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PostPosted: Sun Apr 03, 2005 12:22 pm 
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The difference between the thicker fans is that you get improved static pressure with a thicker fan (in theory). The thicker ones take less of a CFM hit with additional pressure applied.

The only downside is that quiet 38mm thick fans are more difficult to find.

In your situation, I'd want 38mm thick fans if I could get them. The guy who did the research into 38mm AC fans on this site wanted them for his own watercooling setup.

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PostPosted: Mon Apr 04, 2005 4:05 am 
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In general, thicker fans are capable of overcoming more backpressure from restrictions in case airflow - that's useful when trying to blow through a radiator. You still need to be careful when selecting which brand & model of fan to get - a good 25mm fan may produce better airflow with lower noise than a poor 38mm fan, even with the restriction of a radiator thrown in.

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 Post subject:
PostPosted: Mon Apr 11, 2005 11:58 am 
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slimeballzz, there are really no DC 38mm fans known that are genuinely quiet. If you want 38mm (works better than 25mm in restrictive enviroments i.e. heatercore) and quiet, your only option is really AC.

I would recommend you get the Medium speed Yate Loon from PCTek Online (link). They should go just a quiet as a minVolted Nexus, but give you higher RPM/airflow (and noise) if needed.

Another option is to wait and see how the Aerocool Turbine fans turn out. Here's a forum link where the Aerocool is being discussed. Link

Make sure do make a fan duct. That can make a big difference. Good luck!

DrCR

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 Post subject:
PostPosted: Mon Apr 11, 2005 3:40 pm 
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DrCR wrote:
slimeballzz, there are really no DC 38mm fans known that are genuinely quiet. If you want 38mm (works better than 25mm in restrictive enviroments i.e. heatercore) and quiet, your only option is really AC.

I would recommend you get the Medium speed Yate Loon from PCTek Online (link). They should go just a quiet as a minVolted Nexus, but give you higher RPM/airflow (and noise) if needed.

Another option is to wait and see how the Aerocool Turbine fans turn out. Here's a forum link where the Aerocool is being discussed. Link

Make sure do make a fan duct. That can make a big difference. Good luck!

DrCR

________


Thanks for all the input guys. I do realize AC is the way to go but I'm a noob when it comes to undervolting though it doesn't seem to complicated :D

Was considering those Sunon A2123 fans but might change my watercooling plans. I had a plan this summer to get the BIP III and use 3 Sunon's A2123 fans and get them to run as slow as possible or enough to keep my rig cooled but I may have second thoughts considering the new cooling products coming out =\ and if it's actually worthwhile to go with watercooling again.

As for the Aerocool Turbine fans wouldn't they make a higher pitch whine? Wasn't the theory the more fan blades the higher the whine gets?

Would it be bad to not duct the fans and have them right against the rad?


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 Post subject:
PostPosted: Tue Apr 12, 2005 12:13 pm 
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Well undervolting takes on a totally new light with AC. With DC, it's rather easy indeed, but make sure you know what you're getting into if you go the AC route. I'm not trying discourage you, but I do want to caution you. :)

Hum, haven't heard of a relation between the number of blades and the pitch of the fan. I could be wrong, but I doubt there's really even a correlation there.

Yeah, it is best to make a duct because there is going to be a dead spot where the hub of the fan is if you flush it right next to the rad. Another thought here...The each blade might not move as much air either as you could be only deflecting air, rather than deflecting/pushing + sucking (i.e. Bernoulli effect. This is why a sailboat can actually be moving faster than the wind speed, and why an airplane can actually gain altitude while flying slightly downwards). Do most (any?) axial fan blades have chamber? :shrug:

Not making a duct could make a significant difference, esp. when paired with a SPCR quiet spec fan(s). But you could try without one and see how it works for you.

