Passive HS misconceptions

Felger Carbon · Post by **Felger Carbon** » Thu Dec 15, 2005 4:12 pm

<tongue-in-cheek mode ON>

It's politically incorrect to mount a fan on a passive heatsink. The Ninja, NCU-2000, and HR-01 do not include provisions for fan mounting for that reason. The NCU-2005 and TT Sonic Tower do include provisions for mounting fans, but decent people have no truck with such abominations.

A purely passive HS such as the Ninja, when mounted 1/8" away from a screaming 120mm exhaust fan, is still passive. SPCR, demonstrating how progressive it is, published a review of the Ninja where it was located immediately adjacent to _two_ screaming 120mm fans. But it was still completely passive and noiseless.

A small but common mathematical error: a purely passive HS does _not_ have a 0dBA sound level. You see, the Bel - the fundamental unit of sound level - is the logarithm to the base 10 of (the sound level divided by a reference sound level). If the sound level is zero, the result of taking a logarithm is minus infinity. To get the dB (decibel) level, we multiply minus infinity times ten - uh, my slide rule just melted. Sorry, folks!

<tongue-in-cheek mode OFF>

Full disclosure: I own a Ninja and NCU-2000. It's easy to mount a fan on the NCU using a 30" round shoelace.

Bluefront · Post by **Bluefront** » Thu Dec 15, 2005 4:28 pm

I think that word "passive", is thrown around too much. About all it means on SPCR is "my CPU heatsink did not come with a fan."

Obviously any/all of these so-called passive heatsinks, require air movement provided by a fan. So what if the fan is 3" from the heatsink......that heatsink still requires airflow to keep the CPU cool.

What we really need is a new term/word to describe this sort of CPU cooling. It certainly is not "passive".

Live · Post by **Live** » Thu Dec 15, 2005 6:12 pm

Felger Carbon wrote:The Ninja, NCU-2000, and HR-01 do not include provisions for fan mounting for that reason.

What do mean? The ninja at least comes with fan mounting. HR-01 is not released yet but the only review I’ve seen had a fan on it.

Felger Carbon wrote: A purely passive HS such as the Ninja, when mounted 1/8" away from a screaming 120mm exhaust fan, is still passive. SPCR, demonstrating how progressive it is, published a review of the Ninja where it was located immediately adjacent to _two_ screaming 120mm fans. But it was still completely passive and noiseless.

I still think it is valid to call it passive. You get rid of one fan if you can run your cooler from the back case fan or top PSU fan. The other way is not as easily done. I mean if you have fan on a heatsink it’s not common for it to take the role also of the back fan. So you end up with more fans.

The heatsink can be passive e.g. without a fan but not be able to run in a passive system. Two different things in my book. A passive NB cooler which we have had since the beginning of times has always meant it has no fan on the NB not that you don’t need any airflow over it for it to run ok.

Felger Carbon · Post by **Felger Carbon** » Thu Dec 15, 2005 6:43 pm

[/quote]
What do mean? The ninja at least comes with fan mounting. HR-01 is not released yet but the only review I’ve seen had a fan on it.

Uh, you missed the "tongue in cheek" mode and the fact that I own a Ninja. Yesterday I spent 3 hours trying to get the &#@! wire fan clips to actually work. I finally got the fan sort-mounted - it would slide around instead of staying firmly in place because the Ninja does _not_ provide a fan "seat" which would lock the fan in place. That, plus the fact that movement could bump the fan clip up against my DIMM, shorting it out, caused me to write today that the Ninja does not come with fan mounting.

spolitta · Post by **spolitta** » Thu Dec 15, 2005 9:20 pm

so If I had a truly passive PC should I turn off my ceiling fan to keep the name Passive on my pc? I dont think so, The HS itself is running passive so if there is a air moving from PSU or exhaust the HS is still running passive.
But I know what you mean about the name confusion it makes. maybe we should call it "Passive" and "All Passive"

Felger Carbon · Post by **Felger Carbon** » Fri Dec 16, 2005 2:51 am

[quote="Live"] HR-01 is not released yet but the only review I’ve seen had a fan on it.[/quote]

You wrote that on Dec 15, Thermalright announced the HR-01 on Dec 14. By that time, several on-line stores had HR-01s in stock that they'd sell you for $48-$50. The review you're referring to is the one in Hartware.de, which I've seen several times. I call the Pope (Papst in Danish) fan that's "mounted" on the HR-01 the "vagrant" because it literally has no visible means of support. Either the fan was photoshopped on, or there's an unseen support under the fan for purposes of the photo. Look carefully: there's absolutely nothing holding the fan to the HR-01.

datapappan · Post by **datapappan** » Fri Dec 16, 2005 3:37 am

Passive=needs no forced air flow. This should mean you're left with only self-induced heat convection. Of course this heat then needs to be evacuated, or you get heat buildup.

Point is, putting a passive component in free air should make it function according to spec. Cf. the NB, it's speced at ambient air temp of max +50C, likewise for HHD:s and RAM:s. The Intel CPU spec needs the temp as low as +38C, for their stock HS. They're in a case, which needs its air volume refreshed with cool air, but all components are speced to function with no forced air flow.

