Seasonic is going after the high end gaming market with the M12-700, a modular power supply that has everything: 80 Plus certification, 700W capacity, four PCI express connectors, and Seasonic’s excellent reputation for noise. Oh, and a >$200 price tag to match. Is there an M12 in your future?
October 11, 2006 by Devon
| Seasonic M12-700|
80 Plus Certified 700W ATX12V 2.2 Power Supply
Seasonic is well known for its quiet, high quality power supplies. However,
as good as the internal electronics are, Seasonic has never had the glitz-and-gadget
coolness that seems to pervade the high end market. Their models are sedate
and do not announce their high end status visually. This is beginning to change;
all of Seasonic’s retail models have recently acquired cable sleeving. Still, their
bling factor ranks far below their UV-sensitive, titanium-plated competitors.
The M12 isn’t UV-sensitive (phew!), but it does add an oft-requested high end
feature: detachable cables. It also adds second fan, perhaps in response to
the criticism that their past models have recirculated hot air into the system.
The small, 60mm fan may trigger warning bells for those who have become used
to Seasonic’s benign noise signature, but rest assured that it is not supposed
to turn on until it is needed.
The M12 comes in three capacities: 500W, 600W, and 700W. These capacities —
along with the price — put the M12 squarely at the top end of the market.
These are gaming power supplies, designed to supply with the massive amounts
of power required (or perceived to be required) by two hot video cards and a
high end processor. The 700W model — the highest capacity we’ve ever reviewed
— even sports an extra two PCI Express connectors so that it can be used
in a Quad-SLI system without breaking a sweat.
Pricing is definitely top end: Market price for the 700W model is currently $200~220. The 600W model can be found for $165~190, and the 500 is at around $140.
Three models: 500W, 600W, & 700W.
Detachable cables: A first for Seasonic’s retail series.
Feature Highlights of the Seasonic M12 (from Seasonic’s
|FEATURE & BRIEF||COMMENT|
Dual Magnetic Amplifiers [Mag-Amp]
Cross regulation tolerance on +12V lines are improved from standard 5%
to 3% for optimized stability.
|Do you need 3% regulation?|
Most systems seem to do just fine with 5%, but overclockers may benefit.
|Double Forward Converter|
Advanced topology for the highest efficiency.
|So that’s how|
they do it…
Multiple +12V Outputs
Enhanced +12V current capability broadens utilization possibilities.
has it that the four +12V lines are not so independent…
High Reliable Aluminum Electrolytic Capacitors
Top quality components increase product life & reliability.
|Reliable components may|
be the most important feature in a power supply.
Super High Efficiency [up to 85%]
Optimal solution for low energy consumption, noise & heat.
|Not quite as efficient|
as Seasonic’s 80 Plus certified models, but still very, very competitive.
|Active Power Factor Correction|
Reduces line loss & power distortion.
|Standard on Seasonics|
for a long time, and increasingly common on other high end units.
Smart and Silent Fan Control [S2FC]
Smart thermal control to balance noise and cooling.
|The same excellent controller|
that made Seasonic’s past models so quiet.
|Super Quiet Dual Fan|
Cooling [12cm & 6cm ball bearing fan]
Reduces hot spots and improves cooling while remaining quiet.
"Dual Fan" don’t often go together in a power supply, but if anyone
can make one, it’s Seasonic.
| Soft-Mounting Rubber|
Reduces fan rotation & vibration noise.
|Soft mounting is generally|
good for noise quality.
|Ultra Ventilation [Honey|
Doubles the airflow & lifespan with half the RPM & noise.
|A feature since the Seasonic’s|
first 120mm PSU — the Super Tornado — two generations ago.
|Detachable Modular Cables|
Use precisely the cables you need, enhance system airflow and minimize clutter.
|This is the whole point|
of the M12 — without these it would just be an S12 with an extra fan.
|All in One DC Cabling|
Supports PC, IPC, workstation, server, & dual CPU systems.
|ATX12V & EPS12V compliant.|
Dual CPU and/or GPU systems are the only systems that are likely to demand
anywhere near the rated capacity.
|Universal Video Card|
Supports all multiple PCI-E video cards technologies.
|Longhand for dual / quad|
|Patented Easy Swap Connector|
Unplug the connectors easily & quickly.
|Useful… but less so|
now that IDE drives have almost disappeared.
|Universal AC Input [Full|
Plug & run safely anywhere in the world.
|Nice. Normal in retail|
Seasonic PSUs for several years.
|3 Year Warranty|
Our Commitments to superior quality.
but nice to have.
The feature list for the M12 is copy-and-paste identical to the feature list
of the recently released S12
Energy Plus, with only three minor changes to distinguish the two product
If some our comments in the table above seem familiar, it’s because they are.
If Seasonic can copy and paste marketing material, we can do the same. After
all — our opinion of the features hasn’t changed; why use different words
to say the same thing?
OUTPUT SPECIFICATIONS: Seasonic M12-700
100V ~ 240VAC @ 50/60Hz (Auto Range)
Maximum Output Current
The 700W capacity is backed up by a +12V line that is 56A strong. The rail
is nominally split into four rails, but this is only to satisfy the arcane requirements
of ATX12V — requirements that have been unofficially waived for over a
year. In reality, there is only a single +12V rail. Thanks to Johnny Guru for
excellent detective work in his review of the M12-700 for this discovery..
The exterior finish is classic Seasonic: Matte black, accented by the stainless
steel of the wire fan grills. In other words, it’s functional and it won’t look
out of place, but there is no bling to speak of.