...if you ever get the urge to start a thread in the watercooing forum, send me a PM and I'll do my best to help answer your questions or make general comments there. :)

DrCR

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 Post subject:
PostPosted: Tue Apr 12, 2005 2:08 pm 
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Haha yeah I'm going to have to do some more research before I get into AC fans.. :D

Well I could be wrong but I always thought that the more blades on a fan, the higher the pitch frequency noise it would emit while the less fan blades you have the lower the pitch frequency. But there would be a tradeoff because the fan with more blades would work better in a restrictive setup while the fan with less blades will not do as well.
That's just my therory so correct me if it's wrong! :wink:


As for watercooling stuff thanks for the tips on the duct. We can discuss this later in the water cooling forum if I ever decide to go with it. :wink:


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 Post subject:
PostPosted: Tue Apr 12, 2005 2:51 pm 
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slimeballzz wrote:
That's just my therory so correct me if it's wrong! :wink:

As for watercooling stuff thanks for the tips on the duct. We can discuss this later in the water cooling forum if I ever decide to go with it. :wink:

I really don't know, so I can't correct you. I really doubt it though. With that said, someone in the know my correct me lol.

Sure thing, anytime. :) Just send me a PM so I know to head over there. My time to spend here come in short spurts, but if I get an email notification of a PM or post, I come right over.

Good luck!


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 Post subject:
PostPosted: Tue Apr 19, 2005 12:22 am 
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Will these fans run on 170VDC or 120v halfwave/rectified AC?

Also, what is it about AC motors that makes them so much quieter? The metal frame and rotor? I have some older EBM (Papst) 12v metal fans and the bearings produce a constant pinging so it can't be the metal alone. Is the low bearing/motor noise of these fans a product of the larger rotor mass?

I know that the DC's brushless electronics switch on and off abruptly which causes instantaneous torque and results in a ticking sound. Maybe the smooth AC sine wave and/or heavy rotor minimizes this jerky acceleration.


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 Post subject:
PostPosted: Tue Apr 19, 2005 10:00 am 
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Solid Snake wrote:
...


Hum, I would think so. Not sure though. It's been a while since Physics and I haven't gotten to Analytical Chem yet. Maybe they would, but might not be able to spin up on their own?

There's nothing inherent about AC fans. It's these particular AC fans. Bear also in mind, if your shooting for Nexus or sub-Nexus (which is acheivable with the recommended AC fan) noise levels, your going to have to slow the fan down more than just running them at 120V AC. I'm not even sure what kind of RPMs 170V DC would give you. (half as well? Where's my Physics book...)

Acceleration I would think would bascially be a non issue...unless you're rebooting your machine every minute or so lol. :lol:

DrCR

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 Post subject:
PostPosted: Tue Apr 19, 2005 12:24 pm 
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This is a late response to the question on 38mm vs 25mm thick fans. I don't frequent this board much anymore.
1) the thicker fans handle backpressure considerably better than the 25mm fans, the airflow isn't reduced as much when mounted on a radiator. However the 25mm fans have such a better starting airflow vs noise characteristic that you get better airflow vs noise with the 25mm Nexus than with any 38mm fan (unless you go with the 38mm AC fans listed). Having used all the above options on a Black Ice Pro II radiator I would recommend going with the Nexus, the advantage of the AC fans over the Nexus is not that large and isn't worth the trouble for somebody who isn't comfortable working with AC and speed controlling them.

2) Why are the AC fans so quiet? it's a combination of almost no motor noise, very low bearing noise (on these models), also the 5 bladed design makes for less noise than the 7 bladed nexus because of the lower blade noise frequency. The major noise sources in DC fans are the motor tick noises and bearing noises. At some point as you increase the fan speeds the air/blade noise becomes dominant and all the rest goes out the window no matter what kind of fan you have. One other factor is that the AC fans are HEAVY metal frames and rotors.

3) The AC fans I use run at around 100-110v although they are specced as 230v fans. You cannot run them on half wave rectified AC. You can use series resistors, series capacitors, transformers and autotransformers to get the voltage you need. There are many options. I would not recommend standard Triac/SCR dimmer circuits as they usually do not work at all, and if they do they tend to generate a lot of noise.


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 Post subject:
PostPosted: Tue Apr 19, 2005 12:42 pm 
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Thanks for your input ferdb. Good to "see" you again.

