X-650: Seasonic hits Gold

blog image

The X-series power supplies achieved 80 Plus Gold nearly a year ago, and they’re finally on the market now. Is Seasonic’s best also SPCR’s most highly recommended? Yes. Read all the details here.

Product
X650 650W (SS-650KM) computer power supply
Sample Supplier
Seasonic USA
Manufacturer
Seasonic Electronics
Suggested Price
US$179

In the four years since its inception, 80 Plus has successfully become a major benchmark for computer power supplies. It was ostensibly a program to reduce electricity demand, sponsored by a consortium of power utilities in the US, and aimed initially to promote higher AC/DC conversion efficiency in computer power supplies. The first target was 80% conversion efficiency; hence the name of the program. Since then, 80 Plus has been widely accepted by the industry, and the original single 80% category was expanded to reflect higher goals: Bronze, Silver and Gold. The highest category, Gold, calls for 90% efficiency at 50% of rated load, at 87% at 20% load and 100% load. With the massive proliferation of PSU brands in the past few years, efficiency and 80 Plus approval became an important marketing differentiator, with money and energy savings as well as eco-friendliness the oft-mentioned benefits.

Seasonic has been a primary innovation leader in computer power supply design and manufacturing over the past decade, and a pioneer in high energy efficiency. Seasonic-made PSUs have also dominated the top ranks of SPCR’s Recommended PSU list for years (under its own brand and under the brands of its clients, such as Antec and Corsair). All the way back in October 2008, Seasonic became one of the first to achieve the Gold 80 Plus award for its then upcoming 550LT, 650KM and 750KM models. The 650KM model under review here is one of the first 80 Plus Gold PSUs available on the market in North America.

The X-Series is a logical followup to the M12D series released last year. The M12D achieved 80 Plus Silver rating, with assured 85% minimum efficiency at all power levels. The M12D-850 we reviewed last December remains at the top of our recommended power supplies. It’s interesting to note that the X-Series does not include any "super power" models thus far.

As with the M12D-850W review sample, Seasonic included a few extras in the reviewer’s package: A small auxiliary PCB which contains the DC-to-DC converter, a reviewer’s guide and other technical documentation on an optical disc.

PACKAGING & FEATURES


The gold-black retail box is bigger than most others from Seasonic in the past, except for the M12D series.


The back of the box is packed with technical promotional details.

Seasonic X-650 FEATURE HIGHLIGHTS (from the
web product page)
FEATURE & BRIEF Our comment
Core Features
80PLUS Gold Certified Super High Efficiency Assured 90% power conversion efficiency.
DC to DC Converter Design; Patented DC Connector Module with Integrated VRM [Voltage Regulator Module] DC-to-DC conversion for the lower voltage lines is not unusual, but Seasonic’s implementation is unique.
Patented Hybrid Silent Fan Control The fan does not spin at low loads, making it silent. Hybrid suggests a cross between passive and active cooling.
Sanyo Denki San Ace PWM Silent Fan

Presumably a variant of the superb fan used in the M12D. PWM speed control probably makes semi-passive operation practical.

"Green Innovation" Features for Extended Product Life, High Quality, High Efficiency, and Competitive pricing
High Reliable 105°C Japanese Capacitors

Many high end PSUs flaunt this feature, including Seasonic’s own M12D series.

Conductive Polymer Aluminum Solid Capacitors These advanced caps are also used on motherboard.
Super High Efficiency [up to 90%]
Green solution for lowering energy consumption, noise & heat.
OK.
Dual Sided PCB Layout
Better utilization of PCB space to enhance quality and performance.
OK.
Tight Voltage Regulation [±3%] More stringent than the ±5% recommended by the Intel ATX12V PSU design guide.
Ample +12V Output 54A (648W) on a single rail. We’ve come full circle from the madness of multiple 12V lines so popular a few years ago.
Safety: UL/CUL, TUV, CE, CB, CCC, FCC Class B, C-Tick, GOST-R, UkrTEST, BSMI, Semko Very good.
Protection from short circuits (SCP), over voltages (OVP), over power (OPP), over temperature (OTP), and over current (OCP) The more the merrier.
Universal Input, Active PFC Like just about every PSU
on the retail market… but Seasonic was
the pioneer with these features on computer PSUs.
MTBF: Over 150,000 hours at 25 Deg C. excluding the DC Fan. Very good.
Seasonic 5 year warranty Very good!
Net Weight: 5.82 lbs (w/o cables)
Size: W150 x L160 x H86 mm
Slightly longer than normal.

