Zalman CNPS9900DF Dual Fan Flower Heatsink

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

Stock Fan Measurements

As we mentioned earlier, the fans are attached using metal stands so they lack the traditional square frame housing found on most case fans. However, the impeller and blades are similar in size to standard 120/140 mm models. The CNPS9900 MAX was equipped with a 1600 RPM fan while the CNPS9900DF uses lower speed variants.

Zalman CNPS9900DF: Stock Fan Measurements
Voltage
Speed (Front)
Speed (Center)
Combined SPL@1m
12V
1060 RPM
1370 RPM
32 dBA
9V
870 RPM
1070 RPM
26 dBA
7V
710 RPM
830 RPM
20 dBA
6V
610 RPM
700 RPM
17 dBA
5V
520 RPM
550 RPM
14 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

We're not crazy about different size fans on one heatsink due to possible intermodulation effects on noise. It's also inefficient if each fan's individual noise output is significantly different, i.e. one fan drowning out the other when set to the same voltage/PWM setting. The CNPS9900DF wasn't bad in this regard despite a 300 RPM difference at full speed. The center 140 mm model was the faster fan and thus produced more noise, though subjectively, it sounded better.

At full speed the pair generated a pretty loud 32 dBA@1m but if you're noise conscious, the fans can be reduced down to about 14 dBA@1m through voltage control; the starting voltage was 4.8V and 4.0V for the front and center fan, respectively.

The quality of noise emitted by the 9900DF was simply put, bad. It generated tonal peaks at multiple frequencies in the 150 to 1,000 Hz range. It made an unpleasant, harsh drone. At lower speeds, there was also an underlying "wobble" to the sound, as if one of the fans was off-kilter. This effect was audible in each individual fan, but particularly in the front model, so it wasn't a result of interaction between the two. The overall acoustics were very disappointing as Zalman's previous model, the CNPS9900 MAX, actually had a fairly nice sounding fan for a change.

The cooler's mismatched fans contributed to the 9900DF's poor acoustics. Both fans had noticeable tonality but they also had distinctive noise signatures. The front fan had a harsher, lower pitch profile, and was the main source of the aforementioned "wobble" effect. The center fan had a smoother profile with a higher pitch but it produced a dry, undesirable hum.

Test Results

Zalman CNPS9900DF vs. CNPS9900 MAX
Fan Voltage
CNPS9900DF
CNPS9900 MAX
SPL@1m
°C Rise
°C Rise
SPL@1m
12V
32 dBA
43
41
32~33 dBA
9V
26 dBA
46
42
26~27 dBA
7V
20 dBA
48
45
20 dBA
6V
17 dBA
50
47
16 dBA
5V
14 dBA
53
49
13 dBA
°C Rise: Temperature rise above ambient (22°C) on load.

To our surprise, the CNPS9900DF turned out to be less proficient than its single fan predecessor, the CNPS9900 MAX. Despite its second fan and larger heat dissipation area, the DF performed 2~4°C worse depending on the fan speed.

The main culprit for its disappointing performance was the heatsink's concave base. Despite tightening the cooler to the point that the bolt threads were almost completely stripped, the thermal compound pattern left behind showed poor contact, with large tendrils of TIM all over the surface, which only happens when there are significant air caps between CPU and heatsink base. When good contact and pressure is achieved, most of the compound is squeezed out toward the sides; that obviously didn't happen here.



Previous 1 2 3 4 5 6 Next

Cooling - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: