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Seasonic S12 Energy Plus: Efficient Power for Connoisseurs

October 5, 2006 by Devon
Cooke

Product
Seasonic S12 Energy Plus
550 & 650


550W & 650W ATX12V 2.2 Power Supply
Manufacturer
Seasonic
Electronics Co., Ltd.
Market Price
550W: US$120~150

650W: US$150~170

Seasonic's power supplies have long held a place of high esteem at SPCR. They
have a well deserved reputation for producing some of the quietest, most efficient
power supplies on the market. The S12 series needs no introduction to regular
readers; it has topped our recommended list since we reviewed the S12-430 in March
2005.

The fundamentals of the S12 series are strong, but that hasn't prevented Seasonic
from trying to make them stronger. The S12 Energy Plus is a variant of the S12
that has been tweaked to meet the tough efficiency requirements of the
80 Plus program
: 80% efficient at 20%, 50%, and 100% load. While many high
end power supplies have peak efficiency above 80%, not many are
able to sustain that efficiency across a wide range of loads. To date, we know
of only two other retail power supplies that can: The
FSP Zen
, and the SilverStone
Element Plus
. Counting both models of the Energy Plus, that makes a total
of four retail power supplies approved by 80 Plus. That's a pretty exclusive
club, folks.

The Energy Plus models are derived from the
80 Plus certified SS-400HT
that we looked at last year — which is a lower power version of
the S12 500W and 600W models.
This was the first 80 Plus certified power supply we examined, intended for system integrators and not widely available.

There is some question about why a retail power supply should bear the 80 Plus logo. The 80 Plus rebates are available only to system integrators who use approved power supplies in complete PCs. It is one reason why there are so few retail 80 Plus models on the market. This suggests that an 80 Plus mark for a retail power supply is primarily useful for marketing purposes. The 80 Plus mark is becoming the Good Housekeeping Seal of Approval for energy conscious computer consumers. That Seasonic would make and market such a product is no great surprise. They have been pioneers in pushing the efficiency envelope, and after some five years of effort in the retail marketplace, are well-recognized as a top quality brand in the geek community. A mark such as 80 Plus helps to push their hard-earned reputation onto a larger audience. So from a marketing point of view, it makes perfect sense.

Seasonic's marketing literature makes much of the "Dual Forward Converter"
design that allows such high efficiency, but the official
80 Plus logo on the box matters more than how they managed to get it. Something
similar could be said about the "Dual Magnetic Amplifier" circuit
that allows the Energy Plus to regulate the +12V lines to a tight 3%. It's a
nice feature to be sure, but it's the tight regulation that counts, not the
way it's achieved.

Seasonic has always catered to the high end, but, if it can deliver what it
promises, the S12 Energy Plus may create a new product category that is above
even the original S12. This is a power supply for connoisseurs. While the extra
efficiency and tighter voltage regulation certainly reflect a better underlying
design, the practical benefits of these improvements are likely to be pretty
insubstantial except for users who push their systems to extremes.



The box displays the 80 Plus logo prominently.



Floppy connectors come on their own adapter since they are rarely needed.

FEATURE HIGHLIGHTS

Feature Highlights of the Seasonic S12 Energy Plus
(from
Seasonic's
web site
)
FEATURE & BRIEF COMMENT
Dual Magnetic Amplifiers [Mag-Amp]

Cross regulation tolerance on +12V lines are improved from standard 5%
to 3% for optimized stability.
Generally a good thing, especially in high stress systems.
Double Forward Converter
Design


Advanced topology for the highest efficiency.
High efficiency translates
into more than energy savings. It also cuts the heat output and makes lower
noise levels possible.
Multiple +12V Outputs

Enhanced +12V current capability broadens utilization possibilities.
Rumor
has it that the four +12V lines
are not so independent...
High Reliable Aluminum Electrolytic Capacitors

Top quality components increase product life & reliability.
Reliable components may
be the most important feature in a power supply.
Super High Efficiency [up to 88%]