SPECIFICATIONS

The most complete specifications are found in the manual.

Seasonic SS-650KM Specifications
AC Input
90~264VAC 8~4A 50/60 Hz
DC Output
3.3V
5V
12V
-12V
5Vsb
25A
25A
54A
1A
3A
125W
648W
12W
15W
650W
Operating Temp: 0~50°C, 100% Continuous Power @ 50°C

Unlike the M12D-850W which is not assured to provide full output power above 40°C, X-650 is spec’d to provide 100% rated power to 50°C. This spec is more typical of server class PSUs than desktop PSUs.

Keep in mind that the testing for 80 Plus approval is done at normal ambient room temperature. The 80 Plus Testing Guidelines (PDF) specify only that "ambient temperature shall be maintained at 23°C ± 5°C throughout the test." In contrast, the ambient temperature of the SPCR test system is directly proportionate to the load. At low load, the air intake is at or just above room temperature, but as load is increased, the temperature rises steadily. Typically, with a fan-cooled PSU, the intake temperature in our test system reaches 45~50°C at >600W loads. This is an extremely tough test condition, as PSU efficiency naturally drops off at high and low loads; combine high load with high temperature and it’s essentially a torture chamber. It does replicate reasonably well the conditions that prevail in a typical tower PC. For full details, please
refer to SPCR’s
PSU Test Platform V4.1
.

VISUAL TOUR

Opening up the big retail box reveals a level of luxurious packaging not encountered with any Seasonic brand products in the past. The PSU is not only cradled in closed cell foam, it’s in a soft velvet draw-string bag. All the modular cables are in a dual-compartment puch as well.


Luxurious packaging…


…for all the parts.



All 13 sleeved output cables are modular.



These are the reviewer’s extras.

The power supply’s casing is a departure from the normal dual C-shaped clamshell. The metal feels thicker and is fitted together very precisely — though Seasonics have always been excellent in this regard. The black and gold color scheme continues in the paint job and labels.


Still a 120x25mm fan with hexagonal hole vent for intake…


…as well as exhaust.

There’s no question of which output cable fits into which socket.


Surprisingly, no heatsinks are visible through the fan intake grill. A little tag warns, "Temperature Activated Fan Rotates Only When Required" — probably an attempt to stave off returns by consumers who think the fan is broken when they discover it doesn’t spin upon power-on.

OUTPUT CABLES

1 – ATX connector (580mm) 20+4 pin
2 – CPU connector (580mm) 4×2 (8-pin)
1 – CPU connector (580mm) 2×2 (4-pin)
4 – PCIe (580mm) 6/8-pin
2 – three SATA connectors (750mm)
1 – two SATA connectors (480mm)
1 – three 4-pin peripheral connectors (750mm)
1 – two 4-pin peripheral connectors (480mm)
1 –
two floppy drive connectors on Y adapter (150mm)

Drive connectors come on different lengths of cables, a nice touch for those seeking the tidiest cabling in their PCs.

INSIDE

The removal of four screws allowed the fan panel to be removed. Compared to previous Seasonic models, some very significant differences are visible:

  • There is only one large heatsink, way off to one side. No wonder it was not visible from the outside.
  • The connector to the fan is 4-pin, as expected for PWM control.
  • Airflow impedance looks to be modest.
  • The isolation of the lower voltage circuitry to the daughter PCB appears to have minimized clutter on the board; that plus the absence of multiple soldered output cables.
Postscript Note, Nov 5/09: It was pointed out to us by a sharp-eyed reader that the internal photos shown below are from an X750. We had just received the X750 sample when this review was being posted, and photos of both PSUs were taken at the same time. The photos of the two samples got mixed up accidentally; the two PSUs look identical internally except for the value of some of the capacitors, which are all rated 105°C. Rest assured that there was no confusion or mixup about the test results; they are for the X650 we tested and the conclusions remain unchanged.


Only one large heatsink, oddly almost out of the airflow path of the fan.



