SPCR's Fan Round-Up #2: 120mm Fans

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SCYTHE S-FLEX & KAMA FLOW SERIES

Ambient noise at the time of testing was 19 dBA.

Kama Flow SA1225FDB12L (1,000 RPM)
Brand Scythe Power Rating 0.13A
Manufacturer ? (Sony bearing) Airflow Rating 38.9 CFM
Model Number Kama Flow SA1225FDB12L RPM Rating 1,000±10% RPM
Retail Availability Japan Only Noise Rating 15.8 dBA
Bearing Type FDB Header Type 3-pin
Hub Size 1.89" Starting Voltage 6.6V
Frame Size 120 x 120 x 25 mm Number of Samples 3
Voltage
Noise
RPM
CFM
Power
12V
22 dBA@1m
1040 RPM
43 CFM
0.61W
9V
~20 dBA@1m
800 RPM
32 CFM
0.38W
7V
<19 dBA@1m
610 RPM
23 CFM
0.27W
5V
<19 dBA@1m
410 RPM
14 CFM
0.19W
@25 CFM (7.4V)
<19 dBA@1m
650 RPM
25 CFM
0.30W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
22 dBA@1m
1040 RPM
29 CFM
0.61W
9V
~20 dBA@1m
800 RPM
21 CFM
0.38W
7V
<19 dBA@1m
610 RPM
16 CFM
0.27W
5V
<19 dBA@1m
410 RPM
11 CFM
0.19W
@20 CFM (8.4V)
<19 dBA@1m
740 RPM
20 CFM
0.35W

We discovered the Scythe Kama Flow in our roundup of 80mm fans, where it was the only fan to equal the Nexus 80 for quietness and noise quality. Its only downside? A lack of availability outside of Japan.

Scythe also sells a 120mm version of the Kama Flow in Japan, and it promises to be just as good as the 80mm version. However, international users stand a better chance of getting their hands on the bigger version — or at least one that is very, very similar. Scythe's S-Flex fans look — and sound — almost identical to the Kama Flow, and these are available internationally. Both fans use Sony's S-FDB bearings, both have the same blade design, and both are characterized by three tiny pinholes in the center of the hub. In fact, the only discernible differences that we could find were the design of the frame (S-Flex is double-ribbed and seems slightly heavier), and the speed ratings.

It seems likely that there are other "unofficial" models in this line as well — most of Scythe's recent heatsinks have featured quiet, low speed fans that sound very similar to the S-Flex / Kama Flow, including the odd 100mm fan found in the Scythe Infinity. The common thread appears to be the S-FDB bearing, which Scythe has licensed from Sony.

Slow Version: S-Flex SFF21D (800 RPM)
Brand Scythe Power Rating 0.10A
Manufacturer ? (Sony bearing) Airflow Rating 33.5 CFM
Model Number S-Flex SFF21D RPM Rating 800 RPM
Retail Availability Yes Noise Rating 8.7 dBA
Bearing Type FDB Header Type 3-pin
Hub Size 1.89" Starting Voltage 8.9V
Frame Size 120 x 120 x 25 mm Number of Samples 1
Voltage
Noise
RPM
CFM
Power
12V
~20 dBA@1m
850 RPM
32 CFM
0.34W
9V
<19 dBA@1m
620 RPM
23 CFM
0.27W
7V
<19 dBA@1m
430 RPM
14 CFM
0.24W
5V
Stall
Stall
Stall
Stall
@25 CFM (9.5V)
<19 dBA@1m
650 RPM
25 CFM
0.28W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
~20 dBA@1m
850 RPM
23 CFM
0.34W
9V
<19 dBA@1m
620 RPM
16 CFM
0.27W
7V
<19 dBA@1m
430 RPM
11 CFM
0.24W
5V
Stall
Stall
Stall
Stall
@20 CFM (10.8V)
<19 dBA@1m
750 RPM
20 CFM
0.31W

The S-Flex is available in three different speed ratings: 800 RPM (SFF21D), 1,200 RPM (SFF21E), and 1,600 RPM (SFF21F). Most users will probably be interested in the -D or -E variants which are around the 1,000 RPM mark that is generally the fastest a 120mm fan can be run quietly. The Kama Flow fits right in between these models at 1,000 RPM.


The S-Flex package includes a Molex to 3-pin adapter with an RPM monitor cable.

The Kama Flow's noise character was almost identical to its smaller brother. It was quiet, very smooth and had just a touch of whine at full speed. It also sounded almost identical to the Nexus and measured identically as well. The only real difference was that the Kama Flow sounded slightly more tonal, which unfortunately made it a bit easier to hear. The noise had other similarities as well; both fans produced predominantly low frequency noise, and both vibrated enough that they may be prone to resonance if hard-mounted.

