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PostPosted: Wed Dec 13, 2006 8:54 am 
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Jose Hidalgo wrote:
Thanks Mike, now THAT'S clear about SilenX 74-11. :D And I think it deserves to be said "officially". Maybe in SPCR news ?


"Breaking news! We've run a quick test on the SilenX 120 mm fan, and it turned out to be exactly as unremarkable as we thought it would be!"

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PostPosted: Wed Dec 13, 2006 9:38 am 
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:lol:

Well, at least people would know. Because not all the people seem to think that the 74-11 is so unremarkable as you have just said. Not all the people go dig into SPCR forums to find such information.

So at least people would be informed. And I believe that's precisely SPCR's purpose, unless I've missed something. :wink:

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PostPosted: Wed Dec 13, 2006 2:12 pm 
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I'm surprised at the Nexus sample variance, I've always heard/ read that they had higher QC than Yate Loon - something that has been used to explain their higher price.

Looking forward to the next review(s), it's great to have so many fans reviewed in a scientific, controlled and reproducible manner. I agree that it'd be very informative to have some sort of impedence test thrown in to see how fans cope with static pressure, but, huge amount of work aside, the results would still only be valid under that particularly set of conditions (eg. that particular heatsink/ case grill etc). However, it would be good to see how a standard Antec grill compares with a wire grill and an open hole, just to confirm MikeC's guestimate of how much airflow is reduced by each type.

Also interested to see how Yate Loons (particularly the D12SL-12) stack up - price per decibel of those fans is pretty hard to beat (there you go, another metric to compare!)


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PostPosted: Wed Dec 13, 2006 2:29 pm 
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qviri wrote:
jaganath wrote:
Is SPCR interested in quiet PC components or punishing some guy who probably doesn't even work for the company anymore for something he did 4+ years ago?


Right, and interestingly enough, Peter Kim doesn't work anymore for a company he started, and the "Contact: peter@silenx.com" field in WHOIS information for silenx.com doesn't refer to this Peter. Gotcha.


"Gotcha"? WTF is that supposed to mean? So the guy still works there. My point still stands: SPCR is a quiet components review website, so whatever the misdeeds of the founder the fans should be reviewed (as Mike has already stated they will be but you wrongly suggested they would not). I suggest you refrain from putting words in Mike's mouth; you are no more an official mouthpiece for SPCR than I am so it would be best for you to remember that.


Quote:
"Breaking news! We've run a quick test on the SilenX 120 mm fan, and it turned out to be exactly as unremarkable as we thought it would be!"


Wow. Sarcasm. What are you, 5?


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PostPosted: Wed Dec 13, 2006 3:02 pm 
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Quote:
(as Mike has already stated they will be but you wrongly suggested they would not). I suggest you refrain from putting words in Mike's mouth; you are no more an official mouthpiece for SPCR than I am so it would be best for you to remember that.


Errr? I'm afraid you must have misread. In my first post on page three, I restated what I've read one of the mods say about the SilenX fan, then I gave a potential reason why SPCR would not want to review these. I did not say they will not be reviewed. My next two posts had nothing to do with whether SPCR will or will not review these fans either. Sorry if I came across unclear.

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PostPosted: Wed Dec 13, 2006 3:35 pm 
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Jose Hidalgo wrote:
:lol:

Well, at least people would know. Because not all the people seem to think that the 74-11 is so unremarkable as you have just said. Not all the people go dig into SPCR forums to find such information.

So at least people would be informed. And I believe that's precisely SPCR's purpose, unless I've missed something. :wink:


Jose....you really make it sound like you have some massive $1 million dollar bet on whether silenx fans suck. It's strange how much focus you have on something that's been proven to be an average fan at best. The 80mm test has already proven one of their fans is nowhere near as silent as the noctua, scythes, and nexuses of the world. Since most of their fans are in the same family, it seems likely they'd have the same noise characteristics... although who knows what silenx has up their sleeve.

I totally overlooked that silenx 80mm fan myself since I was more focused on the good ones, but there's one example right there for you to refer people to. I don't think it's really needed to show every size and shape of fan to prove a point, although I'm sure Mike has more fans in the pipeline. Absolutely no professional site is going to waste time posting a comment about a specific manufacturer saying "This thing SUCKS!". They'll always try to give a product a fair shake and give a good conclusive review. I hope you find some better fans to focus on now!


