Negative pressure heatsink

Cooling Processors quietly

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Japesgalore
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Joined: Sat May 21, 2005 12:34 pm

Negative pressure heatsink

Post by Japesgalore » Sat May 21, 2005 12:57 pm

Hi all, I'm new here and new to the idea that computers don't necessarily have to induce bleeding ears. I have found the content on this site most informative, whether it be the reviews or the forum discussions, and far more sincere than most other 'non-silent' websites. Now, onto my kvestion.

Sooner or later, when £s permit, ill be putting together my fist custom pc. I've pretty much settled on keeping my sapphire toxic graphics card and getting the temjin 6 case, tagan 480 power supply, Nexus 'DampTek' acoustic sponge, 2x Akasa Amber 120mm and 3x Akasa Amber 80mm fans, epox 939 motherboard, Corsaid 4400 ram, and some sort of mid-range processor from either Venice or San Diego. My aim is quietness, as opposed to silence, with some overclocking potential.

The heatsink I'll most probably get is the Akasa Evo 33 (AK-913) which, from the very, very few reviews I've seen of it, seems pretty decent. It is in tower form, allowing me to make the most of the wind tunel design of the case. It also mounts easily and has thermal paste pre-applied. I hope silentpcreview will have a chance to write one of their own great reviews on it.

I would like to know whether mounting two fans onto it will bring benefits. It seems from reading reviews of similar style heatsinks that this approach doesnt always pay off, as in sometimes there is no difference in temperature only an increase in decibels. Who has experience of this sort of setup? It makes sense to me to have slight negative air pressure in the cooler, eg having the front fan rotate at 1800 rpm and the rear at 2000 rpm. The front will also have the Thermaltake ducting mod on it, if anyone out there has something to say on it.

Im interested to hear what you lot have to say on this or anything else about my system, cheers.

StarfishChris
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Re: Negative pressure heatsink

Post by StarfishChris » Sat May 21, 2005 2:33 pm

Welcome to SPCR!
Japesgalore wrote:I would like to know whether mounting two fans onto it will bring benefits. It seems from reading reviews of similar style heatsinks that this approach doesnt always pay off, as in sometimes there is no difference in temperature only an increase in decibels. Who has experience of this sort of setup? It makes sense to me to have slight negative air pressure in the cooler, eg having the front fan rotate at 1800 rpm and the rear at 2000 rpm.
I don't think it will do much other than create more noise. The side openings are small enough that most airflow will come through the front, you shouldn't need another fan to help you there.

Regarding the rest of your system: why so many fans? Few people around here have more than 3 (PSU, CPU, case). A mid-range processor, high-ish card and a couple of hard drives will work fine with a single 120mm fan.

Japesgalore
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Post by Japesgalore » Sat May 21, 2005 3:08 pm

At the front of the case there are fixings for one 120mm fan and one 80mm. At the back there is only the 120mm - its at the bottom, opposite the front 120mm fan. I was considering getting that push pull thing going on on the heatsink, between the two 120mm case fans. Hence, 5 fans in total (not including the two on the psu and the one on the arctic silencer thing on my graphics card - all are very quiet themselves). There will be roughly equal pressure in the case (less dust) and quick airflow along the bottom from which the relatively low-speed heatsink fans can draw from and expel right into the path of the 120mm exhaust.

I do need decent cooling if I'm going to be overclocking to a fsb around 275, getting my cpu at around 2750Mhz (hopefully). I think, given the amount of heat all this will generate, that my fan setup and selection is the quietest possible. None of the Akasa's are rated over 20dB (their figures of course, but I have heard good things). The one doing the sucking on the heatsink will be turned up a little and is rated at being 23dB when at 2000rpm. It will help channel the air coming down through the ducting mod which itself might help to lower volume and improve cooling (except reviews have shown mixed results).

Somewhere on this site I read that combining multiple fans of the same volume increases overall noise only marginally, even less when they are as low as 20-odd decibels. So, when combined with the DampTek stuff (anyone have any experience with it?), I think the overall volume will still be less than 30dB. I have no idea how loud that actually is, but I think it will be perfectly acceptable given my not-so-stringent standards, while also running a pretty powerful system. I think anything that improves upon the hoover that is my current FSP psu will be a godsend.

I am still interested to hear from people who have direct experience with mounting two fans on their heatsink, e.g. the owners of this site. Even better, who has tried this out in a Silverstone TT06 Temjin 6 case?

Ok, so maybe im not a devoted noise hater like most members of this forum, but I really would like to have the best of both worlds.

