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Which fans/pump to use – 2xgpu 1xcpu lownoise?

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Jun 1, 2008
I am planning to put together a watercooled desktop ‘soon’. I’m using the Mountain Mods Ascension case (I have a spare one from a previous build) and plan to bolt radiators to the back, so space is not an issue. I would rather go with extra radiators, with slower, quieter fans rather than a maximally efficient loud loop. I would like a single loop system, with 2xGTX1080 (factory overclock only) 6900X CPU (moderate overclock, 3.8-4.0 GHz), 2x Nemesis GTX 4x120 radiators, 1x Nemesis GTX 3x120 radiator (radiator overkill = slower fans). Ideally, I want the system to be low-noise, with the fans hitting around 25 dB total (lower is better, but this might be the realistic floor), and single loop, with the ideal loop as reservoir->pump->CPU->4x120 radiator->gpu1->gpu2->7x120 radiator (4x+3x)->reservoir. The minimum flowrate should be a reasonable 1 GPM. I have some ideal choices for fans and a pump, but might have to go with second choice if they can’t handle it:

First up, what pump should I use?
Ideally, I’d want to use a single MCP655 pump, tuned to around 70% power for noise control. Unfortunately, with 2 GPUs, a CPU, and 3 mid-restriction radiators, I’m not sure a single pump’s going to cut it and get 1GPM at this restriction level. The MCP50x has the power, but not necessarily the flow rate, and seems a bit loud. The MCP35x2 or EX-XTOP Revo Dual D5 are definitely options, but 1) seem like overkill and 2) have PWM speed management, which means I really have no control over the pump noise, when compared to a pump I can dial in manually and leave alone (trust in my motherboard to make everything nice is not a happy option). Can I get away with a single MCP655? What if I don’t use the Revo dual top and instead put two 655’s in series (reservoir->pump->pump->cpu) both tuned to 50-75%? Would that work, or am I really not getting much extra there? If I absolutely have to, I know I can split this into two loops with a 655 on each, but I’d really rather not. I’d also much rather have larger, quieter pumps (D5) than small, noisy ones (50x).

Next up: fans
There are 15 case slot fans (6 front going in, 6 back going out, 3 top going out) and 22 radiator push-pull fans (11 slots, going into the case). This leaves the case at positive pressure (6in, 11radblockedin, 9 out), but that’s fine with me because 1)I hate cleaning dust and 2) the case fans/pressure don’t matter too much, as the real cooling is done via the external bolted-on radiators, which aren’t going to care about internal case temperature as long as there’s airflow. 3) Did I mention dust?
Ideally, I’d like the 37(!) fans to hit about 25 dB total or lower (which isn’t happening, but hey, I can dream).

The fans I’m eyeing for this are:
22x Noctua P12 w/ULN @ 1.21 pressure, 900 RPM, 37 CFM, 12.6 dB in push pull on radiators
15x Noctua S12 2/LN @ 0.73 pressure, 900 RPM, 49 CFM, 11 dB on case (with a filter over the front 6 for dust control)
This gives be about 28 dB total noise 10*Log10(22*10^1.26+15*10^1.1)=27.7ish which is pretty close to my goal.

I’m not sure if 900 RPM is enough for the radiators to cool 2 high-end GPUs and an mid-overclocked CPU though, even with the overprovisioning on surface area: If I have to, I can upgrade to:
22x Noctua F12 w/LN @ 1.83 pressure, 1200 RPM, 44 CFM, 19 dB in push pull on radiators
15x Noctua S12 2/LN @ 1.19 pressure, 1200 RPM, 63 CFM, 18 dB on case (with a filter over the front 6 for dust control)
Unfortunately, this will give me a bit over 34 dB of noise, or about 4-5 times as loud  Can I get away with the quieter fans?

As an aside, are there any good filters I could put on the input fan side of the radiators to help with dust control without excessively restricting airflow? Although I’d love to say I’ll be cleaning out the radiator fans every few months, in reality, I’ll probably be lucky to get around to it once a year, and dust happens. There don’t seem to be many filters designed to fit on top of radiator fans, sadly. I could cut some pantyhose/Swiffer filter to fit, but this might halve airflow, which might be an issue if I’m using the 900RPM fans? Ideas?

Thanks for the advice!

1)cpu, 2xgpu, 11x120 rad, can I use 1 MCP655 pump for 1 GPM? If not, what (quiet) pump(s)?
2)900 RPM push/pull @0.73 pressure okay for 11x120 radiators, or do I need up upgrade to much louder 1200RPM fans?
3) Any dust filters I could use with the radiators?
My suggestion to you is this.

1. Grab a pair of D5 pumps in serial since they are quieter than DDC pumps. I run a MCP35X2 and is audible at 35%-40% PWM. I create a curve for them so when I'm gaming and folding they will sound off but I don't hear them as much since I use a headset. My headset is technically worn 24/7 when I'm on the PC whether I'm listening to something or not. I guess I'm just used to it for a while now.