Where do you hang out now? ProCooling? Or do you just not spend as much time online?

Edit: Then again, he might not even see this lol. :lol:

DrCR


Last edited by DrCR on Tue Apr 19, 2005 6:39 pm, edited 2 times in total.

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 Post subject:
PostPosted: Tue Apr 19, 2005 5:40 pm 
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I found an easy and cheap way to control AC fans with low DC voltage. This will make it possible to control AC fans with any circuit designed to control DC fans (manual/thermal control). I'll be posting it on my site within a few days.


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 Post subject:
PostPosted: Tue Apr 19, 2005 6:39 pm 
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Cool. Awaiting a link. :)


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 Post subject:
PostPosted: Tue Apr 26, 2005 7:09 am 
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DrCR - I just don't around to any forums much these days. Doing other things. Everytime I don't 'hear' my computer running anymore I'm glad I found spcr forums to answer all my noise woes.
As for speed controlling the AC fans, I found the 5 watt pots I mentioned in that AC fan thread to be the simplest cheap and quiet solution for speed control. They are just small enough to mount on a 5 1/4" drive bay panel. You need one pot per fan. I designed a few active solutions that allowed temp control of the fan speed etc, but they aren't really needed with a water cooling setup. Just dial up the speed you need with a pot and you are set.


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 Post subject:
PostPosted: Tue Apr 26, 2005 10:07 am 
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Just be sure to watch out and do your math. It's a good idea to work out a spreadsheet.

I smoked a 5W pot with the SP100A-1123XST. This is not too surprising since at .26A @ 115V = 30W!!

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 Post subject:
PostPosted: Tue Apr 26, 2005 10:08 am 
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sthayashi wrote:
...I smoked a 5W pot ...


I swear you quoted it like that on purpose. :lol: :lol: :lol:

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 Post subject:
PostPosted: Tue Apr 26, 2005 10:18 am 
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I smoked it, but I didn't inhale. Too smelly :lol:

Yeah I wrote it badly, but I can't stress enough the seriousness of burning electronics at Mains level voltages. And keep in mind that I was paranoid about working with AC. Every connection I soldered was taped and heatshrinked, and I still screwed up :o.

Had I not tested it carefully, I could have easily started an electrical fire.

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 Post subject:
PostPosted: Tue Apr 26, 2005 12:44 pm 
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ferdb wrote:
...

Yeah, I know what you mean. I've spent a lot more time working on my RC airplane models. Once I start up school again this fall, that will have to go too though lol. This internship has me spoiled. No homework!


Good thing you didn't start an electrical fire sthayashi. Smoking that could really wack your braincells... :wink: :wink: :lol:


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 Post subject:
PostPosted: Tue Apr 26, 2005 5:10 pm 
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Yes I should have made it clearer that the 5W pots are only suitable for the 230v fan models running on 120v that I mentioned in the threads or fans with similar current drain. Other than that you should definitely calculate out possible power dissipations. If you run into power dissipation limits with the pots you might try instead to use a series capacitor or a transformer/autotransformer to get the speed you want.

sthayashi wrote:
Just be sure to watch out and do your math. It's a good idea to work out a spreadsheet.

I smoked a 5W pot with the SP100A-1123XST. This is not too surprising since at .26A @ 115V = 30W!!


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 Post subject: stupid question
PostPosted: Mon May 16, 2005 8:19 am 
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What does PWM stand for?? :oops:
( sorry if it sounds stupid but that acronym is used loads of times in this thread and never defined .. ) :cry:


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 Post subject:
PostPosted: Mon May 16, 2005 9:13 am 
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Pulse Width Modulation

http://www.netrino.com/Publications/Glossary/PWM.html


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 Post subject: Re: stupid question
PostPosted: Mon May 16, 2005 6:17 pm 
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SpaceDreamer wrote:
What does PWM stand for?? :oops:
( sorry if it sounds stupid but that acronym is used loads of times in this thread and never defined .. ) :cry:
Don't feel bad. While I was lurking around SPCR I had to search around Google a bit to actually figure that one out. :P

Most "specialist" forums like this could use a glossary page, even if they don't use a whole lot of acronyms. Hmm... maybe I should suggest one?

