JBL 1200 cooling

[jomark911]

Hi guys.
I'm now facing a new problem.
I use jbl mpx 1200 amp to drive my passive subs.
Amp was bought some 7-8 years ago from a friend and tech , with the fan disconnected. Reason was the noise.
He told me he would do it , and that i wouldn't have any troubles.
Well a few days ago i had to take it for service since one channel was not working at all , and the other had developed a wooing noise.
Thankfully the hybrids were ok , and only the electrolytic caps all of em were changed.
Ok amp is working fine.
BUT the noise from the fan that was reconnected is unbearable. To much noise. That is at first or second stage. I don't want to imagine what will be on the third stage. It is a 24vdc fan 120mm wired by two cables.
I was thinking of changing it to a NOCTUA , but the only noctua heavy duty with enough airflow is a 140mm that will not fit.
Any ideas?
Thanks in advance.

 

[Vini darko]

Hi you could cut the positive wire and add a resistor to reduce fan speed. Some experimentation would be required to get it right for you. Fortunately resistors are a dime a dozen.

 

[jomark911]

It depends on how you see it. From witch point of view .
With 240m3 of air per hour needed , obviously the amp needs some cooling.
I suppose QSC guys are not so stupid , but probably they are chippies to select this fan.
Amp needs cooling , this fan produces 53dba noise.
I've found a noctua that goes on 40dba , i guess it will do the trick. I'm not gonna render it baked again . 200e for the repair was a bit expensive.

 

[Vini darko]

I understand. Wishing you the best of luck finding a fan that can move 36CuFt/min@24V that runs quiet. I suspect a compromise will force itself on you.
I looked up the manual and some pics of the amps guts. Very nice piece

 

[jomark911]

Well i ordered a noctua, the one i said above.
Hopefully when it arrives i'll put ti in and see what i get.
Thanks for the wishes.

 

[Berwhale]

If you can't get enough flow with a single fan, you could add two fans in series, one inside, one outside the case. Alternative, if you have space, fit a 140mm fan outside the case using a 120mm to 140mm fan adapter...

https://www.amazon.co.uk/Bgears-Fan-Adapter-140mm-120mm/dp/B0043GMY1U

Also, this may be an option: https://www.overclockers.com/fan-mufflers/

You can probably tell i've spent some time making my PC quiet My current desktop has 5 Noctua fans on isolation mounts and the Nuctua PWM speed controller: https://www.amazon.co.uk/Noctua-NA-FC1-4-Pin-PWM-Controller/dp/B072M2HKSN

 

[jomark911]

Ok thanks a lot. I'll let you know.

 

[jomark911]

As a side note , my pc also runs some noctua fans.
Two , on the main cpu cooler , one in sandwich mode the other on the front of the cooler.
The main exaust fan also being a noctua 120mm , ultra quiet. Another two installed on the psu and on the side of the gpu adding some extra air.
Last two cool my hdd;s .

 

[jomark911]

Ok so i bought out of amazon a 24v NOCTUA nf a14 ppc ip67 fan. Silent up to 12vdc , way noiseless than the JBL's own fan, which i'm going to install through an adaptor from 140mm to 120mm . All ok .
This fan is 10DB quieter than the std at full speed 3000rpm's.Way more quieter at lower speeds. Also the the air supply is greater , at 263 cmh . Now i'll have to wait for the adaptor to be delivered.

 

[jomark911]

Beautiful Fan. Shown on front of a packet of Dunhill.s to estimate the size difference.