Twigathy
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Post by Twigathy » Sat May 21, 2005 3:34 pm

To be honest, you really dont need that many fans. Im running an Athlon 64 3000+ with an XP-90 mounted on top on an MSI K8N Neo2 mobo. In terms of fans, I have an 80mm exhaust (Nexus, so quiet and ~1200RPM, not undervolted) and a 92mm Nexus running at 12V (again, around 1200RPM) on the Heatsink. Idle is around 35C, Load 42C. PSU is a Nexus 4090, thats 400W, with a 120mm fan. The chipset has an EVIL little fan, and i've just ordered a zalman hedgehog to combat this. Graphics card also has a little fan but im not going to work on that, its undervolted so I cant hear it at the moment. Note that I also have 2 hard drives, a DVD burner as well. Graphics card is a Radeon 9600 Pro, idling at 35C and load ~40C.

In summary, DUDE! WHY SO MANY FANS! You really, really dont need them. Honestly, even my puny airflow Nexus' are doing the job well :)

SpaceDreamer
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Post by SpaceDreamer » Mon May 23, 2005 7:48 am

as a general rule, installing several fans in series in a computer is pretty useless.
Installing them in parallel would be better, but apparently you can't do that on this heatsink, because the only openings are the fans openings...

Same thing for the case fans:
instead of having the front ones blowing inwards and the rear ones blowing outwards,
you should try to have them all work in parallel
( for example, all case fans blowing inwards, and let the psu be the only exhaust ),
and see if there is any improvement. I noticed an improvement in my case, and I sometimes find people on the forums saying the same.

Japesgalore
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Post by Japesgalore » Mon May 23, 2005 8:14 am

Hmmm, somehow I doubt that 2x 120mm and 1x 80mm fans facing inwards, with one relatively low speed psu exhaust, could be beneficial. However, when the time comes, I might give it a go. In fact, I wouldn't know how to arrange the heatsink fan(s) if I did that. Are you aware of how this case is designed - the mobo is upside down.

I'll probably just be stubborn about it and assume that having the wind tunnel effect is a good thing. I'll most definitely have one fan on the heatsink because I reckon I won't use the plastic wind tunnel supplied with the case. The rest of the case should get better cooling and so hopefully the psu wont run as loud.

What I really want to know about is having two fans on the PSU. No speculation please, and no comments about the rest of my system, just tell me what you know about push-pull configurations on heatsinks, OK?! ;-)

I HAVE seen positive results, but also a few neutral/negative ones. Is there a proper way to do it? Hence I ask about ensuring negative pressure, as opposed to having turbulence caused by the rear fan not being able to keep up with the front.

Your suggestions ARE being taken on board, cheers.

Straker
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Post by Straker » Mon May 23, 2005 10:24 pm

using a single 120mm bottom intake here + 80mm PSU and 92mm exhaust, no problems with a 2400MHz Winchester, 3 HDs and an X800XT. i only use the intake fan to cool suspended drives.

two fans on the PSU is probably kind of silly, you'd probably be better off just cutting out grills etc on the PSU to improve airflow through it. the only real "rule" is that you should try to have equal areas for both intake and exhaust.

the reason you thought adding a second identical fan doesn't add much noise is probably because of how we perceive sound - if you have a noise source and add another identical one, nothing magical happens, the noise is still being doubled. it's just that the dB scale is logarithmic, so two 28dB sources = 31dB, not 56. a 10dB increase = 10 times as much power and only sounds twice as loud. think about it the other way, though - means it takes a fair bit of work to get something quiet.

Japesgalore
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Post by Japesgalore » Wed May 25, 2005 3:05 am

MOOOOOOOOOOOOOOOOOOOO!!!!

Look, I don't care what you think of the rest of my pc. I keep saying I'd much rather know about heatsink cooling. Im definitely not goign to be opening up my psu to be removing fans and/or cutting vents. The Tagan has two low speed 80mm in a push pull config for a very good reason, and its rated very, very highly.

Give me feedback on heatsinks, only heatsinks, particularly ones with two fans!!!!!!!! Ok, so I'm probably on the wrong site to be discussing this as y'all be using passive setups. Its just that soooo many people on the net talk complete plop, even 'professional' reviewers. I know the people working for SilentPCreview have their heads screwed on so I'm hoping, most of all, that one of them can give me some definitive info.

Thanks. And, believe me, the anger in this post is genuine. . . AAAAARRRGGGGGGHHHHHHHH!!!!!!!