The fan has good geometry and rugged bearing housing, identical in design to the excellent fan used in the M12D series. The current rating of 0.13A suggests both modest speed and high energy efficiency. A rubber pad lies between the fan and the intake grill panel, presumably to minimize vibration transfer from the fan.


All of the circuitry on the main PCB has to do with conversion from AC to 12VDC; the DC/DC conversion to the lower voltages takes place on the daughter board which also holds the output connectors.


Note 105°C KMR primary filter capacitors and main step-down transformer. The vertically positioned PCB is the DC/DC Connector Module with Integrated VRM.



A close-up of both sides of the DC/DC Connector Module board supplied to reviewers.

One of the most important aspects of the DC/DC Connector Module is that it keeps the outputs at 12VDC through most of the PSU. By making the conversion from 12VDC to 5VDC and 3.3VDC on this module, the losses inherent in low voltage electricity transfer are minimized. Only the 12VDC line has to run from the main PCB to the DC/DC Connector Module, which keeps internal wiring and soldering (both sources of higher energy loss) to an absolute minimum. The illustration below from Seasonic explains the difference between the X-series design and conventional modular output PSU design.

As with the fan in the M12D, the quality of the fan seems more than skin deep. This Sanyo Denki has extremely low friction bearings. Some basic free air tests on the spare fan were run to glean a bit more information.

Sanyo Denki San Ace S1212P4M61 fan
MEASURED DATA
Voltage
RPM
SPL@1m
12V
1920
32 dBA

PWM speed control will allow this fan to start and run at extremely low speed, probably below 500rpm. Seasonic’s term, Hybrid Silent Fan Control, attempts to explain that the fan only starts when necessary and stops when it’s not. The following is Seasonic’s explanatory illustration.

TESTING

For a fuller understanding of ATX power supplies, please read
the reference article Power
Supply Fundamentals
. 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 V4.1
. The testing system is a close simulation of
a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

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, in
general, 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.

The 120mm fan responsible for "case airflow" is deliberately
run at a steady low level (6~7V) when the system is run at "low"
loads. When the test loads become greater, the 120mm fan is turned up to a higher
speed, but one that doesn’t affect the noise level of the overall system. Anyone
who is running a system that draws 400W or more would definitely want more than
20CFM of airflow through their case, and at this point, the noise level of the
exhaust fan is typically not the greatest concern.

Great effort has been made to devise as realistic
an 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 we test the PSU to full
output 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 40W and 300W, 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 power draw of several actual systems
under idle and worst-case conditions.
Our most power-hungry overclocked
130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W
DC peak 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 the most power hungry dual
video cards today might draw as much as another 150~200W, but the total should
remain under 500W in extrapolations of our real world measurements.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that PSU 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.

TEST RESULTS

The ambient temperature was 21~23°, and the ambient noise level was 11
dBA.

OUTPUT, REGULATION & EFFICIENCY: Seasonic X-650

DC Output Voltage (V) + Current (A)

DC Output

AC Input

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.25
0.97
12.25
0
5.03
0.96
3.37
1.42
0.1
0.1
22
33
65.1%
12.25
0.97
12.25
1.72
5.03
1.93
3.37
1.42
0.1
0.1
43
55
77.3%
12.23
1.91
12.23
1.71
5.03
1.92
3.36
2.72
0.2
0.2
66
80
82.6%
12.22
1.87
12.22
3.39
5.02
2.84
3.36
2.56
0.3
0.3
92
106
86.6%
12.22
3.79
12.22
4.89
5.02
5.44
3.36
3.88
0.3
0.5
150
170
88.3%
12.19
5.67
12.19
6.55
5.01
5.34
3.36
5.21
0.3
0.7
199
219
90.8%
12.13
8.56
12.13
6.55
5.01
7.90
3.35
6.44
0.4
1.0
251
274
91.7%
12.17
9.47
12.17
9.49
4.98
9.61
3.35
7.56
0.4
1.0
302
329
91.7%
12.14
12.25
12.14
12.32
4.96
12.66
3.34
13.05
0.5
1.2
402
453
88.8%
12.13
14.83
12.13
15.40
4.93
14.44
3.35
14.18
0.5
1.2
501
564
88.9%
12.11
21.20
12.13
21.40
4.95
15.14
3.35
13.87
0.5
1.2
650
744
87.4%
Crossload Test
12.07
21.20
12.05
23.44
5.00
0.98
3.38
0.96
0.5
2.5
557
615
90.6%
+12V Ripple (peak-to-peak): <13mV @ <250W ~ 18mV
@ 650W
+5V Ripple (peak-to-peak): <10mV @ <200W ~ 12mV @ 650W
+3.3V Ripple (peak-to-peak): 10mV @ <200W ~ 14mV @ 650W
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings. It is a tiny portion of the total, and errors arising
from inaccuracies on these lines is <1W.
OTHER DATA SUMMARY: Seasonic X-650
DC Load (W)
22
43
66
92
150
199
251
302
402
501
650
Intake °C
21
21
23
24
30
35
34
32
35
38
42
Exhaust °C
22
22
25
29
35
39
39
39
43
46
56
Temp Rise °C
1
1
2
5
5
4
5
7
8
8
14
SPL (dBA @ 1m)
n/a
n/a
n/a
n/a
12
13
14
16
31
31
32
Power Factor
0.95
0.96
0.98
0.99
1.00
1.00
1.00
1.00
1.00
1.00
1.00

