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 Post subject: 4ea 80mm fans tested at equal airflow and 3"
PostPosted: Wed Apr 16, 2008 12:27 pm 
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Location: Klamath Falls, OR
Sunbeam Silent Core Fan 1500RPM 21.5CFM
SilenX New Version (high pitch)
Scythe Kama Flex 2000RPM 27CFM
Enermax Marathon 1500RPM 24CFM

Ambient noise 29.5dBA (daytime), 3" microphone distance (geometrically same as 120mm fan at 4.5"), sensor RPM 824RPM for all fans.
Code:
Sunbeam  11.89V 1594RPM 39.6dBA
Marathon 10.48V 1411RPM 34.5dBA
Kama Flex 7.90V 1404RPM 37.3dBA
SilenX    8.79V 1380RPM 34.9dBA

Lowest pitch at top, highest at bottom. The 80mm Kama Flex did not score as well as its 92mm version, which was the quietest of the 92mm fans tested. The winner is the Marathon, especially since it does not depend entirely on high pitch to achieve a low noise level. Once again, SPCR has reported problems with their Marathon sample that my sample does not exhibit. Everybody's unfavorite, the SilenX, had the highest pitch and the second-lowest noise level. The Sunbeam fared a little better when previously tested at .5" mike distance.

I chose the highest microphone distance that would allow staying above the ambient noise level with a margin I was comfortable with. The idea here is to compare fans, not to obtain absolute noise levels.

edit: corrected Kama Flex nominal RPM and CFM


Last edited by Felger Carbon on Mon May 05, 2008 1:35 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sat Apr 19, 2008 12:52 pm 
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Location: Edmonton, Alberta, Canada
Thanks for taking the time to do these comparisons!
I was hoping you might clarify the data, tho:

What do you mean when you say "sensor RPM 842RMP for all fans" and then in the data chart you specify different RPM values such as 1404RPM for the Kama Flex?
Now that I think about it, can you please include a legend for the different parameters in your data table? I'm not sure what to make of the voltages either (are they starting voltages or simply the voltage at the accompanying RPM?)


On a completely unrelated note, you seem to have access to quite a few fans... I don't suppose you might also have access to the 2000 & 2500 RPM variants of the Kama Flex 80mm fans? The reason I ask is that I'm going to be putting together a HTPC in an Antec Fusion Black case and will swap the PSU's fan with either the sleeve-bearing fan that comes with the Ninja Mini or one of the Kama Flexes. Another poster on here mentioned that the 1500RPM version doesn't start at the ~4V that the PSU fan header puts out, so I was hoping that, if possible, you could do me the huge favor of testing starting voltages if you happen to get your hands on those fans and run your standard battery of tests on them?
I know from reading another user's post on here that the minja fan will work perfect, but I like the idea of a Fluid-dynamic-bearing for better longevity and (theoretically) better acoustics. I could not find either the Marathon or SilenX you tested on the stores' websites that I use...

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Gaming rig: Tt Tsunami,P5Q Pro,Q9450 w Ninja,8GB RAM,4870 1GB w S1,WD 640GB,SB X-Fi Plat,ZM-MFC2.Kama PWM in PSU,others S-FlexEs.
HTPC: NSK2480,GB GF9400,E5200 w/ Minja,4GB RAM,WD GP 1.5TB,Nova DVB-S. Minja PSU fan,S-FlexEs case fans.


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 Post subject:
PostPosted: Sat Apr 19, 2008 4:02 pm 
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Location: Klamath Falls, OR
Since the sensor RPMs are all the same (that's the "equal airflow"), the other RPMs are the fan RPMs. Note that different fans require different RPMs to achieve the airflow - the one with the lowest fan RPM is the one that has the highest fan pitch, etc. The voltage is the fan voltage required to run at that fan RPM - gives you an idea of how much faster that particular fan could run, if necessary.

I have access to any fan that's sold on-line in the US of A that I'm willing to shell out my $ for. Which is why I don't test all fans and all models. The result is, I test only those fans that interest me personally.

The Sunbeam Rheostat I use for the variable fan voltages is a really lousy test vehicle for fan starting voltages. The output stage is a Darlington emitter follower, so after setting the voltage under no load whatever, then turning on the power suddenly, the voltage drops considerably during the short start surge - and does so too fast for my eyes or other equipment to follow. So any starting voltage I measure is significantly higher than the real value.

I confess that selecting only fans that are available at a particular reader's favorite vendors is a concept I had not previously considered! :P


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PostPosted: Sun Apr 20, 2008 4:12 am 
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Hello,

Ah -- the sensor is the propeller, and when it's RPM's are 824 (or whatever), that's when you take the fan speed.

The name "sensor" was confusing, because it makes it sound like it was part of the fan...