If you look at MB specs, they don't say you need air flow to function (they usually don't spec temperature at all, maybe they rely on the CPU spec, +38C in Intel's case). If that would have been the case, you couldn't fit a heatpipe sink with "horizontal" flow, e.g. the AC freezer - it wouldn't give enough flow for the components around the CPU (MOSFETs, RAM, NB).

As for passive PSUs, I checked the manual for the Antec Phantom. It only states you need proper cooling of the case for other components cooling needs, since you can't rely on a PSU fan (which isn't there). It's speced at +65C, but states no need for special cooling - it relies fully on the heat being conducted to the PSU casing, and then further, ? not stated. Of course it will take advantage of case cooling fans to be cooled, so, here again you can argue the term passive.

I'll stop the rant her for now, to be continued...

/ datapappan

sun.moon · Post by **sun.moon** » Fri Dec 16, 2005 4:35 am

Bluefront wrote:I think that word "passive", is thrown around too much. About all it means on SPCR is "my CPU heatsink did not come with a fan."

Obviously any/all of these so-called passive heatsinks, require air movement provided by a fan. So what if the fan is 3" from the heatsink......that heatsink still requires airflow to keep the CPU cool.

What we really need is a new term/word to describe this sort of CPU cooling. It certainly is not "passive".

Good idea.

"Why keep it simple, when it can be complicated" - translated German saying.

What about just simply -- fanless --

jaganath · Post by **jaganath** » Fri Dec 16, 2005 5:44 am

A small but common mathematical error: a purely passive HS does _not_ have a 0dBA sound level. You see, the Bel - the fundamental unit of sound level - is the logarithm to the base 10 of (the sound level divided by a reference sound level). If the sound level is zero, the result of taking a logarithm is minus infinity. To get the dB (decibel) level, we multiply minus infinity times ten - uh, my slide rule just melted. Sorry, folks!

So what is the dB level when something makes no noise? 0.0000001db? Or is it not possible for something to make ZERO noise, because when you get down to the atomic level you can hear the molecules moving about?

Vulcan · Post by **Vulcan** » Sun Dec 18, 2005 8:32 pm

Since when does cooling have anything to do with politics?

And, your logic is off... But I don't even want to go there.

Post by **Rusty075** » Sun Dec 18, 2005 8:56 pm

jaganath wrote:So what is the dB level when something makes no noise? 0.0000001db? Or is it not possible for something to make ZERO noise, because when you get down to the atomic level you can hear the molecules moving about?

0dB does not equal zero noise. The zero decibel point is set at the established threshold of human hearing. (a sound energy level of 1*10^-12 W/m2) Sound levels below this point have a negative dB. Our lab SLM, for example, can read down to -24dBa. Mathmatically, the dB level with no sound energy at all would be negative infinity.

jfrjimenez · Post by **jfrjimenez** » Tue Dec 20, 2005 8:51 am

I'd imagine that a truly passive system is one in which the cooling system has no moving parts, since noise is caused by vibration. Under this logic, the Zalman TNN series is basically the only thing to fit the bill.

Aris · Post by **Aris** » Tue Dec 20, 2005 10:19 am

from a marketing standpoint, all they have to do is prove that in one specific instance it will do what they state it will. and i bet if you put a low power cpu in open air without a case with the completely passive ninja on it, it would be adequit cooling. hence, they can market it as a 0db product. and as rusty stated, 0db is not no noise, its the threshold of human hearing. so yes they can say its "passive" and yes they also can say its "0db" and they are correct in both instances.

in the end, you can take just about any product, and find a situation in which it doesnt work like it says it will. (eg: you have a fanless psu from antec, the ninja passive on a p4, and SLI 6600gt passive). from a technical standpoint, each piece "should" be able to run completely passive, but together in an enclosure with no airflow and it will fail.

this is why you need to think outside the box, and choose components more wisely to achieve the desired result of low noise.

Post by **Rusty075** » Tue Dec 20, 2005 12:56 pm

Aris wrote:from a marketing standpoint, all they have to do is prove that in one specific instance it will do what they state it will.

No, from a marketing standpoint you don't even have to do that. You could take a lump of lead, bolt a mounting clip to it, and throw it in a plastic clamshell with words "PASSIVE HEATSINK" on it in great big letters.

There are plenty of products out there that can't live up to their marketing, computer-related and otherwise.

ronrem · Post by **ronrem** » Fri Dec 23, 2005 2:39 am

Lets not confuse things. You can have a passive component,yet not a fully passive system. It is now possible to have a powerful computer running with just a single low speed fan in the whole system,and virtually no noise. Furthermore,that can be affordable,done at a price that a few years ago got you a cheap no frills Celeron. Going totally passive is possible-but that takes more specialized technology and gets expensive

Passive HS misconceptions

Passive HS misconceptions

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Re: Passive HS misconceptions

Re: Passive HS misconceptions