Nexus NX-5000 Silent PSU

Power
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8. FAN, FAN CONTROLLER and NOISE

We attempted to monitor the fan voltage for the 2-wire Muhua fan, but found that the voltage remained railed to the 12V line throughout the test, in spite of audible cues that the fan was spinning faster. This implies PWM control, or some kind of ground level control, so instead we relied solely on the more relevant SPL readings and our hearing to monitor the fan performance.

The slowly spinning Muhua fan did not register on our measurement system, the SPL remaining unchanged at the ambient of 11 dBA@1m from idle all the way up to 150W. It was barely audible from even 30cm in our anechoic test chamber. The fan finally started speeding up around 200W, a fractional increase rounded up to 12dBA@1m, with no real perceivable difference in the sound. The first perceivable difference was heard at 250W (31ºC intake), where the fan finally sped up to a slightly more audible, calm "wooshing" sound at 14 dBA@1m, more from air turbulence than the fan's bearing.

The fan's noise increased most noticeably at 300W (32ºC intake), to a more audible 22 dBA@1m. To take a reading in the anechoic chamber, the cooling fans in the loading apparatus must be turned off to ensure they do not contribute to the noise level. This decreases the amount of heat pushed into the "hot box" test fixture, decreasing the thermal stress on the power supply under testing. Very soon after the loading apparatus' cooling fans were turned off, the NX-5000's fan would slow down, implying that a 32ºC intake is perhaps a threshold for the NX-5000's fan controller. Above 32ºC/300W, the fan noise increased steadily, up to a maximum of 25 dBA@1m at full load. Even this noise level is just a quiet, smooth rustle of moving air, which is very impressive for a 530W PSU at full load.

The screen captures below from the SpectraPLUS audio spectrum analyzer should be self-explanatory. Note that the noise floor of the anechoic chamber is just under 11 dBA. The red line is the ambient level of the chamber without any noise sources.


Idle to about 200W. Peaks are seen at 400Hz and 200Hz, and are related to commutator buzz and what little turbulence is audible at this level.


At 250W, the fan becomes slightly more audible at 14dBA@1m, with smooth, low tones dominant.



At 300W, a very noticeable jump in fan noise is seen, with a broad spectrum that translates to something more like a fuzzy white noise.


As the noise increases past 400W, we mostly hear increasing volume on the lower pitched hum from blade turbulence and the bearing.

Outside the Hot Box

In a modern high performance case that has independent cooling airflow for the power supply, thermal conditions are much milder than in a conventional case or in our test box. The PSU does not have to work nearly as hard to exhaust hot air from the downstream components. As in our most recent PSU reviews, a noise/load test was performed out of the hot box to simulate noise performance in a modern, high performance case.

Nexus NX-5000 SPL: In Hot Box vs. Out
Power load
200W
250W
300W
400W
530W
in hot box
12
14
22
24
25
out
12
12
12.5
14
19
Measurements are SPL in dBA@1m

On the test bench with ambient room temperature at 23¬įC, the Muhua fan managed to stay under a barely audible 14 dBA@1m all the way up to 400W, and peaked at 19 dBA@1m, which is noticeably quieter compared to its already superbly quiet performance in the test box.


COMPARISONS

The comparison table below shows the SPL versus Power Load data on all the PSUs tested in the anechoic chamber thus far.

Comparison: Various PSUs Noise Vs. Power Output in Anechoic Chamber
Model
90W
150W
200W
250W
300W
400W
500W
6-700W
850W
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
Coolermaster M700W
14
14
18
21
25
27
34
34
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
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
Corsair CX400W
22
26
32
35
35
35
35
n/a
n/a
The green boxes represent >30 dBA@1m SPL.

The Nexus NX-5000 is one of the quietest power supplies reviewed in the anechoic chamber, and though it is louder than the Nexus Value 430 at 300~400W, it's practically inaudible below that power load, and still has reserve to spare for dual-GPU systems, 8 hard disks, or whatever other components you feel it must power.

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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