Which is better? (silent 12v or undervolting)

Remonster · Post by **Remonster** » Mon Aug 21, 2006 10:08 pm

I have wondered this for a while and I thought you guys could help me, I am slowly piecing together my next computer (won't build until March...) and I am weighing each choice very carefully as I want this system to be perfect, but when it comes to choosing case fans, I am unsure if it is better to get a very quiet fan or to get a higher CFM fan and undervolt it through the use of a fan controller?

For example the Scythe S-FLEX is generally accepted to be the quietest 120mm fan available right? So would I be better off getting the D model (800RPM) or getting the E or F models and slowing them down with the fan controller?

Lawrence Lee · Post by **Lawrence Lee** » Mon Aug 21, 2006 10:44 pm

I prefer undervolting higher CFM fans. There are cases when the fan is TOO quiet and if you want it to run faster, there's nothing you can do about it (over-volting a fan is never a good idea). Plus if you have it controlled you can have it as quiet as you want it assuming it can start up at that voltage.

I keep every single one of my fans controlled either by the motherboard thru Speedfan or through my Sunbeam Rheobus and I wouldn't have it any other way.

Remonster · Post by **Remonster** » Mon Aug 21, 2006 11:06 pm

So what you're saying is I should get the SFF21F (1,600RPM; ~70CFM at 28dBA) and have it controlled through a fan controller. This makes sense to me but I was just wondering if this fan at 7v or 5v would be as quiet as the 800RPM SFF21D?

jaganath · Post by **jaganath** » Tue Aug 22, 2006 1:52 am

For example the Scythe S-FLEX is generally accepted to be the quietest 120mm fan available right?

No. Nexus, Yate Loon and Globalwin NCB 120mm are quieter.

JazzJackRabbit · Post by **JazzJackRabbit** » Tue Aug 22, 2006 4:39 am

Concerning RPM, I can't think of a scenario where you would need more than 1350RPM to cool your PC effectively, unless you have a very constricted air paths and very restrictive air intakes. To the OP 1600RPM will probably be an overkill, depending on your rig 1000-1350 should be more than enough.

DrCR · Post by **DrCR** » Wed Aug 23, 2006 5:26 pm

jaganath wrote:
For example the Scythe S-FLEX is generally accepted to be the quietest 120mm fan available right?
No. Nexus, Yate Loon and Globalwin NCB 120mm are quieter.

I'd better adjust the sticky....

cpemma · Post by **cpemma** » Sat Aug 26, 2006 3:28 pm

Remonster wrote:I want this system to be perfect, but when it comes to choosing case fans, I am unsure if it is better to get a very quiet fan or to get a higher CFM fan and undervolt it through the use of a fan controller?

I'd go for very quiet 120mm fans and still undervolt them. Look at the numbers. An 80mm Panaflo L1 will give 24cfm at 12V and probably do a decent cooling job in a good case. A 120mm Nexus Silent will give 37cfm at 12V. Cut the Nexus back to 24cfm and you've the same cooling power in a quieter system.

Simplified, but you get the idea?

Thomas-BP2 · Post by **Thomas-BP2** » Sat Sep 02, 2006 3:19 pm

According to http://www.stillepc.dk, the Scythe S-Flex SFF21D beats the Nexus Real Silent fan at default 12V. I found a 120mm fan review from March this year, where they include the three 'new' Scythe S-Flex fans (SFF21D, SFF21E, and SFF21F).

You can find the comparison tables here. You don't really need to understand Danish to read the tables, because RPM, Volt, dB(A) are the same as in English

Under the first table it says that * means that the sound level was measured at the default 12V. For both tables, 'BlÃ¦ser' means 'Fan', but I guess you could have guessed that.

If you click the link to the pages for the individual fans, then the text under the table with Volt, RPM, and dB(A) means:
** Lowest voltage where the fan does not stop spinning
*** Lowest voltage where the fan will start spinning
Distance between fan and meter: 1 meter
Ambient noise in the room 14dB(A)

They measure the sound level of the fans from 'both ends', so both by providing the fans with 5, 7, 9, and 12V and by adjusting the voltage in order to get exactly 500, 750, 1000, 1250, and 1500RPM (with a laser tachometer).

To get the subjective parts of the reviews in full you will need to learn Danish

They picked winners in three categories:
Best low-noise fan: Scythe S-Flex SFF21D (it runs 800RPM@12V default - 17dB(A))
Best all-round fan: Scythe S-Flex SFF21E / Nexus Real Silent Case Fan (they match each other at 1,000RPM, though at different voltages)
Best powerful fan: Scythe S-Flex SFF21F (flexibility through wide range from powerful cooling to quiet operation with fan controller).

