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Seasonic Goes High End Gaming with the M12

Submitted by Devon Cooke on Mon, 2006-10-09 21:04. Power
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TEST RESULTS


On the test bench...

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 19°C and 19 dBA, 121V/60Hz.

Note that, because of the extremely high capacity of the M12, we were unable to push it to its full capacity — our test rig simply isn't built for such high power. With our test rig maxed out, we managed to draw about 670W from the unit — 30W shy of full load.

OUTPUT & EFFICIENCY: M12-700
DC Output Voltage (V) + Current (A)
Total DC Output
AC Input
Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.19
0.98
12.17
1.74
5.04
0.98
3.40
0.00
0.1
0.2
40.3
62
65.1%
12.18
1.92
12.17
1.74
5.03
2.90
3.40
0.98
0.1
0.3
65.2
91
71.7%
12.17
2.88
12.15
3.32
5.02
1.94
3.39
0.98
0.1
0.4
91.6
120
76.7%
12.16
4.75
12.13
5.02
5.02
3.71
3.38
2.74
0.2
0.6
151.9
189
80.3%
12.15
6.57
12.11
6.46
5.01
4.60
3.37
3.70
0.2
0.9
200.5
240
83.5%
12.14
7.82
12.09
8.10
4.99
6.46
3.38
4.55
0.3
1.1
249.6
298
83.8%
12.13
9.68
12.06
9.64
4.99
7.06
3.36
6.31
0.3
1.3
300.2
359
83.6%
12.11
12.40
12.01
12.67
4.97
10.55
3.34
9.17
0.5
1.7
399.9
483
82.8%
12.09
17.00
11.98
15.68
4.95
12.10
3.32
9.12
0.6
2.1
501.2
615
81.5%
12.07
20.51
11.92
18.77
4.94
14.27
3.30
11.59
0.7
2.6
601.4
751
80.1%
12.03
21.35
11.89
18.77
4.89
21.47
3.26
19.04
0.8
3.0
671.7
864
77.7%
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 M12-700
DC Output (W)
40.3
65.2
91.6
151.9
200.5
249.6
300.2
399.9
501.2
601.4
671.7
Intake Temp (°C)
21
24
28
32
37
38
41
41
42
44
46
Exhaust Temp (°C)
24
26
29
34
39
44
48
51
54
59
64
Temp Rise (°C)
3
2
1
2
2
6
7
10
12
15
18
Fan Voltage (V)
3.9
3.9
3.9
3.9
4.0
4.0
4.7
6.9
9.5
11.2
11.2
SPL (dBA@1m)
21
24
21
21
21
21
25
35
42
46
46
Power Factor
0.98
0.94
1.00
1.00
0.99
0.99
1.00
1.00
1.00
1.00
1.00
AC Power in Standby: 0.3W / 0.08 PF
AC Power with No Load, PSU power On: 8.5W / 0.72PF
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

Standby and no-load performance were both very good; the power drawn in standby was negligible, although the extremely low power factor seemed a bit odd. With power factor taken into account, the power supply drew almost 4VA — more than expected.

The M12 had no issues turning on with no load, and it drew less than ten watts while running. This is good, but not quite as good as the best, which consume about five watts.

2. VOLTAGE REGULATION was very good — within 3% of the nominal value throughout the test. That's quite a feat for a capacity range that spans 700W, but the M12 handled it perfectly. Note that the sudden drop in the +3.3V and +5V lines for the final test is a result of the disproportionate load placed on these lines — they were running at full capacity in order to bring the test point as close to 700W as possible.

3. EFFICIENCY was very good, especially under heavy loads. It remained above 80% through most of the upper test points, dipping below only on the final test point — and that may well be another artifact of the unusual load pattern. All of the M12 models are 80 Plus certified, so it's no surprise that our sample did well.

Unfortunately, efficiency at low loads was not quite on the same level as the upper loads. Efficiency at 65W (a good ballpark figure for idle) was just 72% — lower than any of the other Seasonic models currently on the market. To be fair, a 700W power supply is not really intended for use in a low or midrange system, but it's still disappointing that it is not more efficient in the range where most systems spend most of their time.

4. POWER FACTOR stayed close to the ideal value of 1.00 thanks to active power factor correction.

5. TEMPERATURE & COOLING were very good until about 250W output — just before the fan started to speed up. Above this level, the thermal rise through the power supply rose with every data point, although it was never cause for concern. The 18°C rise at 670W output was a bit on the hot side, but perhaps that's to be expected at such a high output. At that level, the power supply was generating 200W of heat in efficiency losses alone, so perhaps 18°C is not unreasonable. Reasonable or not, we can only hope that it is adequate to prevent overheating... and that nobody ever needs to run their power supply for long at this level.

