cpu fan dba threshold for after-market purchase

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My newely self-assembled desktop is running great with the exception of
the cpu fan noise.

It's an ECS motherboard with Intel Pentium-D lga775 socket running at
2.66 ghz (no overclocking).

My intention is to purchase an after-market cpu fan but there are so
many to choose from I decided to purchase based on the noise rating in

The one I'm considering is the Spire CoolWave III (SP503B0-1) rated at
26.2 dba, 2400 rpm and 41 cfm.

Does 26.2 dba indicate a quiet fan? Middle of the road quiet fan? Still
noisey fan?

What number shoud I be shooting for? Where should my threshold be?

Any help is greatly appreciated.

Thank You

Re: cpu fan dba threshold for after-market purchase


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Don't do it, just as other products are questionably rated,
so are heatsink noise ratings.  In particular, manufacturers
of heatsink "products" only recant the fan manufacturer's
free-air rating (yet another variable subject to scrutiny)
which in itself isn't applicable to finished product, in

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Avoid Spire, junk fans.  If that's what you want though,
relube the fan every year or so to prolong it's life.

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Question is really whether it cools well enough, since the
primary criteria is always a reasonably larger diameter and
thickness, fan, then the method of fan speed reduction-
either by motherboard control, user intervention (such as
adding a series power resistor), or no intervention at all
meaning a the stock speed has to be enough for full load as
you can more easily reduce fan speed than (safely) increase

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Generally speaking 26dba is fine, but it's not directly
comparable to some other 'sink with a different dba rating.
It should be, and would be if these were terms aimed at
engineers, but alas these are marketing terms for PCs where
the law can't keep up with the excuses to do some creative
fudging for marketing purposes.

overall though, that fan should be relatively quiet, the
remaining issue is the quality of the metal hunk under it
(at conducting heat), and the fan lifespan (since it is low
quality, whether you actually _would_ lube it, or if you
would wait till it makes noise (which will be better than
nothing, but once making noise it is wearing far faster than
if it had enough lube all along, replentished lube before it
starts going dry).

I could be optimistic and hope they have corrected their
past mistakes, that when they sepc "ball bearing" that they
really mean a DUAL ball bearing fan, but typically it is not
the case, they probably use one ball and one sleeve in it
which is often the worst combination as it makes it harder
to lube the sleeve without contaminating the ball bearing.

I suggest you take a look at the 'sinks at
http://www.newegg.com , as there are often user reviews that
will mention noise levels.

Re: cpu fan dba threshold for after-market purchase

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First of all, every company and review site measuring noise, uses
a different method. No two sound ratings can be directly compared,
unless they were measured by the same individual, with the same
sound meter and weighting choice. Ideally, an anechoic chamber should
be used, with no hard drive or PSU noises present in the chamber.
Not many review sites will bother with those details.


As for an analysis of your cooling requirements -

A Pentium D 805 has a TDP of 95W.


The Spire cooler has a thermal resistance of 0.355 C/W.

Assume the room temperature is 25C. A well cooled computer case
has an internal temperature of 32C. You can measure the motherboard
temperature, and see how well you are doing. Substitute your
measured motherboard temperature, for the 32C in the following
equation. If your computer case temp is over 32C (which it well
could be), then the requirements for your CPU cooler become
more stringent. If the computer room is not air-conditioned,
that means you need to pay more attention to the number of
fans in the case, and the amount of ventilation holes in the
computer case.

CPU_temp = 32C + (0.355 C/W * 95W) = 65.7C

The thermal spec on the Intel web page says 64.1C, so the cooler
you plan on buying is not good enough. You need more fan speed
and more noise :-)

There are some links to heatsink reviews here:

The ThermalTake Big Typhoon can run its fan at full speed, and
is virtually inaudible. This article rates the thermal performance
at 0.30 C/W (since ThermalTake did not put a thermal resistance spec
on their web page). Re-evaluating the equation above gives:


CPU_temp = 32C + (0.30 C/W * 95W) = 60.5C (< 64.1, so it is OK)

In the same review article, the Zalman CNPS7700 got a rating of
0.25C/W . It comes with a fan speed control, so you can try
different settings to get the desired effect. The middle speed
setting of the CNPS7700 makes the same noise as the Big Typhoon.
The CNPS7700 got a rating of 31.9 to 38.7 dBA, where the room
background noise level was 33 dBA (I don't know how they managed

CPU_temp = 32C + (0.25 C/W * 95W) = 55.8C  [CNPS7700]

With any of these large coolers, there can always be issues with the
fit of the cooler within the computer case. The CNPS7700, for
example, has a habit of bumping into the PSU casing, unless the
socket is far enough away from the edge of the motherboard.

So, have a look around, and try to get thermal resistance ratings
for the coolers. That allows you to select your cooling
solution with a little more "science". Always check the cooler
manufacturer's web site, for any motherboard compatibility info
they might offer. For example, depending on the location of the
CPU socket on your ECS motherboard, the CNPS7700 might bump into
your power supply. A large computer case makes it easier to cool
your computer, and also makes more room for a large cooler.

Another way to state the above equation, is in terms of the
thermal performance of your computer case. Measure the room
temperature. Measure the computer case temperature (sometimes
called the motherboard temperature). The difference between those
two numbers is a measure of how well the computer case cooling
works. A well cooled case has a "delta" of 32C-25C = 7C. At
any point in time, you can now predict the CPU temperature (the
casing of the CPU):

CPU_temp = current_room_temp + the_delta + (theta_R * TDP)

which for the Zalman cooler, in a well cooled computer case, is

CPU_temp = 25C + 7C + (0.25C/W * 95W)   [must be less than 64.1C]

The hotter your computer room is allowed to get, the better the
CPU cooler has to be. In summer, it will be a lot more than

Have fun,

Re: cpu fan dba threshold for after-market purchase

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Take a look at:


--Bob Day

Re: cpu fan dba threshold for after-market purchase


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If you want something very quiet and on sale, possibly this

The fan may be too low an RPM to spin reliably if used on a
motherboard fan  header with a fan speed control
implemented.  In such cases, one of the other Panaflo "M"
series in the 12V versions would be a better alternative.
Drawback is no fan RPM signal but perhaps some of their
others have it, I'm too lazy to check at the moment but you

Re: cpu fan dba threshold for after-market purchase

All ...

Thank you very much for the replies and for taking the time and energy
to walk me through coolers 101.

I checked out the newegg links posted up-thread by Bob and Kony and the
Thermaltake CL-P0257 Blue orb II looks like it might be just what I
need -- notwithstanding having to remove the motherboard to install it
(probably a small price to pay).

Thanks again


Re: cpu fan dba threshold for after-market purchase

Remember to get some thermal compound when you get your cooler, if it
doesn't come with some.  I've used Arctic Silver in the past.  Well, I'm
using it in the present too, to be technical.


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Re: cpu fan dba threshold for after-market purchase

Thanks for the heads-up Clint.


Re: cpu fan dba threshold for after-market purchase

The best source for info on quiet fans is, in my humble opinion,

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