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7. COOLING
The temperatures marked in the main test results table need some
explanation. Normally, for a fan-cooled PSU, a thermal sensor is moved around
a bit during warmup at ~200W load to find the "hot spot" on the exhaust
grill where is attached using friction. This provides consistent enough readings
of the exhaust air temperature. With a fanless PSU, there is no force airflow,
so where should the sensor go? For the Seasonic Platinum 520W, it was placed
on the grill atop what appeared to be one of the hotter spots in the PSU, directly
over the large transformer. But this data is probably not very useful. To be
honest, without an array of thermal sensors which can be placed at many spots
all around the interior, monitoring the temperature of a fanless PSU is futile.
In any case, the unit did not suffer any temperature overload shutdown during
the testing.
As mentioned earlier, the Seasonic X-400 fanless PSU, with much
smaller heatsinks, sailed unscathed through a 15-hour
torture test at full load in a 53~57°C hot box two years ago. I did
not run this sample in a test like that, but in normal use, the 520 Platinum
should hold up fine even in hot weather.
8. NOISE, PART 1
There was some trace of tonal noise at level too low for it to
be registered in the anechoic chamber with the microphone a meter away. It was
more than a single frequency peak, there being a bit of lower frequency buzz,
albeit very low in level, as well as higher frequency whine that was a bit more
audible. The main source of noise was the 5V Standby line. Placing a 0.4A load
on that line always provoked a 4.7 kHz tonal peak that proved to be audible
from about 2' away in the anechoic chamber.
Outside the chamber, in a completely undamped and therefore reverberant quiet room (17~18 dBA), the audible distance was about the same; at a meter I could not hear it, but at 2' I could. Changing the 5Vsb load to 1A made the
tone disappear altogether, but dropping it to 0.1A or 0.2A changed the frequency,
to around 6 KHz; this was discovered using the mic at 1' distance with the spectrum
analyzer.
The 4.7 kHz whine, traced to 0.4A load on the 5Vsb line. Note the close
approximately one foot distance of the microphone from the PSU. |
The question is whether this noise is...
Atypical or typical? This is one the hardest questions for any product
reviewer to deal with: Whether the characteristic of the sample is analomous
or normal. If the items are inexpensive, like fans, then getting even a dozen
samples to check out is not difficult, and testing that many samples helps
answer the question of consistency and what is likely to be typical. Mind
you, when goods are mass produced in the thousands, 12 is still a paltry sampling
(as any statistician would tell you). But when it's a high ticket item in
short supply, even a dozen samples are impossible. I asked Seasonic to send
me whatever other samples they can spare. They say they will try and get me
one in the next 10 days or so.
Audible in a PC in normal use? I have assume that few users would
use a fanless PSU in PC with lots of other noisy components. They'd use it
in a quiet PC. So would this level of tonal noise be audible in a PC with
broadband noise of less than 20 dBA@1m, in a relatively quiet room? My guess
is... no for most users most of the time, but yes for some users, some of
the time. This is assuming a fairly select, aurally sensitive group of users
— which fanless PC components always attract. The frequency of the noise
is not high enough to be affected by the age-related decline in high frequency
perception, either.
There is no simple answer to these questions. I need to examine more samples,
and hear back from end-users in the field. At time of writing, the first small
shipment of Seasonic Platinum 520 PSUs were already sold out at Newegg. Some
SPCR readers must be among them; please tell us about your experience on the
discussion thread for this article.
Discussions with Seasonic
I discussed my findings with Seasonic, and they immediately arranged to have
the sample flown back to their Taiwan headquarters overnight for their engineering
team to examine. The acoustic phenomenon I described had not been enountered
before. All the early samples for reviewers had been double-checked for normal
operation before being shipped. They needed to find out what was different with
this unit and if had changed, how and in what way. In the meanwhile, they asked
me the favor of not publishing my review until they could at least get a handle
on the problem. My review would probably have been the first out, and I appreciated
that a negative one would have hurt, so I chose to be helpful. I wanted them
to solve the problem anyway, it was certainly in the best interest of the Silent
Computing Community. That was in early November.
9. NOISE, PART 2
Here we are a month later with sample #2 which just arrived late Friday. The
feedback from Seasonic on the problem with my original sample was somewhat murky.
