Quieten NX-3500 air noise

Lifecycle · Post by **Lifecycle** » Tue May 11, 2004 8:33 am

I've had my Nexus NX-3500 for a few months now and have reached the point where I am pretty happy with it but for one small fact...

After an half an hour or so of usage, the temperature rises in my case to the point where the NX-3500 speeds up and I get a small amount of air noise coming out of the back. It isn't huge but it is more noise than when the PC powers on from cold, and it is noticable. I'm wondering if anyone else gets a similar issue with the NX-3500 or other thermally controlled PSU's and if so, what the best way is to go about sorting this out?

I know that ultimately the answer is "produce less heat and it won't speed up", but I don't think I really have a huge power-hog of a system (see my sig) and I would have thought that the NX-3500 would stay as quiet as it does when my PC is first booted (i.e. blissfully quiet!)...?

Points to note are:

- I have a negative pressure case setup. Two rear YS-Tech "silent" fans (normally around 1800rpm default) are running at 5-7v, plus the 120mm fan of the NX-3500. Another 80mm YS-Tech "silent" @ 7v sits on the CPU. All these are practically silent to me (or at least, at a level that doesn't bother me).

- Case temp is around the 30 degrees C mark and CPU around 45 after an hour or so of games playing. i.e. pretty low/reasonable.

- CPU is an old TBird 1.4Ghz underclocked to 1Ghz. Graphics card is an ATI 9600 Pro Ultimate (passive), with the lower of the rear exhausting YS-Tech's drawing air directly over the backside heatsink (due to the mounting in the case).

I guess my point is, I can't easily see how to get this setup any quieter or get the heat down without replacing more parts, and am looking for pointers as to what to do about my speeding-up PSU exhaust.

Any ideas/comments appreciated.

afrost · Post by **afrost** » Tue May 11, 2004 9:41 am

hardwire the fan to 5V and it will never ramp up

Post by **MikeC** » Tue May 11, 2004 9:49 am

Try the back exhaust fans in reverse -- blowing in. Just see what happens.

Lifecycle · Post by **Lifecycle** » Wed May 12, 2004 5:54 am

Thanks Mike. I'll give this a try.

I am a bit concerned about the upper rear layout of this case because I have the PSU fan sitting directly over the CPU 80mm fan and then two more 80mm fans directly next to it, so it's pretty crowded with fans around that area. I was wondering if this might be causing problems with airflow which could cause the PSU to trap more heat.

Along these lines, I was thinking of removing one of the 80mm exhausts. This would also reduce noise further still (although not by very much) but may cause the PSU to ramp even more.

I guess some experimentation is needed!

tay · Post by **tay** » Wed May 12, 2004 7:56 am

The 2 80mm fans could be starving your PSU for air. Although not ideal to blow the PSU air into the case, it will give you a very clear indication if this is the case. Plus it shouldnt be so bad since your system isnt drawing that much power. Unfortunately it is difficult to duct 120mm fan psu's but I'd love to see someone do it.

rmac · Post by **rmac** » Thu May 13, 2004 6:35 pm

I also have the Nexus 3500. I had the option of installing a 120 Nexus fan in the rear of my sonata that I hard wired to 5v. After that, all I could hear was air flow noise. I put some acoustic foam on the wall behind the case and now it is very quiet. The foam works well for the low freq. air movement noise. MBM temps at 24C idle in a 20C ambient.

magic_p · Post by **magic_p** » Fri May 14, 2004 10:30 am

Air flow noise is all the noise I have with the NX-3500 too, but is pretty significant in my machine. It's much louder than the Nexus "Real Silent" fans I have and they are supposed to be louder (at least Nexus' rated dBA for each part shows the fans at 22.8 and the PSU at 19.2). The reality is that the NX-3500 is much louder than the fans.

I realize the dBA ratings from the manufacturers don't mean a whole lot, but still, I was expecting aty least the noise to be in the same range, but it's not even close.

I'm going to try reversing the exhaust fan in the rear to suck in, hopefully reducing the amount of hot air running through the PSU.