One thing that is unusual is the size: The M12 is about two centimeters longer
than usual so that the extra fan can be accommodated. On top of that, the detachable
connectors require clearance beyond the back panel, increasing the required
amount of space even more.
Things don’t look too unusual from this angle.
The 60mm fan on the back panel is slightly off-center, where it blows directly
over the main transformer. A small note below the fan reads "Temperature
activated fan. Rotates only when required" — a fine detail that
should help cut the workload of help-my-fan-isn’t-spinning calls for Seasonic’s
tech support team.
The back panel holds a 60mm fan and cable connectors.
Note the two different styles of connector. The thin five-pin sockets are
and SATA plugs, while the two six pin sockets are for PCI Express.
The M12 uses the same basic circuit as Seasonic’s S12-500 and S12-600, as well
as the more recent Energy Plus models. The layout of the PCB is identical; so
it seems that the differences between Seasonic’s new models are only skin deep.
At heart, they all use pretty much the same electronics.
The electronics are almost completely unchanged from other Seasonic models.
The heatsinks match the ones found in the newer Energy Plus line, and are smaller
and block less air than the heatsinks in the original S12’s.
The heatsinks are the new ones found in Seasonic’s Energy Plus series.
Airflow through the power supply is quite good. On the whole, components are
widely spaced, and the new heatsinks do not impede air too much. Airflow should
be much the same as any other power supply with a 120mm fan, especially at lower
loads when the 60mm fan on the back panel hasn’t started. When it does come
on, the smaller fan serves as spot cooling for the main transformer and the
other electronics between the two main heatsinks. It will also prevent exhaust
heat from escaping back into the system — an effect that can be quite substantial
at higher loads.
There is a gap between the back panel and the PCB to make room for the fan
and the cable sockets.
An secondary heatsink provides spot cooling for the diode bridge rectifier.
Seasonic’s usual high quality parts.
Seasonic has not changed their fan manufacturer, so the fan is the usual smooth
sounding model from Adda. The 700W model gets the high speed version, as befits its capacity.
Fortunately, this fan sounds almost identical to the medium speed fans that
Seasonic has used in the past. It simply has a higher top speed.
This high speed Adda fan is actually fairly quiet when undervolted.
The secondary fan is also an Adda, model AD0612HB-A71GL — the 60mm equivalent
of the main fan. It’s noise character is unknown to us — generally we avoid
fans below 80mm because their small size means a high rotation speed —
and greater noise — is needed to generate significant airflow. However,
working in tandem with the 120mm fan, it may be able to spin slowly enough to
The 60mm fan is an Adda too.
Both fans are powered by the same fan header, which means that both receive
the same voltage from the fan controller. This seems to contradict Seasonic’s
claim that the 60mm fan will not turn on until it is needed — if both fans
receive the same voltage, they should both be spinning all the time, right?
Well, not quite. Seasonic has been quite smart, and has realized that the 60mm
fan starts at a higher voltage than the 120mm fan. By setting the default voltage
between the minimum voltages required by the two fans, they have ensured that
the 120mm fan will start consistently, while the 60mm fan will only start when
the voltage rises above its default level.
However, this approach has a major drawback: The voltage required to start
a fan is typically much higher than the voltage at which it stalls. This means
that, once it has started, the 60mm fan will keep spinning even when it is
no longer required. Seasonic has made it possible to delay when the smaller
fan starts, but they have not made it possible to turn it off once it has started.
A single fan header with a splitter cable powers both fans.
CABLES AND CONNECTORS
The individual cable sets are listed below:
There are more cable sets than there are sockets to plug them into.
Only the SATA, IDE, and PCIe connectors are detachable; the main ATX and AUX
connectors are permanently attached, as they are guaranteed to be in use. All
of the cables are sleeved in black vinyl mesh, and the IDE plugs have grips
for easy removal.
Connectors of every type are plentiful. There are a total of eight SATA plugs,
ten IDE plugs, and four PCIe plugs to choose from. Lower capacity models
of the M12 only have two PCIe connectors, but even that is two more than anyone
needs for a quiet system. A word to the wise: A system that uses all four PCIe
plugs will not be quiet, no matter how hard you try.
There is good news and bad news about Seasonic’s implementation of detachable
cables. The good news is that it is foolproof: It is completely impossible to
plug the cables in the wrong way, which makes it much harder to accidentally
fry a valuable component. The bad news is that there will always be at least
one permanently attached cable that is not in use. Seasonic has included the
4-pin and 8-pin +12V connectors on separate cables, which means that one will
always be spare. This seems a little odd — why not just use a 4+4-pin plug
like most power supplies? [Editor’s Note: One of Seasonic’s technical representatives told me some time ago that this is actually one of the requirements of the EPS12V requirements — separate plugs for each of the Aux12V connectors.]
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
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:
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
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)
Intake Temp (°C)
Exhaust Temp (°C)
Temp Rise (°C)
|Fan Voltage (V)|
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.
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
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
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.
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
The one meter recording
The one foot recording is
More details about how
we make these recordings can be found in our short article: Audio
Recording Methods Revised.
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
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
Power Distribution within Six PCs
Seasonic S12-330 PSU, New
Seasonic S12 Energy Plus:
Efficient Power for Connoisseurs
Antec Neo HE 430 Power Supply
80 Plus hits Retail: Silverstone’s
* * *
Much thanks to Seasonic
for the opportunity to examine this power supply.