Just go out and tell/blog/write/etc people the best choices for fans and refer them to silentpcreview for reviews and facts. I stand by that policy and it's really the best each individual can do...unless they want to make their own review site ;)

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PostPosted: Wed Dec 13, 2006 5:46 pm 
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BTW, juste one question about bearings :

In the round-up we can read about Nexus' bearings : "sleeve bearings that are inappropriate for horizontal mounting or high heat situations".

On the other hand, Noctua's bearings are SSO type, which doesn't seem to be listed on your "Anatomy of a silent fan" article ( http://www.silentpcreview.com/article690-page1.html ).

Are SSO bearings appropriate for horizontal mounting or high heat situations ? Thanks in advance.

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PostPosted: Wed Dec 13, 2006 6:06 pm 
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Quote:
I disagree. Here's why:

So those pics tell something. What? That there was a lot more low frequency noise in the Noctua recording than in the Nexus. But having just listened to both 1ft/12V recordings, in both, I can hear more low freq noise in the latter part of the recording than in the beginning. (I'm not sure why this is so.... it's possible that there was some intermittent low frequency background noise during recording that was inaudible to us.) IS it possible that you sampled the early part of the Nexus recording and the latter part of the Noctua recording?

I can tell you, having just listened to both fans for a few minutes, that there is no such audible bass difference.

Even if this bass difference was there, you would be very hard pressed to hear it because human hearing sensitivity to low freq sound at low level is so poor. (Which is why the bass from most stereos -- even very good ones -- seems so lacking at low volume; music always sounds more natural and full at higher volume.) The Munson-Fletcher curves show this clearly. If the difference your ffts showed were at 3kHz, we'd hear it instantly, but at <100Hz, it's not so evident.

For all of the above reasons, I don't think fft plots are that useful. They just require even more explanation and it's very easy to misinterpret their significance. As demonstrated here: The differences your fft images show either do not exist or are not audible. Yet, looking at them, you'd think they sound like night and day -- they do not.

EDIT: And RH's query demonstrates perfectly that FFT charts are not self-explanatory. (No, I did not cue him to do make the comment... although it does seem perfectly timed. Laughing




Hello Mike,

the fft was an average over the whole 12v nexus recording, the noctua recording I skipped the first few seconds as there is erroneous 25-30hz content. Your say your playback reveals no audible difference, but Devon mentions this "presence" in real life. Even SOTA playback systems are only an approximation.

While your not convinced, an fft could be useful in explaining the noise composition of fans, "this is the blade noise, this is the wooshing air noise" Just like you link off the main article to testing procedures, maybe linking off to fan noise composition could be done, this way not overcomplicating the main article and confusing many readers. While there are many people here who just want to know which one is best, there are people (I believe) in the forums willing to soak up such knowledge.


My issue is by testing the fans on their own, while clearly it is the best way to do it, the testing and reporting fails to cover the fan/case interaction.

Lets take the scenario as follows. Someone has read the article and decides to put a fan on their case. Now this person doesn't have the latest antec p180 but a generic case with .7mm panels that rings like a bell. Assume they have used one of our suggested methods of decoupling the fan from the case, so there is minimal mechanical excitation via the fan housing.. The noctua has a better chance of exciting the case then the nexus from acoustical power. By how much we don't know.

When I can get my hands on a noctua (no stock in Australia due till Feb), I'll test the scenario out, compare to a YL/nexus and write up a nice little article with data. Be a nice little project for me. At the same time I'm going to play around with a YL/nexus in a case with helmholtz resonators, knocking 12db off the ~130hz and ~260hz peaks would really be something. I've tuned listening rooms with great success, a pc case should be great fun. A nexus will lend itself to attenuation with a resonator and some absorptive lining of an exhaust pipe a lot easier then the noctua.


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PostPosted: Thu Dec 14, 2006 6:56 am 
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Greetings Jose,

Jose Hidalgo wrote:
BTW, juste one question about bearings :

In the round-up we can read about Nexus' bearings : "sleeve bearings that are inappropriate for horizontal mounting or high heat situations".

On the other hand, Noctua's bearings are SSO type, which doesn't seem to be listed on your "Anatomy of a silent fan" article ( http://www.silentpcreview.com/article690-page1.html ).

