Enermax Eco80+ 500W PSU

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7. FAN, FAN CONTROLLER and NOISE

The fan controller holds the fan speed down until absolutely necessary. The fan didn't speed up significantly until the 200W output load was reached — above the maximum output for most normal usage patterns.

For once though, our highest praise isn't for the controller but the fan itself. If we had reservations about resonance and directional noise the last time we saw an Enermax fan, these concerns are no more; the noise profile of the Magma fan is outstanding. The highest SPL we measured was 33 dBA@1m, and this was only after 15 minutes at maximum output capacity. As a maximum noise level, that's an excellent result — only 3 dBA off our (somewhat arbitrary) 30 dBA line between noisy and quiet.

More importantly, at realistic loads, it remained well under that 30 dBA line, and often under 20 dBA. Other than certain dead-of-night exceptions, most environments are above 20 dBA, and thus noise below this level can be considered close to inaudible. The Eco80+ was below 20 dBA for all loads below 250W. Let me restate that in practical terms: In the vast majority of surroundings, for the vast majority of systems, the Eco80+ is likely to be inaudible.

Most impressive of all was the baseline noise level at 90W and below where I was unable to hear it in our anechoic chamber from our usual operating position of one meter. I had to hold my ear up to the unit — I would guess within eight inches — to hear the faint hum that indicated that the fan was spinning at all. Our SPL meter agreed — it did not rise above the 11 dBA ambient level, though a small increase was visible in the frequency graph.

Describing the quality of the noise seems a little moot, since it took great effort to get the fan spinning fast enough for noise quality to matter. So, as a footnote: The noise quality was smooth and generally low pitched. Unusually for a fan, the pitch did not increase much with speed, making the speed changes less noticeable.

11 dBA@1m / <90W. Yes, the fan is spinning here. The noise profile at 90W and below just barely registers in our anechoic chamber — quite an accomplishment. Most of the energy is concentrated below 400 Hz where we are less sensitive to noise. 19 dBA@1m / 250W. The frequency response of the fan is clearly visible by this time, mostly concentrated between 150 and 400 Hz. Above 2,000 Hz, there is almost nothing. 26 dBA@1m / 300W. The fan is now plainly audible. The frequency spectrum hasn't really changed too much, but there's a lot more energy in the 600 to 2,000 Hz range. This is where the ear is most sensitive, and accounts for the large jump in SPL reading. The fan is still mostly invisible above 2,000 Hz, and the few peaks that are visible here are hard to hear because of the masking effect of the lower frequencies.

One thing we've been examining with especially quiet power supplies is how the power supply performs outside the tough thermal conditions of our standard test. The recent popularity of cases that isolate the power supply from the rest of the system make this a relevant question, as the cooler intake air allows the fan to run slower and quieter. We examine this by rerunning some of the high load tests with the power supply in free air, away from the tough thermal conditions of the hot-box.

The results were quite dramatic: Even at full load, the SPL remained below 30 dBA, and at 400W, SPL dropped from 32 dBA@1m to 23, which soubd subjectively like half the noise. If you can keep the rest of your system stable and below 23 dBA at a sustained load of 400W, this reviewer will be very impressed (in fact, he'll probably invite you to write an account of how you did it for SPCR).

Enermax Eco80+ SPL: In Hot Box vs. Out
Power load	90W	150W	200W	250W	300W	400W	500W
in hot box	<11	12	16	19	26	32	33
out	<11	<11	12	16	20	23	28
Measurements are in dBA@1m

COMPARISONS

The comparison table below shows the SPL versus Power Load data on all the PSUs tested in the anechoic chamber thus far. It's difficult to rank them, as the measured SPL varies with power load. The Eco80+ is louder in our hot box at 300W than many of the others, but at below 200W, it's one of the quietest. Overall, the Eco80+ compares favorably with the best of the best for a <250W system; if it is used in a thermally advanced chassis with seperate air intake for the PSU, then that power ceiling would move up another 100W.

Comparison: Various PSUs Noise Vs. Power Output in Anechoic Chamber
Model	90W	150W	200W	250W	300W	400W	500W	6-700W	850W
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
Enermax Eco80+ 500W	<11	12	16	19	26	32	33	n/a	n/a
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

Although the fan curve of the Eco80+ seems to rise more quickly than some of the the other PSUs at the top of the list, its extremely low baseline noise and excellent noise character make it a superior choice for regular use scenarios (<250W). In practical terms, there is very little difference between the top six or so power supplies on this list. They're all pretty near silent.

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.

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