Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

Seasonic PRIME Titanium Efficiency
(~25ºC Ambient Temperature Testing)
% Titanium
650TD 750TD 850TD
10 90% 93.1% 93.2% 92.9%
20 94% 94.2% 94.2% 94.1%
50 96% 96.3% 96.2% 96.1%
100 91% 94.8% 94.8% 94.8%

We usually expect to see an 80Plus Titanium certified unit to borderline pass or even fail the certification requirements during our testing. This is because we are supplying 230V AC to the unit and most models have been optimized for an 110V AC input, as the certification requirements are significantly lower and makes it slightly easier for the designer to meet them. Seasonic positively surprised us because all three of the new PRIME Titanium units are extremely efficient, easily meeting the stricter 80Plus Titanium performance requirements with an input voltage of 230V AC. The top efficiency of all three units is ~96.2% when operating at 50% capacity, with a nominal load range (20%-100%) efficiency average of 95.1% (650W model) to 95.3% (750W/850W models). The low load efficiency with the PRIME Titanium PSUs operating at 10% capacity is above 84.5%, which is much higher than the peak efficiency many low-cost PSUs can hope to achieve. Still, the efficiency of the units once they reach 20% capacity is so high that the thermal losses actually seem to drop instead of increasing.

Please note that we had the hybrid fan mode disabled during our testing in order to showcase the low load noise levels with the fan turned on. With the hybrid mode turned on, the fan starts when the load reaches about 20-25% of the unit’s rated capacity.

The internal operating temperatures of the Seasonic PRIME Titanium are very low, which is to be expected with such an efficient design. The cooling fan initially appears to have a “ladder” behavior, increasing its speed in steps in relation to the load, but the thermal control circuit is actually linear. When the units are operating in an ambient temperature environment, the speed increases are just very small in relation to the fan’s operating range, which appears as a step-like behavior on a chart. The fan of any of the three units did not even reach 50% of its rated speed at maximum load under these operating conditions, operating way below its optimal range and barely reaching audible sound pressure level figures.

The hybrid fan mode is the only thing that does not make much sense with these three units. If the setting is set to off, the fan will start as soon as the PSU is powered on regardless of the load, but will still retain its minimum possible rotational speed until the thermal control circuit decides that it needs to spin faster. The fans of the PRIME Titanium units are inaudible when running at such low speeds. If the setting is turned on, the fans will start before the point they become audible with the setting turned off, meaning that there is no practical difference at low loads whether the fan is spinning or not. Considering that the fans of the units are inaudible when spinning at their minimum speed, it might be wise to keep the hybrid mode turned off. Lower operating temperatures can only increase the longevity of a PSU, even one as good as this one.

External and Internal Design Hot Test Results: Hot Box at 45-50ºC
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  • Laststop311 - Monday, April 10, 2017 - link

    I have a crucial mx 300 2TB for my storage and im waiting for 256GB optane SSD's to switch that over the boot drive and most used apps. I am not bothering with the caching version.
  • Laststop311 - Monday, April 10, 2017 - link

    o and i got it the 2tb ssd or 476 out the door here on sale
  • Laststop311 - Monday, April 10, 2017 - link

    no optical drive all drive cages removed for max airflow as well. I am the most proud of the build if u cant tell it's in my bedroom and i cant even hear it when i sleep. I'm so ecstatic.
  • Laststop311 - Monday, April 10, 2017 - link

    email me is u need help building this exact PC i promise there isnt a single person that wont be thrilled to have it jtarmeni1 (AT) (g)(mail(dot)com
  • Laststop311 - Monday, April 10, 2017 - link

    and dont bother with any ram above 3400mhz cas 14 3400mhz provides the best performance of all ram trust me i tried.
  • Laststop311 - Monday, April 10, 2017 - link

    the higher timings negates the performance and u spend more money, until they release 3600 cas 14 3400 cas 14 is the fastest
  • jo-82 - Monday, April 10, 2017 - link

    Am i the only one who finds 40 dB(A) @ 50% load (300W) out of the question?
  • Exodite - Tuesday, April 11, 2017 - link

    No, though I've come to the realization that you have to treat dB measurements as an internal metric for each article/site and not an universal truth.

    Variations due to measuring methodology, equipment and ambient sound level means dB measurements don't compare well across different reviewers/sites.

    Personally I prefer always-on equipment such as case and CPU fans to idle <20 dB and load noise, including GPUs, <30-35 dB so I reckon I'm in a similar position. Some reviewers, a surprising number even, have ambient sound levels higher than I'd tolerate even a fully loaded computer to make.

    More than that dB measurements fail to pick up sound characteristics. A great fan/cooler can be tolerable at higher dB levels because the only real sound tends to be from moving air, a soft "whoosh" if you will. The bad ones add ticking or grinding, for example I find the default Radeon fans to be completely intolerable at any load level. And even fanless equipment may be saddled with electrical noise that cut right through the case and ambient sound.

    In the end you really have to listen yourself to make a judgment and if that's not an option rely on a comparison to a unit you've heard yourself that's been tested by the same reviewer/under the same conditions.
  • Laststop311 - Tuesday, April 11, 2017 - link

    u wont be disappointed with a 750 watt seasonic prime. The fans dont even turn on until u hit 375 watts of power draw. Which basically means even maxing out ur cpu isnt enough to turn them on. You have to play a game and most games utilize like on averahe 80% of ur cpu and yea the fan on the psu is dead silent when it does spin. Concentrate and getting a quiet GPU. Get a triple slot with GPU with a HUGE heatsink and adjust the fan profile till right before you hear it. The highe heatsink makes yup for the large speed. I really like the triple slot gpu's with 3x 100mm FDB fans plus nh d15s noctual cooler using liquid metal paste and the awesome titanium rated seasonic psu. With 11 blade fractacl venturi high flow fans with thge drave cages inside removed. this way you need no static pressure so even on low speeds the air pushes deep into the case and since its 2x 140mm inttake 1 140mm GP14 fractacl exhaust yu get positive pressure meaning you only have to clean the case once every 2-3 years as only microscopic particloes get in. You can run the fasn all at the lowest speed before you hear it even with good overclocks. I sleep right next to the bed thats how quiet it. Seriously I will facetime you thru the build for 45 buvks an hour. And teach you all the tricks to deaden every vibration while keeping all ur components in the 70C's or less
  • Laststop311 - Tuesday, April 11, 2017 - link

    its the best build in the world if u want silence and still a lot of power, yes no9t the max power but if you all u care about is gaming at 1080 with 144hz which imo is better then 2560x1440 and 60hz by a far as well a 4k at 30-60hz by far

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