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Coolermaster Silent Pro M700W power supply

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Coolermaster Silent Pro series power supplies are clearly aimed at quiet-loving PC enthusiasts. The 700W model was recently in our torture chamber. Read on to find out how it fared.

April 17, 2009 by Mike
Chin

Product
Silent Pro M700W
RS-700-AMBA-D3
700W ATX12V Power Supply
Manufacturer
Coolermaster
Market Price
US$125~150

Coolermaster is a long-established brand in cases, associated originally with high-end aluminum designs. Today, the brand’s product range includes heatsinks, cases of both aluminum and/or steel, as well as power supplies and many other computer peripherals. It is one of the biggest case brands in the retail market. Four separate power supply series are offered: Real Power, Silent Pro, iGreen, and eXtreme Power. The M700W is the top of the Silent Pro range; the other models are 500W and 600W rated.


At first glance, the box seems ordinary, but it’s not.

The full color sleeve comes off to reveal a rather unusual box design.


The top portion hinges out into two sections. The PSU seems well protected inside. The CD contains a PDF user’s manual. Lighter and cheaper than paper, perhaps. Note the black silicone rubber graskets. More on them later.

FEATURE HIGHLIGHTS

Coolermaster Silent Pro M700W Feature Highlights (from the Coolermaster web site)
FEATURE & BRIEF Our Comment
The single rail is with up to 50A on the 12V rail, delivers where it counts and won’t have any problems powering even the most demanding SLI
OK
Flat modularized cable design to eliminate clutter and improve airflow inside the chassis
OK
Energy efficient design that meets 80 Plus requirements 80 Plus certified is not exceptional now. Coolermaster does have three models in both Bronze and Silver 80 Plus categories, but this model is not one of them.
Two 6+2 pin PCI-e connectors for multiple graphic card set up Standard for a 700W model.
Protection: OVP / UVP / OCP / OPP /OTP / SCP / OLP Fairly standard.
Compliant with Intel standard Intel ATX12V V2.3 & SSI EPS 12V V2.91 OK
Green power design that meets energy star, blue angel requirements Expected in a high-end PSU.
Super silent operation with intelligent 135mm fan speed control We’ll find out.
Copper + aluminum heat sink design which results in more efficient heat transfer and dissipation. OK. It’s a difficult claim to confirm.
Japanese-made capacitors . Presumably the high quality ones.
Unique silicon pad eliminate the vibration between PSU and chassis It’s an interesting accessory, adds to the "Silent" marketing.

SPECIFICATIONS

The specifications table at the Coolermaster web site was rather garbled, the left and right column entries often no bearing any relation to each other. The table below is what I believe Coolermaster intended.

Model RS-700-AMBA-D3
Type Intel ATX12V V2.3 & SSI EPS 12V V2.91
Dimensions 150(W) x 86(H) x 150(L) (mm)
Input Voltage 90~264V (Auto Range)
Input Current 12A@115Vac, 6A@230Vac
Input Frequency 47~63Hz
PFC Active PFC >0.9
Power Good Signal 100~500ms
Hold Up Time >17ms
Efficiency 85% Typically
MTBF >100,000hrs
Protection OVP/ UVP/OCP/OPP/OTP /SCP/ OLP
Output Capacity 700W
Operation Temperature 0~40°C (Nominal Input Voltage)
Fan NEMKO / TUV / CE / GOST / C-tick / / UL / FCC
Certification 135mm ultra silent fan
Connector SLI / 80 Plus

Output power details are shown in the label on the PSU itself.

EXTERNAL TOUR

The M700W has the standard black finish with chrome wire fan grill. The 135mm diameter fan is a bit bigger than the standard 120mm. The mesh exhaust grill is nicely open for airflow. There’s an on/off switch and AC power socket.


You may not be able to see them clearly here, but the modular cables are flat, like PATA cables.