StarfishChris
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Post by StarfishChris » Wed May 25, 2005 3:16 am

275MHz is a large overclock, and mounting two fans on it is not going to give you any significant cooling power. At stock speeds (at least) I'd go as far to say as you can go passive with the wind tunnel... Why do you think neutral pressure will help? Two fans creates more noise, and I doubt you will see a SPCR reviewer use such a setup. (Perhaps it's necessary with that heatsink. If so, I'd get a different one, personally. I really don't think there is a need for it.)

frankgehry
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Post by frankgehry » Wed May 25, 2005 4:49 am

I understand you frustration and everything, but it usually helps to have a link or a picture of the heatsink you are proposing to use. There is a very detailed review of a dual fan setup at this link -

http://www.silentpcreview.com/article201-page1.html

Well I think something is mentioned about dual fan setups at the end of the review, but read the follow-up forum discussions and I'm sure the posts will be more focused. There is also another heatsink, a coolermaster hyper 6 which has the potential to use dual fans. Again read the followup posts.

http://www.silentpcreview.com/article167-page1.html

It seems like you have already answered your question. No, having two fans is usually of no benefit. But, I still think it would be interesting to skip the akasa, and use a 38mm thick fan to provide some additional pressure. Or maybe two 38mm's in a push pull arangement. You have to experiment just like the reviewer who tested the thermaltake.

The two vs one fan controversy really involves a 120mm fan pushing xx cfm compared to two 80mm fans pushing the same xx cfm, or one 120mm fan at 12v vs 2 120mm fans at 6v. Iin the last case two fans at 6v are quieter. - FG

I would also like to hear how the akasa fans turn out. They are made by ys tech and my low spd model is very quiet.

EDIT: I took a look at the akasa heatsink and it is very cool. The fan is rated at 4000 rpm and at that speed there is no way it can be quiet. I would go with the two fans are quieter concept and use a push pull configuration. I would use low speed 38mm thick JMC's or Bi-sonics.

Japesgalore
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Post by Japesgalore » Wed May 25, 2005 6:47 am

Phew, now we're getting somewhere. ;-)

Here's a link to the Akasa for anyone else interested.

http://www.akasa.co.uk/spec/coolers/spec_ak_913.htm

Here's a link to the ThermalTake Ducting mod ill be putting on the front.

http://www.thermaltake.com/accessories/DuctingMod.htm

This aught to help reduce noise and temps. I'm thinking it would be preferable to have the fan angled into the air coming from the 120mm front case fan - less turbulance by 'slicing' through it? There'll be extra air getting to my ram also. Even if it does didly-squat in terms of performance, it'll still look good through my windowed and blue'n'red-neoned case.

The front HS fan will be plugged into the power supply and running at 1800rpm. The rear fan will be hooked up to the speed controlled, set at the minimum rpm of 2000. The negative pressure should then help the ducting mod, as I've heard there's some gap in it (for the screws?) that lets some air escape. The negative pressure may also bring some extra air through the slits in the side of heatsink. Finally, all the hot stuff gets propelled directly into the path of the 120mm exhaust. The loudest fan in the case will be the HS rear at 23dB. I'll be having some of that Mutemat stuff as well to help muffle things.

I can't wait to sort all this out actually. Might have to post some pics after its done cos I reckon its got great potential to look real classy - especially with what I have planned with the neon tubes. None of that 30cm cold cathode cheep stuff, ill be spending £40 or so on 'real' neon lights... Another link?

http://www.optxbystreetglow.com/ultrami ... ttubes.htm

Frankgehry, can I just confirm that in the edit you suggest that I SHOULD go for the push/pull? Can you provide links to the JCMs and Bi-sonics? I live in the UK btw so i guess my supply may be a little limited compared to the US.

Thanks

frankgehry
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Post by frankgehry » Wed May 25, 2005 7:24 am

Yes, that's what I would do. That's what Mike Chin does with the Coolermaster Hyper 6 with two panaflo L1A's and it was a lot quieter than the single stock fan at higher rpm's.

I like JMC fans. You can look them up at www.jmcproducts.com.
Bi-sonic's are good too, but my source only supplies them w/o rpm sensing and bare wires, but the prices are good.

In the uk you would need to find a big electronic supply house instead of quietpc or a dinky computer store. The link is www.mouser.com and search for dc fans. They also have adda fans which would be good also. Maybe the adda's would be available in the uk. They have some addas at www.ichbinleise.de. I like them and have ordered a lot of fans.

You could aslo get a medium or high speed panaflo from www.dorothybradbury.com. The other fan that I would consider is a delta low speed triple blade. I just got an 80mm and really like it. They are available at www.sidewindercomputers.com. You can get a delta 80x38 triple blade low speed that would look very cool attached to both sides of the akasa.

Bi-sonic makes either the 80 or 92mm nexus so it is very good. I believe they have some 80x38mm fans too. Have fun. - FG

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