Zalman CNPS9900 LED: The End of the Nines

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POSTSCRIPT: Zalman CNPS9900 LED Unshrouded

Jan 9, 2009 by Lawrence Lee

After some discussion with Zalman, we found it prudent to test the 9900 LED without the offending shroud to see what effect it would have on performance and acoustics. With the fan exposed on the sides, the fan has better access to fresh air and there is more space for heat to dissipate. There was also the possibility that the shroud increased vibration.


Zalman CNPS9900 LED
Fan Voltage
With Shroud Without Shroud
SPL @1m
°C Rise
SPL @1m
°C Rise
39 dBA
34 dBA
32 dBA
29 dBA
24 dBA
23 dBA
16 dBA
17 dBA
Load Temp: CPUBurn for ~10 mins.
°C Rise: Temperature rise above ambient (21°C) at load.
°C/W: based on the amount of heat dissipated by the CPU (measured 78W); lower is better.

As it turns out, the unshrouded heatsink performed significantly better. Between 12V and 7V there was a 2-3°C improvement, but more importantly the CPU was 6°C cooler at 5V. With the fan puttering at low speed, it was difficult to exhaust hot air through the fins of the front side of the cooler. Removing the head-band allowed heat to escape in all directions.

Acoustics were also significantly improved at 12V and 9V. The character of the fan was unchanged but without the plastic encapsulating it, it sounded less 'hollow' — an effect that was amplified at higher fan speeds. There was barely a measurable SPL difference at 7V and 5V. The shroud was actually fitted very snuggly all around so there wasn't any noticeable change in the amount of vibration.

CNPS9900 vs. Top Coolers
@ 16 dBA
°C Rise
Thermalright U120E
Thermalright HR-01+
Xigmatek HDT-S1283
Noctua NH-U12P
Zalman CNPS9900 (Unshrouded, 17 dBA)
Zalman CNPS9900

The modified CNPS9900 at 5V perfomed much better, coming within a few degrees of the heatsinks we consider to be elite (at approximately the same noise level).

We're glad to see the CNPS9900 improve so much with a simple modification, but we believe a few more tweaks could make it an even better cooler. Without the shroud, it is a possible to use a bigger and therefore more efficient fan, preferably one that sounds smoother than Zalman typically uses. We also recommend narrowing the gap between the fan and the two sides of the heatsink. This can be done by making the fins larger, bending the heatpipes so they're closer together, or by simply utilizing a thicker fan.

With these new findings there may be some life left in the nines yet. Perhaps we'll see a CNPS9950 in the near future?

Discuss this article in the SPCR forums.

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