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AF or SP Fans for Intake?


BobT36
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I read that SP fans were for Radiators and AF were for intake.

 

However after just buying an AF120 Quiet, and about to put it in, I realise that my case doesn't have 3cm of "Unrestricted" space, due to the HD Cage, and probably the front filter too. (pics attached)

 

Will an AF struggle here, as in should I buy the SP version instead? Or do you think the AF will handle it alright.

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Edited by BobT36
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Yes, I would say this is a better job for the SP series or any other hybrid flatter blade (like the ML series). There is a lot of restriction in there and no fan is going to move a truckload of air. For drive cooling and getting air through thick mesh paneling, a slow turning flat blade will work. The AF series will still move air through there, but even without all the resistance it is not a very effective fan for direct cooling.
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Thanks! I read a bit more and did find people saying they don't work well with filters or HD cages, I have BOTH there heh.

 

What would you use the AF fans for then, top or bottom? Every case I've seen has a HD cage at the lower part and optical drive section above it, so I can't see anywhere that would be "unrestricted".

 

Looked at the ML line but my mobo only has 3 pin headers, so I guess I'm left with the SP one for the lower-bottom then ya?

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AF fans work great for exhaust and on wide open intakes with little resistance, either in case mesh or dust filter form. The thin, steeply raked blades make less air noise and move a higher volume of air, but the trade-off is a very wide dispersal cone and diminishing return when obstructed. So, for internal exhaust they work great. Pulls air from a wide area, moves a lot of volume out, and does so with little noise. Most people have drives, filters, or heavy mesh on the front of the case. Also, a flat blade fan like the SP does a better job of direct cooling, so if you have things that benefit from this (m.2 drives, PCH, dual GPU set-up, etc.), the more focused flow has advantages.

 

Most 120mm fans fall somewhere in between those two archetypes and have a moderate number of blades with a moderate angle. The ML and HD series are in that category, along with many other models. Most people do well with the hybrid, but I think a SP model is appropriate for that spot in front. You don't need to blast it. It just needs to keep a little flow going.

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Thanks! I'll have a look at an SP120 for the front then, and decide whether to go for the Quiet or Performance model. I'm thinking Performance since you can step it down with the included resistor ya?

 

Shame I can't get a non-LED SP140 since there's room for one. Apparently the LED versions aren't as good, so I'll have to go with a 120.

 

 

Once I install the SP120 I'll have that as the front intake, and the two H80iv2 fans as the rear exhaust. So wondering where to put my now redundant AF120 Quiet.

 

Would you recommend using the AF120 as a top exhaust, or side-intake? I've been doing a bit of reading about air flow and how positive pressure is more favoured, so I'm thinking using it as an intake on that side panel? (pic 3) I'll need to make a filter though. I was looking at some filters on Amazon but I'm now thinking of using some of the gf's old tights, that way I can stretch them across the whole fan slot (140mm), but screw through them to mount the 120AF fan. I presume the AF model will be able to handle that fine as long as it's not too dense? As there's nothing behind it at least.

 

Here's some more pics of my case, (no idea which model it is though, got it in 2012..). The last pic shows around where the AF would be if used as a side intake. I presume this won't create any deadzones yeah?

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Edited by BobT36
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If the choice is 1x120 or 1x140 for the front intake, I would prefer a 140mm fan. It will be less buzzy and get more air into that area. Regardless, I have used cases with the single front intake and a pile of drives. That fan will never have much effect on the internal case temps, but it is better than nothing. You could pop out the LEDs from a SP140. At similar noise levels, the SP140 LED will move air than a SP120 (i.e, SP140@600, SP120@1000 rpm). Still, not likely to affect temperatures and more likely to affect your psyche when trying to listen for tiny differences. There are also other offerings in the 140mm size class that are 3 pin and appropriate. They just are not made by Corsair.

 

If I could use any tool, I likely would want the low speed SP120 in the side door. It has a more focused flow and will be better for direct cooling on the GPU and sound card(?) below. However, you have an AF120 and don't want to waste it. I am going to recommend leaving the top open for reasons I will explain next. Thus, use the AF120 in the side door to supplement the air intake into the case. This would be less obstructed than the bottom slot, but if the side door location proves too noisy (often noticeable because of proximity and ear level if on desk), move it to the bottom. An AF120 on the bottom is fine for bringing air in, although if on carpet down below this will be a major carpet furball conduit.

