140mm vs 120mm fans

[qstoffe]

Hello, I'm asking for your experience between 140mm and 120mm fans. In my experience I've always gotten worse results with 140mm fans when I consider low noise / cpu and gpu temps.

At what rpm would a 140mm fan be generally comparable noise-wise to a 120mm fan spinning at ~500rpm?

Also I'm thinking that 140mm might produce a larger "airflow tunnel" while a 120mm fan can produce a smaller tunnel but with more "force" at the same noise level.

I previously had 5 x 120mm case fans of Noctua NF-S12A spinning at ~500 rpm.
I replaced them for 5 x 140mm Be-Quiet SilentWings 2 spinning at ~380rpm.
I'm getting about the same temps as before. But at night I can hear a low sounding hum from the 140mm fans that wasn't present on my 120mm fans.

I've also tried Noctuas NF-P14 140mm fan (came with a CPU-cooler I bought) but with the same findings. IMO 140mm fans seems to have a "heavier" low sounding hum.

What are your opinions about this?

[quest_for_silence]

At what rpm would a 140mm fan be generally comparable noise-wise to a 120mm fan spinning at ~500rpm?

In my experience usually at no more than 300rpm: at 350rpm my Antec TruQuiet 140 is more noticeable than my best 120mm running at 500rpm.

I previously had 5 x 120mm case fans of Noctua NF-S12A spinning at ~500 rpm.
I replaced them for 5 x 140mm Be-Quiet SilentWings 2 spinning at ~380rpm.
I'm getting about the same temps as before. But at night I can hear a low sounding hum from the 140mm fans that wasn't present on my 120mm fans.

I guess that it's mainly a matter of fans/enclosure interaction: often, within a given noise floor due to airborne/airflow noise, "cavitation"/resonance noise is more evident with an higher airflow (such as a 5x140mm should be over a 5x 120mm setup). Take note that also frame/blade design may affect the fan noise spectrum (incidentally your BeQuiet should have a non conventionally shaped frame).

[edh]

It may depend upon your case. If you have 4x 140mm fans it's going to be quite a large case without much airflow focus. Just the jump up to 140mm does mean that the case itself has to be bigger so may no longer be so ideal for cooling as there is more of a possibility of air being wasted. Can you perhaps upload a picture of your case to see how air may be moving through it?

Something also to consider with 140mm fans is that some are based upon 120mm fan designs and are just stretched so aren't an ideal design. This is less of a problem now but was certainly an issue with early 140mm designs which tended to be louder for equivalent airflow.

You have also moved from the NF-S12A to the Be-Quiet Silentwings 2 so it could also just be the difference between the two fan designs rather than their size alone.

[qstoffe]

It may depend upon your case. If you have 4x 140mm fans it's going to be quite a large case without much airflow focus. Just the jump up to 140mm does mean that the case itself has to be bigger so may no longer be so ideal for cooling as there is more of a possibility of air being wasted. Can you perhaps upload a picture of your case to see how air may be moving through it?

Sure. The case is Fractal's Define S.

In my experience usually at no more than 300rpm: at 350rpm my Antec TruQuiet 140 is more noticeable than my best 120mm running at 500rpm.

I think you might be correct. I've droped all fans down to 300rpm.

I guess that it's mainly a matter of fans/enclosure interaction: often, within a given noise floor due to airborne/airflow noise, "cavitation"/resonance noise is more evident with an higher airflow (such as a 5x140mm should be over a 5x 120mm setup).

Again I think you're correct. I actually have 6 case fans (had before the replacement from 120mm aswell). My bad. The 6th fan is on the side panel right next to the GPU. I've noticed that the noise comming from this fan is a little bit louder than the others so I've dropped it down to 250rpm. It's a good thing that my motherboard kickstarts all fans during boot. Otherwise I don't think it would start at that low rpm. So far the temps seems to be pretty much the same, maybe 1 degree higher CPU during idle. I'll have to get back on the noise level after tonight since ambient noise during the day, like my monitor, pretty much drowns the noise coming from the fans.

[qstoffe]

Update: Soooo after a while I couldn't stand the noise from the BeQuiet SilentWings. They "seemingly" got louder every night. Now I have replaced all fans with 6 x Antec True Quiet 140mm fans. I'm running them at ~250rpm. I've also cut away the fan grill meshing in the case (in the back and on the side) as this restriction seemed to add to the noise.

Now my PC is barely audible again and my monitor is yet again my loudest Component. At least when in idle mode.

[~El~Jefe~]

Update: Soooo after a while I couldn't stand the noise from the BeQuiet SilentWings. They "seemingly" got louder every night. Now I have replaced all fans with 6 x Antec True Quiet 140mm fans. I'm running them at ~250rpm. I've also cut away the fan grill meshing in the case (in the back and on the side) as this restriction seemed to add to the noise.

Now my PC is barely audible again and my monitor is yet again my loudest Component. At least when in idle mode.

Very nice! You have answered much of questions in one shot. I am a big "fan" of 140mm fans. They are just so superior at cooling down a system, can't really compare them to 120mm in terms of cooling. I like to do SETI@home while I am away from my computer. 140's keep it cool. I was wondering about the truequiets but now i will just buy them tonight. (i need replacements for the ones that came with case