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TEST RESULTS
For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units. Those who seek source materials can find Intel's various PSU
design guides at Form
Factors.
For a complete rundown of testing equipment and procedures, please refer to
SPCR's PSU Test Platform
V.3. The testing system is a close simulation of a moderate airflow
mid-tower PC optimized for low noise.
In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows incremental
load testing all the way to full power for any non-industrial PC power supply.
Both fan noise and voltage are measured at various standard loads. It is a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C at full power. This is impossible to achieve
with an open test bench setup.
Note that the low speed 80mm fan responsible for "case airflow" in the thermal simulation rig is deliberately kept at a steady low level (~6V) even when the PSU is operating at very high power and the PSU fan is spinning fast enough to drown out any noise contribution of the "case fan". This is to keep a level playing (thermal) field for all the PSUs tested, but it is admittedly somewhat unrealistic. Most users will want to increase airflow in the case if their system is drawing that much power from the PSU frequently or on a long term steady-state basis. Keep in mind that some PSUs will actually perform more quietly in a real system with higher case airflow than in our low airflow thermal test box.
Great effort has been made to devise as realistic a quiet operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are too many variables in PCs
and too many possible combinations of components for any single test environment
to provide infallible results. And there is always the bugaboo of sample variance.
These results are akin to a resume, a few detailed photographs, and some short
sound bites of someone you've never met. You'll probably get a pretty good overall
representation, but it is not quite the same as an extended meeting in person.
REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output
(even >600W!) in order to verify the manufacturer's claims, real desktop
PCs simply do not require anywhere near this level of power. The most pertinent
range of DC output power is between about 65W and 250W, because it is the power
range where most systems will be working most of the time. To illustrate this
point, we conducted system tests
to measure the maximum power draw that an actual system can draw
under worst-case conditions. Our most powerful Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC from the power supply under
full load — well within the capabilities of any modern power supply. Please
follow the link provided above to see the details. It is true that very elaborate
systems with SLI could draw as much as another 100W, perhaps more, but the total
still remains well under 400W in extrapolations of our real world measurements.
SPCR's high fidelity sound
recording system was used to create MP3 sound files of this PSU. As
with the setup for recording fans, the position of the mic was 3" from the exhaust
vent at a 45° angle, outside the airflow turbulence area. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.
INTERPRETING TEMPERATURE DATA
It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.
When examining thermal data, the most important indicator of cooling efficiency
is the difference between intake and exhaust. Because the heat
generated in the PSU loader by the output of the PSU is always the same for
a given power level, the intake temperature should be roughly the same between
different tests. The only external variable is the ambient room temperature.
The temperature of the exhaust air from the PSU is affected by several factors:
- Intake temperature (determined by ambient temperature and power output level)
- Efficiency of the PSU (how much heat it generates while producing the required
output)
- The effectiveness of the PSU's cooling system, which is comprised of:
- Overall mechanical and airflow design
- Size, shape and overall surface area of heatsinks
- Fan(s) and fan speed control circuit
The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is important:
It represents the ambient temperature around the power supply itself. Subtracting
the intake temperature from the exhaust temperature gives a reasonable gauge
of the effectiveness of the power supply's cooling system. This is the only
temperature number that is comparable between different reviews, as it is unaffected
by the ambient temperature.
On to the test results...
Ambient conditions during testing were 22°C and 17 dBA, 121V/60Hz.
The two models performed almost identically, so the data
for the two units was amalgamated into a single set. The majority of the
data presented below comes from our test of the 550W model. Data from the 650W
test can be identified by the green background in the data table. Variations
between the two tests are noted in the text where it is pertinent.
|
OUTPUT & EFFICIENCY: Seasonic S12 Energy Plus 550 / 650
|
|
DC Output Voltage (V) + Current (A)
|
Total DC Output
|
AC Input
|
Calculated Efficiency
|
|
+12V1
|
+12V2
|
+5V
|
+3.3V
|
-12V
|
+5VSB
|
|
12.23
|
0.98
|
12.21
|
1.75
|
5.03
|
0.00
|
3.41
|
0.99
|
0.1
|
0.2
|
38.8
|
56
|
68.8%
|
|
12.21
|
1.92
|
12.21
|
1.75
|
5.04
|
1.95
|
3.41
|
0.96
|
0.1
|
0.4
|
61.0
|
82
|
74.7%
|
|
12.20
|
1.91
|
12.18
|
3.33
|
5.02
|
2.88
|
3.40
|
2.78
|
0.1
|
0.5
|
91.4
|
116
|
78.6%
|
|
12.18
|
3.84
|
12.16
|
5.00
|
5.02
|
4.67
|
3.39
|
3.73
|
0.2
|
0.8
|
150.0
|
183
|
81.9%
|
|
12.19
|
6.64
|
12.17
|
4.98
|
5.04
|
6.38
|
3.42
|
4.56
|
0.3
|
1.1
|
198.4
|
234
|
84.8%
|
|
12.13
|
7.80
|
12.09
|
6.49
|
4.98
|
8.03
|
3.37
|
7.56
|
0.4
|
1.4
|
250.2
|
297
|
84.3%
|
|
12.10
|
7.80
|
12.06
|
9.65
|
4.97
|
9.75
|
3.35
|
7.59
|
0.5
|
1.6
|
298.6
|
355
|
84.1%
|
|
12.06
|
12.38
|
12.02
|
11.29
|
4.94
|
12.15
|
3.33
|
10.97
|
0.6
|
2.2
|
399.8
|
482
|
82.9%
|
|
12.02
|
16.01
|
11.98
|
14.34
|
4.92
|
14.23
|
3.31
|
13.28
|
0.7
|
2.7
|
500.2
|
616
|
81.2%
|
|
12.00
|
15.95
|
11.95
|
17.26
|
4.87
|
16.54
|
3.30
|
14.86
|
0.8
|
3.0
|
551.8
|
692
|
79.7%
|
|
11.98
|
20.93
|
11.98
|
18.90
|
4.91
|
18.90
|
3.30
|
16.11
|
1.0
|
3.0
|
650.1
|
820
|
79.3%
|
|
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings of the DBS-2100
PS Loader. It is a tiny portion of the total, and potential errors arising
from inaccuracies on these lines is <1W.