AC Power in Standby: 0.3W / 0.1 PF
AC Power with No Load, PSU power On: 7.2W / 0.70 PF
NOTE: The ambient room temperature during
testing can vary a few degrees from review to review. Please take this
into account when comparing our PSU test data.

1. EFFICIENCY This is a measure of AC-to-DC
conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency
or better at all output power loads. 80% efficiency
means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost
as heat within the PSU. Higher efficiency is preferred for reduced energy consumption
and cooler operation. It allows reduced cooling airflow, which translates
to lower noise. The 80 Plus Gold standard requires 90% efficiency at 50% of rated load, and 87% efficiency at both 20% load and full rated load.

At the super low 20W load, efficiency was quite good at 65%. Efficiency rose quickly as the load was increased. 80% efficiency was reached around the 60W mark, broke 85% before 90W, and it crested 88% at 150W. It probably reached 87% at 130W (which is 20% of rated power). At 200~400W, the likely operational load for a typical system in which a 650W PSU would be installed, >90% efficiency was reached. With higher load, and higher operational temperature in the SPCR test box, efficiency dropped a bit, but still remained above 87% even at full power, at over 40°C operational temperature.

These are excellent results, as expected, the best efficiency results on any PSU tested thus far. Note that the 80 Plus testing is done at typical room temperature (18~28°C) while our test conditions feed the heat of the PSU output back into its operating ambient, which makes for a much hotter, more demanding high power load test.

2. VOLTAGE REGULATION refers to how stable the output voltages
are under various load conditions. The ATX12V Power Supply Design Guide calls
for the +12, +5V and +3.3V lines to be maintained within ±5%.

At all load
levels, the critical 12V line was within 0.25V (~2%) of 12V, and even at the
highest loads, it never dropped below 12V. This is excellent
performance. The 3.3V regulation was within 0.07V, while the 5V line was off by 0.05V (2%) at most. The sample exceeded Seasonic’s own stringent 3% spec for voltage regulation.

3. AC RIPPLE refers to unwanted "noise"
artifacts in the DC output of a switching power supply. It’s usually very high
in frequency (in the order of 100s of kHz). The peak-to-peak value is measured.
The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V
line and 50mV on the +5V and +3.3V lines. Ripple on all the lines was excellent at all power levels, generally staying under 10mV through the lower half of the power range. Even at maximum power, the 12V ripple stayed under 20mV. It’s the best ripple we’ve measured on any PSU test sample.

4. POWER FACTOR is ideal when it measures 1.0. In the most
practical sense, PF is a measure of how "difficult" it is for the
electric utility to deliver the AC power into your power supply. High PF reduces
the AC current draw, which reduces stress on the electric wiring in your home
(and elsewhere up the line). It also means you can do with a smaller, cheaper
UPS backup; they are priced according to their VA (volt-ampere) rating. Power
factor was very good for this model, running no lower than 0.96 at any point
during normal load testing.

