jessekopelman, dhanson865, and everyone:
PSU positioning and cooling configuration in a case has a very significant impact on the (fan)rpm-to-output load curve. Compared to SPCR test results, depending on which PSU, I'd guesstimate that the hinge point on a good PSU noise/load curve could be pushed right (or up) perhaps 100W or more.
The SPCR PSU test rig was designed at a time when there were no cases that provided an independent cooling zone for the PSU; almost all PC cases simply had the PSU on the top back, as per ATX tower spec, sucking in from above the CPU/GPU area and blowing it through the PSU. The hot air flow through the PSU got even worse and more direct when 120mm fan PSUs came on the scene. The SPCR hotbox tester was a good replication of a thermally realistic PC environment for the PSU.
Things have changed. Since I first started doing PSU reviews some 7 years ago, the number of P180-esque cases with PSU intake vents far from the CPU/GPU heat has grown in a big way. Especially recently. Antec has P183, P193, mini P180, 1200, 901, 300, 200. Silverstone has RV01, RV02, FT01, FT02, TJ10, TJ09, PS02. Coolermaster has Centurion 590, cm690 (3 v.), Gladiator 600, HAF922, HAF932, acts840, Cosmos (2 v.). Even Thermaltake has a handful - v9 (2 v.), Element (3 v.) Level 10, Spedo. Lian-Li: Armorsuit PC-P50R, pcx1000, PC-A71, PC-A10, etc..... Among HTPC cases, the concept seems to be implemented even more widely these days.
The point is this: The DIY aftermarket case makers get it. Whether through simple imitation chasing the P180's market success or a real understanding of the technical benefits, it doesn't really matter: Cases that provide cooler air for the PSU are now pretty easy to find.
In this context, SPCR PSU reviews may no longer be quite as uniquely useful as they once were. It may actually be preferable to test with the intake pulling normal room air, because that's the type of case most silencers can/should/would choose.
It might actually be time to stop testing PSUs in the hot box.
I would certainly not entertain fan mods in one of the very quiet PSUs; I'd simply make sure it never got exposed to high enough temperature for the fan to ramp up... by using a case with a separate air intake vent for the PSU.
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