It might be a language issue, as Seasonic's engineering team does not have much
English, and I have no Mandarin. There seemed to be two primary messages:
- First, the acoustic noise was caused mostly by new components used in achieving
the higher efficiency, particularly for the <1W standby that's stipulated
by the European Union ErP Directive (2009/125/EC) to reduce phantom power
consumption. It's not clear whether Seasonic has developed a solution or whether
my first sample was just particularly bad.
- Secondly, they have a tough time measuring or hearing this noise because
it is at such a low level, and Taipei is a noisy place. I did visit Seasonic
headquarters in one of my trips to Computex, and while it is not a particularly
noisy building, it is in Taipei, on the Northern side, and nowhere in Taipei
is very quiet. There are no homes with the kind of quiet I have in my house,
for example, except in Gigabyte's underground anechoic chamber. Hmmm... perhaps
Seasonic should knock at Gigabyte's chamber door?
So in the end, the news from Seasonic engineering on the issue of the first
sample noise is unclear and inconclusive. I will assume, for the time being,
that it was an anomaly, Seasonic is aware there many be other samples with the
same issue, and they are working on resolving the issue (if there is one which
makes some samples noisier than others). At least I have another sample to consider.
So what of the second sample?
The first thing I did was to examine it physically. Check: No change from the
previous sample, and no, it is not the same one.
Secondly, I hooked it up on the power load tester in the anechoic chamber and
powered it up with a ~120W load, a mix of the various lines, including the 5Vsb,
of course.
My intial observations, a foot away from the PSU:
- No high pitched whine. Good!
- But wait, there is a trace of a lower pitched tone. Not really a whine,
that term suggests something higher pitched. This is more in the midband,
more like a buzz. Move back a couple feet and it's gone. Move back close,
and it's still there. Change the load settings, and there are some very subtle
changes in pitch, affected most by the load on the 5Vsb line. Power up the
acoustic measurements computer, calibrate the mic and take some quick measurements.
From a meter, nothing registers above the normal ambient. Move the mic to
1' from the PSSU, and a sharp spike shows up in the spectrum. See it captured
below.
There are two tonal peaks in the second Seasonc 520W Platinum sample:
One at just under 500Hz, another smaller one at about 1.3kHz. Note the
level of each -- about -7 dBA, and -10 dBA. |
- Some things to note about this spectrum capture:
- The ambient noise was higher because it's been poring hard all day in
Vancouver, and the drain pipes make a bit of a racket when it's raining
this hard. No way to damp that out. Hence the blue line is higher than
usual; the red ambient reference was captured on a quiet evening.
- The two spikes are in the midband, which might make them more audible,
but they are also much lower in level than the 4.7kHz tone of the original,
which was at about +1 dBA with the mic at the same distance. These are
-8 and -11 dB lower in level.
- After an hour running at the same load setting, the noise did not change.
- Outside the chamber, the audibility of the buzz was limited to perhaps
1.5', at least for me, in this environment (and yes, with the slightly
higher ambient cause by the rain's pitter patter.)
In the end, I have to conclude that if this second sample is more representative,
Seasonic doesn't really have a problem, although a small handful of highly sensitive
people in the world might disagree. Do I think the first sample is an anomaly?
Yes. It was much more readily audible and annoying than this one is, and no
one in their right mind at Seasonic would have sent me or anyone related to
SPCR a product with extraneous noise.
Spot checks of performance at various load points was done on the second sample,
and the results were within 1W (or better than 1%) of the readings on the first;
i.e., within my test equipment's margin or error. The amazing voltage regulation
was the same.
