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FANS
The stock fans are two identical 80x25mm models, positioned directly over the
back I/O panel, which is exactly where these fans should be. The fans are well-positioned
to extract the heat from the CPU, the VRM on the motherboard, and the nearby
graphics card as well.
Both cases have the same fans, although the Silverstone case specification
pages cite slightly different data for them. There's no reason to believe they
are different. When the fans were turned on and monitored one by one, we could
discern no significant audible or airflow differences. In both cases, the fans
have wire guards on both sides, which seems a bit paranoid. One wire guard adds
some minor impedance to airflow; two adds more.
Both cases have 80mm fans with wire guards on both sides.
The trailing edge of the blades is parallel to the struts (red and yellow
dashed lines).
This is not a good acoustic design choice.
Web searches for Silentmatic turned up Silverstone fans on eBay, and searches
for the model number turned up nothing useful at all, so all we really have
is the data on the fan label, and Silverstone's contradictory noise / airflow
data from their case specs. The model designation SFA8025MS-12N tells
us something too: It's 80x25mm, Medium speed, Sleeve bearing. So here's our
summary of given data about the fans:
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Given Data: SFA8025MS-12N Fan
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Size
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80 x 25mm
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Rated voltage
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12V DC
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Current
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0.11A
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RPM
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1800 or 2100
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SPL
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19 or 21 dBA (@1m?)
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We did not run a complete set of tests on the fan, but a few basic measurements
were made on all the fans. They measured the same, although one sounded very
slightly buzzier than the others. The results are shown below.
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Measured Data: SFA8025MS-12N Fan
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RPM
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1750
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SPL
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19~20 dBA@1m
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They are pretty quiet fans. Two of them together measured 22~23 dBA@1m in free
air, outside the case. Of course, in the case with the cover on, the noise jumps
quite bit due to the effects of...
1) cavity resonance — the enclosed air in the case actually has resonances
which get "excited" by the noise of the fans.
2) mechanical coupling — any vibrations from the fans get conducted into
the chassis, which then vibrates in sympathy, causing addtional noise.
Cavity resonance is virtually unavoidable; mechanical coupling can be eliminated
with soft mounting.
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