Felger Carbon · Post by **Felger Carbon** » Sat Sep 02, 2006 4:14 pm

Thomas-BP2 wrote:According to http://www.stillepc.dk, the Scythe S-Flex SFF21D beats the Nexus Real Silent fan at default 12V.

Of course. A good 800RPM fan will always be a lot quieter than a 1000RPM fan. The Nexus, if undervolted to 800RPM, has its noise level drop 5.8dBA and will probably be slightly quieter than the S-Flex D at the same RPM.

If you want the quietest 12V 120mm fan, then you want the one with the lowest RPM (and hence also the lowest CFM!). By using a fan controller such as the Zalman Fan-Mate, you can pick your RPM (up to the maximum of that fan). This gives you more flexibility.

And the money you'll save buying a ~$4 YL D12SL-12 or a ~$6 Globalwin NCB will pay for the Fan-Mate.

Thomas-BP2 · Post by **Thomas-BP2** » Sat Sep 02, 2006 6:33 pm

I have no experience with either the Nexus or the Scythe yet, but based on the review I mentioned I will go for the Scythe next time I buy new fans. I am not a fan boy of any of the companies, I only judge from the review where they are compared.

These are the comparisons from their tests:

Equal rpm comparison:
Nexus: N/A dB(A)@500rpm, 15dB(A)@750rpm, 20dB(A)@1000rpm/1024rpm (top speed)
SFF21D: 14dB(A)@500rpm, 16dB(A)@750rpm, 17dB(A)@887rpm (top speed)
SFF21E: 15dB(A)@500rpm, 16dB(A)@750rpm, 20dB(A)@1000rpm, 25dB(A)@1250rpm (top speed)

Equal voltage comparison:
Nexus: N/A dB(A)@404rpm(5V), 14dB(A)@625rpm(7V), 16dB(A)@795rpm(9V), 20dB(A)@1024rpm(12V)
SFF21D: N/A dB(A)@ N/A rpm(5V), N/A dB(A)@446rpm(7V), 15dB(A)@639rpm(9V), 17dB(A)@887rpm(12V)
SFF21E: N/A dB(A)@438rpm(5V), 15dB(A)@701rpm(7V), 19dB(A)@948rpm(9V), 25dB(A)@1267rpm(12V)

Nexus is a bit better at equal rpm (though SFF21E is equal to Nexus at 1000rpm), but SFF21D is a bit better at equal voltage (though SFF21E has 34rpm more than Nexus at 5V which is too little for SFF21D to spin). Technically, SFF21D is half as noisy as Nexus at 12V (tecnically noice doubles for every 3dB, but subjectively it sounds like double for every 7-10dB).

As I said, SFF21D beats Nexus at 12V, which is factual based on the test. From these results, I think it is fair to say that, in general, the Nexus matches the S-Flex fans or that the S-Flex fans match the Nexus. As they also note in the test, all the tested fans, except for the SFF21D, need to be undervolted in order to provide a performance that can start being called quiet!

Both the Nexus and the Scythe fans are available in Hungary (YL is not), but Nexus is a bit more expensive. Therefore, from my point of view, the Scythe fans are better than Nexus - why should I pay a bit more to get the same performance?

As all the fans have 7 wings and are pretty much shaped identically, my guess is that, in terms of CFM, there is no significant difference when the fans are compared at the same rpm!

jaganath · Post by **jaganath** » Sun Sep 03, 2006 12:39 am

As I said, SFF21D beats Nexus at 12V, which is factual based on the test

Yes, but this is not surprising as the SFF21D spins 200rpm slower than the Nexus at 12V; it is not an apples-to-apples comparison. All other things being equal, a slower fan will always be quieter than a faster fan, but it will also produce less CFM.

As all the fans have 7 wings and are pretty much shaped identically, my guess is that, in terms of CFM, there is no significant difference when the fans are compared at the same rpm!

Correct.

Both the Nexus and the Scythe fans are available in Hungary (YL is not),

I normally get my Yate Loons from Silencio, he ships anywhere in Europe for a very reasonable price.

cpemma · Post by **cpemma** » Sun Sep 03, 2006 2:21 am

Thomas-BP2 wrote:As all the fans have 7 wings and are pretty much shaped identically, my guess is that, in terms of CFM, there is no significant difference when the fans are compared at the same rpm!

First I agree - as I've said elswhere "State of the art is such that the main difference between a cheap generic fan and a more expensive one is quality".

However, fan noise comes from at least three sources;

Wind noise - main influence blade speed, and usually the loudest contributor to the total,
Motor noise - influenced by speed, but more variety across different fans from bearing design and tolerances,
"Electronic" noise, an effect such as clicks and growls produced by interaction of commutation switching with the motor bearings.

