Will I lose much airflow if I run my fan @ 7V?

[Xp]

I have an intake case fan, 80mm Panaflo. Because it's quite noisy, I wanted to run it @ 7Volts, cause it's easy to do.
Is there a big difference in airflow between 7V and 12V?

 

[darth maul]

Ya there really is a big difference in airflow. Take for instance, every review I have read of PCmods baybus, they all state they used ~9~volts on the veriable setting, cause anything lower would either stop the fan completely, or the amount of airflow was way to low. See the problem is the fan needs a certain amount of voltage to spin up, and it needs a certain amount to keep spining. If you really need something try one of those $20 bay buses, 4 switchs with 3 positions; off-on-variable. Seems like a deal, and so much cheaper the reostat buses. But then you can always try the 7volt mod, and see if it works for your needs.

 

[Cosmo3]

What Panaflo fans do you have? The L1As are quiet, if you have the M1As or H1As they do make more noise. L1as are fine for case fans and should keep your noise level down. I am not sure that running fans at 7 volts is a good idea, yes I have done it in the past but some fans won't even run at 7 volts and some say although I am not sure it is true that doing the 7 volt mod isn't good on the power supply.

 

[BeauJangles]

How would a 7 volt mod damage a powersupply? It is supplying 7 volts to the 7 volt rail, so instead of taking power from the 12 volt rail the fan is taking it from the 7.. Honestly, I doubt it does any damage whatsoever.

 

[Danzilla]

<< How would a 7 volt mod damage a powersupply? It is supplying 7 volts to the 7 volt rail, so instead of taking power from the 12 volt rail the fan is taking it from the 7.. Honestly, I doubt it does any damage whatsoever. >>

What 7v rail? I understood the 'Mod' as using the voltage potential between the 5 and 12 volt sources (12 - 5 = 7). If you were dealing with a battery source, or the voltage difference between two passive devices, there wouldn't be any problem. Using the difference between the two positive sources of an active power supply is something else. I'm not sure of any solid reasons for not doing it, but I would avoid it. I think it would be safer, and not much more difficult, to add a variable resistance (dimmer switch) to reduce the current flow.

D.

 

[evolotion]

I have allways frowned upon the 7 volt mod (even though i am useing it because my case is to loud and i cant sleep with it on ) Allthough it is not a great idea to do this on a switching mode psu (which the magority are, i believe) the fact is that fans draw a very small current and so the psu can handle it. If you were to draw a couple of amps, then you would start seeing problems. I have not seen any posts about fried psu's because of it, yet!