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 Post subject: Are variable speed fans annoying in themselves?
PostPosted: Mon Jun 18, 2012 11:29 am 
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I'm wondering whether systems that automatically vary case fan speeds might be more annoying than the fan noise they attempt to alleviate. I recall an old CPU fan I had that would ramp up under load and how terribly annoying it was to hear it speed up, cut back down, up again, down again.

I'm not sure whether this is an issue with low speed fans varying from, say, 300 RPM to 1200 RPM, but it's still a concern to me if a system goes from totally silent to "not very silent at all" and I wonder if I wouldn't find it more comfortable just using fixed fan speeds, even if it isn't the quietest option.

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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Mon Jun 18, 2012 11:52 am 
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Your past experience was probably with a small fan that sometimes ran very fast, whereby the reving up created a tonality of its own. Todays fans of about 120mm rotating with a relatively slow maximum RPM of upwards 1200 doesn't really have that problem. While I tend to generally prefer finding an ideal level for each fan and leave it there, I do so mostly because a well controlled variation of fan speed isn't always possible and rarely very easily achieved. In the end, give it a try and see how it works with your current setup. If putting together a system with all new parts or with an unfamiliar motherboard I'd recommend having a backup plan for running continually on a set speed.

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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Mon Jun 18, 2012 2:45 pm 
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I think you may be assuming that a 300 to 1200 rpm PWM fan is going to increase and decrease its speed in a straight line. In practice PWM fan control is all about avoiding the constant increase/decrease in fan speed that a control strategy like that would involve. For example Asus motherboards have a number of preset fan control profiles which can be set in the BIOS. One of these profiles - Silent - will hold a PWM fan at its minimum speed until the CPU temperature reaches 40C. Only then will it start to increase the fan speed to restrain processor and system temperatures. So under idling to light system load conditions with moderate ambient temperatures you would get a fixed fan speed with the Silent profile. With a fan like the Scythe SY1225SL12LM-P PWM this would result in a fan speed in the 300-400 rpm range. You can modify what the Silent BIOS mode provides with Fan Xpert, and with the Asus motherboards that support Fan Xpert 2 there are even more options. For example you can set a fan to not run at all at startup but turn on at a set CPU temperature, for example 50C. The speed of 3 pin fans can be controlled using the Asus motherboard fan controls and Fan Xpert 2, but the range will be more limited than it is with PWM. Typically a 3 pin fan is controllable in the 60-65% to 100% range.

If you must, you can set a fixed fan speed using Fan Xpert but at a set CPU temperature, probably something like 75C, the fan speed will increase to 100%. It does mean that at CPU temperatures below this level you could have a completely constant fan speed. With the SY1225SL12LM-P for example you could have a constant speed of 500, 800 or 1200 rpm without needing to deploy fixed speed 3 pin fans. The high temperature switch to 100% is obviously there as a safeguard.


Last edited by lodestar on Mon Jun 18, 2012 10:48 pm, edited 3 times in total.

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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Mon Jun 18, 2012 2:52 pm 
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There is something to be said for just running your fans at a straight speed.

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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Wed Jun 20, 2012 7:20 am 
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Short answer: no, if properly controlled.

What you described was poor, perhaps linear control of a loud fan. Using good control with efficient coolers and silent fans will make sure the transitions are not jarring and the sound levels remain sane - or indeed silent.

Long answer: No, and here's why.

I have always loved and used manual fan control since the day I discovered PC silencing in 2004 or so. The automatic fan control in those days either sucked hard or did not exist, the first still being true of (cheaper) systems today. When you know what you are doing, you can easily avoid fan zig-zagging and excessive volume levels. Software like Speedfan and most recently Asus' Fan Xpert+ and Fan Xpert 2 can be used for this, as can some smarter hardware controllers, but the controllers are becoming a thing of the past as motherboards get better features. Abit already showed the world that controllers were redundant with their µGuru many moons ago (LGA775 days).

To give you an example, I have the Asus P8Z77M-PRO motherboard with Fan Xpert+ that allows me to set the fan profiles, presented as "curves" (drive/temperature graph), manually. My current setup involves 4 fans: two low-RPM intakes, one static RPM CPU cooler fan and one exhaust. I don't count the PSU as it is silent and non-controllable.

Here's some profiles: http://imgur.com/a/9B4Eu.

The first profile is the CPU cooler profile. I use a fan running at a static speed I find comfortable for cooling the CPU in any situation. This gives me not only unchanging noise, but predictable cooling behaviour, helping avoid zig-zagging through a controlled change of the temperature reading used as the profiles' "trigger" value.

The second profile is the exhaust fan. It uses a linear profile, which used to be the most prevalent type in cooling systems of old (and still is in most of the cheapest ones). This gives a direct, immediate response to temperature rise and I prefer it because it's important to exhaust hot air ASAP to prevent heat buildup under load. You can typically use a small motor, high CFM fan for unimpeded exhaust, meaning the response will not be very audible (or in case of my Noctua, noticeable at all) but still effective.

The third and last profile is the intake fans. They use a progressive profile (well, as progressive as three-point control allows), which means that the fans respond to heat depending on the level rather than the absolute figure: the fans only speed up a little when there's not much heat, but respond more aggressively as buildup or high load occurs. They've also been cut more slack in regards to the trigger level to be reached. I've raised the bottom drive level to emphasise the progressive profile's difference to the linear; I prefer to run at the minimum of 41 % drive (700 RPM for these fans).

The points on the temperature scale were chosen through rigorous testing.