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 Post subject: Re: stupid question
PostPosted: Tue May 17, 2005 4:29 am 
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BrianE wrote:
Hmm... maybe I should suggest one?

Or start one your self. :)


SpaceDreamer, definitly don't feel bad. I actually didn't figure out what it was myself until later in my quest for quietness. Basically instead of decreasing the voltage from 12v (which would be called undervolting), PWM simply pluses 12v. So the fan is getting 12v or nothing. The determining factor for the fan's speed is how long 12v is left on/off. Some fans don't take to well to this non-steady stream of current.

Take care,
DrCR

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 Post subject:
PostPosted: Sat May 21, 2005 11:54 am 
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Question, first post mentions the Sunon AC fans A2123HST sleeve versions HAVE 7 BLADES...I've just been to a store in my country, we have lots of sunons here, no panaflos just sunons and the model has 5 blades and the blades are from plastic not aluminium.... is this the model ferbd was talking about in his posts or not?
we also *have* [we have it but not on stock - sales rep] the LST versions...if i decide to buy them i'll drop by and do a little comparisson...but i'd like to see a picture of the A2123HST with the seven blades..maybe i have some totally different model in my country mislabeled....though i've looked on Sunon's website and the picture looks like 5blades also.

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 Post subject:
PostPosted: Mon May 23, 2005 8:13 pm 
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DyJohnnY wrote:
Question, first post mentions the Sunon AC fans A2123HST sleeve versions HAVE 7 BLADES...I've just been to a store in my country, we have lots of sunons here, no panaflos just sunons and the model has 5 blades and the blades are from plastic not aluminium.... is this the model ferbd was talking about in his posts or not?
we also *have* [we have it but not on stock - sales rep] the LST versions...if i decide to buy them i'll drop by and do a little comparisson...but i'd like to see a picture of the A2123HST with the seven blades..maybe i have some totally different model in my country mislabeled....though i've looked on Sunon's website and the picture looks like 5blades also.

Try looking on page 15 of this Sunon catalog (pdf)

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 Post subject:
PostPosted: Mon May 23, 2005 10:15 pm 
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ok... looked through it... still looks exactly like the one i saw, 5 blades instead of 7.
DP 20x AS2123XXX 120x120x38mm AC 220V fans
edit: will modify pic, wrong capture...
edit2: this is ok now, i was wrong about 1 thing, frame is of aluminium, blades are plastic.
Image

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 Post subject: Re: The Top SPCR Quiet 120mm Axial Fans Compared + 120mmAC F
PostPosted: Wed Jul 13, 2005 1:00 pm 
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DrCR wrote:
The Nexus "Real Quiet Fans" are astounding fans in the 80mm, 92mm, and 120mm categories. They work flawlessly on PWM and undervolt on DC fairly well considering their low 12V CFM. The only potential negatives about the 1200mm is its orange color, its lower 12V CFM numbers (not an issue at all for most everyone though), and price compared to the Globes.


1200?! Sign me up for one! :wink:

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 Post subject: Re: The Top SPCR Quiet 120mm Axial Fans Compared + 120mmAC F
PostPosted: Fri Jul 15, 2005 8:01 pm 
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^ fixed. :)


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 Post subject:
PostPosted: Sun Jul 17, 2005 10:31 pm 
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I'm interested in buying a Nexus 120mm fan, but I want to run it at 5V. The problem is that I heard the Nexus has issues running at 5V? At 7V, is the thing dead silent? I don't need it to push that much air. Also are there any fan controllers out there that will ensure the fan is only getting 7V? I notice the ones with knobs aren't very reliable since there is no way to tell if I'm at 7V or not.


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 Post subject: Awesome thread!
PostPosted: Wed Sep 07, 2005 9:36 pm 
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Thank you all...this was the most helpful thread I could find for a newb like me :)

~ Chris ~


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