Are SSO bearings appropriate for horizontal mounting or high heat situations ? Thanks in advance.


Earlier in this thread, someone linked to the page on SSO bearings, and they appear to be a variation on fluid/sleeve bearings; and if so, they would have the same limitations.

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PostPosted: Thu Dec 14, 2006 7:06 am 
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What would be the risk then, if mounted horizontally ?

My HTPC, like most HTPCs I suppose, is horizontal, and its design is very similar to mCubed's HFX Classic. So I need to have a horizontal fan on the bottom to push some air into the case.

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PostPosted: Thu Dec 14, 2006 7:09 am 
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Hello Jose,

The "risk" is that the bearings will wear out faster than they otherwise would. Have you considered the GlobalWin NCB fan, which has ceramic bearings?

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PostPosted: Thu Dec 14, 2006 7:55 am 
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Thanks Neil.

No, I'm afraid don't know that fan. It wasn't included in your latest roundup, was it ? If SPCR has reviewed it, I'd be happy to have some more information.

Otherwise, I think I'll take the risk and buy a Noctua anyway. I intend to use the fan at very low speeds (around 600 rpm), so even if it's mounted horizontally I think its bearings won't wear out too soon (I hope so !).

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PostPosted: Thu Dec 14, 2006 12:27 pm 
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I wonder if there are any published studies on sleeve bearing life in horizontal and vertical orientations? In my very limited experience (n=1 :)) the D12SL-12 in my FSP green PSU has been fine for nearly 3 years, as long as I've had the D12SL-12 as the case exhaust. Admittedly, I don't have a high powered system (and therefore hot PSU), but perhaps a straw poll in the forums might shed some more robust, if still anecdotal, light on the matter.


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PostPosted: Thu Dec 14, 2006 12:46 pm 
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mattthemuppet wrote:
I wonder if there are any published studies on sleeve bearing life in horizontal and vertical orientations?

My experience is, if there's a horizontal problem, it's either with pushing air down or pushing up, never both. A GW NCB 120mm is fine pushing up, but slows down pushing down. A Nexus 92mm is just the opposite. I think it's reasonable to assume that "slowing down" indicates increased friction and thus a potential problem.

I'd suggest not using any fan horizontally if it slows down from its normal vertical RPM in the orientation in which you're going to use it.


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PostPosted: Tue Dec 19, 2006 1:41 pm 
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Re: SilenX fans:

SilenX's latest crop of fans are based on Globe's Verax line, so I suggest looking for reviews of that if you're interested. We'll get to a full review of the SilenX eventually, but until then I would ask that you take Mike's comment in the spirit that it was meant. It was a quick, subjective evaluation, not an "official word" that it's crap.

Re: SSO bearings:

These bearings were developed by Noctua, and I was able to find very little objective (i.e. non-marketing) information about them, so I didn't do much than comment in passing. The best source of information is a review in French, where they actually disassembled the bearing. Unfortunately, my French is not good enough to get more than a general idea of what the review says, but it's very extensive.

With respect to orientation, I suspect that SSO bearings probably escape the orientation problems of classical sleeve bearings, despite being a sleeve-derived design. Most "hybrid" sleeve bearings that have been developed (Hypro, Hydro wave, FDB, etc.) were developed to address the shortcomings of the original design, orientation problems foremost among them.


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PostPosted: Tue Dec 19, 2006 2:20 pm 
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link1896 wrote:
the area filled in on the graph to the left, like in the noctua graph, are bass frequencies.

it is of importance as lower frequency sound is harder to attenuate then mid frequencies, and can excite cases panels and case cavity resonances, but conversely, mid range sounds are more annoying to humans due to their sensitvity to mid range frequencies (matches up with frequency range of the human voice)


In addition, lower frequencies roll off much more quickly as you move away from the source, and at the levels that we're looking at, the frequencies below <100 dB are almost guaranteed to be inaudible outside of a foot or two. I have to wonder why a subjective comparison of the two fans did not reveal low frequency differences. I find it interesting that you attribute the "presence" to a larger amount of low frequency noise, but I don't understand why you draw this conclusion.

