Seasonic M12 500W | Reports

By: Jonathan Kwan
January 4, 2007

It's not everyday when you need an exotic power supply such as a Tagan TurboJet 1100W power supply; we can trace its roots back to the simple reason that exists behind all this -- the fact that not everyone has a Core 2 Quad, a couple of 8800GTX and an array of hard drives humming in their cases for such a large power requirement. While most people would be more than glad to own a unit for whatever purposes, many of the APH readers asked me to review a quality midrange power supply that's suitable for the masses. So, what aspects are the priorities of power supplies residing in this part of the market? Besides standard requirements such as power, efficiency, and general quality, we would also see if it can achieve objectives such as how silent it is as it is as powerful, as well as for midrange consumers -- the price (Or how it is justified for a reasonable cost). There's maybe a handful of quality power supply manufacturers out there, but the Seasonic M12 500W that's been sitting inside my case for the last few weeks is something to be in the spotlight today.

Our review unit came in a relatively large box using UPS Ground from Seasonic's office in the US. It came on December 15, 2006, according to our records, but what the heck -- this makes the Seasonic M12 500W the first review of 2007. Yay!

Oh, and by the way, if you are thinking about the same thing as me, the M12 may sound like a gun model, but last time I checked, Seasonic does not make firearms!

Upon opening the cardboard shipping box, it appears to us that the Seasonic M12 500W came in retail packaging. With a flap box sealed by a thin layer of clear plastic wrapping, there's nothing fancy here -- but we'd also like to say it's great no-frills packaging that's in fact very practical and easy to open.

Seasonic is one of the oldest and most reputable power supply makers amongst computer enthusiasts. Well known for high efficiency, high quality, and quiet power supplies, chances are that you've used one whether you know it or not -- they sell PSUs under their own name as well as OEM for companies such as Antec and Corsair. Seasonic's approach focuses primarily on the primary purpose of the power supply, and to achieve its primary objective without being loaded down by other things and missing its main goal. Since the priority of this main goal is very high, how will the Seasonic M12's approach to the modular power supply market achieve the primary purpose of this product?

Out of the box, product brochures of the M12 and the company’s S12 are included along with a warranty information sheet. A manual and a "Powered by Seasonic" case badge also came out of the package.

The Seasonic M12 itself is tightly wrapped in a custom bubble envelope with a few attached cables out on the side. The following included connectors along with quantity and attachment information as listed below:

1x Main motherboard 20+4 Pin (Attached)
1x ATX12V 4 Pin (Attached)
1x EPS12VEP 8 Pin (Attached)
1x FDD 4 Pin - Dual connectors (Detached Molex Converter)
4x Molex 4 Pin - Total 10 connectors (Modular)
3x SATA 4 Pin - Total 8 connectors (Modular)
2x PCIe 6 Pin (Modular)

Notice that the 4 pin ATX12V block and 8 pin EPS12VEP block are separate cables. This is a standard requirement, therefore a single 4+4 pin block is not implemented instead. All cables are sleeved.

Before we examine the physical aspects of Seasonic's M12 500W power supply itself, let's take a look at the voltage rails. A total of 24A of power can be provided on the +3.3V rail, 30A on the +5V rail, and quad +12V rails at 18A each. Interestingly, when compared to the Tagan TurboJet 1100W, that unit also has 4x12V rails at 20A each. A question arises as you might wonder, how can the ratings be so close together according to specifications, while the wattage rating is so far apart?

A quick glance beneath the +12V table shows that the 4x+12V rails can only provide up to 38A of power. Mathematically speaking, 18A*4 is 72A, not 38A. A look inside the power supply unit itself (We'll go over this shortly after) reveals that the Seasonic M12 500W does not really have 4x12V rails; but instead theoretically implemented by splitting it into four "virtual" rails. This provides as advantage as certain components such as high power requirement graphics card can significantly load down on a single +12V rail; and with a quad "virtual" rail would suit better for this purpose. As all things come at a cost, you will not receive the advantage of quad independent rails in regards to aspects such as electrical noise.

This moves back to our topic of 18A*4 rails for a total of 38A power. What that really means is each of the quad virtual rails can provide up to 18A of power, but the combined +12V single rail prior to the split can only provide a total of 38A of power. Mystery solved!

A physical look at the Seasonic M12 500W. The humble approach to power supplies proves interesting -- no fancy LEDs, no shiny coating -- just matte black with specification stickers on the side. As that lady in The Simpsons who owns a restaurant Homer met after killing the alligator in Florida would have said, "I like it". A RoHS sticker indicating Seasonic's RoHS compliance resides on the left of the specifications label we've just examined moments ago.

The open honeycomb mesh at the back is quite common with power supplies implementing a 120mm fan at the bottom to create less air resistance during heat exhaustion, since no fans are installed to directly draw out air at the back. A small switch takes its place beside a male power input jack as a standard amongst PSUs. A voltage switch is not present because the Seasonic M12 will automatically detect voltage and adjust accordingly without manual user intervention.

The main 120mm Adda fan sits behind a fan grill at the bottom. Interestingly, the fan grill is actually installed on the inside of the power supply under the metal sheet instead of over it. The 8 ring fan grill should allow adequate airflow into the power supply with minimal resistance.

A second Adda fan sized at 60mm resides at the back of the power supply for additional cooling when required. Over the last few weeks, I haven't seen the fan turn on yet -- signifying not enough heat is being or has been generated for this requirement. Seasonic designed the fan to activate at a higher voltage than the main 120mm fan, as this is essential when connected to the same header internally -- otherwise both will turn on at the same time.