Post by **MikeC** » Fri May 14, 2004 11:27 am

magic_p wrote:Air flow noise is all the noise I have with the NX-3500 too, but is pretty significant in my machine. It's much louder than the Nexus "Real Silent" fans I have and they are supposed to be louder (at least Nexus' rated dBA for each part shows the fans at 22.8 and the PSU at 19.2). The reality is that the NX-3500 is much louder than the fans.

This comment has been raised before recently, and there is a logical reason why this is so, even when the manufacturer is being diligent and honest with SPL measurements:

1) Both the fan and the PSU are measured by themselves in an anechoic chamber, generally away from any other objects.

2) The PSU's best measurement is usually cited, and it is at min load in room temp.

3) In a real environment (IE, a PC case) several conditions change the noise of the PSU, but not much for the fan.

-- The fan is usually run at a set speed by the user. For SPCR users, this is probably <12V. Chances are, the amount of vibration transmitted into the case is fairly low.

-- The PSU fan, on the other hand, is probably not going to stay at idle.

-- The PSU fan is in a small enclosed space (the PSU casing) which has resonances of its own (the air within it as well as the parts it is made of). Both of these become significant sources of noise as the PSU fan speeds up

-- The PSU typically weights 3~5 lbs. This weight hangs off the back panel of the case in a kind of cantilever. The hanging weight actually increases the transmission of vibrations from the PSU fan into the case, and causes higher levels of resonance noise than your quiet low speed 80mm fan by itself.

Put all these factors together and you can see why a PSU with a quiet fan is typically louder than the very same fan used as a case fan. (Probably louder even running at the same speed unless both fans are at absolute min...)

magic_p · Post by **magic_p** » Sat May 15, 2004 8:09 am

magic_p wrote:I realize the dBA ratings from the manufacturers don't mean a whole lot, but still, I was expecting at least the noise to be in the same range, but it's not even close.

I guess maybe this wasn't as clear as it should have been. I know and realize that manufacturers cannot provide real world use noise data. It's not possible to test every case and every config, so as you said, they use an anechoic chamber so they have a standard config that will be repeatable under the conditions they used.

The reason I think that the airflow noise is so signficant with the NX-3500 is the direct comparison I've made with a lower rated Antec True480. The noise levels with the Antec are far better in my server. The difference is that in my server the noise I hear from it is lower volume and pitch. I have more heat and similar components (7200.7 drives, Thermalright w/Panaflo L1A, etc.) The Antec PSU is less noisy.

In any case, do you think that a PSU silicon gasket would help to dampen the noise? I have one coming in Monday, along with some other things, that should make a difference if what you are saying is correct.

Post by **MikeC** » Sat May 15, 2004 9:06 am

magic_p

Maybe the NX3500 fan has ramped up much higher than you think? If it is running at close to min, it should be considerably quieter than the Antec...

unless you have a brand new Antec? They are revamping their entire line of TruePower and SmartPower models for lower noise. I have a few samples that just came it, no chance to examine them yet....

Jan Kivar · Post by **Jan Kivar** » Sat May 15, 2004 2:20 pm

rmac wrote:I also have the Nexus 3500. I had the option of installing a 120 Nexus fan in the rear of my sonata that I hard wired to 5v. After that, all I could hear was air flow noise. I put some acoustic foam on the wall behind the case and now it is very quiet. The foam works well for the low freq. air movement noise. MBM temps at 24C idle in a 20C ambient.

OT -- Does everyone's 120mm Nexus fans start at reliably at 5V? Also, has anyone tried the lowest startup voltage?

IIRC the fancontrollers in those Fortron/AOpen/Nexus PSUs have a minimum voltage of about 3-4V, so low voltage operation should not be a problem per se...

Cheers,

Jan

magic_p · Post by **magic_p** » Sat May 15, 2004 2:44 pm

MikeC, no it's an older True480, it doesn't even have the SATA connectors on it. Maybe you are right about the speed it's running at. It's possible I'm creating enough heat, even at stock speeds to cause it to spin up faster.

