Antec CP-850: Unique PSU with Top Performance

Power
Viewing page 6 of 7 pages. Previous 1 2 3 4 5 6 7 Next

8. NOISE and FAN CONTROL

The voltage across the fan leads could not be monitored due to the use of PWM for the speed control. However, the reason we monitor the fan in the first place is for the noise, and SPL was well recorded here.

The noise level at startup was inaudible at 12 dBA@1m, at least from one meter distance. Only within about 6" of the unit could the fan or any electronic noise be heard. Amazingly, this sound level was maintained all the way to over 200W load. This is about as quiet as the Nexus Value 430 at low load, but the CP-850 maintains the low noise to a much higher power load, like the Seasonic M12D-850, 14 dBA@1m to over 300W.


The audio spectrum was benign and extremely low in amplitude to over 200W load
.

The first sign of any audible increase occurred at 250W, when the SPL went up to 14 dBA@1m. It was not until 400W load that the noise finally became plainly audible at 26 dBA@1m. Beyond that power level, the fan ramped up in speed more or less linearly, reaching the maximum of 44-45 dBA by 600W load. The character of the fan was generally good, with a bit of chuffing at some middle speeds, but no obvious or annoying tonalities.

9. COOLING

The CP-850 kept itself very well cooled, especially at the highest loads. It was at 10°C rise or lower through the whole range until the maximum power load. The mere 12°C rise through the PSU at full 850W (for about 20 minutes after 2-3 hours of continuous load testing) was very impressive. It is, in fact, a record: The next coolest PSU at that load was the Seasonic M12D-850 with 19°C rise. Most others anywhere near this power level climb way past 20°C rise, and most move into double digit temperatures past ~400W. It's probably safe to say that the superior cooling can be attributed to the combination of the powerful fan and the straight-through design which makes the airflow more effective.

Noise & Cooling: The Unique Case of the CP-850

In each of the three compatible Antec cases, the CP-850 mounts on the bottom, and the intake for the PSU is quite separate from the rest of the system. In the P193 and P183, the PSU intake vent is entirely separate, and in the model 1200, a direct path can be maintained to the opposite, wide-open, front vent. This means that our extreme hot box test conditions never apply to the CP-850; in other words, SPCR's test environment is unrealistically hot for the CP-850.

In view of this anomaly, an additional test was run at a single very high power load (a repeat of the crossload test) to consider the thermal, acoustic and efficiency consequences of operating the CP-850 in a much cooler environment.

The CP-850 was positioned so that it sat only partly atop the opening of the hot box, with its fan pointing away from the rising hot air. The panel facing the open hot box still got hot, as did the hot box, which almost immediately reached 55°C without the added benefit of the PSU's fan helping to exhaust the hot air.

Here's a summary and comparison of the results:

CP-850 Crossload Test (703W load) in Hot Box vs Open Air
location
AC
Efficiency
Intake
Exhaust
Hot Box
dBA@1m
hot box
874
80.5%
40°C
50°C
40°C
43
open air
871
80.7%
27°C
33°C
55°C
24

Out of the hot box, the temperature at the PSU intake plumetted 13°C, which dropped the exhaust temp to just 33°C. As a result, the fan did not ramp up in speed much; it measured only 24 dBA@1m here. This is at 700W load. AC power consumption was just a touch lower, not really significant, but perhaps attributable to lower operating temperature.

The above test data makes the CP-850 the quietest PSU ever tested, albeit in a non-standard way for SPCR. Still, this is much closer to the thermal environment of a powerful PC in an Antec P183, P193 or 1200 case. We can't say for sure that these cases would always provide such a low (27°C) temperature at the intake of the PSU fan, however. Your room temperature might will be higher than that in summer.

If the room temperature was under 25°C, it's quite conceivable that the in-case (P193, P193 or 1200) noise/power curve would look like this:

Antec CP-850 SPL (dBA@1m): In Hot Box vs. P183 case (guesstimate*)
Model
90W
150W
200W
250W
300W
400W
500W
700W
850W
in P183
12
12
12
12
12*
14*
20*
24
40*
in hot box
12
12
12
14
14
26
40
44
45
*These points are guesstimates; the rest were measured.


Previous 1 2 3 4 5 6 7 Next

Power - Article Index
Help support this site, buy the Antec CP-850 850 Watt CPX Power Supply Unit from one of our affiliate retailers!