COMPARISONS
The comparison table below shows the SPL versus Power Load data on PSUs tested
in ambient room temperature, typically 20~24°C. By SPL at 1m, it tops the table;
the question whether the tonal noise in my sample is typical.
|
PSU Noise (dBA@1m) vs. Power in Ambient
Room Temperature
|
|
Model
|
90W
|
150W
|
200W
|
250W
|
300W
|
400W
|
500W
|
6-700W
|
850W
|
|
Seasonic 520 Platinums
|
<11
|
<11
|
<11
|
<11
|
<11
|
<11
|
<11
|
n/a
|
n/a
|
|
Kingwin Lazer Platinum LZP-550
|
<11*
|
<11
|
<11
|
<11
|
<11
|
<11
|
16
|
n/a
|
n/a
|
|
bequiet! DPP 10 550W
|
<11
|
<11
|
<11
|
<11
|
<11
|
12
|
15
|
n/a
|
n/a
|
|
Seasonic X-400 Fanless
|
<11*
|
<11
|
<11
|
<11
|
<11
|
<11
|
n/a
|
n/a
|
n/a
|
|
Enermax Platimax 60v0W
|
<11
|
<11
|
<11
|
<11
|
<11
|
12
|
18
|
24
|
n/a
|
|
Enermax Modu/Pro87+ 500
|
11
|
11
|
11
|
11
|
11
|
11
|
18
|
n/a
|
n/a
|
|
Corsair AX850
|
<11
|
<11
|
<11
|
11~13
|
12
|
13
|
17
|
24
|
35
|
|
Seasonic X-650
|
<11
|
<11
|
<11
|
<11
|
<11
|
16
|
27
|
32
|
n/a
|
|
Nexus NX-5000
|
11
|
11
|
12
|
12
|
12.5
|
14
|
19
|
n/a
|
n/a
|
|
Antec CP-850
|
12
|
12
|
12
|
12
|
12
|
14
|
20
|
24
|
40
|
|
Enermax Eco80+ 500W
|
<11
|
12
|
12
|
16
|
20
|
23
|
28
|
n/a
|
n/a
|
|
Antec TP-750
|
12
|
12
|
12
|
14
|
15
|
27
|
31
|
40
|
n/a
|
|
Seasonic G360
|
<13
|
<13
|
18
|
24
|
34
|
39
|
n/a
|
n/a
|
n/a
|
|
CoolerMaster Silent Pro M2 720W
|
15
|
15
|
15
|
15
|
15
|
16
|
22
|
31
|
n/a
|
|
Cougar GX-700
|
15
|
15
|
15
|
17
|
21
|
25
|
35
|
35
|
n/a
|
The comparison table below shows the SPL versus Power Load data on all the
PSUs tested in the hotbox. It's difficult to rank them, as the measured SPL
varies differently 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.
Again the Seasonic 520 Platinum tops the table.
|
PSU Noise (dBA@1m) vs. Power in Hotbox/Anechoic
Chamber
|
|
Model
|
90W
|
150W
|
200W
|
250W
|
300W
|
400W
|
500W
|
6-700W
|
850W
|
|
Seasonic 520 Platinums
|
<11
|
<11
|
<11
|
<11
|
<11
|
<11
|
<11
|
n/a
|
n/a
|
|
Seasonic X-400 Fanless
|
<11*
|
<11
|
<11
|
<11
|
<11
|
<11
|
n/a
|
n/a
|
n/a
|
|
bequiet! DPP 10 550W
|
<11
|
<11
|
<11
|
<11
|
<11
|
13
|
22
|
n/a
|
n/a
|
|
Enermax Platimax 600W
|
<11
|
<11
|
<11
|
<11
|
12
|
16
|
21
|
24
|
n/a
|
|
Kingwin Lazer Platinum LZP-550
|
<11*
|
<11
|
<11
|
<11
|
<11
|
16
|
22
|
n/a
|
n/a
|
|
Enermax Modu/Pro87+ 500
|
11
|
11
|
11
|
11
|
14
|
20
|
23
|
n/a
|
n/a
|
|
Corsair AX850
|
<11
|
<11
|
12
|
15
|
18
|
25
|
35
|
38
|
39
|
|
Seasonic X-650
|
<11
|
<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
|
|
CoolerMaster Silent Pro M2 720W
|
15
|
15
|
15
|
15
|
16
|
21
|
25
|
32
|
n/a
|
|
Seasonic M12D 850W
|
14
|
14
|
14
|
14
|
14
|
24
|
37
|
42
|
42
|
|
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
|
|
Seasonic G360
|
<13
|
17
|
23
|
30
|
39
|
39
|
n/a
|
n/a
|
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.
*<11 or 11= below the ambient of our anechoic chamber; immeasurably
low @1m 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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