[Overclockers.com]

65 Fans Tested on a Megahalems
by ehume

The Megahalems comes with no fans of its own. You can choose your own fans, but what fans do you get? How well do they cool your system? How loud are they? When I decided I wanted to cool a 4GHz Core i7 860 with a Megahalems, I figured I would test a few fans and see how well they did. Needless to say, I sort of got carried away. I tested 65 fans in many configurations. Read all about it.

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[Dooms101]

I can tell a ton of effort was put into this. Great job! I'll be using this as a reference when buying fans in the future, thanks!

[MIAHALLEN]

Nice job ehume....I posted a link over at XS

[bing]

Thanks for the great result, Ehume.

Btw, looking at your fans collection, are you going to open a shop soon ?? ...d/k









.

[Ilden]

This is a useful resource for air and water coolers alike. Thanks.

[EarthDog]

Wow.. very nice writeup!

[RyoGTO]

This was incredibly helpful. I mean it. Thank you so much. I just ordered 2 R4-L2R-20AC-GP's for 7 dollars each. Never would have been able to make such an educated decision without this post. Seriously, thanks!

[Knufire]

Thank you very much. This test basically made my decision about fans, I'll be going with 2 Panaflo HS.

[Meathead]

Would have been nice to break the fans up into 120x38/120x25 and sleeve-bearing/ball-bearing but overall very good info

[trents]

What? No Deltas in that mix?

[Dooms101]

I didn't see my new fan in this one, although it showed up in this same review posted over at overclock.net; the Rosewill RFX-120BL. It's on order, but I am still wondering if it's any good to be used in a push/pull using a KingWin XT-1264 cooler. =/

[I.M.O.G.]

Look again Dooms, its there you must have overlooked it.

[ehume]

The chart is in three pieces. The Rosewill RFX-120 is in the lower third.

There are also two 25mm Deltas there.

[mcvan]

This is a very interesting, ambitious roundup that's unfortunately very flawed in acoustic SPL measurements.

Originally Posted by 65 fans on megahalems article --

Sound pressure is measured in decibels, abbreviated as dB. The standard weighting is type A, abbreviated dBA. The SPL meter reports sound pressure levels (SPL) in tenths of a decibel. However, the meter specifications say it is accurate to 0.5 decibel above 30 dBA, so in the tables the SPL values were reported in 0.5 dB increments. When there is no extraneous noise, the basement where the fans were tested has a SPL of under 10 dBA, so background noise did not interfere with SPL measurements. The SPL measurements were made at 10 cm and converted to the standard 1 meter equivalent by subtracting 20 dB. Because a fan is loudest at its face, the reported SPL is 10 cm from the fan intake face. Note that your setup will have its own acoustics, so the noise at 10 cm may not drop off as rapidly as theory says; but these measurements are designed to allow us to compare fans, so they were converted to the standard measure: one meter (1 m).

Problems:

1) The Tenma 72-942 SLM used can only go down to 30 dB, so how did the author know the ambient in the room was 10 dBA?

2) Specs on this sound level meter that I found state accuracy to be ±1.4dB at 1KHz, 94dB; not the 0.5 dB claimed by the author. It may go up/down in 0.5 dB steps, but that is not its accuracy.

3) There's no mention of any calibration done on the meter, which means we don't know how closely the meter meets reference SPL standards.

4) The mic was placed 10cm or 4" away from the fan intake face, and the SPL reading converted to the standard 1 meter equivalent by subtracting 20 dB. How did the author come to this odd conversion formula? Never mind; these kinds of SPL conversions from "close mic" results rarely (if ever) work.

Examining the actual SPL reported in this review for fans I've also measured in the anechoic chamber, I can say that these results are all over the place. Mostly they appear to be too high, by up to 9 dBA compared to the anechoic chamber 1m SPL tests I've done on samples of some of the same fan models.

5) There's no mention of how many samples of each fan model were tested, so I presume just one -- which is really not good enough considering how much samples can vary acoustically, sometime due to subtle damage in shipping alone.

I appreciate the enormous time and effort that must have gone into this test project, but the resulting data is of dubious value. The author's subjective comments are far more useful than the SPL results or any analysis based on SPL vs temperature. Obviously, the thermal results are worthwhile, possibly even invaluable... if you could assign accurate SPL values and subjective acoustic ratings to the fans.

SPCR is working on fan analysis using a similar approach, but in an anechoic chamber with a reference quality calibrated SLM, spectrum analyzer and audio recorder. The results there would be really interesting to compare -- at least for the cooling (temperature) results. (See prelim methodology article here: http://www.silentpcreview.com/Fan_Test_System_2010
_________________
Mike Chin,
Editor/Publisher, www.silentpcreview.com

[ehume]

The published specs on the unit were changed sometime after it was purchased. It actually reads in 0.1 decibel increments. The meter reads down below 30 dBA, but I treat them as ever greater approximations the further they fall below 30 dB.

Decibels are a semi-log scale. Multiplying a distance times ten is in theory equivalent to dropping the measured SPL by 20 dB. Of course, you never get that theoretical dropoff due to case acoustics.

I would expect essentially any fan to sound louder working against resistance than in free air. See this pdf from Nidec as an example. In any case, the SPL readings from industrial fans were close to theiir published specs. As for fans sold to consumers, well . . . I don't trust the specs so I measured the fans.

The point of posting the numbers is simply a way of comparing fans on a mount. These are relative values and cannot be compared with any other setup, just with each other.