So slowing any fan down will give a great reduction in noise, but then the more subtle differences from (2) & (3) come into play. These last two are a major topic here, with same-model fans varying depending on the production date, storage conditions, etc, and models such as Nexus Real Silent that we can expect consistency from are highly prized. But we don't all use them, many members have found alternative fans that they're very happy with. Just a case of Your Mileage May Vary.

andaca · Post by **andaca** » Sun Sep 03, 2006 6:35 am

jaganath wrote:
For example the Scythe S-FLEX is generally accepted to be the quietest 120mm fan available right?
No. Nexus, Yate Loon and Globalwin NCB 120mm are quieter.

NOT TRUE. IMO.

jaganath · Post by **jaganath** » Sun Sep 03, 2006 7:16 am

There's absolutely no point just saying "not true" (caps lock is not obligatory on this forum BTW), say which ones you are referring to (there are several S-Flex models) and bear in mind the above caveats about comparing at identical RPM's.

Thomas-BP2 · Post by **Thomas-BP2** » Mon Sep 04, 2006 2:15 am

jaganath wrote:
As I said, SFF21D beats Nexus at 12V, which is factual based on the test
Yes, but this is not surprising as the SFF21D spins 200rpm slower than the Nexus at 12V; it is not an apples-to-apples comparison. All other things being equal, a slower fan will always be quieter than a faster fan, but it will also produce less CFM.

Jaganath,

I am not trying to pick a fight with you and I do realize that you feel strongly about the Nexus fan being the best fan par none.

If you look at the review I linked to, then you will see that it is full of apples-to-apples comparisons. The review is based on rpm apples, voltage apples, and subjective apples. The only thing that would make the review even better is if they had the equipment to compare airflow and static pressure apples as well. Sure, I have the big advantage that I understand what the reviewers are commenting in Danish, but that is a language technicality and has nothing to do with the validity of their results.

I am not trying to diss you or anybody else on this forum; I am merely offering a link to the most authoritative fan comparison I have been able to find on the Internet as a resource that all forum members and visitors are free to decide whether they want to use when looking for a fan or decide not to use.

As you can see from my brief descritption of the test, it offers a recommendation for those who are looking for quiet out-of-the-box fans, those who are looking for fans with a focus on undervolted noise levels, and those who are looking for fans with a focus on undervolted rpm performance. In this way, they offer good advice to the broadest possible range of quiet computing enthusiasts!

Btw, thanks for the Silencio link.

jaganath · Post by **jaganath** » Mon Sep 04, 2006 10:09 am

Thomas, I think it's great that you are bringing more objective information about quiet fans to SPCR; this is one area that has really suffered from total neglect in terms of official reviews on SPCR for a long period of time, so I applaud that and I encourage others to follow your example. However, here on SPCR we are looking for the most CFM for the least dB, so saying that an 800rpm fan is quieter than a 1000rpm fan is not very meaningful, as this is a simple result of the laws of physics as laid out in the Fan Laws:

http://www.vent-axia.com/sharing/fanlaws.asp

http://www.comairrotron.com/engineering_notes_02.asp

http://www.cpemma.co.uk/fanlaws.html

So you can see that a fan's noise emissions are primarily determined by the RPM at which it is spinning, however CFM varies with the cube of the diameter and RPM, which is why bigger fans move more air for less dB.

So, in conclusion, I hope you can see why I do not consider noise measurements taken at different RPM's to be an apples-to-apples comparison. I don't want to cause offence, I consider us all seekers after the same truth.

Thomas-BP2 · Post by **Thomas-BP2** » Mon Sep 04, 2006 4:10 pm

Jaganath,

For somebody who does not want a fan speed controller or who connect their fans with 7, 6, or 5V, comparing two fans at equal voltages is 100% apples-to-apples, but that does not mean that fan speed controller supporters are forbidden to compare fans at equal rpm which is 100% apples-to-apples as well, but from a different point of view. We are beginning to talk in circles, because it seems to me that you are clinging on to your Nexus fan with the technical measurement of 1 dB(A) difference as your only justification.

You are looking at the issue from your personal point of view with no tolerance for anybody with different preferences. If you are right, that SPCR is only for people who are "looking for the most CFM for the least dB" based on your point of view, then I guess I do not belong here, because I cannot hear a difference of 1dB(A) (especially if produced inside a PC case) and I do not have the luxury of being able to ignore the costs of my PC gadgets. Besides, while you continue to look for the most CFM with your Nexus I will continue to look for adequate cooling of my rig with the lowest possible noise - and at the highest performance/price ratio.

Nothing in life is black and white only and I feel it is more than a little presumptuous when somebody comes with fundamentalist statements about what is right and what is wrong. What you have defined as the truth is not the truth I am looking for. Sorry for my sarcasm, but your hijacking of the ultimate quiet computing truth is like a hi-fi enthusiast claiming that hi-fi enthusiast are only those people who build their systems to play classical music!

