Ghetto mod on my SLK900

[JKeefe]

An 120mm fan that does 190cfm? Could you post a link?

[EDIT: typos fixed]

http://www.sidewindercomputers.com/delffb1212eh.html

 

[Banyan]

sidewindercomputers are good people... thanks for hte headsup on that fan.

from here

Also note the power requirements of the FFB1212EHE, there is a 3.00 amp startup requirement too.

what the hell does that mean exactly for the "ignorant"...?

 

[treepop]

He is talking about how much power is required to actually get the fan moving......which is a way people can judge how fast they can run the fan......for noise issues....this is a big concern....I think this is what he was refering to

 

[JKeefe]

Fans generally take more current and voltage to start than they do to run. Considering most fans don't even use 1A, let alone 3, I thinks its a subtle warning that you need some massive power supply to get the thing going.

Note that the 80mm Tornado is rated at "only" 0.76A

 

[Banyan]

so would, say, a truepower 380 have problems with two of these things??

 

[CrashOveride]

so would, say, a truepower 380 have problems with two of these things??

Probably if you have a whole system hooked up to it was well.

 

[JKeefe]

so would, say, a truepower 380 have problems with two of these things??

You're not seriously considering putting these in your case...

They run at 59dB. That will cause permenent hearing damage over time. You do not need 190CFM in a desktop case. That is overkill.

 

[CrashOveride]

You're not seriously considering putting these in your case...

They run at 59dB. That will cause permenent hearing damage over time. You do not need 190CFM in a desktop case. That is overkill.

Its not really much louder than a Tornado.

 

[squeakygeek]

You forget, decibels are logarithmic. Either 10 more db is twice as loud, or 6 more db is twice as loud. I've heard both. No pun intended.

 

[CrashOveride]

I suppose... its still only 3 decibles louder than a tornado...

Just find a bad assed pot and stick it on.

would this work?
http://www.allelectronics.com/cgi-bin/category.cgi?category=470015&item=RHE-25&type=store

A light dimmer might work... or would the fan be too powerful

 

[squeakygeek]

I suppose... its still only 3 decibles louder than a tornado...

Just find a bad assed pot and stick it on.

would this work?
http://www.allelectronics.com/cgi-bin/category.cgi?category=470015&item=RHE-25&type=store

A light dimmer might work... or would the fan be too powerful

It doesn't sound like much (no pun intended), but 3 db more could mean 50% louder.

 

[Banyan]

atfer years of loud guitars and music the noise level doesn't matter to me

 

[Amorphus]

3db louder is twice as loud, dude.

squeakygeek - the +10=*2 thing isn't for decibels, unless its a different scale. we use db(A) here.

I've heard the +10=*2 for brightness of stars, but thats about it... (there probably more)

 

[Susquehannock]

3db louder is twice as loud, dude.

> > > > > > > > > > > > > > > > > > > >

Yup.

 

[login211]

so is this a slk800a or slk900a?? topic says slk900 but your post says slk800a....

 

[pik4chu]

so is this a slk800a or slk900a?? topic says slk900 but your post says slk800a....

looks like an slk 800 to me...


and btw

that fan is 3 Amps @ 12 Volts = 36 watts.... need one hell of a pot for that one, let alone two

no big deal for noise, mine runs at atleast 50-55dbA, hehe

 

[squeakygeek]

3db louder is twice as loud, dude.

squeakygeek - the +10=*2 thing isn't for decibels, unless its a different scale. we use db(A) here.

I've heard the +10=*2 for brightness of stars, but thats about it... (there probably more)

I always thought db(a) was decibals average. So it's not decibals? I'm confused.

 

[JKeefe]

dB can be weighted either A or C. They are just different ways of lookign at data that may be clustered in one particular frequency range.

Plain old dB is dB(f) or flat decibels (no weighting). dB(C) generally approximates human hearing (accounting for the resonances of the ear canal and such), and dB(a) is generally used in industry measurement, hence its use for fan noise ratings.

EDIT: The above is incorrect. Please see my post below for the proper information.

 

[squeakygeek]

Do you know the scale of each one? Someone earlier said the a scale was every 3 dba was twice as loud. the c scale would be more useful. Do you have any idea of how to convert to the c scale from a? Also, the scale of the c scale?

 

[JKeefe]

Ok, acoustics education time (they'll make me earn my degree yet...):

From The Science of Sound, Thomas Rossing

Because of the wide range of pressure stimuli, it is convenient to measure sound pressures on a logarithmic scale, called the decible (dB) scale. Although a decibel is actually a means for comparing two sounds, we can define a decibel scale of sound level by comparing sounds to a reference sound with a pressure amplitude 2x10^-5 newtons per square meter, assigned a sound pressure level of 0 dB.

This just says that a certain arbitrary SPL is set at 0 so we can attach a meaningful number to every other SPL. Note that you can have SPLs that are negative, although they are so quiet as to be meaningless to the human ear.

SPL is what the human ear interprets as how loud something is. There is a mathematical measurement of loudness, measured in units called sones, but no one uses it. For all intents and purposes, if something has a high SPL, it is loud. If something has a low SPL, it is quiet or inaudible.

It is worth reviewing the difference between sound pressure level, sound power level, and sound intensity level, since all three are expressed in decibels ... Sound power level expresses the strength of the source, irrespective of the location of the source and the observer. Sound intensity level expresses the rate at which energy flows across a unit area. For a free progressive wave, the intensity is proportional to the square of the sound pressure. Thus, a doubling of the sound pressure results in an increase of 6 dB in sound presure level, whereas doubling the sound power increases the sound power level by only 3 dB. Similarly, a ten-fold increase in sound pressure represents a 20 dB increase in sound pressure level, but a ten-fold increase in sound power increase the sound power level by 10 dB.

So, a noise seems twice as quiet or twice as loud every 6 dB it changes. In the computer world, if your fan seems twice as quiet after you turn it down, its SPL has dropped by 6dB.

The 3 dB drop is when half of the noise-making stops. For example, if you have a choir singing a note at constant volume, and then half of the choir stops singing, the SPL drops 3 dB. Note that the choir is not half as quiet with only half of the members singing.


Here's the stuff on measurements and scales. This is contrary to what I wrote above. I need to read my textbooks more. Ignore the higher posts with conflicting info.

Sound level meters have one or more weighting networks, which provide the desired frequency responses. Generally three weighting networks are used; they are designated A, B, and C. The C-weighting network has an almost flat frequency response, whereas the A-weighting network introduces a low-frequency rolloff in gain that bears a rather close resemblance to the frequency response of the ear at low sound pressure level.
Measurements of sound level are usually made using the A-weighting network; such measurements are properly designated as L(A) or SPL (A) in dB, although the unit dBA or dB(A) is often used to denote A-weighted sound level ... Inside a building, the C-weighted sound level may be substantially higher than the A-weighted sound level, becasue of low-frequency machinery noise, to which the ear is quite insensitive.

So, C is flat (or almost), not A. There is still a true flat measurement dB(f), not mentioned in the text, but it is only usefull for purely arbitrary measurements. The fact that fan noise is measured in dB(A) is good, because it means we can have a reasonable expectation of how loud a fan will seem when we first plug it in.