A 135mm fan, obligatory black finish. No vents other than the main exhaust.
The multiple mounting screw holes, repeated on the other side, are unusual.


The attached cables are conventional, nicely sleeved.


Fairly standard output socket array.

Multiple mounting screw holes on this side are very unusual.

OUTPUT CABLES

The Coolermaster Silent Pro M700W comes with many output cables.

Permanently wired, sleeved:

  • 1 – 18" cable w/ ATX 20+4-pin motherboard connector
  • 1 – 22" cable w/ Aux 12V 4+4-pin connector

Flat Modular:

  • 2 – 18" cable w/ 6+2-pin PCI-Express connector
  • 3 – 29" cable w/ 3x SATA connectors
  • 1 – 29" cable w/ 2x 4-pin Molex and 1x floppy connector
  • 1 – 29" cable w/ 3x 4-pin Molex connectors

INTERIOR

The components are laid out on a tidy PCB that fills the available space.


Conventional layout, nicely spaced heatsink fins.


The geometry of the 11-blade 135x25mm fan and look good, the trailing edges of the blades not parallel to the struts, which usually helps to minimize the tonality of the turbulence noise. (See Fan Blade Geometry on page 3 of the
Anatomy of the Silent Fan for more details.) The brand is Young Lin Tech, and it’s rated for 2.4W, which is low as such fans go. The DFS in the model designation suggests a sleeve bearing, while the M at the end implies medium speed. The company website, www.yltc.nc, is clearly identified on the fan hub, but the sites lacks information about any 135mm diameter fans.


The UL file number E320127 listed on the UL/CSA mark of the label is registered to Coolermaster, but this PSU is not manufactured by the company. The telltale signs for us are the heatsinks. We’ve seen this unique design before, in an Enhance 360W. We’re certain that Enhance Electronics, who sells almost nothing direct to the consumer under its own brand, is the original maker of the product. It has a strong reputation.



The pair of primary capacitors don’t look too special, but the brand name was obscured by positioning.



Buried under the mess of output cable connections on the other side are high quality SMC secondary capacitors.

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 10~11 dBA, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.


Coolermaster PSU in test rig in anechoic chamber.

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 over 1000W.
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, cooling is the main concern, not the noise level.

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

Ambient conditions during testing were 21°C and 10 dBA. AC input was 121V,
60Hz. One important thing to keep in mind is that since this power supply is sold exclusively in the EU where 220~240VAC is the rule, the efficiency numbers will be 2~4% higher than our results for most users. A quick check on efficiency at 240VAC input is done on section 7 below.

OUTPUT & EFFICIENCY: Coolermaster M700W

DC Output Voltage (V) + Current (A)

Total DC Output

AC Input

Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.25
0.98
5.04
0.95
3.36
0.96
0.1
0.1
21.7
33
65.8%
12.25
0.97
12.25
1.75
5.00
0.96
3.36
0.94
0.1
0.1
43.2
55
78.2%
12.25
1.87
12.25
1.74
5.02
1.88
3.35
1.79
0.2
0.4
64.1
80
80.1%
12.25
1.87
12.25
3.49
5.00
2.79
3.31
1.76
0.2
0.4
89.9
109
82.5%
12.28
4.68
12.28
3.48
4.95
5.41
3.30
5.39
0.3
0.5
151.1
180
83.9%
12.26
4.72
12.26
6.74
4.95
6.03
3.28
6.12
0.3
1.2
200.2
239
86.3%
12.28
7.62
12.28
6.71
4.92
7.84
3.27
7.88
0.4
1.4
252.3
304
84.7%
12.30
10.40
12.30
9.94
4.90
7.74
3.27
10.03
0.5
1.4
301.1
363
84.8%
12.30
11.44
12.30
12.98
4.86
12.35
3.24
12.07
0.5
1.5
400.8
492
83.3%
12.31
13.63
12.31
18.03
4.81
19.70
3.24
14.73
0.7
1.5
550.0
703
78.0%
12.30
22.00
12.30
20.06
4.80
18.20
3.22
18.10
0.8
1.5
698.6
897
77.9%
Crossload Test
12.11
22.08
12.11
23.4
5.15
0.97
3.35
0.96
0.1
0.1
560.7
679
82.6%
+12V Ripple: 62mV max @ 700W
+5V Ripple: 21mV max @ 700W
+3.3V Ripple: 17mV max @ 700W
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: Coolermaster Silent Pro M700W
Target Output (W)
20
40
65
90
150
200
250
300
400
550
700
Intake (°C)
21
21
22
23
27
33
31
33
32
38
39
Exhaust (°C)
22
23
25
29
34
41
44
48
46
61
64
Temp Rise (°C)
1
2
3
6
7
8
13
15
14
23
25
Fan (V)
4.2
4.2
4.2
4.2
4.2
4.6
5.7
7.6
8.9
12.2
12.2
SPL (dBA@1m)
14
14
14
14
14
18
25
27
30
34
34
Power Factor
0.83
0.95
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99
0.99

