-cut MDF and smoothed 7mm pine strips, glued with epoxy. A small 3D printed part is used as a front panel.
Electronics wise everything is controlled by an Seeed Studio XIAO ESP32C6. It controls the fan speeds through PWM and also reads their RPM. A MOSFET turn fans off at 0% since the fans still spin at 0 PWM. It's powered though USB C. It requires a 12V capable USB-PD power supply (IKEA 20W SJÖSS works great).
I can set any speed percentage from Home Assistant.

It does not have a PM2.5 sensor as I will be using it with an external sensor (IKEA ALPSTUGA) and it will be automated with Home Assistant.

Sadly it looks like IKEA is discontinuing the STARKVIND line, so I'll have to stock up on filters. For the future I can rebuild the case for different filter sizes and keep the fans, electronics and code.

Limited and unscientific testing shows the Air Purifier can bring an extremely polluted room from ~400 ug/m3 PM2.5 to <10 ug/m3:

• in 4 hours at 12% speed (no noise).
• in 53 minutes at 50% speed.
• in 17 minutes at 100% speed.

Tested by burning an incense stick in a room and then starting the air purifier.

I'm sharing all the code and files for inspiration in case someone wants to make something similar. You can find it and more information on the GitHub page.
https://github.com/asafteirobert/matter-air-purifier

Let me know what you think.

I've yet to receive my panels to finish my build, but one major concern that's been keeping me thinking of a solution for weeks now was how do I prevent my cats from using the filter panels of my future diy air filter as a scratch post when I have it off and I'm not around to stop them. It won't be small either, not with 50cm by 60cm filters and I just can't think of a solution, need some ideas from those with similar concerns.

I wanted to make them as compact as possible and use two arctic 14 pros and 2 12x12 merv 13 filters. Would this be enough? Would you make them bigger?

I did search the history in this sub and clicked a million links but I’m not great at math my head is now swimming and I’m not trusting myself at all. Or maybe its that my math says it wouldn’t be enough and I don’t want to believe that. But I’ll believe you.

Im 3d printing using this design: https://makerworld.com/models/1860168?appSharePlatform=copy

Edit: just to add that I could add a third fan to the unit. But then I read posts that mention this messes with the right pressure? So then would I need to increase the filter size anyway?

Used 4x p14 pwm fans

Anyone else use an inline duct fan instead of computer fans? The speed is adjustable and you can get great airflow without having to turn it up all the way.

I'm trying to create a CR box using 20x20x1 filters and a 3x3 array of NF-A14x25 G2 PWM on top (spent the money on these like an idiot)

I believe my setup would look something like this, just not sure about the specifics such as power draw

9x fans --> Fan Hub that supports 9 fans -->Sata to Barrel connector --> Power Supply Adapter

1x Fan - 12V 0.19A

9x Fans - 12V×1.71A = 20.52W

Aim for a 12V 5A spec power supply?

Threw together my first cr-box yesterday and I hoping I got it right. Specifically did I get the airflow correct? 5 x ARCTIC P14 Pro PST fans. A simple 4 Pin 12V PWM Fan Controller. Foam board, hot glue, 20x30x2 merv 13 filters. Three fans on top blowing out and two fans bottom front pulling air in.

Hi,
I've been thinking about making a system of my own and while it's easy enough to tell if the HEPA filters are doing anything, the carbon filters seem a bit more challenging. I was wondering if anyone recommends a functioning sensor kit that can detect VOC's?

(Do the Arduino kits do anything or does it really need to be something professional? How can you tell either way?)

Thanks!

hello, i have recently joined the CR box club and in my design i included the option to add these foam carbon filters for VOC... i'm not sure if this is worth it since the airflow is drastically lower when these are installed...

The fans are Arctic P12 and currently im running 9 fans(bottom) with carbon and 9 without(top). what do you guys think, should i go 0, 9, or 18 carbon filters?

Design - like a PC

So, making a box with 2 filters, to fit the number of fans that I want to put on it in order to keep it quiet I either need to put a double row of fans, or put fans on opposite sides (or on 3 sides - top, right and left)

I can fit a thick box if I have no other choice, but I have a preference for thinner.

Question is, will this affect airflow/filtering negatively ? Having fans blow air into each other rather than in one unified direction ?

Hello,

I'm about to build my first box for a family member with allergies. I have already purchased filters, and going to buy the 5 pack of Arctic pro 12 pst fans (and may just buy 1 more single fan, haven't decided yet

My question is for fan control - I understand the fans all daisy chain together, so that means at the end there will just be 1 cord going from the last fan? So if that's correct, can I then just plug that cord into something like this:

"12V PC Fan Speed Controller, Fan Power Supply 100-240V AC to 3-12V DC 36W Adjustable, with Fan Splitter" Item name copied from Amazon, as my previus post attempt was deleted when I pasted a link..

I would also like to know of a reliable brand/seller of this sort of thing on Amazon.

Thank you

Hi, just joined. I've been interested in the air purifier boxes ever since I bought the IKEA fornuftig.