The first trigger point should be above idle and typical load - in my case this is under 35 °C. This way fans will stay at a steady RPM in normal use, silent fans and efficient coolers having no trouble staying inaudible at these levels.

The second trigger point defines the first stage of controlled cooling (between points 1 and 2) and should be above typical maximum load - I went with 45 °C in this example, can easily stretch to 50-55 degrees. For this stage I find the maximum comfortable noise level of my fans first (usually under 1000 RPM for 120 mm fans), then set the computer to run a "typical maximum load" task like defragmenting or a virus scan and adjust the fans down until I find a comfortable and stable temperature level. This stage takes the most learning (patience, really) at first as you have to tweak the fans as a system and at varying load. The end result is efficient cooling response to loads over regular use with fans still running at comfortable levels - very nice when the PC is left idle and AV starts, for example. The longer you make this stretch, the smoother (more gradual) the response is.

The last trigger point could be used to make the cooling three-stage, but I don't like making big jumps in fan control for fear of stressing the delicate electronics. This should essentially be the point where you don't want your temperatures getting any higher, and I usually set it just below TCase (in layman's terms, this is a value given for the CPU over which they should not be allowed to heat, even though it will not break the CPU to do so). In this case it's 65 as the i5-3570K has a TCase of 67.4.

This is what I use for a gaming and work PC. If you never game or do anything heavy-duty like that, you could make the profiles even more refined by using the last trigger point to create a smoother stage 2. Then again, in a computer that runs intensive tasks like folding or rendering for long stretches of time, static fan control is a strong candidate, as you can try and find a comfortable level at maximum stress and just leave the PC there - peace of mind with minimum effort.

Sorry if the latter part of the post got a bit long, but this is such rudimentary stuff I felt like shedding light on the basics through example. :idea:

Edit(s): double post got what was supposed to be v2. :P

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Last edited by Das_Saunamies on Wed Jun 20, 2012 7:28 am, edited 1 time in total.

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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Thu Jun 21, 2012 3:23 am 
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Das_Saunamies wrote:
Software like Speedfan and most recently Asus' Fan Xpert+ and Fan Xpert 2 can be used for this, as can some smarter hardware controllers, but the controllers are becoming a thing of the past as motherboards get better features. Abit already showed the world that controllers were redundant with their µGuru many moons ago (LGA775 days).

Lots of modern boards still support just a single case fan. :( So I can't agree.
Even Fan Xpert only supports control based on CPU temp, doesn't it?

Having all fans run at a static rpm means optimizing for the worst case. If you've got a CPU and GPU that can consume a lot of power, optimizing for the worst case may not be ideal.


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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Thu Jun 21, 2012 3:28 am 
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I can see where you're coming from Olaf, but HDDs can be cooled with minimal airflow, GPUs have their dedicated coolers, chipsets are a non-issue now and that just leaves the self-sufficient PSU and CPU. I think it's good enough for most people to just have CPU to go by, it's pretty reactive to most if not all tasks a system goes through. It would be better if we had more of course, but this is pretty good already - I know I've been able to replace even the BigNG with software control.

And if you want fan control, why would you buy a board with that kind of limited control when there's better, affordable options. I haven't even seen such limited boards recently, but maybe that's because I don't look in those categories. :P

Static is a special build. It's hardly the best for silence, but it is ideal for getting away with the least effort and expertise. ;)

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Case: FD Define Mini
Parts: P8Z77-M Pro µATX, i5-3570K @stock, N650Ti-1GD5/OC, G.Skill 2x4/1600/CL9 DDR3U, Xonar DX, WD G 1 TB, m4 128 GB, RX-5300 PSU
Cooling: Noctua NH-U12P SE2 + Scythe SS PWM, 2x Noctua NF-P12
Extras: Eaton UPS, Dell 24" EIPS, Ducky kb, SteelSeries m, Synology DS213j NAS
idle & load: CPU 32 °C & 44 °C @ 300/600 & 600/800 RPM, GPU 35-65 °C @ 1200-1650 RPM


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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Thu Jun 21, 2012 5:55 am 
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Das_Saunamies wrote:
GPUs have their dedicated coolers

Yes, but most non-references designs don't exhaust (hot) air, so case fans are still required. Even if they do exhaust air, some intakes are handy to have.
Quote:
And if you want fan control, why would you buy a board with that kind of limited control when there's better, affordable options. I haven't even seen such limited boards recently, but maybe that's because I don't look in those categories. :P

Because the Asus site sucks and it's hard to find info on fan headers and control. It's Asus H61 boards I've got.


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 Post subject: Re: Are variable speed fans annoying in themselves?
PostPosted: Wed Jun 27, 2012 12:58 pm 
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Alrighty. I've been lulled into a la-la land of fantastic products because I've just been knee-deep in the better designs. I tend to forget there's still a world of crap out there that's being hoisted onto people for no other reason than profit.

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Case: FD Define Mini
Parts: P8Z77-M Pro µATX, i5-3570K @stock, N650Ti-1GD5/OC, G.Skill 2x4/1600/CL9 DDR3U, Xonar DX, WD G 1 TB, m4 128 GB, RX-5300 PSU
Cooling: Noctua NH-U12P SE2 + Scythe SS PWM, 2x Noctua NF-P12
Extras: Eaton UPS, Dell 24" EIPS, Ducky kb, SteelSeries m, Synology DS213j NAS
idle & load: CPU 32 °C & 44 °C @ 300/600 & 600/800 RPM, GPU 35-65 °C @ 1200-1650 RPM


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