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PC WATERCOOLING RESOURCES
A fair amount of web research was done on PC water cooling to bolster our knowledge.
One of the most detailed and comphensive we found is Martin's
Liquid Lab, described by Martin thus:
"This site is voluntarily built upon science, engineering, testing,
reviewing, and sharing information with my fellow water cooling community...
This site is funded entirely by my donated time, my donated testing equipment,
my donated testing hardware, community donated hosting, and donated parts
to test and review that comes from manufacturers, vendors, the community,
and myself. It is entirely a donation & volunteer community based effort
for the good of the community."
Other useful sites we drew upon include:
ASSESSING BASICS: PUMP ACOUSTICS
Even before considering any other components we felt it was important to get
a handle on any unfamilar noise-making components already on hand. There were
really only two: The three Gelid fans on the big radiator and the VisionTek
EK-SBAY DDC 3.2 PWM reservoir-pump combo. Fans are easily replaced if too noisy,
so we focused on the pump.
Neither VisionTek nor EKWB provide any acoustic data on the pump, which is
a Laing DDC-3.2. The primary specifications are reproduced here:
- Motor: Electronically commuted ball bearing motor
- Rated voltage: 12 V DC
- Power consumption: 18 W
- Maximum head pressure: up to 5.2m
- Maximum flow rate: up to 1000 L/h
- Maximum liquid temperature: 60°C
Pressure and flow rates are probably significant parameters in liquid cooling,
but we don't know quite enough to say whether these numbers are good enough
for the ~400W GPU + CPU loop we are considering. The maximum liquid temperature
specification of 60°C gave us pause. We've routinely seen GPU temperatures
at >80°C at full tilt in our stress testing of both video cards and the
recent gaming systems. If the pump in this system isn't rated for operation
with water hotter than 60°C, given that temperature in a liquid loop will
tend to equalize over time, does this mean we need to keep the GPU and CPU temperatures
below 60°C? The airflow needed for such a level of cooling could mean really
high fan RPM, and ultimately, a lot more noise than we want.
Putting this thought aside, the reservoir/pump was connected to the ASUS P8Z77-V
Pro that we've been using as a fan test platform for a couple years. The pump
is powered by a legacy 4-pin Molex connected directly to the PSU, and a second
lead is connected to the PWM CPU fan header of the motherboard. SpeedFan was
used to control the speed of the pump; the control arrangement worked just as
intended. The reservoir/pump was placed atop a soft piece of foam to prevent
the benchtop from resonating and adding to the pump noise.
The acoustics were not good. As we noted many times in the past, water pumps
for PC component cooling have a considerably worse acoustic signature than typical
DC axial fans used in computers. High tonality, especially in the upper registers
of the audio spectrum, combined with high vibration makes the VisionTek EK EK-SBAY
DDC 3.2 PWM reservoir-pump a very difficult component to use in a quiet PC.
Even at the slowest setting, it sounds reminiscent of a fan with ball bearings
about to fail there's a screechy quality that pervades, albeit at much
lower SPL (sound pressure level) than at higher speeds. We could use the elastic
suspension mechanical decoupling method that has served so well for HDD vibration
damping for years, but the screechy quality was so prevalent that even the damping
afforded by being wrapped in my hands did not change it. The absence of liquid
in the reservoir and pump may have exacerbated the noise, as water has acoustic
damping properties, but we were doubtful that it would have more than a marginal
Laing DDC-3.2 pump in VisionTek EK EK-SBAY DDC 3.2 PWM reservoir-pump
has PWM controllable speed range of 1225~4485 RPM.
It's easy to see the high tonality of the acoustic signature.
When set to the lowest speed, initially, the SPL is just 18 [email protected], but
after 20 seconds or so, the prominent screeching indicated by the peaks
450, 700 and 900 Hz begins, and the SPL actually rises to the same level
as at full speed. There may have been bearing damage here. The only way
to stop this noise was to press down hard with both thumbs directly atop
It was decided this is not a device we can effectively damp enough to use in
our quiet PC. And while it could have been an issue specific to our sample,
we did not want to waste time trying out more samples of the same model pump.
Better to jump ship early.
NOTE: The cause of this screeching noise
was identified. It is a resonance caused by the motor spinning in the empty
water reservoir. Filling it with water completely eliminates the noise. My apologies
for any negative effects of my original report on this reservoir/pump to EK,
VisionTek and/or Laing. See the Postscript dated 15/01/2015 and followed up
27/01/2015 on the last page of this article.
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