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TESTING
Testing was done according to our
unique heatsink testing methodology, and the reference fan was profiled
using our standard fan testing
methodology. A quick summary of the components, tools, and procedures follows
below.
Key Components in Heatsink Test Platform:
Test Tools
- Seasonic
Power Angel for measuring AC power at the wall to ensure that the
heat output remains consistent.
- Custom-built, four-channel variable DC power supply, used to regulate
the fan speed during the test.
- Bruel & Kjaer (B&K) model 2203 Sound Level Meter. Used to
accurately measure SPL (sound pressure level) down to 20 dBA and below.
- Various other tools for testing fans, as documented in our
standard fan testing methodology.
Software Tools
- SpeedFan
4.32, used to monitor the on-chip thermal sensor. This sensor is not
calibrated, so results are not universally applicable; however, results should be comparable with other results on this test bench.
- CPUBurn
P6, used to stress the CPU heavily, generating more heat that most
realistic loads. Two instances are used to ensure that both cores are stressed.
- Throttlewatch
2.01, used to monitor the throttling feature of the CPU to determine
when overheating occurs.
Sound pressure level (SPL) measurements were made with the fan powered from
the lab variable DC power supply with no other noise sources in the room. The
ambient conditions during testing were 18 dBA and 22°C.
Load testing was accomplished using CPUBurn to stress the processor, and the
graph function in SpeedFan was used to make sure that the load temperature was
stable for at least ten minutes. The fan was tested at four voltages: 5V, 7V,
9V, and 12V, representing a full cross-section of its airflow and noise performance.
MEASURED TEST RESULTS
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Zalman CNPS8700 LED
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|
Fan Voltage
|
SPL
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Temp
|
°C Rise
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°C/W
|
|
12V
|
40 dBA
|
38°C
|
16
|
0.21
|
|
9V
|
33 dBA
|
39°C
|
17
|
0.22
|
|
7V
|
28 dBA
|
41°C
|
19
|
0.24
|
|
5V
|
24 dBA
|
45°C
|
23
|
0.29
|
Load Temp: CPUBurn for ~20 mins.
°C Rise: Temperature rise above ambient (22°C) at load.
°C/W: Temperature rise over ambient per Watt of CPU heat, based
on the amount of heat dissipated by the CPU (measured power of 78W).
SPL: Noise measured in dBA@1m distance with high accuracy B &
K SLM |
@12V: Performance was superb with the CPU temperature rising only 16°C
above ambient but at the cost of very turbulent and aggressive noise. Measuring 40 dBA@1m, it was a far cry from the maximum 33 dBA cited by Zalman... and completely unacceptable to SPCR.
@9V: The noise level dropped dramatically though it was still a curse on our sensitive
ears. The temperature difference was barely measurable, which was a good sign.
@7V: The fan was much more bearable but still annoying with an evident buzz
and slight rattle. Performance suffered by only two more degrees than at 9V.
@5V: The noise level finally crossed the border into what we would consider
quiet territory. At 1m in our quiet lab it was audible but unintrusive.
For a 67mm tall heatsink, the CNPS8700's performance was commendable. With
only a three degree difference between 12V and 7V, it's clear that Zalman could
have easily used a quieter, slower fan with minimal negative effect
on its cooling ability. There were no surprises with this fan. It's basically the one used in the 9700, and measures and sounds just about the same, within typical sample variance range. It's not a nice sounding fan except at the lowest speeds.
NOISE RECORDINGS IN MP3 FORMAT
Each of these recording starts with five seconds of "silence" to let you hear the ambient
sound of the room, followed by 10 seconds of the fan's noise at 5V, 7V, 9V and 12V. The five seconds of "silence" is inserted between each 10 second stretch of fan noise to help you remember the reference ambient.
HOW TO LISTEN & COMPARE
These recordings were made
with a high resolution, studio quality, digital recording system, then
converted to LAME 128kbps encoded MP3s. We've listened long and hard
to ensure there is no audible degradation from the original WAV files
to these MP3s. They represent a quick snapshot of what we heard during
the review. Two recordings of each noise level were made, one from a
distance of one meter, and another from one foot
away.
The one meter recording
is intended to give you an idea of how the subject of this review sound
in actual use — one meter is a reasonable typical distance between
a computer or computer component and your ear. The recording contains
stretches of ambient noise that you can use to judge the relative loudness
of the subject. For best results, set your volume control so that the
ambient noise is just barely audible. Be aware that very quiet subjects
may not be audible — if we couldn't hear it from one meter, chances
are we couldn't record it either!
The one foot recording is
designed to bring out the fine details of the noise. Use this recording
with caution! Although more detailed, it may not represent how the subject
sounds in actual use. It is best to listen to this recording after you
have listened to the one meter recording.
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