Optimal solution for low energy consumption, noise & heat.
No power supply we've
ever tested has managed 88% efficiency in our admittedly tough test rig.
Perhaps at 240VAC input and low operating temperature?
Active Power Factor Correction
[99% PF]


Reduces line loss & power distortion.
Standard on Seasonics
for a long time, and increasingly common on other high end units.
Smart and Silent Fan Control [S2FC]

Smart thermal control to balance noise and cooling.
The same excellent controller that
made Seasonic's past models so quiet.
12cm Ball Bearing Cooling
Fan


Increase airflow and lifetime, reduce rotation speed and noise.
Most power supplies use
12cm fans these days.
Soft-Mounting Rubber
Cushions


Reduces fan rotation & vibration noise.
Soft mounting is generally
good for noise quality.
Ultra Ventilation [Honey
Comb Structure]


Doubles the airflow & lifespan with half the RPM & noise.
A feature since the Seasonic
Super Tornado two generations ago.
All in One DC Cabling
Design


Supports PC, IPC, workstation, server, & dual CPU systems.
ATX12V & EPS12V compliant.
Dual CPU and/or GPU systems are the only systems that are likely to demand anywhere near
the rated capacity.
Universal Video Card
Support


Supports all multiple PCI-E video cards technologies.
Longhand for dual PCIe
connectors.
Patented Easy Swap Connector

Unplug the connectors easily & quickly.
Useful... but less so
now that IDE drives have almost disappeared.
Universal AC Input [Full
Range]


Plug & run safely anywhere in the world.
Nice. Normal in retail Seasonic PSUs for several years.
3 Year Warranty

Our Commitments to superior quality.
Hopefully unnecessary,
but nice to have.

SPECIFICATIONS

OUTPUT SPECIFICATIONS: Seasonic S12 Energy Plus 550
AC Input
100~240VAC 50/60Hz
AC Input Current
10A
DC Output
+3.3V
+5V
+12V1
+12V2
+12V3
+12V4
-12V
+5VSB
Maximum Output Current
24A
30A
18A
18A
18A
18A
0.8A
3.0A

Maximum Combined

170W
492W (41A)
9.6W
15.0W
550W


OUTPUT SPECIFICATIONS: Seasonic S12 Energy Plus 650
AC Input
100~240VAC 50/60Hz
AC Input Current
12A
DC Output
+3.3V
+5V
+12V1
+12V2
+12V3
+12V4
-12V
+5VSB
Maximum Output Current
24A
30A
18A
18A
18A
18A
0.8A
3.0A

Maximum Combined

170W
624W (52A)
9.6W
15.0W
650W

The specifications for the two Energy Plus models are identical except for
the combined load on the +12V rail, just as it should be. In real use, this
is really the only number that matters; real world conditions dictate that the
vast majority of power is pulled from the +12V lines.

The fact that increased capacity only shows up as combined current on
the +12V lines raises an interesting question: Just how separate are
the four +12V lines. Some
knowledgeable members of the SPCR forums have done some digging
, and discovered
that in reality there may only be one or two lines. The discussion is specifically
about Seasonic's new M12 line and its rebranded twin from Corsair, but given
its similarity to the Energy Plus series, many of the points apply equally to
both series. Things get quite technical, but the summary is this:

  • Lines are only "separate" insofar as they have separate current
    limiters on each line. The original source is often (but not always) the same.
  • The purpose of having multiple rails is to limit the total VA from one line
    to 240VA, which means a limit of 240VA ÷ 12V = 20A on each line.
  • The circuit board does not identify contact points for either +12V3 or +12V4.
  • One user has reportedly been able to draw as much as 30~40A from a single
    cable set, which should certainly have tripped a current limiter if the rails
    were actually as specified. We were able to perform a similar test on the
    Energy Plus.

Only Seasonic knows for sure, but it seems quite likely that the four "separate"
+12V lines are not separate at all, but are just there to satisfy the standard-setters
at ATX12V and EPS12V. The practical consequences of having a single +12V rail
are actually more positive than negative. While a small degree of safety is
lost by isolating the rails, the convenience of not having to watch where each
peripheral is plugged in outweighs the loss.

