USB fans and ambient temperature

[-Jim-]

Hi Andrein,

IMHO, anything that moves air won't be truly "silent" but just varying degrees of quiet. I decided to put two on top of my Denon AVR-X4400H (Not that it needed them both but as I bought two, I thought I should make certain they both worked. They did.).

As per above, I was going to grab my infrared temperature gun, and see where the warmest area of the X4400H's case is after a bit more of my latest Rock & Roll Hall of Fame BluRay but I decided to test both fans first (with the concert on at a suitable volume).

I remembered your post and did grab my sound meter but as it's minimum is 50 dB (C weighted). The room ambient was below this and of course at 3 feet I got nothing with both running on medium speed. It took until I was about 4 inches from them when the meter gave me a reading at 50 dB or so. I know there is an equation for sound extrapolation as distance changes, and if I find it' I'll do the math and advise. But using my ears. I can't hear them from my chair with nothing else on; never mind when Journey is belting out a couple of hits when being inducted into the Rock & Roll Hall of Fame!

I think these AC infinity S7 fans are a real bargain. At the price on Amazon (especially with free delivery from Prime) they are a steal if they can continue to perform, and out last their 2 year warranty.

Just my 2 cents...

 

[PENG]

I know there is an equation for sound extrapolation as distance changes, and if I find it' I'll do the math and advise. But using my ears. I can't hear them from my chair with nothing else on; never mind when Journey is belting out a couple of hits when being inducted into the Rock & Roll Hall of Fame!

I am going to save you time. The formula is

dB drop = 20*LOG10(X), X is the multiples of the distance where you obtain the spl reading.

Example:

If you get 50 dB at 4 inches, you will get approx. 50-6=44 dB at 8 inches, and 50-12=38 dB at 16 inches.

X dB to subtract
1 0
1.1 0.84
1.2 1.58
2 6.02
2.5 7.96
3 9.54
3.5 10.88
4 12.04
5 13.98
9 19.08
15 23.52

So that 50 dB at 4 inches will become 50-23.52 = 26.48 dB at 5 ft , that should be lower than your background noise.

 

[Andrein]

Jim, Peng, based on what you wrote, it should be quiet enough for me. Thank you for useful information.

Continuing waiting for my fans comming from US

 

[OldSchool Days]

Hi,

Just ordered 2 of these 120mm usb fans that many recommend on this forum. Wondering how efficient this will be if the ambient temperature in the room is about +25-27c? Have a bigger blower in the room but it is quite noisy and hope to reduce noise but keep my devices cool.

I live in UK and dont have air conditioner.

Andrei.

Im using 2 fans for my Amp sucking air out form the amp, just get a used phone or any 12 volt DC adapter , as long its 1 amp, and connect your fans to it , if fans are loud put a resister to it fans will be moving slow with no noise.

 

[-Jim-]

I am going to save you time. The formula is

dB drop = 20*LOG10(X), X is the multiples of the distance where you obtain the spl reading.

Example:

If you get 50 dB at 4 inches, you will get approx. 50-6=44 dB at 8 inches, and 50-12=38 dB at 16 inches.

X dB to subtract
1 0
1.1 0.84
1.2 1.58
2 6.02
2.5 7.96
3 9.54
3.5 10.88
4 12.04
5 13.98
9 19.08
15 23.52

So that 50 dB at 4 inches will become 50-23.52 = 26.48 dB at 5 ft , that should be lower than your background noise.

Thanks Peng.

 

[PENG]

Thanks Peng.

Hey Jim, have you tried the different speeds yet? It is possible that two running in the slowest speed sound quieter than one running in medium or high speed.

 

[-Jim-]

Im using 2 fans for my Amp sucking air out form the amp, just get a used phone or any 12 volt DC adapter , as long its 1 amp, and connect your fans to it , if fans are loud put a resister to it fans will be moving slow with no noise.

These AC infinity S7 fans each have a 3 Speed controller built in. No need for any "modifications".