2. Grab the Gentletyphoon PWM fans. They are still the best radiator fans in the market with a few others not too far behind them. They have the best all around performance including audibles. They seem to be sold out ever since they've come back in the market for sometime now. One place that I do know that usually have them are Modmymods or PPCS. They do seem to be out of stock everywhere but there still might be some inventory left. I hope they restock in all of these places as I might be upgrading to these fans towards the end of the year possibly.

Now with all that said, how are you looking to monitor and control with such a vast system? We're pretty much in the same boat here as I went down the premium route and purchased a controller and monitoring system called the Aquaero 6 XT. It controls my pumps and fans through a curve as well as the LED lighting. I should warn that it does have a bit of its own learning curve. If this a bit too much added to your project and budget, you could just go the cheaper way and just use PWM/Voltage Fan hubs connected to your MB.

I also have a flow meter which I usually recommend for big loops because its nice to know the flow of the loop and helps find its efficient sweet spot (1.0-1.5GPM) as well as having it as a warning system when there's things going wrong not visible to the human eye. It has saved me in the passed actually as I witnessed my loop's flow deteriorate slowly before I did a full tear down and found the culprit.

As for dust filters, check this site out and see if they have what you need. They are usually the go to place for case dust filters.

Hope this helps and hope to hear from you.
Suggestions response

My suggestion to you is this.
1. Grab a pair of D5 pumps in serial since they are quieter than DDC pumps. I run a MCP35X2 and is audible at 35%-40% PWM. I create a curve for them so when I'm gaming and folding they will sound off but I don't hear them as much since I use a headset. My headset is technically worn 24/7 when I'm on the PC whether I'm listening to something or not. I guess I'm just used to it for a while now.
Yup, that’s what I was afraid of with the MCPs. I’m leaning toward the 2x655’s at 50-70% manually set in serial, good to know that will work
My suggestion to you is this.
2. Grab the Gentletyphoon PWM fans.
I’m actually specifically trying to avoid the 15’s, which you linked. I have a a few 15 and a lot of 13 GT PWMs around from previous builds. The 13s aren’t made anymore, and their performance numbers aren’t as good as other newer fans. The 15s, at 1850 RPM 26dB a piece, are a lot louder than I want, and the static pressure on them is only 2.06 with 58 CFM. The Noctuas, on paper, are much better in terms of noise and pressure (F12, P12) or CFM (S12), and Noctua’s generally pretty accurate in their specs (unlike the Cougar Typhoons which look great on paper but are a lot louder than advertised). I also don’t want to use PWM fans, as hooking together so many to the motherboard becomes iffy, and I don’t want to have to use a fan controller to turn them down and up manually. The plan is, with so much radiator space, to just keep them all running at a constant 900 (or 1250) RPM regardless of system usage. My main concern is that the 900 RPM fans might not be enough to keep the system cool. If I upgraded the radiator fans to GT-15’s, I’m looking at a 40 dB computer. 42 If I upgraded the others too. Eww.

My suggestion to you is this.
Now with all that said, how are you looking to monitor and control with such a vast system?
My previous build had a lot of monitoring, hardware, flow controls, fan controllers, lighting controls, temperature sensors, etc. built in, and I found after the first 2 months, after everything was stable, I more or less didn’t touch them for the next few years. This time round, I’m going with the less is more approach. I’m not going to be doing any large overclocking, and given that I’m designing the system to be low-noise, I really don’t see the need for a fan controller, PWM fans, or extra temperature monitoring sensors. I’d rather just plug the fans into standard molex/3pin and let them spin away at 900/1200 max RPM all day. Fan controllers are only really needed to throttle back high RPM fans for daily use, or customize high-RPM fans to work at extremely low RPM, neither of which I’m doing (unless I go with the GT-15s, which I don’t want to do). A flow meter would be nice, but adds restriction. Still, something like http://www.performance-pcs.com/koolance-ins-fm18d-coolant-flow-meter-with-display.html seems a good compromise - easy to read, fairly cheap, and looks like its fairly low-restriction.

My suggestion to you is this.
As for dust filters, check this site
Yup, seen those already, they look wonderful! Those are actually the ones I plan to have going on the front 6 fans. I was really looking for solutions for the radiator fans. Those don’t really seem like they’d fit over the radiator fans. Edit: OOH! they added a section for HardwareLabs radiators since the last time I bought from them! Problem solved!

Still need lots of help with fans,
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Update: most of the questions answered. I will use 2x655 Vario pumps with an EK Dual top, DCIMFlex radiator shields, single loop, with an inline flow monitor. Here is the remaining question:

I have a loop with 2 GTX1080 cards (factory overclock only) and 1 6900K processor (moderate overclock to 3.8-4.0Ghz). I am cooling it a 1 GPM with 11x120mm radiators (HardwareLabs Nemesis GTX 2x4 + 1x3) with fans in a push-pull setup, giving me a loop TDP of about 750W to dissipate.