AC Power in Standby: 0.3W
AC Power with no load: 5.1W
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. EFFICIENCY This is a measure of AC-to-DC
conversion efficiency. The ATX12V v2.2 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.

80% efficiency reached at a low 64W load, which represent less than 10% of rated power . This is excellent performance, better than the 80 Plus standard certification demands. as this load. The broad peak of 80~86% was reached at 64~500W, with a maximum of 86.3% at 200W. Efficiency dipped below 80% above 500W, dropping to 77.9% at full load. Overall efficiency can be regard as excellent.

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%.

The voltage lines were stable, especially the 12V line, which started a bit high at 12.25V, and stayed near this level all the way to full load with no more than 0.06V variance. The 5V and 3.3V lines also stayed within spec, even at full load. The worst case was a sag of 0.2V (4%) on the 5V line at full load; hardly cause for concern.. Voltage regulation in the crossload test was very good on all lines.

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 was very low through most of the range, and climbed gradually as load was increased. The 62mV peak on the 12V line is very good, way below ATX12V guidelines. The 5V and 3.3V lines showed only trace amounts of ripple. at mid-power and lower, the ripple on 12V line dropped to 20mV or below, and stayed in single digits on the other lines.

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. PF on our sample was uniformly excellent from the lowest loads to the highest.

5. LOW LOAD PERFORMANCE is significant mainly to minimize energy waste and with system that demand very low power; the latter can cause some PSUs not to start. Standby performance excellent with just 0.3W draw. The unit powered up with no load, drawing just 5W, suggesting it will have no trouble with very low power startup/idle systems..

6. CROSSLOAD TEST – Basically the load on the 12V line was maximized while the load on all the other lines was minimized. Voltage regulation on all the lines was very good, and ripple stayed well within limits. There were no other changes.

7. 240 VAC INPUT

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 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: M700W @400W Output
VAC
AC Power
Efficiency
244V
584W
85.6%
120V
608W
82.2%
110V
617W
81.1%
100V
627W
79.8%

There were no surprises here. Our sample’s efficiency improved by ~2.5% at the higher VAC, and dropped about 1% for each 10V drop in VAC. Voltage regulation and ripple were unchanged.

8. NOISE and FAN CONTROL

The noise level at startup was a very low 14 dBA@1m. The quality of the sound was smooth, but up close, there was a surpring amount of low frequency growl. This aspect of the sound disappeared when the PSU was lifted off the niche in our load tester, so it’s very likely that the noise is the result of some interaction between the PSU fan’s noise/vibration and resonances in our test box. The included rubber gasket can probably suppress much of the vibration that might otherwise be transmitted from the PSU into the case. Why there is a gasket for the output side of the PSU (which would normally be inside the case) is not clear. Perhaps some of the Coolermaster cases allow the PSU to be mounted from within.


The spikes between 150~200 Hz correspond to the growl mentioned in the text
.


