As far as I can tell, SPCR and I are (almost) basically saying the same thing.

I completely agree it undervolts well, at 24dBA and below it's the best fan I've tested in open air--ever. Just look at my graph. It beats a Petras Yate Loon and an S-Flex E! I agree that at 5V it is effectively inaudible. Note that "effectively inaudible" is not the same thing as "silent." I could still hear the air moving. The dBA meter was picking some minor noise as well (the air moving). Take it more than a foot away from your ear and you'll be hard pressed to hear much of anything though. That is true for all the fans in this mini-roundup except the S-Flex E (where at 5.5V and below I just couldn't hear it unless my ear was basically obstructing the airflow and causing its own turbulence). I had really high expectations for this fan at 5V and it was the best-in-test at 5V from an noise-to-airflow point of view. But it wasn't silent.

You may think that's not a big deal...but take a Mountain Mods Ascension or Duality or something else with a lot of fans and mount 12+ of these suckers. At 5v, you'll hear them. Just one is at the noise floor, but 12 of them is a whole ~10.5dBA higher than just 1--rising far above the noise floor. That's where a fan that individually falls below the noise floor is going to be important. I'd bet you won't hear the S-Flex E's at 5V. I bet you won't hear Slip Stream Ls at 7V (guess). That said...the Slip Stream M is pushing significantly more air than both of them

In my tests of MANY Yate Loon and Panaflos...I can't get consistent enough starting voltages to report. This Slip Stream M started at 4.27V. SPCR's started at 2.4V. Their Slip Stream H started at 4.3V, maybe mine will start at 3.5V. For my M, below 4.27V it wouldn't even creek or chirp. This D12SL-12 I had for this test was the lowest starting YL I've ever seen...at around 2.2V. I've really been hard pressed to find any consistency

I also agree the Slip Stream M is smooth and consistent, but so was the PTS YL SL (basically a Nexus)...and the S-Flex E...and the retail P12. I'd rank the S-Flex E the smoothest, YL SL 2nd, Slip Stream M a close 3rd, and the retail P12 a close 4th. None of these fans were bad in open air. Hence, "All fans are good here, really....there's no winners or losers." For the record, this S-Flex E is smoother than what I remember the previous one to be.

As for the radiator testing....there's something going on with the Slip Streams. Like I said in my write-up "Well beyond the point of turbulence noise...it was like the fan was increasing its RPM...significantly." I've observed it on all Slip Streams. I have a hunch there's a piece of circuitry in there that says "when current changes like so-and-so, increase RPM" where so-and-so happens to be the characteristic of how current changes when a fan is put up to a fan filter or a radiator. In fact, last night I did a little research and this older thread in the SPCR forums tentatively confirms what I've been seeing: http://www.silentpcreview.com/forums...ic.php?t=48336. And in correlation with Bluefront's testing...fan filters don't cause horrible airflow.

Heck, if you ditch the noise data and go merely by CFM to voltage data for all the fans, Slip Streams fare kinda well. But the noise is what's killing it. That's why the graph is so far to the right and away from all the other fans--it's not poor airflow, it's an unexpected increase in noise.

As for the Slip Steam M vs. the P12....if you click on my fan filter mini-review a few lines up, it trades punches in terms of airflow.

I mean...I'm telling it like I see it here. I've actually been kind of nice to the Slip Streams considering: 1) I failed the Noctua S12s out of hand due to their ineptness on a radiator (not unlike a Slip Streams') and 2) the Slip Stream CFM ratings are almost as bogus as SilenX CFM ratings.

Ugh, I talk too much