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http://neilblanchard.blogspot.com/


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 Post subject:
PostPosted: Sun Apr 20, 2008 3:28 pm 
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Location: Klamath Falls, OR
NeilBlanchard wrote:
Ah -- the sensor is the propeller, and when it's RPM's are 824 (or whatever), that's when you take the fan speed. The name "sensor" was confusing, because it makes it sound like it was part of the fan...

Yes, the propeller is the "airflow sensor". If two (or more) fans have the same sensor RPM, then they have equal airflow (equal CFM).

My bad, I've done enough of the equal-airflow comparisons that I think everybody else knows by now what's going on. What do you think of my equal-airflow comparisons? Useful? No?


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 Post subject:
PostPosted: Sun Apr 20, 2008 6:51 pm 
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Hi FC,

They are useful! (As long as we are not confused...)

What diameter is the propeller? Some fans push air out in a cone, and some have a more cylindrical (or at least a narrower cone); so this might affect the results, if it is not large enough to "catch" all the air...

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http://neilblanchard.blogspot.com/


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 Post subject:
PostPosted: Mon Apr 21, 2008 12:49 am 
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Location: Klamath Falls, OR
NeilBlanchard wrote:
What diameter is the propeller? Some fans push air out in a cone, and some have a more cylindrical (or at least a narrower cone); so this might affect the results, if it is not large enough to "catch" all the air...

The sensor propeller is a 5.82" (called 6"), cut down to 80mm. This provides a heavy (good) high pitch (good) sensor. Because it's heavy, the sensor has less tendency to rapidly ramp its RPM up and down (has to do with gyroscopic effects due to the cheap sensor propeller shaft not being lubricated). Because it's high pitch, the rapid ramping is further reduced.

[I initially thought a lightweight sensor with low pitch would be desirable. This project has been a good learning experience for me! :wink:

How the fans push the air is a property of the size of the fan and its CFM. The higher the CFM, the higher the velocity of the air molecules and so the slower the "spread" of the air column. Since I test all fans of the same size and at the same airflow (CFM), the "spread" of the different fans is the same.

I prefer "equal airflow" to "same CFM", because when seeing "CFM", one is conditioned to seeing a numeric value. My tests don't care about numeric values, just equal airflow (as signified by equal sensor propeller RPMs).


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 Post subject:
PostPosted: Thu May 01, 2008 5:16 pm 
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Location: US
Thanks for testing/reviewing these fans! Your tests seem to be a very good and useful way to measure noise levels at constant CFM across the board.

Now, in your humble opinion, which would you opt for today for a case fan - the 80mm Kama Flex or the tried and true Nexus? If there isn't much of a difference, then the added cost wouldn't be worth it I suppose for the Nexus. Thanks...


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 Post subject:
PostPosted: Fri May 02, 2008 2:03 pm 
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Location: Klamath Falls, OR
floepie wrote:
Now, in your humble opinion, which would you opt for today for a case fan - the 80mm Kama Flex or the tried and true Nexus?

Under no circumstances would I ever use a case that's cooled by an 80mm fan. In general, where there isn't much airflow resistance - no filters, no HSF with tightly spaced fins - I would go with the Kama Flex. The lower-pitch Nexus may prove superior where there's high airflow resistance... but I try to avoid high airflow resistance. At the moment my two computers on this desk collectively use 220mm, 120mm, 100mm, 92mm, and 60mm fans. I'm not using any 80mm fans at all.


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 Post subject:
PostPosted: Mon May 05, 2008 11:56 am 
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Just a few questions: How could it be that at 7.9V, the Kama Flex spins virtually at its rated speed?

Secondly, it seems what you are saying regarding the Kama Flex is that because it has relatively high pitched blades, it is not all that well suited for high resistance. Is that a general rule? It would seem intuitively that a high pitched fan, which presumably focuses the air flow around the hub of the fan would be more well suited for high resistance, forcing the air through whatever is in front of it, whereas a low pitched fan would produce more of a cone-shaped flow, whose radius would increase from the front of the fan.


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 Post subject:
PostPosted: Mon May 05, 2008 1:53 pm 
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floepie wrote:
Just a few questions: How could it be that at 7.9V, the Kama Flex spins virtually at its rated speed?

Secondly, it seems what you are saying regarding the Kama Flex is that because it has relatively high pitched blades, it is not all that well suited for high resistance. Is that a general rule?

I just checked, and my "L" Kama Flex is 2000RPM, 27dBA. Thank you for pointing out my error; I've corrected the first post (1500RPM is an "SL").

Are you at all familiar with the variable-pitch propellers on small commuter prop-jet aircraft? They begin the takeoff at lowest pitch, and increase the pitch gradually as the aircraft speeds up. At cruise, the prop is at its highest pitch. This acts as a continuously-variable "gearbox", keeping the engine running at a constant, optimum speed.