The growl remains at 250W load

The fan voltage did not change until the 200W mark, when SPL rose to 18 dBA@1m. The overall noise character was still smooth, mostly broadband, with a bit of growl. Beyond this load, the fan speed increased steadily, reaching 25 dBA at 300W. The 30 dBA point was breached at around 500W load, and the maximum fan voltage of 12.2V was reached at 550W load, with a relatively low 34 dBA SPL.

There was a healthy degree of hysteresis in the fan control. It kept the fan from ramping up and down audibly.

9. COOLING

Like most quiet power supplies, the M700W keeps itself cool enough, but its fan should not be counted on to keep the PC case cool. As expected with a hogh efficiency power supply, the exhaust temperatures stayed modest at lower loads. Above ~250W, the exhaust and intake temperatures seemed a touch higher than usual. There was no misbehavior associated with overheating.

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


Nexus Value 430

11
11
16
18
18
19
n/a
n/a


Seasonic M12D 850W

14
14
14
14
14
24
37
42


Enermax Modu82+ 625*

13
13
14
15
16
26
36
37

Coolermaster M700W

14

14

18

21

25

27

34

34

Chill Innovation CP-700M

15

15

15

15

17

30

34

34

Antec Signature 650

15

15

15

18

18

28

36

47

SilverStone DA700
18
18
18
18
23
32
35
41

NesteQ ECS7001

22

22

22

21

23

25

36

37

PCPC Silencer 610
20
24
24
24
24
30
40
50
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.

The green colored blocks are 30 dBA@1m or greater SPL readings. The PSU that stayed quiet (under 30 dBA) to the highest load is not in this table because it has not been tested in the anechoic chamber: The Zalman ZM1000, which stayed below 30 dBA to almost 600W load. It’s idle noise is probably not low enough to match the M12D-850W , the Enermax, or the Signature 650; its measured SPL in the live test room was 20 dBA@1m, a dB or two higher than the others.

It’s difficult to rank the Coolermster M700W. The SPL at low loads puts it high on the rankings, but it also ramps up in noise more quickly than many of the others.

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.

CONCLUSIONS

The Coolermaster Silent Pro M700W is clearly a quiet power supply, one with high efficiency and excellent electrical performance. Its noise level at lower loads is low enough to make a computer that’s inaudible at idle and low power. While the overall SPL never gets that high, the rate at which the noise rises is almost linear, which makes the unit a touch louder than its competitors in the middle load range (200~300W) that represents real power demand in many current enthusiast systems.

The efficiency numbers alone are enough to show that this PSU has quite up-to-date technology. It is not possible to reach >85% effieicny at any load with older technology. The very low 0.3W power draw in standby is notable, as is the mere 5W draw with no load power on.

For gamers, the noise difference between this and many other quieter PSUs we’ve reviewed is probably moot. Many gaming PC rigs will reach the 300W load, at which point, many other fans in the system will be ramping up enough to obscure the differences in power supplies. The M700W does deliver good clean power, and fairly quietly even at high load, so there’s a lot going for it.

For the quiet PC enthusiast, the noise at <200W is more important, and the noise level of this model is low enough to compete with some of the best rated silent PSUs… but the 700W rating is overkill. The rubber mounting gasket is a nice touch, and it could actually help reduce noise in some cases, although the results will be very system- and case-specific. All in all, the Coolermaster Silent Pro M700W is a modern, efficient, high performance power supply quiet enough for the vast majority of users.

Our thanks to Coolermaster for the M700W sample.

Check the current price of the Coolermaster Silent Pro M700W

* * *

SPCR Articles of Related Interest:
Power Supply Fundamentals
SPCR PSU Test Rig V.4
Chill Innovation CP-700M
Seasonic M12D-850

SilverStone Decathlon DA700 power supply

Modu82+ 625 Power Supply: Enermax to the Forefront

Corsair HX520 & HX620

* * *

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