Seasonic M12II-430 modular cable PSU

TESTING

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.4. 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, 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.

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.

TEST RESULTS

Ambient conditions during testing were 21°C and 20 dBA. AC input was 121V, 60Hz.

ANALYSIS

1. EFFICIENCY

The M12-II is 80-Plus certified, so we already know it's efficient. Our test sample reached its peak of almost 85% around 200~250W — right where a high end system is likely draw it's peak power consumption. At the lower end, it hit 66% at 20W and 75% at 40W, which are excellent results. Bear in mind that most systems spend most of their time idling within this range.

All these results are are within a percent or two of the results we got for S12II-380. There's little doubt the two models are based off the same circuit, though the S12II-380 had a slightly tweaked efficiency curve appropriate to it's lower capacity.

2. VOLTAGE REGULATION was excellent under ordinary test conditions, staying within ±3% though all the normal tests. The crossload test stressed things a little more, pushing the +12V line to as low as 11.56V, but this is well above the minimum acceptable voltage of 11.40V. The crossload test is tougher than any realistic load, and it's unlikely the lines will ever be stressed like this in real usage.

3. RIPPLE was higher than the recently reviewed S12II-380, but still well within the ATX12V specification, and modest compared to most tested power supplies.

4. POWER FACTOR was close to perfect across all loads, as is the norm for most power supplies with active correction circuitry. It wasn't quite perfect at the very low end, with a ratio of 0.93 at 20W, but this is a lower load than the M12-II will ever realistically face.

5. LOW LOAD TESTING revealed no problems starting at low loads, and power consumption with no load was stellar at 6.7W.

6. TEMPERATURE & COOLING

It's difficult to know exactly what to think of the cooling system in the M12-II. As noted, the cooling system in Seasonic's "II" series power supplies has been heavily tweaked, and there is now much more space for air flow freely through the power supply.

The thermal measurements didn't reveal much — results were in line with most other power supplies we've tested. However, there was a bit of an anomaly just as the fan began to speed up at ~200W: Here, the intake temperature dropped slightly as the increased fan speed suddenly began to pump hot air out of the test box at a faster rate. As a result, the thermal difference between intake and exhaust jumped suddenly and then decreased at the next point of measurement. It's not clear whether this anomaly can be attributed to the better airflow through the M12-II or not. In any case, there's little question this PSU can keep itself cool.

7. FAN, FAN CONTROLLER and NOISE

The fan controller started just below 4V, and climbed up to stabilize at 4.1V. This is normal behavior for Seasonics. The noise level at 4.1V was residual, measuring just barely above ambient. Qualitatively, the noise was a very low, smooth hum.

The fan controller began to increase at the 200W mark — a little lower than we would like, and earlier than Seasonic's other recent models, including the S12-II. Above 200W, the noise was beginning to become intrusive, and by 250W, it was definitely too loud. The fan controller seemed to react more quickly than usual for a Seasonic to changes in load, and the changes in fan speed were audible. However, once the controller picked its level, it stayed at a more or less constant voltage without audible wavering. The steeper noise to temperature (or load) curve could be due in part to the higher air turbulence noise that quarter-area plastic baffle over the fan must create at higher velocity.

Help support this site, buy from one of our affiliate retailers!

Search: All ProductsComputersPhotographyElectronicsSoftwareVideo GamesMoviesMusicBooksToysOfficeJewelry & WatchesApparelHealth & BeautyHome & GardenBabies & KidsFlowers & GourmetSporting GoodsMusical Instruments