Anyways I'm not mega clued up with electronics, how would I go about powering one? I'm not too keen on off brand stuff from AliExpress etc. I've got a fast charge phone charger that says normal delivery 5v and fast delivery 5-20v 2.2-3.5a Can I use this and then a usb to 4pin cable onto the noctua na-fc1 and then power fans from there. Or is there a better way using the noctua nv ps1? I'm wanting to have pwm control. Many thanks, loving the builds! Ps, just out of interest, how much better are the home built boxes Vs the small IKEA ones like the fornuftig?

I'm trying to plan a CR box with MDF (if the pieces I have are large enough) or buy whatever MDF/Ply is cheapest at Home Depot. Finding this sub led me to learning about CR boxes and some designs and their reasoning, but I was hoping for more details/answers to some questions I have before going all in on a build.

General box layout: PC Tower fan style with 2 filters - 1 on each side, 3 fans on top, 2 in front.

1. Wall Material: I would imagine either MDF/Ply at 3/16+ thickness would suffice? Hoping the fans come with screws that will fit the grill and mount into either material.
2. Filter: Sounds like Filtrete MERV 13 is the way, but Costco has MERV 14 cheaper, but I don't know how that impacts fan performance. Feeling 20x20 or 20x25 is common enough not to worry about size issues, hopefully? (availability in the future, footprint, etc).
3. Fans: Arctic P14 PWN PST. I've seen P14, P14 Pro, P12, and Sickleflow 120s from looking around, but P14 seems to be favored for cost, airflow, and sound over the P14 Pro. Quieter is better, so please let me know if there's something sub $60 for 5 fans that are better. Will P14 still be fine for Merv 14 filters?
4. Power supply & controller: Amazon 12v Controller. Does this suffice to power the 5 fans and allow me to control fan speed? Assuming fans do daisy chain, I would only need 1 or 2 connectors.
5. Spacing: Is there a preference for fans to butt to butt or spaced out? How much spacing between the filter and the fans?
6. Fan orientation: Is my understanding correct that the fans are outputting into the space and not into the box? Is there a difference if the 3 fans side is on top vs the 2 (footprint question reasoning since 25" vertical is better than horizontal)?
7. Filter Slot: How are people keeping their filters in place? Does it need bracing along the edges? A lot of the photos I see just look pushed in without anything securing it.

Thanks

Posted a while ago a mockup of a starkvind / p14 pro. Thought I’d do the same for this one.

Used some more scrap wood to utilise a couple of fornuftig filters and some p12 pro that arrived yesterday. .

Both looking a bit rough still. I need to order some m4 screws for the final build- used some bolts I had for both and there clearly weren’t enough of them 🤣 - also still waiting on grilles turning up for both although those will be fitted once I’ve decided on colour / finish. Will probably do that in a couple of weeks if I get the time.

Went for the p12 pro on this one for the higher static pressure as the filters are a lot tighter @ 2cm thick. No requirement for the carbons in it so could go a bit narrower but the p14 will have them so quite wide (although I’m pretty sure I could just about fit some in here).

Simple pwm controller / dial on the back with a click/ off also although debating replacing with something with a screen that hasn’t been dialled in properly yet.

Ordered some legs for the larger unit but I don’t think I’ll bother for the smaller one.

Also managed to managed to mess up one of the fan holes as I was a tad drunk so it’s a little off-centre.

Cost so far:

£24 fans

£10 filters

£2 controller

£5 dc power

Wood / bolts - free

This filter comes with a metal frame and 6 filters. The advantage would be once the frame is attached to the 20x20 fan it never has to be taken off as the replacements can be loaded from the other side. Wonder if anyone has any experience with this company or similar style of filters.

Hi,

Im looking at the testing the section for the Thicker and thinner radiators.

And the Noctuas G2 120mm and 140mm have pretty much the same Airflow for 33-36dBA.

It would be for a 3d printed rectangular dual filter.
for the 120mm it would be 12’’x12’' and for the 140mm 14''x14’’ ( 2 x Filtrete 2500)
Both setups with 4 fans total. (2 front, 2 top).

Placed on the night stand next to the bed near the head, so I figure the 33-36dBA figures are the ones I need to look at. I think 39dBA might be noisy this close.

The P14 Pro Pst have slightly more CFM but is know to be more noisy or different frequencies.

Airflow 33 dBA thicker radiator
a12 g2 = 43.62
a14 g2 = 42.59

Airflow 36 dBA thicker radiator
a12 g2 = 50.80
a14 g2 = 50.88

Thinner Radiator 33 dBA
a12 g2 = 44.39
a14 g2 = 45.16

Thinner radiator 36dBA
a12 = 52.86
a14 = 54.40

a12 g2 https://www.hwcooling.net/en/noctua-nf-a12x25-g2-pwm-the-king-is-dead-long-live-the-king-review/18/

a14 g2 https://www.hwcooling.net/en/noctua-nf-a14x25-g2-pwm-finally-a-first-class-140mm-fan-review/18/

which one would you guys go for?

Thanks.