I want to run 22x Noctua P12 fans in ULN mode (1.21 pressure, 37CFM, 900RPM 12.6DDB ea) to cool this. They will likely have DCIMFlex radiator shrouds over them (20% efficiency loss).
Will these fans be enough for this loop?

If I have to, I can upgrade to NF-F12s (1.83 pressure, 1200 RPM, 44 CFM, 19dB) but this is a last resort, as it will make the computer about 4x as loud, and I want a build as quiet as possible.

No, I don't want PWM fans or GentleTyphoon-15 1850 RPM fans.

Thanks for the help!
If noise is such an issue and having that much rad I would doubt you'd need push pull. Those rads (according to the manufacturer at least) are designed for low speed fans anyway
Yes, they are, and reviews show them having a very impressive RPM-cooling curve for even low RPM fans. However, everything I've read shows that for a given noise level, you're much better off using a 2 quieter fans in push-pull rather 1 louder fan in push-only. I certainly don't mind running the 900 RPM fans in push/pull noise-wise, and they would generate less noise than even a push-only 1200 RPM fan, but I'm not sure if they would be able to handle the heat dissipation, hence the question. There seems to be no point going push-only if space isn't an issue (which it isn't) since an equivalent noise push-pull setup is always going to be more efficient than a push-only.

Edit: Unless you're implying that the lower-speed fans would be adequate even in a push-only setup with that much rad? Please clarify. (In which case thanks for the answer!)
I'm saying you're likely fine with the 900's in just push with that much rad, if I saw the specs right those are 54mm thick rads with 11x120 total size. I'm definitely not an expert on this so I'd let others chime in as well but I think you'd be alright
Have you tested the GTs at low RPM? I've been told that they're super quiet at low levels as most fans aren't, hence why they're the king of the hill still.

Also check out EK Vardars (F120? I think but not sure) and Noiseblock Eloop B12s.
Ah great! Good to know on the 900s.

To run the GTs at low RPM, I would need a dedicated fan controller with all 22 fans wired to it via a series of splitters, which is something I'm trying to avoid (and the main reason I'm trying to avoid GT). This would take up unnecessary space, cost, cabling, and effort, compared to a basic molex-chain and low noise adapter setup. The static pressure on the GTs max's out at 2.2, and doesn't seem to beat the pressure-designed Noctua NF12, in noise or pressure in the F12's 1200-1500 RPM range. At extremely low speeds (900RPM range) the pressure on the GTs drops off sharply. They used to be king of the hill, sure, but they're starting to show their age outside of the 1500+ RPM range. I would also need one for the Vardars (1850RPM, 30db base). There's actually an older GT version, GT-13, which I have, which naturally runs at 1250 RPM, but again, the Noctuas are better in that range. There's also a GT which runs even slower, but it's not made anymore, and I don't have any.

The Eloop's definitely deserve further consideration - I'm surprised I haven't heard of them before. The downside is, they offer half the static pressure of the Noctuas. On the plus side, they might be quieter. Looking into them, it seems that I would need the B12-1 or B12-2's.

The -1s offer about half the pressure of the noctuas, and very similar airflow, at 8dB, instead of 13. Using these as radiator fans would reduce system noise from
28dB to 25dB

The higher performing option, the -2, offer 2/3 pressure of the louder noctuas, and have about 20% increased airflow, and would reduce system noise from 34db to 33dB.

So on paper, at least, that rules out the -2s

Looking at the -1s, it doesnt seem like a 50% pressure loss is worth a 3dB savings...but let's google a bit more and see...after all, practical reviews beat MFR listed specs every time. Amazon doesn't carry them :( but Performance PCs does, but theyre low on stock, as does FrozenCPU (but Frozen's are a ton more expensive). The NB's also look a hell of a lot better than the ugly Noctuas, but that's not such a big deal to me.

I can't find any direct tests of the -1s, but there's a few reviews of the F12/GT15/NB PWM versions, so we'll use that...As far as I can tell, they're definitely better than the Noctua's at high RPM, and either very similar or slightly worse at low RPM depending on who you ask. However, the deal breaker is that the NBs apparently stick slightly out of the casing on one side, so you can't use them with either the radiator dustshroud I was planning on using, or on the pull side of a radiatow. Awww...they're pretty, but with a 50% pressure loss, no push, and iffy shroud installation, I'm still looking at 900Noctuas, especially if I can avoid the 1250s, as jaymz suggests. (I might even try the Noctuas in push-only if I think I can get away with it!)

Still, those NB's have some amazing potential, and I'll have to keep an eye on them, especially the next time I need high-RPM case fans for a build! Thanks for letting me know about them, and they were definitely worth a couple hours of googling and graph studying to discard for this round!
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I run these fans, and under most circumstances, they are inaudible. I have them connected to a powered spliter, which is controlled by my motherboard, and they only ramp up past 1000RPMs under heavy gaming load or better. They don't have many in stock, though.

There is a slower version as well, that is in good stock at PPCs. That would be my recommendation, based on my experience with the eLoop model. However, I've heard great things about those Noctua fans as well.