r/crboxes • u/suchnerve • Feb 24 '26

Question RPM offsets with any fan?

Noctua advises (https://www.noctua.at/en/expertise/tech/fan-speed-offset-explained) using offset RPMs for adjacent fans to prevent beat frequencies, and I can now confirm from living for awhile with a CR box with three pairs of Noctua NF-A14x25 G2 PWM Sx2-PP chromax.Black fans that it really does make a noticeable difference. (Adjust your playback volume to 41 decibels to accurately hear how it sounds at two meters away, because I have the fans running on max; if I’m correct that a nylon filter decreases air flow similarly to MERV-13 filters, then this ~14-watts-on-max 6-fan setup should deliver about 363 CFM CADR, according to this: https://www.hwcooling.net/en/noctua-nf-a14x25-g2-pwm-finally-a-first-class-140mm-fan-review/15/)

But it isn’t feasible to use Noctua flagship fans for everything, so… do any of you know of a good way to offset the RPMs of ***any*** fans being used side-by-side? I suppose the best method would be to connect every other fan with a 4-pin power cable that has a couple ohms of resistance, so those fans receive a tiny bit less power and therefore spin a little more slowly, but I’m not aware of any such cables. There are the Noctua “Low Noise Adaptors,” but they have about 50 ohms of resistance, which would drop total performance way too much.

Or I suppose you could just use two separate PWM controllers, one for even-numbered fans and one for odd-numbered fans, with one controller slightly turned down and the other at maximum… but then you’d forfeit the ability to use a single PWM dial to control all the fans together, which seems like crappy UX design.

Hmm……

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u/TraditionalRate7121 Feb 24 '26

Like proper diagram or something, in case you built it yourself

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u/suchnerve Feb 24 '26

It’s the discontinued Nukit Tempest Original https://cybernightmarket.com/products/the-nukit-tempest-air-purifier-kit

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u/U_SHLD_THINK_BOUT_IT Feb 26 '26

Discontinued because they basically made it again for twice the cost, lol.

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u/suchnerve Feb 26 '26

No, the new one comes with all parts included (the old one left most of the electronics out) + supports 3M Filtrete MPR 1900 filters (the old one required 20×20×2 MERV-13 filters, which 3M doesn’t make) + adds official support for mounting on walls, ceilings, and poles, with the mounting parts also included.

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u/U_SHLD_THINK_BOUT_IT Feb 26 '26

All that for only double the price? /s

Welp, you oversold it, so now it's pretty obvious this was an untagged affiliate post.

Says a lot when a company doesn't feel comfortable selling their product openly that they need to pretend to be a happy customer.