 

EDIT: SP120 (Quiet edition vs Performance). It is the same fan, just with a 1400 rpm max vs 2400. You already have a pair of the Performance fans on your radiator. If you were going PWM, you could say it won't matter, but with DC you are going to be limited on the low end to something like 60% of max. Thus the minimum speed on the High performance 2400 pair is going to be somewhat high. I would prefer the Quiet version. Anything more than 1400 will be very noticeable. You like can make your own sound evaluations from what you have on the radiator. And do be careful about product listings. There is a PWN and DC version for both. Some retailers get a little careless in how they display the model number.

 

Having run for a similar layout case with a H80i in the rear slot for quite a while, I recommend leaving the top open. In your system, the H80i and its fans serve two purposes. One is to release heat from the radiator out the back. The other is general case exhaust. You likely have noticed you get higher CPU temps when under a consistent GPU load and moderate CPU load than when running a CPU only 100% benchmark. This is a result of the GPU warming up the local area. By leaving the top open, the H80i and its fans can bring in cooler outside air through the top mesh. In a constricted case with less than ideal air pathways, this can make a big difference in keeping CPU temps down in all load types. Putting the AF120 as exhaust up top would disrupt the H80i's fan from bring air in. Using it as top intake causes too much turbulence from my experiments. This is an example where passive is better. You can probably get a rough idea of how much air the H80i is pulling through by holding a post-it-note above the top mesh. Mine would still there like it was glued when the H80i fans where in top form. This is ultimately a better source of intake air than you get though any other pathway and it goes to the most critical area.

 

Yeah, I am going to skip the usual positive vs negative pressure discussion today. Case cooling works by removing the existing warm air from the case (exhaust) and then bring in new air to replace it (intake). Ideally, you want those two values to be similar. There are some cases with a lot of open mesh where some measure of positive pressure can be used to force exhaust through the mesh. I have a couple of these. You do not. Regardless, if you want to tweak your intake/exhaust ratio, do so by altering fan speed. Don't get too carried away trying to calculate maximum in/out flow rates. The fans will not move that volume of air when in place and the whole thing is a very rough process of estimation. Not too many people run their fans at the max anyway, but still for some reason try use those values when calculating.

Edited by c-attack
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Thanks C-attack, that was very informative.

 

I agree about leaving the top free, didn't think that of course the H80iv2 fans can pull air in that way rather than expel it, which will cool the CPU and RAM. Makes sense. I generally see that having one-way air flow is better, so in at the bottom, out at the top-back, rather than trying to create multiple streams.

 

And yeah I wouldn't want to waste the AF, so I presume with a thin filter made from tights, and the behind part being free (empty space under the GPU), installing it on the lower-right spot on the side door would be best.

 

Sound shouldn't be an issue since my PC is on the floor at the lower-left of my desk, with that side panel on the opposite side to me. Also I have wooden laminate floors, so I think one on the bottom might pull up a bit too much dust (I have to clean my PSU bottom-filter at least every two weeks and there's noticeable dust). I'll move it if the side becomes a problem though, or it gets too arsey to open my case, since I'll have to disconnect the fan each time. If the side will work better though then I'll put up with it as long as it fits.

 

Hmm I sorta would like a SP140mm fan for the front, it's just I read that the non-LED variants had better performance, albeit only having 120mm versions available: https://www.anandtech.com/show/9737/the-corsair-sp140-led-af140-led-sp120-af120-fan-review

I was looking for a Corsair one to match the new H80iv2 ones I got, and I have a rattly, loud old Xigmatek in the front. I'm open to a different brand's 140mm if it's better than corsair's 120SP, I just don't know enough about the different brands and models.

 

As to performance vs Quiet, will the max 1400rpm be enough for gaming then? Especially to pull air through the front filter and HD cage. I presume general airflow will be fine as the rear stock H80i fans are performance, plus the AF120 in the side will help. I understand that the minimum speed of a Performance fan would get annoying though if it's loud while just browsing.

Edited by BobT36
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As a radiator fan, an SP140 LED is so-so. However, it is just fine as a case fan when there is light to moderate resistance. There is a relationship between maximal airflow volume and the "pressure" generated by the fan. While technically this is not the static pressure reading quoted (that's amount of negative pressure to reduce RPM to 0), there is a relationship. Essentially, if you want a high pressure fan with tight focus, you must give up maximal volume capability. Conversely, if you want maximal airflow, you must give up focus and the ability to overcome resistance. Since either extreme isn't ideal in every circumstance, most fans split the middle with medium rake and a medium number of blades. This is particularly true for 120mm fans where 95% are a hybrid design. I like that Corsair makes AF and SP designs, but they are specialized tools and not everyone needs to jump on either end of the spectrum. Thus, the SP140 LED while moderate in stack pressure, also has better airflow than a similar 140mm fan with a wider, pressure orientated blade. Incidentally, almost all 140mm "pressure fans" will look like that. There are very few consumer models that look like a SP120. Probably relates to mass of the blades, but regardless you won't find a pie plate looking 140mm. That also would be not be ideal. While congested, your pathway is less restrictive than a radiator.