Hmm, I guess I'll be playing with it some more on Monday, when I get some more parts in. I'm starting to wonder if maybe the reduction in noise in general in the room is making me more sensitive to the noise from the Nexus PSU. I can now stand in the middle of the room and hear both my PVR (Antec Overture) and my workstation. I used to be only able to hear the workstation, it was loud enough to drown out everything else. The server still has a lower noise signature than both of those so who knows.

magic_p · Post by **magic_p** » Sat May 15, 2004 5:36 pm

I need to apologize. I've made a pretty stupid mistake. While playing with fan orientation and some other things in my machine earlier tonight I found that the NX-3500 is NOT the source of noise in my system. In fact it's my Panaflo L1BX. As I was playing around with things at one point I forgot to plug in the L1BX on my heatsink and noticed that all of a sudden my system was drop dead silent. I still had the 120mm Nexus fans running at 11v and the PSU fan was obviously spinning. I immediately thought "I am such a dick head!"

I had attributed the noise to the PSU incorrectly because when the case was all closed up all the noise was coming from the rear of the case. I had already tested the 120mm Nexus fans and knew that made no noise by themselves in the case, that's why I was so confused about the NX-3500.

I do have a fanmate arriving Monday which should kill the L1BX noise completely. I'm really sorry.

kiesus · Post by **kiesus** » Sun May 16, 2004 2:11 am

Hi all,

I've also Nexus 3500 PSU. For me Nexus IS the main source of noise.

My setup is:

- Athlon Mobile 2400+ (1,8Ghz 1,375V) with Alpha PAL8045 & Jamicon 1500rpm (16db) fan set at 8V by motherboard (temps 39-41 idle/load), silent
- Antec Sonata + silencing mat inside
- replaced the 12cm Antec fan with NoiseBlocker 17db fan + fanmate (set to 5V), veeeeery little sound
- Nexus 3500 PSU (loud)
- 2 Samsung 5400rpm silent 160Gb drives (acoustic mode on silent)
- R9700 non-pro with zalman heatpipe & Jamicon 1500rpm set at 8V (no sound)

Now, as I type, I have just replaced the fan on Nexus with NoiseBlocker SX2, put a fanmate on it (5V), and I must say, it is silent. Currently monitoring temperatures (if I have to speed up the fan)

What I am worried about is: If PSU overheats, does it usually break motherboard or other components as well, or is there some kind of fuse, which just stops the PSU from working??

I don't care if my PSU breaks after 0,5-1 year as long as it is silent & doesn't burn the house down

SpyderCat · Post by **SpyderCat** » Sun May 16, 2004 2:29 am

magic_p wrote:I need to apologize. I've made a pretty stupid mistake. While playing with fan orientation and some other things in my machine earlier tonight I found that the NX-3500 is NOT the source of noise in my system. In fact it's my Panaflo L1BX. As I was playing around with things at one point I forgot to plug in the L1BX on my heatsink and noticed that all of a sudden my system was drop dead silent. I still had the 120mm Nexus fans running at 11v and the PSU fan was obviously spinning. I immediately thought "I am such a dick head!"

I had attributed the noise to the PSU incorrectly because when the case was all closed up all the noise was coming from the rear of the case. I had already tested the 120mm Nexus fans and knew that made no noise by themselves in the case, that's why I was so confused about the NX-3500.

I do have a fanmate arriving Monday which should kill the L1BX noise completely. I'm really sorry.

I'm glad you're big enough to clean up the tarnished Nexus reputation. Thumbs up for you !

Lifecycle · Post by **Lifecycle** » Thu May 20, 2004 5:23 am

OK, as I started all this, I'll own up too...

After some experimentation last night, I tried unplugging all my fans for a few seconds (i.e. the Nexus and my HDD were the only moving parts) and... noticable reduction in noise. The air noise is certainly gone.

I guess my YS-Tech "silent" fans aren't quite so silent after all

I've moved them all down to 5v and the CPU is now around 60C full load (up from around 55C at full load @7v). Not great but not dangerous. However, noise hasn't dropped that significantly IMHO.

My two rear case fans are soft-mounted (rubber) so I think that the hard-mounted CPU fan is generating vibration which is the real cause of this noise.

Anyway, just to confirm - the Nexus is quiet and was not causing the extra noise!