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7. FAN, FAN CONTROLLER and NOISE
The fan controller tended to favor cooling over lowest noise at
most load levels. The Cougar was pretty quiet to about 200W load, beyond which
the fan speed/noise rose quite linearly with load.
At minimum load , the fan spins at somewhere around 550 RPM, according
to our calibrated strobe, with a measured SPL of just 15 dBA@1m. This is close
to inaudible in most conditions. The noise level rose to 18 dBA@1m at 200W,
which is still pretty darn quiet, though audible. From 200W to 400W, the noise
climbed almost in a straight line from 18 dBA to 32 dBA. That's subjectively
about a three-fold increase in perceived noise.
The quality of the noise is moot until beyond 200W when it becomes
more obvious. Mostly it is broadband fan noise, quite smooth, centered mostly
in the lower midrange. Overall, it's a relatively benign noise until >400W
load is reached.
Noise in a Cooler Case
One thing we've been examining is how the power supply performs
outside the tough thermal conditions of our standard test. The
recent popularity of cases that isolate the power supply from the rest of the
system make this a relevant question, as the cooler intake air allows the fan
to run slower and quieter. We examine this by running some of the high load
tests with the power supply in free air, away from the tough thermal conditions
of the hot-box.
Outside the hotbox, the fan's increase in speed occurred at a
higher power level, and its rate of increase was lower. This suggests that in
a case with isolated intake vent for the PSU, the GX-700 would remain inaudible
to over 250W load. This covers a majority of PCs.
|
Cougar GX-700 SPL: In Hot Box vs. Out
|
|
Power load
|
90W
|
150W
|
200W
|
250W
|
300W
|
400W
|
550W
|
700W
|
|
in hot box
|
15
|
15
|
18
|
20
|
25
|
32
|
35
|
36
|
|
out
|
15
|
15
|
15
|
17
|
21
|
25
|
35
|
35
|
|
Measurements are in dBA@1m
|
COMPARISONS
The comparison table below shows the SPL versus Power Load data on all the
PSUs tested in the anechoic chamber thus far. It's difficult to rank them, as
the measured SPL varies with power load. The units which are quietest at minimum
load are not always the quietest at midload (100W~300W), which may make them
louder in actual use. Then there's the noise level at 400W and up, which will
determine the quietest PSUs for high power gaming rigs, during actual gaming.
The GX-700 falls in the bottom third of the pack. At the <200W power loads,
the Cougar quiet enough to be considered extremely quiet. But the noise climbs
too quickly with load. Its overall noise curve is closest to the Coolermaster
M700W and the SilverStone DA700, which were at one point, fairly high up on
this comparison table.
|
PSU Noise (dBA@1m) vs. Power in Hotbox/Anechoic
Chamber
|
|
Model
|
90W
|
150W
|
200W
|
250W
|
300W
|
400W
|
500W
|
6-700W
|
850W
|
|
Seasonic X-400 Fanless
|
il*
|
il
|
il
|
il
|
il
|
il
|
n/a
|
n/a
|
n/a
|
|
Enermax Modu/Pro87+ 500
|
11
|
11
|
11
|
11
|
14
|
20
|
23
|
n/a
|
n/a
|
|
Seasonic X-650
|
<10
|
11
|
12
|
14
|
16
|
31
|
31
|
32
|
n/a
|
|
Nexus Value 430
|
11
|
11
|
16
|
18
|
18
|
19
|
n/a
|
n/a
|
n/a
|
|
Nexus NX-5000
|
11
|
11
|
12
|
14
|
22
|
24
|
25
|
n/a
|
n/a
|
|
Antec CP-850
|
12
|
12
|
12
|
14
|
14
|
26
|
40
|
44
|
45
|
|
Enermax Eco80+ 500W
|
<11
|
12
|
16
|
19
|
26
|
32
|
33
|
n/a
|
n/a
|
|
Seasonic M12D 850W
|
14
|
14
|
14
|
14
|
14
|
24
|
37
|
42
|
42
|
|
Enermax Modu82+ 625*
|
13
|
13
|
14
|
15
|
16
|
26
|
36
|
37
|
n/a
|
|
Antec TP-750
|
12
|
12
|
14
|
14
|
18
|
33
|
40
|
40
|
n/a
|
|
Chill Innovation CP-700M
|
15
|
15
|
15
|
15
|
17
|
30
|
34
|
34
|
n/a
|
|
Antec Signature 650
|
15
|
15
|
15
|
18
|
18
|
28
|
36
|
47
|
n/a
|
|
Coolermaster M700W
|
14
|
14
|
18
|
21
|
25
|
27
|
34
|
34
|
n/a
|
|
Cougar GX-700
|
15
|
15
|
18
|
20
|
25
|
32
|
35
|
36
|
n/a
|
|
SilverStone DA700
|
18
|
18
|
18
|
18
|
23
|
32
|
35
|
41
|
n/a
|
|
Nexus RX-8500
|
14
|
14
|
17
|
22
|
28
|
32
|
32
|
33
|
33
|
|
NesteQ ECS7001
|
22
|
22
|
22
|
21
|
23
|
25
|
36
|
37
|
n/a
|
|
PCPC Silencer 610
|
20
|
24
|
24
|
24
|
24
|
30
|
40
|
50
|
n/a
|
The green boxes are >30 dBA@1m SPL.
*il = immeasurably low in any environment
Caution: Please keep in mind that the data in the above table is specific to the conditions of our test setup. Change the cooling configuration, the ambient temperature and any number of other factors, and you could change the point at which the fans start speeding up, as well as the rate of the rise in speed. The baseline SPL is accurate, however, probably to within 1 dBA.
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