M12D-850W: Seasonic joins the Power Race

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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.

  • Seasonic M12D 850W at various loads in anechoic chamber at one meter
    — idle to >350W (14 [email protected])
    — 400W (24 [email protected])
    — 500W (37 [email protected])

Sound Recordings of PSU Comparatives in the Anechoic Chamber

  • Antec Signature 650 at various loads in anechoic chamber at one meter
    — idle to 250W (15 [email protected])
    — 250~300W (18 [email protected])
    — 400W (28 [email protected])
  • Silverstone DA700 at various loads in anechoic chamber at one meter
    — idle to 250W (18 [email protected])
    — 300W (23 [email protected])
  • PC Power & Cooling Silencer 610 at Various loads in anechoic chamber, 22-37 [email protected]: One meter
    This recording ranges over three load levels - 40W, 250W, and 550W.
  • NesteQ ECS7001 at Various loads in anechoic chamber, 18-37 [email protected]: One meter

Older Recordings made with Sennheiser microphone in Live test room

Caution! It's important to understand that these recordings cannot be compared directly to the recordings made in the anechoic chamber. The live room in which they were made echoes and has a noise floor 4~8 dBA higher, the microphone has a much brighter sound quality and a different output level, and even the dBA measurements are wrong below ~25 dBA — they are higher by 2~8 dBA than they would be in the chamber with the new test gear. These recordings are here mostly for the record.
  • Enermax Modu82+ 625W at 20~150W output, 19 [email protected]: One meter
  • Enermax Modu82+ 625W at 300W output, 22 [email protected]: One meter
  • Seasonic S12 Energy Plus 550 at 0~150W, 20 [email protected]: One meter,
  • Corsair TX650W at 250W, 21 [email protected]: One meter
  • Corsair TX650W at 300W, 23 [email protected]: One meter

Ambient acoustics of the anechoic chamber vs the live room - Some of you will be interested to hear this difference. The recording begins with 8 seconds in the anechoic chamber, then 8 seconds in the live room, followed by a few seconds in the anechoic chamber. The SPL levels, as mentioned before, were 11 dBA and 18 dBA respectively. It's interesting to note that the hiss many SPCR forum members attributed to electronic noise is, in fact, not so; it's part of the live ambient, due at least partly, to reflections at higher frequencies in the room. This is obviously absent in the chamber. (However, we did make a change to a new microphone which also has considerably less noise than what we were using before the anechoic chamber, so some of the hiss in past recordings was caused by microphone noise.)


This is an interesting time in power supply development, with all the competition amongst brands and the continuing push to ever higher efficiency. The MD12D 850W is the first 80 Plus Silver model to come our way, but others are coming, and by the middle of next year, the Gold models should be in full production as well.

The M12D 850W is a worthy addition to Seasonic's lineup as its new flagship product in this age of superpower PSUs. The electrical performance of our sample was consistently excellent. Voltage regulation and AC ripple were outstanding. Energy efficiency was excellent, as befits a Silver 80 Plus model. Power factor and cooling were fine, and the build quality, classically Seasonic: Neat and tidy. The technological advancements such as DC-to-DC conversion for the sub-12V lines, high quality Japanese capacitors, and the superb Sanyo Denki fan are well worthwhile.

Acoustic performance is audibly if incrementally improved over all previous Seasonics, mostly due to the excellent low speed performance of its exclusive San Ace 120 fan, and the high efficiency which allows adequate cooling with very low fan speeds. The overall noise at low to medium-high loads is good enough to be tied for best place. By 400W, however, the noise level jumped and continued to rise quickly at higher loads in our test setup. As with most power supplies, the trick for silencers is to keep the power demand below the level where the fan controller pushes the speed up, and to keep the PSU as cool as possible.

It is no surprise that our high power test results don't match the 80 Plus test results which led to the M12D 850W 's Silver rating. The same holds true for the measured efficiency of every PSU we've tested over ~400W load. Our test procedure is much tougher thermally than the 80 Plus test, and power supply efficiency is strongly affected by operating temperature. Too low or too high, and efficiency suffers; there is an ideal plateau temperature range that enables PSUs to achieve optimum operation. We believe our test procedure to more realistically replicate the thermal conditions in actual use, although as discussed earlier, at >600W loads, the test box is probably not cooled well enough.

All in all, the M12D 850W is a very good achievement for Seasonic. The company has clearly joined the power race of retail PSUs but without abandoning the acoustics and efficiency conscious design that has kept its products at the top of the SPCR recommended PSU lists for so many years. Whether the hefty price tag is justified depends, as usual, on the perspective and needs of the individual consumer. For a modest power user ot typical silent PC enthusiast, definitely not. For a typical gamer, perhaps not; the sound effects of the games might drown out enough of the computer noise. But for a gamer who wants both high power stability as well as whisper-quiet performance from his PSU, the M12D 850W is a perfect fit.

Much thanks to Seasonic USA for this review sample.

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SPCR Articles of Related Interest:
Power Supply Fundamentals
Recommended Power Supplies
SPCR PSU Test Rig V.4
Antec Signature 650
SilverStone DA700 power supply
Enermax Modu82+ 625W
Seasonic S12 Energy Plus 550 and 650
NesteQ ECS7001 700W PSU: A Modular Twist
Corsair HX520 & HX620
Zalman ZM1000-HP: Quiet KiloWatt PSU

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