|
|
OTHER DATA SUMMARY: Seasonic Energy Plus 550 / 650
|
|
DC Output (W)
|
38.8
|
61.0
|
91.4
|
150.0
|
198.4
|
250.2
|
298.6
|
399.8
|
500.2
|
551.8
|
|
Intake Temp (°C)
|
24
|
25
|
26
|
32
|
38
|
39
|
42
|
42
|
43
|
49
|
|
Exhaust Temp (°C)
|
26
|
27
|
29
|
37
|
46
|
51
|
52
|
54
|
56
|
63
|
|
Temp Rise (°C)
|
2
|
2
|
3
|
5
|
8
|
12
|
10
|
12
|
13
|
14
|
| Fan Voltage (V) |
3.8
|
3.8
|
3.8
|
3.8
|
3.8
|
3.9
|
5.6
|
9.9
|
11.3
|
11.3
|
| SPL (dBA@1m) |
20
|
20
|
20
|
20
|
20
|
20~21
|
25
|
38
|
40
|
40
|
| Fan Voltage (V) |
3.8
|
3.8
|
3.8
|
3.8
|
3.8
|
4.1
|
5.3
|
9.1
|
10.9
|
10.9
|
| SPL (dBA@1m) |
20
|
20
|
20
|
20
|
20
|
21
|
25
|
36
|
43
|
43
|
|
Power Factor
|
0.98
|
1.00
|
1.00
|
1.00
|
0.99
|
1.00
|
1.00
|
1.00
|
1.00
|
1.00
|
|
AC Power in Standby: 0.6W / 0.16 PF
AC Power with No Load, PSU power On: 11.3W / 0.43 PF
|
|
NOTE: The ambient room temperature during testing
can vary a few degrees from review to review. Please take this into account
when comparing PSU test data.
|
ANALYSIS
1. LOW LOAD PERFORMANCE
The half watt that the Energy Plus consumed in standby is small enough to be
considered irrelevant. Taking power factor into consideration, the apparent
power draw was just under 4VA — not enough to worry about.
No-load performance was also quite good. The power supply had no problem starting
with no load, and the 11.3W it consumed is as good as any other we've seen.
The PicoPSU is the only power supply we've seen that consumes less power with
no load, and that has the advantage of using an external power brick as its
power source.
For some reason, both Energy Plus samples generated a sharp electronic clicking when
no load was applied. The noise seemed to be perfectly normal — the power
supply remained fully functional both during and after the clicking, and both
models exhibited it. The clicking went away as soon as more than 5W were applied
to any combination of voltage lines, so it's more of a curiosity than anything
to worry about. It is not possible to build a system that consumes that little
power.
2. VOLTAGE REGULATION was very good. Both the +12V and +5V lines stayed
within ±2% of nominal throughout testing. The +3.3V line was slightly
less well regulated, showing a variance of ~4%. It should be noted that this
greater variance may well be a mathematical artifact. In absolute terms, the
line fluctuated by ~0.11V — slightly less than the ~0.12V variance
displayed by the +5V line. However, because voltage regulation is measured as
a percentage difference, the +3.3V line appears less well regulated.
All three of the main voltages hit the nominal voltage on the dot either at
or just before full load. The largest variance was typically at the lowest loads,
when all of the voltages were slightly higher than nominal.
3. EFFICIENCY
Efficiency is the raison d'être for the Energy Plus, and it didn't disappoint.
Efficiency for both models peaked just shy of 85% at around 200W output. This
is similar to the efficiency of the SS-400HT — the most efficient power
supply we've tested — and marginally higher than the S12-500 and S12-600
samples we've tested in the past. Both models were above 80% efficiency at 20%
and 50% load, but dipped a hair below 80% at full load. Most likely, the extremely
tough thermal conditions of our test bench caused efficiency to drop more than
it would in a properly cooled system. The margin is also within the error range
of our test rig.
