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REMOVING THE TOP GRILL AND FRONT DOORS
SPCR member theyangster
asked: Why don't you cut out the fan
grills?
Not knowing why I would want to, I looked around and found this
intriguing entry in the forums ("Case fan grills are evil..."), which convinced me that a grill close to
a fan
creates a lot of noise, and even if it isn't close it restricts airflow
considerably. Since I want my system to be both finger and paw proof,
as well as filtered, my options in this space were somewhat limited. I
decided to remove the top case fan grill only. Here is a photo. The
copper on the top left and at the top is the VRM heat sinks. The grey
blob at the top right is the temperature sensor of the fan controller
(described below).
Top fan
after the grill is removed; note VRM heat sinks.
The original P180 spoiler
provides safety, and fits without any mods over the soft-mount screws:
P180 top
case fan spoiler in place: no fingers or paws can get to the fan.
The discussion of air flow
restriction also led me to remove the front swing-out doors over the
P180 dust filters. This is easy: just flip each one open, then press on
the
tab near the top hinge. Removing the top fan grill and front doors is a tiny incremental change, but when the goal is very low noise levels and fan speeds, every bit helps.
Maybe some day if I'm feeling both ambitious
and destructive, I'll cut out most of the metal behind the dust
filters. The Kama Bay would also work better with much larger holes.
USING NOISE MAGIC NMT-3 FAN
CONTROLLERS
The same Edwood
thread in the SPCR forums that got me started on ducting
also talks about the Noise
Magic NMT-2
and NMT-3
fan controllers.
These handy
little devices are designed to be mounted on a corner of an exhaust fan
and control its voltage based on the air temperature. The
NMT-2 and NMT-3 ramp smoothly between 5V and 12V, from
30ºC-50ºC, and
28ºC-42ºC, respectively. I bought one of each to try
out on the top
case fan. Unfortunately the NMT-2 didn't work (the sense signal never
worked, and after a while every fan I tried would start but then slow
to a halt). The NMT-3 worked fine. After some experiments, I ended up
with it mounted on the front/far corner of the top case fan as shown in
the above photo, where it is sampling a mix of VRM and motherboard warm
air. This results in a speed of 720 RPM at idle, 810 RPM while
folding, and 860 RPM running two copies of CPUBurn. I found this
acceptably quiet, whereas other positions resulted in fan
speeds that were noisier than I liked.
One feature of
the NMT devices is that they spin up the fan at 12V then drop to the
variable voltage. I noticed while experimenting with Nexus fan voltages
and
speeds that these fans do not always start at 5V, although once started
they continue to run. Accordingly, I ordered another NMT-3 to control
the
power supply/hard disk fan in the lower chamber. This lets me run that fan
at 5V which results in an inaudible 545 RPM. This gently wafting breeze
is adequate to keep the disks below 38ºC and the power supply
heat
sink
below 45ºC.
As shipped,
the Nexus fan is designed to be run at 12V only, either from a 3-pin
cable providing sensing, or from a 4-pin Molex without sensing. It
didn't take me long to replace all that with a standard 3-pin connector
that could be attached to a motherboard plug, an NMT, or an AcoustiFan
voltage adjustor (of which I now had several). When used with an NMT,
the wiring is quite tidy, as shown in this photo of the lower chamber fan.
For the top case fan, I made the fan cable just long enough to reach
the NMT so it wouldn't dangle into the system.
Lower bay fan with NMT-3
installed and cabling tidied up.
I tried the
CPU and motherboard fans for a while at 12V, and although the cooling
was very good, I found it to be too loud. After a few experiments with
the AcoustiFan adaptors I had lying around, I settled on 720 RPM for
the CPU fan (103 ohms, 7.1V) and 840 RPM for the motherboard fan (78
ohms, 7.9V). With the case closed, the only fan I can hear is the top
case fan, and it is about the same loudness as the buzzing of the
desktop CRT.
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