EXTERNAL OVERVIEW

Physically, the S12 Energy Plus looks identical to the original S12 500 &
600 models. The external casing is the same, as are the position and size of
the vents. The black and silver color scheme hasn't changed, and neither has
the wire fan grill or the open on the back.



No changes to the exterior.

As with all of Seasonic's power supplies, the S12 Energy Plus has a few small
vents on the inside panel. These are intended to reduce back pressure and increase
airflow in an area that would otherwise receive almost no cooling. However,
some people have complained that this vent tends to exhaust unwanted heat into
the system. We think that the relatively small increase in system temperature
is worth the tradeoff for a well-cooled power supply, but not everyone agrees.

The Energy Plus sports all of the slight changes that came with the
recent revision (number three) of the S12 lineup
. Among other things, these
include longer, sleeved cables, more varied connectors, soft grommets for the
fan, and RoHS compliance.



The RoHS sticker is new, but all power supplies in the EU should have one
by now. No sign of an 80 Plus sticker...

INTERIOR

Although the circuit board looks very similar to the higher capacity S12 models
that we've seen, one difference immediately catches the eye: The heatsinks have
changed.



Circuit topology is similar to models we've seen before.

The difference is obvious if you compare the two photos below. The new heatsinks
are a bit smaller, and contain only a single layer of fins. Individual fins are wider,
and there seems to be more empty space in the power supply. It's not clear why
the change was made, but we can think of several possibilities:

  • Airflow Impedance: The new heatsinks block much less airflow than the originals
    and are therefore likely to use airflow more effectively.
  • Noise: Less impedance also means less turbulence noise at a given
    fan speed.
  • Cost: The new heatsinks look smaller, and may be simpler to manufacture.

On the other hand, the older heatsinks had about double the fin surface area,
and we're not convinced that the decrease in impedance is enough to make up
for the loss in cooling. After all, the originals were very effective —
why change a good thing?



New heatsinks. Are they improved?



The original heatsinks had more surface area... but they also impeded
airflow.

FANS

The 550W model uses the same quiet ADDA fan that appeared in the original 500W
and 600W models. Assuming the fan controller hasn't changed, this should mean
that the Energy Plus will be able to live up to the quiet reputation of its
predecessors.



The 550W model uses the same fan found in Seasonic's 500W & 600W S12's.

The 650W model is slightly different: It uses a slightly higher speed fan of
the same make and model line. It can certainly be expected to be louder when
going full tilt, but how quiet it is under ordinary circumstances (running at
~4V) remains to be seen.



The 650W model gets a higher speed fan.

CABLES AND CONNECTORS

Both models come with the same selection of cables and connectors. All cables
are sleeved in vinyl mesh, and IDE drive connectors have grips for ease of removal.
As promised, there are enough connectors for just about any system. Dual CPU
boards are supported by an 8-pin +12V EPS connector, and systems with twin graphics
cards get a pair of PCIe connectors.

There are a grand total of six SATA and nine IDE plugs spread over five different
cable sets, each a slightly different length. The different lengths are unusual
and are clearly intentional; the difference is to great to be sample variance,
and both of our samples were consistent in having cable sets of different lengths.
Perhaps they are meant to take into account the fact that not all cables need
to reach the farthest reaches of the case.



A huge number of output cables and connectors is provided.

Cable Sets

  • 20" cable for main 20+4-pin ATX connector
  • 20" cable for auxiliary 4-pin +12V AUX connector
  • 20" cable for auxiliary 8-pin +12V EPS connector
  • 21" cable for 6-pin PCIe connector
  • 24" cable for 6-pin PCIe connector
  • 24" cable with three SATA drive connectors
  • 27" cable with three SATA drive connectors
  • 20" cable with three 4-pin IDE drive connectors
  • 24" cable with three 4-pin IDE drive connector
  • 28" cable with three 4-pin IDE drive connector
  • 6" adapter from 4-pin IDE to 2 x floppy connectors

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


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 ([email protected])
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 ([email protected])
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 [email protected] 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 [email protected] 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 [email protected] 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.