5. LOW LOAD TESTING revealed no problems starting at very
low loads. Our sample had no issue starting up with no load, either, and the power draw was much lower than normal.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 500W load with 120VAC through the
hefty variac in the lab. The variac was then dialed 10V lower every 5 minutes.
This is to check the stability of the PSU under brownout conditions where the
AC line voltage drops from the 110~120V norm. Most full-range input power supplies achieve higher efficiency
with higher AC input voltage. SPCR’s lab is equipped with a 240VAC line, which
was used to check power supply efficiency for the benefit of those who live
in 240VAC mains regions.

Various VAC Inputs: X-650 @ 500W Output
VAC
AC Power
Efficiency
244V
542W
92.3%
120V
563W
88.9%
100V
575W
86.9%

Efficiency improved around 3.4% with 244VAC input at this load. The sample passed the 100VAC minimum input without any issues. Neither voltage regulation nor ripple changed appreciably
during the test.

7. TEMPERATURE & COOLING

Initially, we had misgivings about the cooling design in the X-650. Even with 80 Plus Gold efficiency, how could a single wee heatsink on the periphery of the fan’s airflow path keep core components cool enough? Yet, testing proved our misgivings were unfounded. Cooling was very good, with °C temperature rise staying in single digits until maximum power. At 650W the temperature rise was still a modest 14°C. The intake temperature moved up/down somewhat during the long test session, dropping when the fan sped up a bit in response to a rise in load/temp, then rising again as heat built up with the next higher load.

8. FAN, FAN CONTROLLER and NOISE

The PWM controller and the absence of a fan speed monitoring line made it very difficult to determine the speed of the fan at various loads. Only two points were determined: Speed at fan turn on was 440~480rpm, and it was 1900rpm at full power. However, the reason the fan speed is monitored in the first place is for the noise, and the key parameter, SPL, was measured at several points through the load testing.

The PSU fan did not spin up at turn-on with a 20W load. In fact, it did not spin up immediately at turn-on even with a 200W load, at least not from a cold start. With the fan not running, the X-650 could be deemed silent. There was no measurable noise from a meter distance in the anechoic chamber. From under 1′ distance, a touch of coil and capacitor whine could be heard, but it was a trace amount no higher in level than any other PSU. The fan started spinning about 10~15 minutes into the 150W load test. The 440~480rpm fan speed measurement is an approximation; there was no way to keep the thermal load unchanged and measure fan speed simultaneously.

The X-650 proved to be the quietest power supply tested, at loads up to 300W. It was very quiet at higher loads as well, but between 300W and 500W, its fan ramped up a bit quicker in our hot box than a few other previously tested quiet champs. Still, it was still very quiet, barely exceeding 30 dBA@1m even at full load. Through much of the practical load range for a 650W PSU — 40W~300W — the unit did not venture beyond 16 dBA@1m in our hot test box. In one of the modern advanced ATX cases with the PSU well insulated from the heat of the other components, the fan of the X-650 may never spin up at such loads.

The screen captures below from our 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.


With the fan spinning slower than 500rpm at 200W, the overall noise of the Seasonic X-650 was virtually identical to the ambient acoustic in the anechoic chamber.
Only the tell-tale spikes (at just -10 to -15 dBA) above 10 kHz indicate the presence of power electronics in the room.


At 250W, the fan became more audible but it was still extremely quiet.


Not much change at 300W.


SPL crested 30 dBA@1m at 400W load; this was about as noisy as the X-650 got. At full load, it measured 32 dBA@1m, presumably with the fan at full speed.

One question asute readers will ask is, "Does the fan stops spinning when the load drops?" This is an issue we’ve seen in other "semi-passively cooled" PSUs: Once it starts, the fan simply does not stop spinning even when load drops way below the load which triggered it to start. The answer is, YES, the fan in the X-650 did stop when the load was reduced below 150W — but not instantly. How quickly the fan stops depends on how quickly the heat is dissipated from not only the PSU but also the case. In testing, this was checked by dropping the load after the fan started, from 200W to 90W. With the "case fan" in the test box at very low speed (~600rpm), the fan in the X-650 stopped after about 2 minutes. Exactly when it stopped was difficult to determine because the fan was running so quietly before it stopped.

Another question some readers will ask is, "To what power level will the fan remain unmoving and silent when the X-650 is used in a case like the Antec P182 (and similar) where the PSU is well insulated from the heat of the other components?" In anticipation of this question, a second load test run was done with the X-650 outside the hotbox, as with the Antec CP-850 PSU.