The 550W model was slightly more efficient (a percentage
point at most) at low loads than the 650W version, while the 650W version maintained
its efficiency closer to full load. Interestingly, at the low power levels that
most systems idle at, the Energy Plus samples were not quite as efficient as certain
other models that we've tested — including some of the original S12 models.
The table below shows the efficiency of several Seasonic Power supplies at 65W
output — a reasonable estimate of average power consumption.
|
Seasonic Power Supplies at 65W Output
|
|
Model
|
S12-330
|
S12-430
|
S12-500
|
SS-400HT 80+
|
SS-300SFD 80+
|
S12 Energy+ 550
|
|
Efficiency at 65W
|
75.5%
|
78.3%
|
75.1%
|
81.5%
|
83.6%
|
74.7%
|
|
Peak Efficiency
|
82.0%
|
81.8%
|
82.0%
|
85.3%
|
85.2%
|
84.8%
|
Of all the Seasonic power supplies
that we've tested on our current test bench, the Energy Plus is the least
efficient at 65W, which is not an unusual idle power level for minimalist systems today. The difference is not huge, especially discounting the two
other 80 Plus power supplies which weren't widely available. The peak efficiency of
the Energy Plus is higher than the regular S12 models, so it is at high loads in the high power systems in which a 550W PSU would be employed that the advantage of the Energy Plus models would become apparent.
4. POWER FACTOR was excellent as usual for Seasonic. For much of the
test, our power meter measured a perfect 1.00 power factor.
5. TEMPERATURE & COOLING
Thermal performance was good at lower levels, and good enough at higher levels.
The temperature rise across the power supply jumped up significantly at around
200W output — just before the fan ramped up. Beyond this point, the thermal
rise stayed around 10~15°C, which is higher than Seasonic's past models.
The thermal rise in the S12-600
was just 7°C at full load — half that of the Energy Plus.
The two models did not differ much in their cooling; the faster fan in the
650W model did keep it slightly cooler at higher fan speeds, but the difference
was never more than two or three degrees, and the temperature rise barely changed
at all.
6. FAN, FAN CONTROLLER and NOISE
One of Seasonic's biggest strengths has always been their fan controller,
which ramps up more slowly and at higher loads than the competition. It's hard
to imagine how this could be improved on, but somehow Seasonic has managed to
go ahead and do it anyway. In the past, we have been impressed if the noise
level stayed under 30 dBA@1m at 250W output — we've never encountered a
power supply that stayed quiet above this level.
The Energy Plus shook loose our expectations and set a new standard for quiet:
At 250W, the fan was just beginning to rise above its minimum level, and it
did not exceed 30 dBA@1m until past the 300W mark. The medium and high speed
fans in the different models sounded more or less identical until they speed
up. Both were very quiet at minimum speed. As long as they weren't spinning
too fast (most of the time), the fan noise was quite smooth and pleasant.
What this means is that the Energy Plus should be close to inaudible in almost
every system. It is child's play to build a system into the 250W envelope that
would never cause the Energy Plus to ramp up. The only systems that require
more power than this either have multiple video cards or are heavily overclocked,
usually both. Even then, it is difficult to push power consumption much above
300W — and systems that consume more than that inevitably have other fans
that are not quiet.
|
Power Supply Fan Noise Vs. Power Output
|
|
Model
|
65W
|
90W
|
150W
|
200W
|
250W
|
300W
|
400W
|
|
Seasonic S12-330
|
21
|
21
|
22
|
30
|
35
|
37
|
–
|
|
Seasonic S12-430
|
20
|
20
|
22
|
25
|
29
|
32
|
37
|
|
Seasonic S12-500/600
|
21
|
21
|
22
|
25
|
28
|
34
|
39
|
|
Seasonic SS-300SFD-80+
|
22
|
22
|
25
|
30
|
34
|
38
|
–
|
|
Seasonic SS-400HT-80+
|
22
|
22
|
22
|
23
|
30
|
36
|
38
|
|
Seasonic S12 Energy Plus 550/650
|
20
|
20
|
20
|
20
|
21
|
25
|
38
|
|
Zalman ZM460-APS
|
22
|
23
|
26
|
29
|
31
|
34
|
37
|
Enermax Liberty
EL500AWT/EL620AWT
|
21
|
21
|
24
|
30
|
35
|
38
|
41
|
The table above does a good job of illustrating how the fan behavior of the
Energy Plus differs from other Seasonic power supplies. All of the power supplies
are similar at lower loads, but that is not where the Energy Plus finds its
advantage. The real difference can be seen at the 250W and 300W marks. In both
cases, the Energy Plus is 7 dBA@1m quieter than the next quietest model —
a substantial and audible difference.
What this means is that, unless you're building a very powerful system, the
acoustic advantage of the Energy Plus will be limited to differences at minimum
speed — which are not huge. Yes, the Energy Plus is close to inaudible
at minimum speed, but so are numerous other power supplies. It's not difficult
to build a mid-range system into the 150W envelope where most of our past recommendations
have remained quiet. Given the expense of the Energy Plus, it only really makes
sense to use it in systems where its acoustic advantage will be noted: In very
high powered systems.
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