Each of these recording have 10 seconds of silence to let you hear the ambient
sound of the room, followed by 10 seconds of the product's noise.

Sound Recordings of PSU Comparatives

HOW TO LISTEN & COMPARE

These recordings were made
with a high resolution, studio quality, digital recording system, then
converted to LAME 128kbps encoded MP3s. We've listened long and hard
to ensure there is no audible degradation from the original WAV files
to these MP3s. They represent a quick snapshot of what we heard during
the review. Two recordings of each noise level were made, one from a
distance of one meter, and another from one foot
away.

The one meter recording
is intended to give you an idea of how the subject of this review sound
in actual use — one meter is a reasonable typical distance between
a computer or computer component and your ear. The recording contains
stretches of ambient noise that you can use to judge the relative loudness
of the subject. For best results, set your volume control so that the
ambient noise is just barely audible. Be aware that very quiet subjects
may not be audible — if we couldn't hear it from one meter, chances
are we couldn't record it either!

The one foot recording is
designed to bring out the fine details of the noise. Use this recording
with caution! Although more detailed, it may not represent how the subject
sounds in actual use. It is best to listen to this recording after you
have listened to the one meter recording.

More details about how
we make these recordings can be found in our short article: Audio
Recording Methods Revised
.

CONCLUSIONS

For a high end, blazing performance, dual-graphics, overclocked monster of
a system, we know of no quieter power supply than the Energy Plus. Acoustically,
the Energy Plus has surpassed our expectations of what is possible from a quiet
power supply and set a new standard. With a fan that doesn't begin to increase
in speed until 250W output, it will take a concerted effort to force
the Energy Plus to become noisy — a nice change from the need to put effort
into preventing added noise.

One question that we have is whether the quieter performance has come at the
expense of cooling and reliability. That's not to say that the Energy Plus is
undercooled, but it doesn't quite measure up to the excellent thermal performance
that we saw in their original S12's. That said, the high 550W and 650W capacity
points mean that they should operate well below 50% load most of the time. With
that much headroom, it's hard to imagine the cooling system being inadequate.

As expected for an 80 Plus power supply, efficiency was top notch, and the
85% peak very close to the highest we've measured. That said, the high efficiency
does need to be put into perspective. A little extra efficiency is nice to have
in a powerful system, but an extra two or three percentage points doesn't work
out to much of an energy saving unless the load is ridiculously high —
which kind of defeats the purpose. In the range that most people will use it,
the Energy Plus models are not any more efficient than Seasonic's existing models.

The biggest strike against the Energy Plus is its price. US$150 for a power
supply is far from pocket change, and there are plenty of cheaper alternatives
that are just as quiet at lower levels. To reiterate: The Energy Plus is a power
supply for connoisseurs: It's engineered beyond what most people need, but if
you're looking for a special power supply for that special system, the Energy
Plus fits the bill perfectly.

Nice as it is, we can't help asking where are the lower capacity models that
perform like the OEM models that we've already seen from Seasonic. We know they
are capable of building a power supply that is 84% efficient at 65W. Where is
the 330W Energy Plus that can match the SS-300SFD for low-load efficiency? Here's
to hoping Seasonic brings one out for energy conscious silent PC enthusiasts.

*

SPCR Articles of Related Interest:

Power Supply Fundamentals & Recommended
Units


Power Distribution within Six PCs

Seasonic S12-330 PSU, New
Sleeved Version


Seasonic S12-430: Our current low-noise champ

Seasonic S12-500 & S12-600
Power Supplies


Seasonic SS-330SFD 80 Plus:
Little Big PSU


Seasonic SS-400HT Power Supply,
80 Plus Version

* * *

Much thanks to Seasonic
for the opportunity to examine this power supply.

Discuss
this article in the SPCR Forums.

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