Seasonic X-400 Fanless PSU

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COMPARISONS

The comparison table below shows the SPL versus Power Load data on all the PSUs tested in the anechoic chamber thus far. No comment is really needed.

Comparison: Various PSUs Noise (dBA@1m) Vs. Output in Anechoic Chamber
Model	90W	150W	200W	250W	300W	400W	500W	6-700W	850W
Seasonic X-400	<10 (immeasurable)						n/a	n/a	n/a
Enermax Modu/Pro87+ 500	11	11	11	11	14	20	23	n/a	n/a
Seasonic X-650	<10	11	12	14	16	31	31	32	n/a
Nexus Value 430	11	11	16	18	18	19	n/a	n/a	n/a
Antec CP-850	12	12	12	14	14	26	40	44	45
Seasonic M12D 850W	14	14	14	14	14	24	37	42	42
Enermax Modu82+ 625*	13	13	14	15	16	26	36	37	n/a
Coolermaster M700W	14	14	18	21	25	27	34	34	n/a
Chill Innovation CP-700M	15	15	15	15	17	30	34	34	n/a
Antec Signature 650	15	15	15	18	18	28	36	47	n/a
SilverStone DA700	18	18	18	18	23	32	35	41	n/a
Nexus RX-8500	14	14	17	22	28	32	32	33	33
NesteQ ECS7001	22	22	22	21	23	25	36	37	n/a
PCPC Silencer 610	20	24	24	24	24	30	40	50	n/a

Caution: Please keep in mind that the data in the above table is specific to the conditions of our test setup. Change the cooling configuration, the ambient temperature and any number of other factors, and you could change the point at which the fans start speeding up, as well as the rate of the rise in speed. The baseline SPL is accurate, however, probably to within 1 dBA.

CONCLUSIONS

Expectations ran high for the X-series 80 Plus Gold Seasonic power supplies, but our first reaction to the X-400 Fanless was admittedly less than enthusiastic. With the X-series already fanless to ~200W load and extremely quiet even after the fan starts spinning, why bother with a fanless one with all the potential headaches? It's a pleasant surprise — nay, a shock! — to find we were very wrong. The X-400 Fanless is the most impressive fanless PSU we've had the pleasure to examine, and we've examined just about all of them over the years. Electrical performance is stellar, the build extremely sturdy and well-executed, the all-detachable cables delightfully user-friendly, and finally, the sheer toughness of the product under extreme heat over long hours of excessive load is head, shoulders and entire torso above most of the other fanless units. Many a fan-cooled PSU would not survive our torture test.

The robustness of this power supply makes it possible to use it in systems with components that could demand the full rated 400W, unlike other fanless PSUs. In the past, users (including us) quickly learned to baby their fanless PSUs and keep them running cool in minimalist systems that drew very little power, perhaps no more than 30-40% of the PSU's rated power. Otherwise overheating and shortened component life could be expected. With the X-400 Fanless, these users will have to unlearn their past lessons, as the X-400 can pump out full power even under extremely hot conditions. This is not to say that thermal issues can be ignored; it's always up to the system builder to ensure adequate cooling and ventilation for components.

Another noteworthy point is that the X-400 Fanless happens to be the only sub-500W ATX12V power supply on the retail market that is 80 Plus Gold certified. That it is also fanless is pretty amazing. Yes, there are some lower power OEM 80 Plus Gold units employed by Dell and other big PC makers, but they're extremely customized for their application with short cables, etc, and not for retail sale. Every other retail-packaged Gold rated PSU is higher power, typically 500W and up. The main reason for the scarcity of lower power Gold models is due to user perceived need for higher power PSUs (a need encouraged, of course, by the PSU vendors) which makes lower power models harder to sell. There is a technical challenge, the difficulty of achieving high efficiency at very low load: 20% of 400W is only 80W. We've long noted how PSU efficiency drops dramatically at lower loads (and also at higher loads, but less so.)

With the solidly performing Silverstone ST45/40NF and perhaps the cheaper 400W FSP Zen, we had felt the fanless PSU market well served. There couldn't be much demand, anyway. But the Seasonc X-400 Fanless (and the soon-to-come X-460 Fanless) might be compelling enough to create a resurgence in fanless PSUs, not only among DIY silent fanatics but more mainstream builders and commercial system integrators as well. Backed by Seasonic's generous 5-year warranty, and their long history of solid customer support on high quality products, the X-400 could be the start of something like a silent fiefdom in the world of computer power supplies.

The Seasonic X-400 Fanless is a superb power supply. It's more than just an X-series PSU without a fan. It stands on its own as a product carefully engineered to serve its function, and it deserves our highest recommendation.

Seasonic X-400 Fanless Balance Sheet
Likes * >90% efficiency in typical use * Silent * Extremely hardy in hot conditions * Electrical performance is tops * Hardly any buzz even close up * Clever, innovative engineering * Great quality components & build * All modular cables * 5-year warranty	Quibbles * Price? (About the only thing we could quibble about... but then all fanless PSUs are pricey; finally, this is one that seems well worth the money.)

Much thanks to Seasonic USA for this review sample.

Seasonic X-400 Fanless: SPCR Editor's Choice Award

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SPCR Articles of Related Interest:
Power Supply Fundamentals
Recommended Power Supplies
SPCR PSU Test Rig V.4.1
X-650: Seasonic hits Gold
Enermax Modu87+ 500W 80 Plus Gold
Silverstone Nightjar ST45NF: 450W Fanless
Silentmaxx Fanless 400W MX460-PFL01 PSU (FSP Zen)

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