For a given airflow, the lower the pitch, the higher the needed RPM and so the higher the noise. If there were not some sort of tradeoff, everybody would build high-pitch fans to keep the noise level down. The tradeoff is, for high-resistance airflows, "low gear" on the "transmission" is best, and that means a low pitch and high RPM.

Examples: The Yate Loon and GW NCB 120mm fans are long-time favorites here at SPCR; they are the two lowest-pitch fans I know of. A very recent favorite is the Slipstream, which is the highest pitch fan I've used. I believe it works best in low-resistance airflows, but its 9 blades seem to make it handle high-resistance better than the 7-blade high-pitch Noctua fan, which is notorious for lousy performance in high-resistance situations.


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PostPosted: Mon May 05, 2008 5:15 pm 
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Great analogy, thanks for the explanation. Perhaps the Kama Flex 80mm 'low speed' would fare better compared to the above competition. I believe it was you who said in another post that a fan rated for a lower speed should be quieter than the same fan rated for a higher speed within the same series at a constant CFM/speed.


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PostPosted: Mon May 05, 2008 10:17 pm 
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floepie wrote:
I believe it was you who said in another post that a fan rated for a lower speed should be quieter than the same fan rated for a higher speed within the same series at a constant CFM/speed.

Well, I thought so. But sometimes not, as my Slipstream500 vs 800 proved. Neil was right, 800 is the Slipstream "sweet spot". I mever nake misteaks! :P


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 Post subject:
PostPosted: Wed May 07, 2008 10:30 am 
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Hello FC!

I'm thinking of putting a 2000rpm Kama Flex 80mm in my Antec EarthWatts 380W, so I wonder if you have tested at what voltage it starts?
If not would you mind doing so?
It it doesn't start at 4V do you think the 2500rpm might do that?

Thank you!

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Antec NSK3480|Antec EA 380W with Nexus 80mm Fan|ASUS P5E-VM HDMI|Core2Duo E4600 2.4GHz|Corsair 2GB 800MHz DDR2|WD Caviar GP 500GB|Scythe Ninja Plus Rev.B+TR Bolt-thru|1x120mm Nexus
Finally inaudiable!


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 Post subject:
PostPosted: Wed May 07, 2008 2:55 pm 
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Fenix wrote:
I'm thinking of putting a 2000rpm Kama Flex 80mm in my Antec EarthWatts 380W, so I wonder if you have tested at what voltage it starts? If not would you mind doing so?
If it doesn't start at 4V do you think the 2500rpm might do that?

What counts is, will the PSU circuit start it? So, spend some kroner and see if it does. Let us other SPCR types know how it works by posting in either the fan or PSU forum?


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 Post subject:
PostPosted: Thu May 08, 2008 9:16 am 
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Location: Sweden
Felger Carbon wrote:
Fenix wrote:
I'm thinking of putting a 2000rpm Kama Flex 80mm in my Antec EarthWatts 380W, so I wonder if you have tested at what voltage it starts? If not would you mind doing so?
If it doesn't start at 4V do you think the 2500rpm might do that?

What counts is, will the PSU circuit start it? So, spend some kroner and see if it does. Let us other SPCR types know how it works by posting in either the fan or PSU forum?


I probably will do that. Unfortunatly they aren't available in Sweden yet so I was thinking of buying them from Germany.
That makes them a bit expensive to buy without knowing if it will work.
So I guess I will have to wait a few months. Maybe a good thing since I will get my tax refund in June :D. I'm planning on spending it on Kama Flex fans and a 2.5" WD Scorpio 320GB drive.

Thanks anyway!

_________________
Antec NSK3480|Antec EA 380W with Nexus 80mm Fan|ASUS P5E-VM HDMI|Core2Duo E4600 2.4GHz|Corsair 2GB 800MHz DDR2|WD Caviar GP 500GB|Scythe Ninja Plus Rev.B+TR Bolt-thru|1x120mm Nexus
Finally inaudiable!


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 Post subject:
PostPosted: Sat Aug 16, 2008 3:35 pm 
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Location: Edmonton, Alberta, Canada
I bought a 2000rpm Kama Flex 80mm to swap into the Antec 380W PSU and it didn't start on the PSU circuit. Thankfully I also have the fan bundled with the Minja, which does. I might give the 2500 model a try when I get around to updating my HTPC since the old HDD I have in there is by far the loudest component, so getting yet another fan doesn't make much sense at this point.

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Gaming rig: Tt Tsunami,P5Q Pro,Q9450 w Ninja,8GB RAM,4870 1GB w S1,WD 640GB,SB X-Fi Plat,ZM-MFC2.Kama PWM in PSU,others S-FlexEs.
HTPC: NSK2480,GB GF9400,E5200 w/ Minja,4GB RAM,WD GP 1.5TB,Nova DVB-S. Minja PSU fan,S-FlexEs case fans.


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