I would interpret your FFT graphs in a very different way. To me, the most important feature of the Noctua graph is not the higher amount of low frequency noise, but the fact that it doesn't have many significant peaks. The noise is a little more broadband than the Nexus, especially in the lower frequencies. My gut feeling is that *this* is the explanation of the "presence", since our ears find it easier to pick out pure tones than white noise. With most of its distinctive characteristics hidden by the white noise, the Noctua is very difficult to perceive. Nevertheless, the noise is there, and is presumably taken in by our ears. We do not hear it because our brain filters it out as something to ignore, so it is only perceived subconsciously — in the form of the psychological "presence" that I described.

I'd be very cautious about reading too much into the extra bass in the FFT graphs, and I agree with Mike's decision not to include FFT information in future reviews. I think I have shown that the same graph can be interpreted multiple ways, and it is not clear how to determine which interpretation, if any is correct.

In any case, the audio recordings and our subjective comments do a more accurate job of capturing how the fans noise character than an FFT graph can. And, if the noise character can be captured through these simple methods, why should we try to explain it via an FFT graph? Including the graph as an explanation is akin to rationalising our subjective impressions, as though we don't have enough confidence in our listening skills to accurately describe our experiences without mechanical aids. Remember that it's the experience we're trying to capture here; explanation should play a secondary role if it has one at all.

In my opinion, the value of an FFT analysis is not explanatory, but predictive. Our subjective impressions can stand on their own without explanation, but the FFT analysis might be able to help predict how the fan would sound under different circumstances. As you said, the additional low frequency noise might make the Noctua more prone to resonance. However, I'm not confident that I can make such predictions with any accuracy, and the difficulty of interpreting the graphs correctly makes me wonder whether such predictions can be made.


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PostPosted: Tue Dec 19, 2006 2:56 pm 
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Thanks Devon for these two great answers ! Keep up the good work ! :D

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PostPosted: Tue Dec 19, 2006 3:50 pm 
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Devonavar wrote:
SilenX's latest crop of fans are based on Globe's Verax line, so I suggest looking for reviews of that if you're interested.

AFAIK, they are not based on Verax. There might be a surface resemblance, but that's all.

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PostPosted: Tue Dec 19, 2006 4:03 pm 
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I have read the french review, and I have noticed this important remark :

Quote:
Par contre, il faut impérativement éviter la position horizontale avec la tête en bas, le bruit du guidage augmente. On entend clairement que la rondelle arrière frotte sur l'extrémité du palier vu qu'il n'y a que ça qui empêche l'axe de tomber. Le niveau de vibration augmente également très sensiblement !

Translation : "on the other hand, it is necessary to avoid the horizontal position with the head down, because the guidance noise increases. You can hear clearly that the back disc rubs on the end of the stage because that's the only thing that prevents the axis from falling. The level of vibration also increases noticeably !"


Question : please look at this picture from Noctua :

Image

On this picture, I guess that what they call "the head" of the fan is up, right ? So in this position, will the air be pushed upwards or downwards ? (maybe we can choose the direction of rotation ? :shock: )

My problem is that in my HTPC project (horizontal case like mCubed's HFX Classic - see attached picture : http://hidalgoj.free.fr/DSC04646.jpg ), I need to place one or two fans at the bottom of the case, in horizontal position, in order to suck air inside the case (upwards), not to push air outside. Is there a way to do this with the Noctua or not ? :oops:

(I'm afraid that I won't be able to do that, but what can I do in that case ?)

Thank you.

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Last edited by Jose Hidalgo on Tue Dec 19, 2006 4:21 pm, edited 2 times in total.

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PostPosted: Tue Dec 19, 2006 4:20 pm 
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Jose Hidalgo wrote:
On this picture, I guess that what they call "the head" of the fan is up, right ? So in this position, will the air be pushed upwards or downwards ?


Downwards.

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PostPosted: Tue Dec 19, 2006 4:24 pm 
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Just as I expected... :(

I'm in big trouble then, so what can I do ? Is there a silent fan that would allow me to push air upwards ? I'm sorry to be quite a newbie with fan stuff, I'd just like to find a solution to my problem... thanks in advance !

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PostPosted: Tue Dec 19, 2006 4:30 pm 
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Sharkoon Silent Eagle,Yate Loon D12SL-12 are alternatives, no idea how the Sharkoon reacts to horizontal orientation, have had the Yate Loon in horizontal (blowing upwards) position in my S12-330 for 12 months, no problems.