 

[-Jim-]

Hey Jim, have you tried the different speeds yet? It is possible that two running in the slowest speed sound quieter than one running in medium or high speed.

I tried the different speeds on both fans just to make certain they all worked. Of course the slower you went the quieter they were. I didn't bother to try to measure as two running medium speed were already inaudible from my Lazyboy.

If you want, I can try to get something definitive, but remember my meter is at the bottom of it's range at 50 dB, and probably not all that accurate.

 

[Andrein]

I c

I tried the different speeds on both fans just to make certain they all worked. Of course the slower you went the quieter they were. I didn't bother to try to measure as two running medium speed were already inaudible from my Lazyboy.

If you want, I can try to get something definitive, but remember my meter is at the bottom of it's range at 50 dB, and probably not all that accurate.

An do measurments when i get my fans. I got quite expensive meter.

 

[Andrein]

Got my fans yesterday. Did not do any measurments but noticed a couple of things. They are really quiet even at high spead. They seem to be lowering the temperature under them but i can see just minor air movement above them. Is that expected? S7 advertised as 104cfm. Cant believe that

 

[-Jim-]

Andrein,

The easiest way to see how much air it moves is stand it up vertically on a table, and hold your hand across the output side when on high speed. It does move quite a bit of air.

Please advise what Receiver you are placing it on, or post a photo how you have it mounted. Then we can comment more.

 

[Andrein]

Andrein,
The easiest way to see how much air it moves is stand it up vertically on a table, and hold your hand across the output side when on high speed. It does move quite a bit of air.
Please advise what Receiver you are placing it on, or post a photo how you have it mounted. Then we can comment more.

Hi Jim,
I just put 2 of s7 fans flat on my a1070. Can take a photo later, but there is nothing special. I tried to test them in vertical position and could detect some air movement on one side of the fan but just from 1-2 inches at high speed. Beyond that there is nothing. Do you see more air movement with your fans?
Also they could make it more obvious which way the airflow will go using some arrows. So that you know which side to put the fan down. Otherwise you have to try and find out yourself. Right now my fans are up the side with small piece of red wire.

 

[PENG]

Hi Jim,
I just put 2 of s7 fans flat on my a1070. Can take a photo later, but there is nothing special. I tried to test them in vertical position and could detect some air movement on one side of the fan but just from 1-2 inches at high speed. Beyond that there is nothing. Do you see more air movement with your fans?
Also they could make it more obvious which way the airflow will go using some arrows. So that you know which side to put the fan down. Otherwise you have to try and find out yourself. Right now my fans are up the side with small piece of red wire.

They are only 52 cfm each, 104 is for both together. The fans are quiet mainly because of the relatively low speed and the soft rubber feet. You should be able to feel the air movement though, even at medium speed. You can also see it by letting it blow to something light on top.

Try plugging them to external USB outlets rated 2 A or higher, instead of the one on the AVR, just to make sure they are not starved for current.

 

[Andrein]

Ye

They are only 52 cfm each, 104 is for both together. The fans are quiet mainly because of the relatively low speed and the soft rubber feet. You should be able to feel the air movement though, even at medium speed. You can also see it by letting it blow to something light on top.

Try plugging them to external USB outlets rated 2 A or higher, instead of the one on the AVR, just to make sure they are not starved for current.

View attachment 25790

Yes, going to try external power supply.

 

[KEW]

I have used a pair of these fans on a 0.5A USB. They worked okay; however when I daisy chained another pair onto the same USB port (the AC infinity fans have port for daisy chaining them) the fans still work, but they are slow enough to spin up that it is clear they did not get enough starting current, so I went to external USB at 2.0A and all is well!

I definitely find two fans on low to be quieter than one on medium.

 

[OldSchool Days]

They are only 52 cfm each, 104 is for both together. The fans are quiet mainly because of the relatively low speed and the soft rubber feet. You should be able to feel the air movement though, even at medium speed. You can also see it by letting it blow to something light on top.

