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- Posted on
March 20, 2007, 5:23 pm
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Several replies already, but how running the 80mm fans you have at a lower
voltage - experiment and see. You can buy variable resistors that you
connect between the power source and your fan and you can adjust the
speed/noise. Personally, I have taken one of my spare molex (white, 4 pin
hard drive power) connectors and swapped the red and yellow wires over. I
plug my fans into that and they run at 5v instead of 12v. Obviously they
don't move as much air, but you can use more of them and you can't hear a
It may not be as much a matter of where as which fans,
though of course some places just don't stock anything
decent, they'd rather buy 50 cent fans and mark them up to
$5 than do same with a fan costing $1.5 in bulk instead.
If the fan is mounted in a non-vertical orientation while
running in the system, use a dual ball bearing fan. If the
fan is on the exhaust side of a heat source and is critical
in operation rather than partially redundant (like a PSU
exhaust fan), also another reason to choose a dual ball
bearing fan. For other uses such as case intake, blowing
into a heatsink, or a case exhaust, a good quality sleeve
bearing fan may suffice, but don't buy into marketing tricks
because there are many people deluded that brands like Yate
Loon or Arctic Cooling are good - they are not, they are
merely quiet for their short lifespans.
Quiet depends on the spec'd RPM at 12V, or you will have to
find a method of lowering voltage, restricting current, or
buying a less common industrial type of fan that has a 3rd
lead that is RPM control instead of another feature (more
common in a PC fan is RPM control, if there is a 3rd lead at
all which is not necessary for case fans, but rarely a
motherboard will require a CPU fan have RPM lead - and it is
very good to have one, though arguably far more important
the lower the quality the fan is... frankly I'd rather a
good fan w/o RPM feedback than a mediocre fan with it.
The major fan manufacturers, not PC parts relabelers, are
the best *sources* (buy source I mean origin, you'd still
buy them wherever you like to shop or by searching for a
seller). Known high quality brands include
Sanyo/Panaflo/NMB, Delta, Nidec, Comair, Sunon, et al.
Avoid the funny looking clear neon led gizmo'd fans, they're
practically all junk. It is possible to use some of them if
you buy a bunch and cherry pick the ones that work the best
then relube them periodically, but IMO most people don't
want to have to do that, a fan should last for the life of
the system and then some.
As mentioned above, pick the RPM for the resulting noise
level. Better quality fans are better balanced and tend to
have less flash on the blades, will often be quieter per CFM
over their lifetime. You will have to determine what
tradeoff of noise vs. airflow to make, as well as whether
your case or heatsink is contributing to the noise, as they
often do in stock form. To put it another way, if you want
to cool a P4 Prescott @ 4GHz with a $5 heatsink wearing a
Zen-Dragon looking fan guard and a 70 x 15mm fan on it,
it'll have to be noisey unless the room is very cold, the
fan just can't move enough air and be quiet doing so.
Generally a fairly quiet fan is one below 3000 RPM. Some
people are pickier than others, and it will depend on the
ambient noise level in the room. Others would consider a
fan relatively quiet under 2000-2500 RPM, ignoring any noise
created by turbulence from nearby obstructions, but others
will want fans even slower, even below 1200 RPM if possible.
We can't really predict which type of person you are or
which environment you have.
If you can't (easily) find the RPM spec for a given fan, you
may find it on the manufacturer's website in the spec sheet
for that family of fan - seldom is there a separate spec
sheet for each model number, so you can't just search for a
specific model usually, rather a size and series of fan. If
that info is unavailable you can roughly gauge the fan speed
& noise level by looking at the rated current or wattage. A
2500 RPM fan is often rated around 0.13A, but beware that
different fan manufacturers may rate them a bit differently,
an RPM spec is safer to use to compare two fans. The same
goes for airflow, CFM - given two fans of the same
dimensions (diameter and thickness), running at the same
RPM, the airflow will be fairly similar between them though
some manufacturers will try to lead you to believe
otherwise. The same can be said about noise levels they
report, particularly 3rd party fan product relabelers, may
use deceptive strategies like merely repeating some
hypothetical figure from the bearing manufacturer of what a
fan "could" do if otherwise designed well, then they put
that bearing in a crap fan, trying to fake the spec and
riding on the name of the bearing manufacturer. A great
bearing will be shot in a far shorter period of time if the
fan motor isn't designed well or the blade/hub balancing
Another factor is fan thickness, a thicker fan can run at
lower RPM to maintain a given airflow rate, but if you want
one to spin VERY slow, and you have a very cool running
system, you might find a thicker fan can't spin slowly
enough, it may begin making a pulsating sound below a
certain point, usually somewhere under 1000 RPM. Otherwise,
any of the aforementioned brands will have low speed models
in any fan family suited to be used in a PC, it is typically
just one letter in the model name that changes. Oddly some
sellers even charge different prices for a different speed
in the same fan, odd because they cost exactly the same all
the way down the supply chain till someone decided to do
wierd things with the prices. It costs no more to make a
fan that runs at 5K RPM than 1K, for example, unless it's a
fan souped up visually with additional turbine fans or some
other thing that they felt would make it more marketable.
I've typed far more than I intended to, but it is because it
is not so simple as pointing you to one model of fan when we
don't know the variables. In any situation, the ideal is
the lowest noise possible while maintaining acceptible
cooling - and we can't know how much cooling you will need.
For many uses, I suggest Panaflo fans in the "L" or "M"
speed. Now some are labeled as NMB/sleeve-bearing type,
though NMB's ball bearing type are good also. The price of
a fan can vary wildly, you could pay $20 or more per fan at
some electronics houses or larger PC parts vendors, or as
low as $1-5 each if you keep an eye out for deals.
http://www.svc.com is one place that often has good deals on
the Panaflo(s), though some have no connector on them.
A large part of the cost buying a small number of fans is
shipping. Hopefully some of the above will assist you in
finding a suitable product at the next place you visit
whether it be local or online. If you feel your fans are
otherwise good quality then you might look into getting a
fan controller instead of replacement fans, though it could
cost as much as the fans do, and many people only feel they
need one because they didn't realize what speed they needed,
or that quieter fans existed... but it is a reasonable
purchase instead of the fans if you were otherwise happy
with them, to just slow them down some.
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