6. FAN, FAN CONTROLLER and NOISE

The fan started at 3.9V — almost halfway between the starting voltages for the two fans (3.3V for the 120mm fan, 4.3V for the 60mm). At such a low voltage, the main fan was barely audible from one meter. The noise character the same low hum that we have come to expect from Seasonic's power supplies.

The fan stayed at its start level until the intake temperature reached 40°C — approximately 250~300W for our test bed. For ordinary systems, this should mean that the M12 will never ramp up and the 60mm fan will never turn on. Only very hot systems — those with multiple processors or graphics cards — need worry about increases in fan noise.

Once the fan speed began to increase, the fan controller was quite sensitive to changes in load, and sudden load swings (caused by random load increases in the settings of our PSU tester) occasionally came with sudden change in noise that drew attention. In addition, once the 60mm fan turned on (at 300W), the noise developed a slight "throbbing" that seemed to be cause by the intermodulation of the two fans. And, as mentioned, once the 60mm fan started up, it never turned off, even when the fan voltage had dropped back down to the default value of 3.9V.

Surprisingly, our sample had an undue amount of buzzing electrical noise with low 12V loads. The noise was worst with a 4A load on the +12V line, and got fainter as the load was either raised or lowered. The buzzing dominated the noise character at our 65W test load and raised the measured noise level significantly. Perplexed and a bit concerned, we checked three other M12 samples on hand. An M12-600 sample was almost identical to the review sample, while another M12-700 reached maximum noise at ~3A instead of 4A (on the 12V line). A fourth sample, an M12-500, exhibited no audible buzzing at any load. With all the samples, the buzzing basically disappeared above 4A load on the 12V line.

It's difficult to verify whether this buzzing is normal or specific to the samples we obtained. Seasonic USA told us that this was the first time they'd encountered such an issue, and promised to examine it in detail. (The current week-long holiday to celebrate the Autumn Moon Festival and "Double 10" National Day in Taiwan will probably delay this investigation.) The fact that one sample did not exhibit the noise suggests some level of sample variance. However, keep in mind that in the high end gaming systems where these PSUs will most likely see service, the problem will never be audible because even at idle, such systems draw more than 4A on the 12V line.

MP3 RECORDINGS

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

The M12 is similar in many ways to Seasonic's recently released (and recently reviewed) S12 Energy Plus series. The two product lines are based on the same electronic design, they are both 80 Plus certified, and they both come in very high capacities. And, they now share the title of quietest power supply. Both are very quiet at idle, and will not get noisier unless pushed by a very powerful system. In fact, the main differences between the two product lines are summed up in the names themselves: The Energy Plus is slightly more efficient, while the M12 (M for Modular) has modular cables.

If you've been dying for a quiet, modular, high power alternative to Antec's Neo HE, the M12 can certainly deliver. The M12 sports the best modular design that we've seen, and its powered by the high quality electronics that Seasonic is known for.

The drawbacks of the M12 are the same ones that we saw in the S12 Energy Plus: The high price and the huge capacities which are overkill for the vast majority of systems. The M12 is wonderful for a high end bar-no-expense gaming rig, but more conventional systems will do better with a model that is more suitably sized. There is one other drawback: The 60mm fan that doesn't turn off. Although it is not loud at minimum speed, it does contribute to noise, and a system that is powerful enough to cause the fan to start will need to be shut down to reset the noise level to the baseline level. The buzzing encountered with our samples can be annoying, but it's very specific to low loads, and it is not likely to be heard in any high power gaming rig, because the power demand even at idle will exceed 4A on the 12V lines.

There's no question that the M12 is a high end product, with a price tag to match. It is targeted very specifically at gamers and overclockers that consider modular cables a mandatory feature — and want to take advantage of Seasonic's excellent general power delivery, efficiency and acoustics. If you fall into this market segment, the M12 should satisfy just about perfectly.

*

SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended Units
Power Distribution within Six PCs
Seasonic S12-330 PSU, New Sleeved Version
Seasonic S12 Energy Plus: Efficient Power for Connoisseurs
Antec Neo HE 430 Power Supply
80 Plus hits Retail: Silverstone's Element Plus

* * *

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

Discuss this article in the SPCR Forums.



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