Try plugging them to external USB outlets rated 2 A or higher, instead of the one on the AVR, just to make sure they are not starved for current.

View attachment 25790

Sorry guys i was abroad for a while so missed some information and discussion from this thread .

(Nice job on the fans ) if you want more fans connect then in Parallel , all plus together and all minus together check the fan amps rating and then DC power supply them according to there Amp rating, ( so if one fans dies still 3 will still work, in seriaes if one dies all will die ) if the fans are 12v dc use 6 volt dc power supply or adapter fans will move slow (keep checking if power supply don't get hot) and if you have 3 speed control kind then run direct on 12 volts of the power supply, using power from the amp internal circuit is not a good idea in case of over load you might damage the amp so save headache and do this way at least you are not messing around amp internal power supply or overload it in anyway.
I am a 2 channel (Pure Analog) old school guy so i build my own speakers.
Soon i will be posting pictures of my hand made 6 Way custom built speakers system they are the beast , all crossover are hand made (with Silver Soldering) with every frequency crossover for each driver and everything is design and build by me and every driver wires and connectors are extreme high quality whatever was available in the market at that time
Enjoy..Music cause Life is too short.................

 

[lovinthehd]

Most of the fan dB ratings I've seen are without spec, no indication of weighting, etc (and wonder if they assume a noise floor, too) so hard to take them too seriously.

 

[Andrein]

Sorry guys i was abroad for a while so missed some information and discussion from this thread .

(Nice job on the fans ) if you want more fans connect then in Parallel , all plus together and all minus together check the fan amps rating and then DC power supply them according to there Amp rating, ( so if one fans dies still 3 will still work, in seriaes if one dies all will die ) if the fans are 12v dc use 6 volt dc power supply or adapter fans will move slow (keep checking if power supply don't get hot) and if you have 3 speed control kind then run direct on 12 volts of the power supply, using power from the amp internal circuit is not a good idea in case of over load you might damage the amp so save headache and do this way at least you are not messing around amp internal power supply or overload it in anyway.
I am a 2 channel (Pure Analog) old school guy so i build my own speakers.
Soon i will be posting pictures of my hand made 6 Way custom built speakers system they are the beast , all crossover are hand made (with Silver Soldering) with every frequency crossover for each driver and everything is design and build by me and every driver wires and connectors are extreme high quality whatever was available in the market at that time
Enjoy..Music cause Life is too short.................

I bought this dual fan package. So you dont need to diy.

https://www.acinfinity.com/component-usb-fans/multifan-s7-quiet-usb-cooling-fan-dual-120mm/

I had trouble with usb 2 (most likely due to usb 2.0 wattage limitation). To avoid this you can buy powered version of the fans or the one above and if it does not work properly you can always buy a 5v power supply on amazon.

 

[lovinthehd]

I bought this dual fan package. So you dont need to diy.

https://www.acinfinity.com/component-usb-fans/multifan-s7-quiet-usb-cooling-fan-dual-120mm/

I had trouble with usb 2 (most likely due to usb 2.0 wattage limitation). To avoid this you can buy powered version of the fans or the one above and if it does not work properly you can always buy a 5v power supply on amazon.

AVR power supply via usb is limited, get a fan within its limits or go external PS.

 

[OldSchool Days]

I bought this dual fan package. So you dont need to diy.

https://www.acinfinity.com/component-usb-fans/multifan-s7-quiet-usb-cooling-fan-dual-120mm/

I had trouble with usb 2 (most likely due to usb 2.0 wattage limitation). To avoid this you can buy powered version of the fans or the one above and if it does not work properly you can always buy a 5v power supply on amazon.

I see these are good fans with Ball bearings
it takes
Current 0.58 A
Power 2.9 W

so you need at least 1.5 Amps between 3 to 7V DC ,, Dc power supply or adapter to use 2 fans, use external power supply it should be fine
Enjoy Music.....