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Question: SP140 worse than SP120


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I've got a Corsair Spec Alpha case and I'm looking to upgrade my cooling a bit by adding two additional fans, either 120mm or 140mm. The case comes with 3x 120mm fans (2x front intake and 1x exhaust), and my potential configurations will be either:


A) 3x 120mm front intake, 1x 120mm rear exhaust, 1x 120mm top exhaust

B) 2x 140mm front intake, 1x 120mm rear exhaust, 1x 120mm top exhaust*


*I'll eventually add the 3rd 120mm as a bottom intake, but will need to wait for a PSU upgrade since my current one only has one rail positioned close to the case floor, and there isn't enough clearance to fit a fan down there.


I've been looking at either the Corsair SP120 or SP140 fans, in order to match the appearance of my build, and also because I'm cheap. I have some concerns, however, since the specs of the fans as listed on Corsair's website don't make any sense.


I expect the SP120's to be louder than the SP140's for similar airflow, yet the specs as listed indicate the opposite! The 140's:

- are 3 dBA *louder*

- have 0.3 mmH2O *lower* static pressure

- have 8 CFM *lower* airflow volume.



Based on these specs, the SP140's are objectively worse than their little brothers for case fan applications. 10.9% louder for 19.8% worse static pressure and 13.5% worse airflow volume. I know these are probably values at maximum fan speed, but even so I'd expect them to scale with RPM so even at 50% I bet the 140's still perform worse than the 120's.


I've double checked to make sure I'm not comparing a high performance to a quiet model or anything like that. The SKU's are CO-9050033-WW (SP120) and CO-9050038-WW (SP140). I can see the greater surface area being beneficial for radiator applications, but that's it.


I'm hoping that someone just bungled the specs when making the web pages and swapped them across models.



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I had forgotten about this and it hasn't come up in quite a while. For those that do not recognize the specifications straight off, these are the SP120 LED and SP140 LED models, not the non-LED SP versions with different blades.


There are a few things that come together to create this.


1) Static pressure is entirely RPM dependent and does not directly correlate with fan performance. I have a nice 40mm fan that blows both of these models out of the water in terms of static pressure with a 2.8mm H20 value. However, it still only moves 9 cfm at 4000 rpm. You need to do the actual airflow vs resistance tests to get a more meaningful set of airflow data points and if I remember correctly, the LED models are anything but linear. The SP120 LED has a higher static pressure value because it runs a higher RPM. Static pressure is the amount of negative pressure it takes to stop a fan at its maximum speed. That's it. It does not mean the SP120 moves more air at 900 rpm.


2) Airflow - Neither of these fans is a great windmill of airflow. I own 12-16 of the SP140 LEDs and I would say its specifications are accurate based on years of use and comparison. I always felt the SP120 LED airflow value was a bit over-inflated and regardless of actual linear airflow, it most certainly does drop off quickly as you move away from the maximum speed. When it was created, the SP140 LED was a unique blade within the Corsair family. Perhaps it was not optimized for maximum flow or it was the first run at a specific design. I think most likely it was optimized for middle RPM use against resistance and that is where the meatier part of its P-Q curve can be found, especially when compared to the existing and then super popular AF140 fan. They had a super high flow fan for high speed. This was meant for lower speeds against resistance.


3) Noise - A 140mm fan at 1000 rpm does not equal a 120mm fan at 1000 rpm. The 140mm blade has more mass and will make more noise at the same speed, but of course move more air. You could make a rough calculus of equivalent airflow and comparative noise and they probably come out about the same when 300-400 rpm apart. However, as you noted and the point of this thread is the SP120 LED airflow value seems a bit high. I agree it is. In this case a 140mm fan at 1400+ is always going to be louder than a 120mm at 1650 rpm. Oh, and the 26 db at 1650 isn't happening either. Neither of these fans are particularly quiet at high speed.



I am not sure what other hardware you have going on, but you may wish to bring the AF120/140 LED fans into consideration. In the 140mm category, the AF140 is a runaway winner on every front unless you are going to bolt it to a radiator. Good airflow and respectable noise at 700 rpm and it will move just as much air as a SP140 at 1400. The 120mm comparison is less clear cut. I am not quite as enamored with the AF120 as the larger sibling and they can be a bit buzzy at speed. That is true of all 120mm fans, but that is a frequent noted observation for that model. Running a bank of 3xSP120 LED vs AF120 LED across the front likely comes down to if you are using a dust filter and if prefer to run your fans as quietly as possible or if you blast away, headphones on demanding maximum airflow. The higher the fan speed, the less resistance (dust filter) is going to matter. A radiator is another matter and I would want the SP series for that.

Edited by c-attack
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Thanks for getting back to this!


I appreciate the explanations about the concerns I had about these two particular fans. Roughly 5 mins after I wrote the original post it occurred to me that the static pressure had something to do with rotation speed.


The interior of my case is largely empty; there's no 5.25" bays, all cabling aside from the mobo and 8-pin PCIe power connections is tucked behind the mobo panel, and I'm only running with a single GPU and a wifi card and no AIO, so there shouldn't be much obstruction within the case. My primary concern with running the AF series fans was that roughly half of the front fascia is solid, and the remaining half has a cosmetic mesh and an integrated dust filter. The front I/O panel also sits within the meshed area, so I estimate that only 45% of the front fascia is actually able to serve as an intake, and with considerable obstruction due to the filters.


I do tend to run my fans on the quiet side, so I was leaning toward the 140's to start with, but was confused by the numbers on the SP120's.

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TMy primary concern with running the AF series fans was that roughly half of the front fascia is solid, and the remaining half has a cosmetic mesh and an integrated dust filter. The front I/O panel also sits within the meshed area, so I estimate that only 45% of the front fascia is actually able to serve as an intake, and with considerable obstruction due to the filters.


Yup, that is the tricky part in all this. Corsair used to recommend a 3mm space on the inlet side of the AF120/140 (or any steep raked blade fan). So if the dust filter is very flush against the fans, that would be a definite restriction. If it has a decent offset from the blade, it may not matter quite so much. I think the case mesh itself is most irrelevant given the spacing, however I have never worked with that case with my own hands, so if there are any Spec Alpha owners out there who have worked with these models or similar, this would be a great time to join the discussion.


You may also be happy to split the difference and go with a hybrid blade style between the two archetypes of SP/AF. Most fans are a compromise of the two and the market has taken a definite shift that way. Also, 3x120 will always beat 2x140. However, looking at the spec page it seems very non-committal about what will fit in the front rail. Take a good look at how a 140mm will fit. If a lot of the fan blade will be obstructed by a mounting rail or anything else, you may get less air and more noise than expected.

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