The +12V voltage remains exemplarily stable except for the very end of the diagram where it is more than 1% above the nominal value at max load. The +3.3V voltage looks good, too, but the +5V bottoms out under load. Anyway, this is not even half as bad as with the above-described FSP Epsilon PSUs, so the cross-load characteristics of this PSU look good overall.
The output pulsation isn’t strong. It is barely noticeable on the +5V and +3.3V rails and does not reach 50 millivolts on the +12V rail, the allowable maximum being 120 millivolts. That’s an excellent result.
The main fan is a 120mm AD1212HB-A71GL model running on two ball bearings and having a rated speed of 2200rpm. It is made by Adda.
The auxiliary fan is a 60mm AD0612HB-D71GL with a rated speed of 4500rpm.
The auxiliary fan was indeed motionless at loads below 260W. It started up only when the PSU had heated up to a certain temperature. It is about at the same moment that the speed of the main fan, which had remained constant at 810rpm, began to grow. The auxiliary fan didn’t stop when the load was reduced back to 250W but kept on rotating at a very low speed at which it did not affect the cooling or noise of the PSU.
At maximum load the speed of both fans is just short of their possible maximums: 2000rpm for the main one and 4200rpm for the auxiliary fan. Of course, this is not silent, but the M12 is generally quieter than most of its opponents. From the PSUs reviewed in this article it can only be challenged by the Cooler Master RS-850-EMBA in terms of noise. The Zalman ZM600-HP is about as quiet as this Seasonic.
The PSU has an excellent efficiency as you can expect from a product with an 80+Plus certification that requires 80% and higher efficiency at 20% from full load in 110V power grids. The maximum efficiency is 86%. The PSU overcomes the 80% barrier at a load less than 100W, but I perform my tests in a 220V power grid. In a 110V grid the efficiency is going to be lower by a couple percent.
So, the Seasonic M12 SS-700HM is a high-quality and quiet PSU that offers good electric parameters and all the connectors sufficient even for a serious gaming station. It is somewhat noisier than the less powerful Seasonic S12 SS-500HT and Zalman ZM460B-APS we reviewed earlier, so you shouldn’t hunt for the SS-700HM specifically unless you need its impressive 700W output power. But if you do need a 700W power source, this PSU is going to be a good choice. Don’t also forget about the detachable cables of the M12. The S12 series doesn’t have this feature.