And, as with the 80mm versions, it was too close to call a clear winner between the Kama Flow and the Nexus. Both were very, very quiet, so the deciding factor has to be something other than noise. The superior quality of the S-FDB bearing gives the Kama Flow an edge here and the wide distribution of the S-Flex takes away the advantage that the Nexus had in the 80mm form factor.

As mentioned, the S-Flex fans sounded more or less identical to the Kama Flow at the same speeds. For practical purposes, they can probably be treated as one and the same, but we did notice two minor variations.

  1. The S-Flex models vibrated less than the Kama Flow, perhaps because of their more rigid frame.
  2. The slowest S-Flex model had a slight ticking that was absent in all of the other samples we tested. It's not clear whether this can be attributed to the lower commutator frequency or if it's just sample variance making an appearance.

The Kama Flow is probably the most usable fan of the bunch. It's 1,000 RPM speed rating offers a lot of flexibility. At full speed, it is probably fast enough for use in very hot systems while still being quiet enough for users who don't seek absolute silence. It also undervolts well, and is inaudible at 7V. Its only disadvantage is its starting voltage, and it should not be used at 5V.

The Low speed S-Flex is probably the best choice for those who just want a drop in solution. It is very close to inaudible at full speed, and should disappear entirely if there are any other significant sources of noise in the system. The fact that it is so quiet at 12V makes it attractive to users who don't want a fan that just works without needing to tinker with it. However, modders will probably want to avoid it, as its extremely high starting voltage makes it useless for undervolting.

The Medium speed S-Flex is the most suitable choice for those who don't have access to the Kama Flow. It's only slightly faster, and it starts quietly and reliably at 5V — an important feature for those who don't have variable speed fan controllers. The high speed S-Flex is also an option. It's definitely too noisy at full speed, but it is very usable when undervolted and can push more air than the medium speed version if necessary.

Medium Version: S-Flex SFF21E (1,200 RPM)
Brand Scythe Power Rating 0.15A
Manufacturer ? (Sony bearing) Airflow Rating 49.0 CFM
Model Number S-Flex SFF21E RPM Rating 1,200 RPM
Retail Availability Yes Noise Rating 20.1 dBA
Bearing Type FDB Header Type 3-pin
Hub Size 1.89" Starting Voltage 4.8V
Frame Size 120 x 120 x 25 mm Number of Samples 1
Voltage
Noise
RPM
CFM
Power
12V
23 dBA@1m
1230 RPM
51 CFM
0.62W
9V
20 dBA@1m
910 RPM
36 CFM
0.47W
7V
<19 dBA@1m
670 RPM
26 CFM
0.37W
5V
<19 dBA@1m
400 RPM
13 CFM
0.29W
@25 CFM (6.9V)
<19 dBA@1m
650 RPM
25 CFM
0.36W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
23 dBA@1m
1230 RPM
34 CFM
0.62W
9V
20 dBA@1m
910 RPM
23 CFM
0.47W
7V
<19 dBA@1m
670 RPM
18 CFM
0.37W
5V
<19 dBA@1m
400 RPM
10 CFM
0.29W
@20 CFM (7.8V)
<19 dBA@1m
750 RPM
20 CFM
0.41W
Fast Version: S-Flex SFF21F (1,600 RPM)
Brand Scythe Power Rating 0.20A
Manufacturer ? (Sony bearing) Airflow Rating 63.7 CFM
Model Number S-Flex SFF21F RPM Rating 1,600 RPM
Retail Availability Yes Noise Rating 28 dBA
Bearing Type FDB Header Type 3-pin
Hub Size 1.89" Starting Voltage 4.0V
Frame Size 120 x 120 x 25 mm Number of Samples 1
Voltage
Noise
RPM
CFM
Power
12V
31 dBA@1m
1590 RPM
70 CFM
1.05W
9V
23 dBA@1m
1190 RPM
53 CFM
0.75W
7V
~20 dBA@1m
890 RPM
39 CFM
0.57W
5V
<19 dBA@1m
550 RPM
23 CFM
0.41W
@25 CFM (5.2V)
<19 dBA@1m
590 RPM
25 CFM
0.43W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
31 dBA@1m
1590 RPM
47 CFM
1.05W
9V
23 dBA@1m
1190 RPM
32 CFM
0.75W
7V
~20 dBA@1m
890 RPM
23 CFM
0.57W
5V
<19 dBA@1m
550 RPM
14 CFM
0.41W
@20 CFM (6.3V)
<19 dBA@1m
770 RPM
20 CFM
0.51W

Noise Recordings

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