2nd load test run with X-650 out of the hot box.

Seasonic X-650 SPL: In Hot Box vs. Out
Power load
90W
150W
200W
250W
300W
400W
500W

650W

in hot box

<10

<10

12

14

16

31

31

32

out

<10

<10

<10

<10

<10

16

27

32

Measurements are in dBA@1m

On the test bench with ambient room temperature at 23°C, the fan in the Seasonic X-650 started at about 340W load. Naturally, it was much quieter to a higher load than inside the hot box. It was quieter at lower loads and slightly noisier at higher loads than the only other PSU we’ve tested in this way, the Antec CP-850.

Antec CP-850 SPL: In Hot Box vs. P183 case (guesstimate*)
Model
90W
150W
200W
250W
300W
400W
500W

700W

850W

in hot box

12

12

12

14

14

26

40

44

45

out

12

12

12

12

12*

14*

20*

24

40*

Measurements are in dBA@1m
*These points are guesstimates; the rest were measured.


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

Antec CP-850

12

12

12

14

14

26

40

44

45


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
The green boxes represent >30 dBA@1m SPL.
*Guesstimates based on the Modu82+ 425’s idle in the chamber and the Modu82+ 625’s load test.

Except at the 400W SPL, the Seasonic X-650 edges out or matches every other PSU. If the above table was converted to a line graph, the X-650 would have the smallest area under the line. Its closest competitors for low noise are the Nexus Value 430, Antec CP-850, Seasonic M12D-850 (and the untested 750W version of this model, presumably), Chill Innovation CP-700M and Enermax Modu82+ 625. However, when efficiency and overall electrical performance are also considered, only the Antec CP-850 and Seasonic M12D-850 are worthy competitors.

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.

MP3 SOUND RECORDINGS

These recordings were made as 24-bit / 88 kHz WAV files with a high
resolution, lab quality, digital recording system
inside SPCR’s
own anechoic chamber
(11 dBA ambient), 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.

These recordings are intended to give you an idea of how the product sounds
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. 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!

Each recording starts with 6~10 seconds of room ambient, followed
by 10 seconds of the product’s noise. For the most realistic results,
set the volume so that the starting ambient level is just barely audible, then
don’t change the volume setting again while comparing all the sound files.

Sound Recordings of PSU Comparatives
in the Anechoic Chamber

CONCLUSIONS

Expectations ran high for the X-series Seasonic power supplies. Not only were they the first 80 Plus Gold approved units, Seasonic promised semi-passive cooling for super quiet operation and fully modular cables as well. It was a long wait since the 80 Plus test results late last year, but all expectations have been clearly met or surpassed by the X-650. It takes the crown in every significant category we can think of — except sheer output capacity.

Seasonic power supplies have been impressing us on the test bench and inside real computers since 2002. The company’s drive to improve acoustics and efficiency has been a constant for the past decade, and the X-650 is a fitting culmination. It’s hard to imagine how this power supply could be bettered in any significant way. As it stands, I’m of the opinion that the Seasonic X-650’s electrical performance is much better than any computer needs a power supply to be.

Acoustically, the X-650 breaks new ground with its effective semi-passive "Hybrid Silent Fan Control", made possible with the combination of a super-quality fan, PWM fan speed control, and Seasonic’s long-heralded intelligent fan control algorithm.

The Seasonic X-650 is a superb power supply. It deserves our highest recommendation.

Seasonic X-650 Balance Sheet
Likes

* >90% efficiency in typical use
* Silent in typical use
* Electrical performance is tops
* Semi-passive cooling really works; fan runs only when needed.
* Clever, innovative engineering
* Great quality components
& build
* All modular cables

Quibbles

* Price?
* Bigger heatsink?

Much thanks to Seasonic USA for this review sample.

SPCR Editor’s Choice Award

SPCR Articles of Related Interest:
Power
Supply Fundamentals

Recommended
Power Supplies

SPCR
PSU Test Rig V.4

Antec
Signature 650

Seasonic M12D-850W
Enermax
Modu82+ 625W

Antec CP-850: Unique PSU with Top Performance
NesteQ
ECS7001 700W PSU: A Modular Twist

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