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PostPosted: Tue Dec 19, 2006 4:57 pm 
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Hello Jose,

As Felger Carbon wrote, the GlobalWin NCB is fine for blowing air up; as in a typical 120mm fanned power supply mounted in a typical tower case. The GlobalWin NCB fan is very quiet, and the bearings are ceramic, and therefore they should do well in warm/hot environment, for a longer time than most other bearings.

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PostPosted: Tue Dec 19, 2006 5:36 pm 
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The GlobalWin NCB fan is not available in France, afaik.


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PostPosted: Tue Dec 19, 2006 5:55 pm 
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Well, shall I get a rope and hang myself right now ? :lol: (thanks jaganath !)

I wonder if fan manufacturers have ever thought about building silent fans specifically designed to push air UP when mounted horizontally. I say this because all the fans I've seen pictures of (including the GlobalWin) seem to have the blades positioned in the same direction, suggesting they are made to function in the same position. If there was a fan designed to push air UP when mounted horizontally with its head up, it would have its blades reverse-mounted when compared to other fans, wouldn't it ?

So I guess that, even if the GlobalWin seems to be "fine" for blowing air up according to Felger Carbon's comment, the fact is that it's probably not meant to function in that position. So that could cause the same problems as with any other fan mounted with its head down : added noise, added vibration, oil leakage and so on. So I'm afraid that Felger Carbon's comment may not prove right in the long term.

For example, I can reasonably suppose that a Noctua NF-S12-800 would be totally inaudible at 5V, even if mounted with its head down. So I could assume that it's also "fine" for blowing air up, because it seems to do that just fine. But would that mean that the Noctua is meant to function in that position ? I don't think so !

And now the final question : would the fan last long in that position ? To that question I would answer "maybe... but only if its rotation speed is really reduced all the time" (at 5V, a NF-S12-800 must rotate at only 400 RPM or so, while still pushing some air).

That could be, if proved of course, a positive factor that could made me take a reasonable risk and buy the Noctua anyway. Unfortunately I'm not sure about that, and only a complete test could prove that eventually... :(

What do you think guys ? Pretty complicated, huh ? :)

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PostPosted: Tue Dec 19, 2006 6:56 pm 
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Hello,

What you're asking for is to have the support struts on the other side -- or to have the fan blades and the rotation go the other way?

Having obstructions (the struts) on the intake side would make a LOT of noise! Try holding a pencil or a pen across the intake side of a fan, and you will hear what I mean -- when you move it close enough to the leading edges of the blades, it will make a "cavitation" noise.

And be careful not to touch the blades with the pen/pencil!

I have the GlobalWin NCB fan in a Fortron Source 300watt PS running in one of the computers under my desk. (The stock Yate Loon medium speed sleeve bearing fan started to vibrate after about 4 years of 24/7 operation.) The NCB fan is very quiet in this position, and it would also work as a case fan, with the frame up vertically. It only "complains" when positioned horizontal and blowing down.

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PostPosted: Tue Dec 19, 2006 7:38 pm 
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Well, what I'd prefer is to mount the fan correctly (with its head up) and have "the fan blades and the rotation go the other way", as you say. But for that, the fan would need to have "reverse blades" (forgive my bad english, I'm doing my best right now) in order to be able to rotate the other way. Is this correct ? I hope I'm clear enough. :oops:

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PostPosted: Tue Dec 19, 2006 7:48 pm 
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Just to try to illustrate with a bit of Photoshop :

Normal blades ------------------------------------------ Reverse blades

Image Image

Is that more clear ?

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PostPosted: Tue Dec 19, 2006 9:27 pm 
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Jose Hidalgo wrote:
But for that, the fan would need to have "reverse blades" in order to be able to rotate the other way. Is this correct ? :oops:

In addition, the motor assembly would have to be designed to seqence the current/magnetic pulses in the opposite direction. This can probably be done without a new motor IC design, but it would require a new PC board. None of this can be done in a hobbyshop. Order at least 50,000 units and they might be willing to do a redesign, after you post bank credit. :D


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PostPosted: Wed Dec 20, 2006 3:06 am 
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Hello Jose,

The only thing that does is reverse the direction that the fan rotates. The air still moves through it in the same direction. I don't see what is being accomplished?

IF the air is made to blow through in the other direction, you have the noise problem caused by the support struts that I mentioned above.

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