I thought I had mentioned the FFB0412HN-5T20 in my gigantic fan post of doom a couple pages back, but alas, I did not. I did mention the EFB, but they're very different fans. The FFB's also have a very...
distinct harmonic because of the turbulence vanes on that family. So I generally hesitate to give them a blanket recommendation.
Here's the data sheet.
HN-5T20's not on the sheet because '5T20' is the function. Look to HN-R00/F00. 6500RPM, 10.59CFM (pretty high for the RPM,) 0.248inH2O, at 36dBA. However, several sites list the FFB0412 as not recommended for new orders. So Delta may be planning to discontinue it. (Would surprise me though. A LOT of companies use LARGE numbers of FFBs.) The
EFB0412VHD-F00 I linked has similar performance but higher RPM, and lower noise due to frame and impeller differences.
As I said: there's a
reason Delta is a top pick at every ODM and OEM, yours truly included. FFB0412's a great fan any way you slice it. Just a question of whether or not you like the harmonics. They are
very unique.
By the way, I keep neglecting to mention, the reason the KDE1204's resonate is the same reason
all MagLevs resonate. I've been positive for years that it's a motor design issue. They were designed for fixed 12V and just tach output. (I literally have piles of KDE1204's because they were the go-to fan for very-long-life fixed voltage applications.) The newer parts have a revised motor that mostly eliminates the harmonic problems when below 12V.