Unfortunately, the voltage requirement for activation and deactivation has a large gap in between, meaning that the fan will remain on once it turns on until your computer has been turned off and back on again. The logic is very simple -- similar to Chemistry, the activation energy is always significantly higher than the energy required to keep it going. What it means is that once the fan has been turned on, as long as a steady voltage that's now below operating threshold will allow the fan to continue spinning because it has momentum to keep it going. Because they are connected to the same header as the 120mm fan, the voltage going through can never be low enough for the fan to deactivate, otherwise the main 120mm fan will also turn off. Therefore, in order for the 60mm fan to deactivate, there must be a long enough voltage interruption, which is only achievable by turning the power supply off and back on again. In other words, your computer must then be turned off and turned back on.

A shot into the power supply, well, kind of. I would have had photos of the actual inside... but remember that SD card that died a while back and took my 700MB worth of photos with it? Let's blame that again. Sigh.

I was going to crack it open again yesterday, seeing that it's always worth it to void the warranty in these reviews -- but I realized the tight cabling was quite restrictive and nothing is really movable; even though the Seasonic M12 is modular, a series of cables such as the main motherboard connector is non-detachable. What I tried to do was place it on the side of my case and remove the screws in attempt to take the cover off. After my Seasonic M12 500W came crashing down onto my Asus P5W64-WS Professional (The M12 is definitely not a light power supply), chances are that it's not the time to open it for the photos. I got stuff from my notes to go over though.

Oh, and my motherboard is still fine!

If you take a look inside, you'll see the Dual Magnetic Amplifiers. The "Mag-Amps" are to implement better control over voltages for better accuracy in voltage output on the +3.3V, +5V, and +12V rails. Although I've seen high end power supplies with a voltage regulation of within 1% (+/-), how achievable that is could be disputable -- and the Seasonic M12, a modular power supply, has a voltage regulation of +/- 3%. Intel specifies +/-10%, however; most quality power supply manufacturers have at least a +/- 5% voltage regulation.

Seasonic's website mentions the Double Forward Converter Design. Being that, it's quite similar to the Seasonic S12 -- the non-modular version -- for maximum performance and efficiency of power supply units. Seasonic also mentions in regards to its High Reliable Aluminum Electrolytic Capacitors. In terms of grammar, it doesn't sound all that well, but anyways, what they are trying to say is that their M12 only has quality capacitors for performance and stability. And of course, no exploding capacitors.

The difference between Seasonic's S12 and M12 (M for modular, as most would suspect), besides the name and modular design, is minimal. A bit of research indicates that those who tested the S12 is loaded with basically the same internal components -- the M12 incorporates an extra 60mm Adda fan at the back for additional cooling and slightly longer.

To be honest, this power supply is not big in terms of physical size at all, especially after playing with the Tagan TurboJet 1100W last month.

The Tests

The Tests section has been removed because it does not comply with APH Networks' power supply review procedure established after the initial publication of this review.

Let's talk about noise. When I reviewed the Tagan TurboJet 1100W last month, I mentioned about a constant, relatively high pitched and clearly audible noise that the power supply generates even though my computer is not pushing it by any means. The implementation is quire different in terms of fans, however. Due to large internal components inside the Tagan, these type of power supplies typically generate more heat and thus require two 80mm fan perpendicular to the components inside to create a strong airflow pattern. Two 80mm fans are used also because of limited amounts of room within the unit.

Seasonic M12's series starts off at base 500W model and has a 600W and 700W variant as well. While 600-700W by today's standard is just moderate to moderately high spec'ed, it's quite interesting because of the implementation of a low-RPM 120mm fan horizontal to the components inside. In general, the Seasonic M12 generates a limited amount of heat as compared to high power units where a potential for immense heat generation is there. Due to this, the 120mm fan remains at a low RPM at all times -- and thus generating a minimal amount of noise. To apply, when I tried out the Seasonic M12 500W outside of my case, only a very faint buzz can be heard from less than three centimeters away. The rest is the sound of calm, very quiet breeze of air.

In general, the Seasonic M12 is a very quiet power supply.

Yes, the Seasonic M12 500W (Or, we can extrapolate and say all Seasonic M12 models) is definitely a quality power supply. From its humble-yet-reliable matte black look, it looks good by itself without external influence. The inside proves very interesting, and we can say that it's quality through the use of components as we mentioned earlier. The rear 60mm fan never turned on for us, but just keep in mind that once it's turned on, it will not turn off until a full power cycle is completed. Definitely a quiet power supply with accurate rails and just a slight voltage drop on its four virtual 12V rails under load. In terms of efficiency, the measured power usage is roughly 20W less than the Tagan TurboJet 1100W in our test scenarios. Is this a power supply worth purchasing? I would love to say, without a second thought -- Yes it is. Some of our friends has done tests on this power supply with professional test equipment, results are excellent -- pulling out rated power without issues, and with virtually no ripple -- absolutely clean power. The modular cables is an added plus -- even though the Seasonic M12 costs more than other power supplies with the same wattage rating, it's worth it for sure. Just remember, you get what you pay for -- and when you can get what you pay for, do so today!

Special thanks to Celia over at Seasonic for making this review possible.

Excellent power supply for the intended market. Clean, efficient, and quiet power supply. A few things here and there that's not really a totally huge complaint, but what the heck -- the Seasonic M12 500W is going to stay in my computer. It's something I would use, and in fact, I am using it right now!