Seasonic X Series XM2 1250 W Review 25

Seasonic X Series XM2 1250 W Review

Efficiency, Temperatures & Noise »

Test Setup



All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Rigol DS2072A oscilloscope kindly sponsored by Batronix, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal three more oscilloscopes (Rigol VS5042, Stingray DS1M12, and a second Picoscope 3424), and a Class 1 Bruel & kjaer 2250-L G4 Sound Analyzer which is equipped with a type 4189 microphone that features a 16.6-140 dBA-weighted dynamic range. You will find more details about our equipment and the review methodology we follow in this article. We also conduct all of our tests at 40°C-45°C ambient to simulate the environment seen inside a typical system with a higher accuracy, with 40°C-45°C being derived from a standard ambient assumption of 23°C and 17°C-22°C being added for the typical temperature rise within a system.

Rigol DS2072A kindly provided by:

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range.







5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.


Hold-up Time

Hold-up time is a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time the system can continue to run without shutting down or rebooting during a power interruption. The ATX specification sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



Seasonic's unit achieved a very long hold-time, which also paves the way for the competition as some of those units failed to even reach the minimum allowed hold-up time.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when it is first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays, and bridge rectifiers; as a result, the lower a PSU's inrush current right as it is turned on, the better.



Registered inrush current was as expected given the increased capacity of the bulk caps Seasonic used.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the SS-1250XM2. The applied load was equal to (approximately) 10% - 110% of the maximum load the PSU can handle, in 10% steps.

We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail could handle while the load on the minor rails was minimal.

Voltage Regulation & Efficiency Testing Data - Seasonic SS-1250XM2
Test12 V5 V3.3 V5VSBPower
(DC/AC)
EfficiencyFan SpeedFan NoiseTemp
(In/Out)
PF/AC
Volts
10% Load8.446A1.973A1.975A0.985A124.68W88.74%1220 RPM40.2 dBA 37.21°C0.879
12.210V5.056V3.338V5.061V140.50W 39.53°C230.4V
20% Load17.921A2.964A2.969A1.185A249.57W92.17%1220 RPM40.2 dBA 37.57°C0.932
12.205V5.050V3.332V5.049V270.77W 40.05°C230.2V
30% Load27.760A3.464A3.483A1.389A374.71W93.05%1220 RPM40.2 dBA 39.03°C0.956
12.199V5.046V3.328V5.035V402.68W 41.95°C230.3V
40% Load37.590A3.961A3.970A1.590A499.47W93.34%1350 RPM40.8 dBA 39.60°C0.969
12.193V5.040V3.323V5.021V535.10W 42.99°C230.2V
50% Load47.092A4.966A4.974A1.795A624.44W93.21%1960 RPM46.1 dBA 40.78°C0.976
12.188V5.035V3.316V5.006V669.95W 44.64°C230.1V
60% Load56.609A5.961A5.978A2.000A749.37W92.98%2350 RPM52.7 dBA 41.93°C0.981
12.182V5.030V3.311V4.993V805.95W 46.47°C230.1V
70% Load66.127A6.966A6.988A2.206A874.23W92.55%2480 RPM54.8 dBA 43.18°C0.984
12.176V5.024V3.304V4.978V944.65W 47.98°C230.0V
80% Load75.660A7.966A8.005A2.415A999.15W92.06%2480 RPM54.8 dBA 44.37°C0.985
12.170V5.019V3.298V4.964V1085.35W 49.58°C230.1V
90% Load85.642A8.469A8.534A2.420A1124.14W91.74%2480 RPM54.8 dBA 44.83°C0.986
12.162V5.014V3.293V4.955V1225.30W 50.33°C230.0V
100% Load95.361A8.985A9.037A3.040A1249.00W91.27%2480 RPM54.8 dBA 46.02°C0.987
12.157V5.009V3.287V4.931V1368.40W 51.77°C229.9V
110% Load105.703A8.995A9.048A3.045A1373.88W90.79%2480 RPM54.8 dBA 46.62°C0.987
12.149V5.004V3.282V4.921V1513.25W 52.74°C229.8V
Crossload 10.096A18.018A18.003A0.000A150.98W82.07%2395 RPM53.5 dBA 44.35°C0.905
12.217V5.027V3.290V5.068V183.96W 49.05°C230.4V
Crossload 2104.108A1.002A1.003A1.001A1278.05W91.60%2480 RPM54.8 dBA 44.97°C0.987
12.148V5.018V3.309V4.994V1395.30W 50.46°C229.9V

With deviations within 0.5%, +12V voltage regulation was incredibly tight. Its other rails also performed very well. The PSU was incredibly efficient in all tests, and we would easily confuse its results with those of a Platinum-certified unit if we weren't aware of its actual certification. Seasonic's changes have obviously made a significant difference in terms of efficiency. We were only let down by its increased noise output with 60% load and above since the cooling fan had to operate at full speed to move hot air out of the enclosure, which produced more than enough noise to displease users who can't tolerate noisy components.
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