 

Also watch out for misleading static pressure numbers. The value is entirely RPM based since it is a measure of how much pressure it takes to stop the fan. Every fan fan has a pittly little static pressure number at 100 rpm. Even the thinnest blade model ever will have a flattering static pressure rating at 3000 rpm. As such, you have to equalize by rpm to compare to fans with different max RPM limits. A SP120 High perf. looks quite high because of the 2400+ rpm speed it is measured at. However, down at 1300 or so, it is a mere 1.29 mm H20. That isn't a poor value, but you can see how critical RPM is to the actual number.

 

I think my preference would be for the side fan (AF120) to pump most of the air in and to leave the front fan as a drive cooler (and this lower steady speed). A SP120 is fine for this. I'll send you some other possibilities. No need to max the AF120 out at 1600 rpm either. Keep it where the noise is comfortable. An extra +15db for 2-3C cooler case is not a good trade unless you are at the limit somewhere.

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Thanks a lot! I've read your PM too. The last one you linked had reviews of the bearing being off and it being rattly though, which is why I'm changing my fans now to get rid of the old rattly Xigmatek one I had in the front.

 

Think I'll still go for the Corsair ones just to keep them all the same and they're easy to get ahold of. And yeah I'll likely use the resistor supplied to notch the AF120 down a tad. I think I'll keep the front one as is though unless it sounds too loud (since it has to deal with that dense filter and the HD cage).

 

I've just tried the AF120 in the side and it fits! Pic included. I'll make a filter out of the GF's tights. Does the airflow design make sense with that there?

 

Also I've just found that my mobo does actually have two 4 pin fan headers! (Only one near enough for the lower-front fan though I think) And two 3 pin. I thought they were all 3! Therefore that opens my options a bit to the ML or PWM fans? Are those generally better? I see there's a non-LED one too.

 

So for the front case fan, which would you say would be the most preferable from the below options? Bearing in mind the filter & HD cage.

 

  • ML140 Pro - CO-9050045-WW - (Is this a SP fan?)
  • ML120 Pro - Corsair CO-9050040-WW
  • SP140LED - CO-9050035-WW
  • SP120 PWM Performance - CO-9050013-WW - (with resistor)
  • SP120 PWM Quiet - CO-9050011-WW
  • SP120 Performance - CO-9050007-WW - (with resistor)
  • SP120 Quiet - CO-9050005-WW

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Yes, the ML fan series is pressure orientated, although with more blade angle and space than SP120. As a result, it will move more air at moderate speed than a SP120 - resistance or not. The real win with the ML series is the bearing type. It is so much quieter at lower speeds. At moderate to high, blade and air noise always make things loud, but I can run 2xML140s on my radiator and they are quiet below 1100. Not many fans can do that, especially when inverted. I would easily recommend the ML140 Pro for the front.

 

Airflow pathways seem logical. If you are going to make a filter for the side, cover both vents. Don't worry about restricting the AF120. It will be fine.

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Cheers, I'll go for the LEDless ML140 then.

 

The MLs have the better bearing, and the PWM are just controllable ya? As in the former is better. But both require 4 pin header, of which I think it will reach up to that top-right one on my mobo.

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  • 3 weeks later...

Well here we are.

 

Got the ML140 installed in the front, the cable reaches fine. It generally runs pretty slow (600-900rpm) though, I presume it will speed up more when stressed. (Doing a clean install so haven't tested yet).

 

Got the AF120 in the side, using the resistor supplied. PC is practically silent! Just a very low hum, rather than the constant whooshing and revving I had before, very nice.

 

I made a filter out of the GF's tights for both vents, as you can see in the pics. I used split pins in the 140mm holes to hold the corners in place, but the middle bits still kept rolling up, so I had to use double-sided tape to get the fabric to stick down (nothing else would stick well to my case metal, AND hold the fabric tight). I then used normal sellatape on top of that to give it some extra binding to the case.

 

As you can see from the outside you can barely tell it's there! The material is fantastic, lets air through easily, but will block dust very well. I dunked the split pins in black metal paint btw so you can barely tell they're there either hehe.

 

Thanks for the advice mate! Much better now and I bet my temps will be much cooler too.

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  • 2 years later...
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