By the way, you may want to prepare yourself for scrapping your Nexus fans, because according to technical measurements (by the site I referenced to) the Sharkoon Silent Eagle 1000 produces 2dB(A) less noise @1000rpm compared to your Nexus and at 15dB(A) it runs 100rpm faster than your Nexus at the same sound level. They conclude that it beats the Nexus on a subjective basis as well. The king is dead, long live the king!

cmthomson · Post by **cmthomson** » Mon Sep 04, 2006 6:29 pm

Thomas-BP2 wrote:By the way, you may want to prepare yourself for scrapping your Nexus fans, because according to technical measurements (by the site I referenced to) the Sharkoon Silent Eagle 1000 produces 2dB(A) less noise @1000rpm compared to your Nexus and at 15dB(A) it runs 100rpm faster than your Nexus at the same sound level. They conclude that it beats the Nexus on a subjective basis as well. The king is dead, long live the king!

Sharkoon fans are constant-speed designs (they maintain speed regardless of voltage, within reason of course). Most folks here prefer controllable fans so that they can make tradeoffs between RPM/noise and cooling.

If Sharkoon were to introduce a golf-ball fan that didn't have that constant-speed feature, then there'd be a lot more interest here.

Thomas-BP2 · Post by **Thomas-BP2** » Tue Sep 05, 2006 2:13 am

cmthomson,

If "maintain speed regardless of voltage, within reason of course" result in that you get a lower speed drop when undervolting and if you at the same time get a good rpm to noise ratio, then I guess it could just as well be seen as a good feature as a bad feature.

From the test of the Sharkoon Silent Eagle 1000, I cannot verify whether it has the constant-speed feature you mention, I can just see that when compared to other fans, using a consistent standard test methodology, then it performs very well - even when undervolted.

I don't know whether the 'golf-ball look' is just marketing porno or if it does make a difference, but I guess the important thing is whether it performs well or not.

If you compare the test results between the Nexus and the SE 1000, then the SE 1000 is a clear winner. If you take price into consideration, then the SE 1000 is a clear winner as well (in Denmark, the Nexus costs abut 80% more than the Sharkoon). If you take CFM/rpm into consideration (Nexus claims 36.87 CFM@1000rpm and Sharkoon claims 36.8 CFM@1000rpm) then the two fans have equal performance in terms of CFM at equal rpm, but that cannot been verified and is 'only' based on the claims of the manufacturers. If you take subjective impression of quality into consideration then the two are equal, but as the SE 1000 is relatively new to the market, there is no basis for comparing the long-term reliability - which, due to lack of a comparable sampling rate, would be unreliable if based on subjective opinions posted on e.g. SPCR instead of on an expensive professional market research. Without assumptions about air-flow, quality, and reliability the SE 1000 performs very well, and in some aspects marginally better than the Nexus.

The 'volt-centric' measurements for the SE 1000 vs. Nexus RS are:
12.0V: 1072rpm@19dB(A) vs. 1024rpm@20dB(A)
9.0V: 849rpm@15dB(A) vs. 795rpm@16dB(A)
7.0V: 658rpm@14dB(A) vs. 625rpm@14dB(A)
5.0V: 477rpm@<14dB(A) vs. 404rpm@<14dB(A)

The 'rpm-centric' measurements for the SE 1000 vs. Nexus RS are:
1000rpm: 18dB(A) vs. 20dB(A)
750rpm: 15dB(A) vs. 15dB(A)
500rpm: <14dB(A) vs. <14dB(A)

Measurement uncertainty is <1dB(A) and there might be a slight product sample variance, but that 'risk' is equal for both products.

Despite the lack of a 'CFM-centric' comparison, the Sharkoon has a better rpm to dB(A) ratio and is one of the fans that www.stillepc.dk recommends. Few forum posters here have been able to say something good or bad about it, but that does not mean that the Sharkoon cannot be recommended, just that it is uncertain whether its long-term reliability is lower, equal, or higher than the Nexus.

Regardless, I will still go for the Scythe S-Flex SFF21D, because I need a fan that is as silent as possible when consistently fed 12V so I don't need to fiddle with a fan speed controller

Tephras · Post by **Tephras** » Tue Sep 05, 2006 1:58 pm

Thomas-BP2 wrote:Few forum posters here have been able to say something good or bad about it

It has not been mentioned very much that's true, but the few comments about it has been almost exclusively positive. Negative comments have mostly concerned the 80mm version when running at 12V.

ckolivas · Post by **ckolivas** » Wed Nov 22, 2006 5:39 am

Here's my review of the 21D: viewtopic.php?t=35981

Which is better? (silent 12v or undervolting)

Which is better? (silent 12v or undervolting)

Re: Which is better? (silent 12v or undervolting)