Hi all,
Just wanted to check something before I do the work.
I have a few Behringer NU4-6000 amps, which cool themselves with a pair of 3" fans that just blow straight through the chassis. The air flow is back to front, and pretty much uninhibited - the chassis is pretty empty, and air is free to flow through.
I'd like to use them in a rack with amps that have front-to-back cooling, so I'd like to open up the NU4-6000s and flip the fans so they also have front-to-back cooling.
They're rarely pushed to their full capacity as I use them for stage monitors, so usually 8ohm on each channel. Occasionally 4ohm.
I can see that for an amplifier with a complex cooling system that it'd be a problem, but for fans that are pretty much moving air across empty space?
Would that be okay?
TIA,
Chris
Just wanted to check something before I do the work.
I have a few Behringer NU4-6000 amps, which cool themselves with a pair of 3" fans that just blow straight through the chassis. The air flow is back to front, and pretty much uninhibited - the chassis is pretty empty, and air is free to flow through.
An externally hosted image should be here but it was not working when we last tested it.
I'd like to use them in a rack with amps that have front-to-back cooling, so I'd like to open up the NU4-6000s and flip the fans so they also have front-to-back cooling.
They're rarely pushed to their full capacity as I use them for stage monitors, so usually 8ohm on each channel. Occasionally 4ohm.
I can see that for an amplifier with a complex cooling system that it'd be a problem, but for fans that are pretty much moving air across empty space?
Would that be okay?
TIA,
Chris
i've always gone the way of exhausting hot air from the case.
as jon mentioned there is less fluff and small debris that accumulates inside (several seasons of touring and subsequent maintenance have confirmed this to me)
although i've never confirmed this another tech once told me that blowing a fan towards a heatsink increases it's temperature.
as jon mentioned there is less fluff and small debris that accumulates inside (several seasons of touring and subsequent maintenance have confirmed this to me)
although i've never confirmed this another tech once told me that blowing a fan towards a heatsink increases it's temperature.
I Believe those fans are mounted this way, because they provide cooling for all the board components. It cools those inductors and the trafo on the right side.
If You want to swap direction, I would put them at the front, maintaining the same airflow.
...blowing a fan towards a heatsink increases it's temperature.Never heard such a thing, but just try it. (sorry whatever I try I can't get that quote box appearing)
If You want to swap direction, I would put them at the front, maintaining the same airflow.
...blowing a fan towards a heatsink increases it's temperature.Never heard such a thing, but just try it. (sorry whatever I try I can't get that quote box appearing)
It is not recommended to suck air in through open vents and trap dust etc in the filter on the way out!
These amplifiers were not made like that, the air flow is from the filter to the exhaust through the components and heat sink, otherwise debris will cover the surfaces inside the amplifier and cause overheating and possible tracking across the high voltage terminals on the power supply.
These amplifiers were not made like that, the air flow is from the filter to the exhaust through the components and heat sink, otherwise debris will cover the surfaces inside the amplifier and cause overheating and possible tracking across the high voltage terminals on the power supply.
I haven't that much experience with cooling amps, but have built quite a few computers. For that I prefer the fans to pull air directly from outside the case through a fan filter. Exhaust fan can be added, but you want the fans for exhaust flow to be lower than intake flow to create a positive air pressure inside the case. This prevents dust from entering the case on other places than the air filters at the intake fans.
These amplifier chassis are sealed and should have air guides making the airflow front to rear, as Crown, JBL and most other professional amplifier manufacturers do.
what do you actually want to achieve by reversing the air flow? reversing the fans only reduce air flow without any positive impact. read on pc forum on positive or negative pressure for pc chassis for your reference.
what i did on my nu3000dsp was to add copper heatsink (for pc chipset memory) and reduced fan speed with additional 32R resistor, main purpose to reduce the noise from the fan since no any silent fan like noctua available for the same size
what i did on my nu3000dsp was to add copper heatsink (for pc chipset memory) and reduced fan speed with additional 32R resistor, main purpose to reduce the noise from the fan since no any silent fan like noctua available for the same size
I thought my first post was pretty clear, but...
I want to make these amps compatible with other amps that will be in the same rack. If some have F2B (front to back) airflow and others have B2F (back to front) then some amps will be sucking in the exhaust air from other amps, and temperatures will rise accordingly.
Thanks for the lead on positive vs negative pressure cooling. The PC guys get really into it! I'll do some reading around there.
JonSnell, please look at the picture and digest the information being presented to you:
- These particular amplifiers have back-to-front airflow
- They do not have air filters
- They do not have any air guides
Cheers, all.
Chris
I want to make these amps compatible with other amps that will be in the same rack. If some have F2B (front to back) airflow and others have B2F (back to front) then some amps will be sucking in the exhaust air from other amps, and temperatures will rise accordingly.
Thanks for the lead on positive vs negative pressure cooling. The PC guys get really into it! I'll do some reading around there.
JonSnell, please look at the picture and digest the information being presented to you:
- These particular amplifiers have back-to-front airflow
- They do not have air filters
- They do not have any air guides
Cheers, all.
Chris
will you stack the amplifier or they will be separated by the shelf floor? i think that 15cm behind the fan already has no significant air flow sucked by the fan propeller. there should be no interference from both fan from different amplifier, unless you stacked 2 nu6000 where the fan position are very close.
get a soft tissue to test your air flow look like and you'll know how they behave. or create the smoke to get better figure, pc guys do those trick
get a soft tissue to test your air flow look like and you'll know how they behave. or create the smoke to get better figure, pc guys do those trick
I would just physically unbolt the fans and remount them inverted, no electrical changes whatsoever.
You *should* have no problems.
In any case, hang a car type oil change reminder tag from amp handle so you remember to open amp every 6 months to vacuum out any accumulated dust/lint/etc.
And I am only half kidding here, I consider that basic maintenance on fan cooled stuff, any kind, dust filters or not and any flow direction.
You *should* have no problems.
In any case, hang a car type oil change reminder tag from amp handle so you remember to open amp every 6 months to vacuum out any accumulated dust/lint/etc.
And I am only half kidding here, I consider that basic maintenance on fan cooled stuff, any kind, dust filters or not and any flow direction.
Thanks for weighing in.
That was my thought, too.
I think these amps have a very simple cooling strategy - pump lots of air through the chassis, relying on volume of air flow rather than directing it to specific places.
Therefore, I think the direction of airflow won't make a whole lot of difference as the amp itself doesn't appear to be temperature zoned (ie, caps and DSP in the cool air flow, then heatsinks, then exhaust). Everything's just in a box with a whole load of air moving through.
Now that festival season has cooled off, I think it's time to open everything up for a clean out. Thanks for the reminder.
In PA use, I don't think I've ever known the fans speed up from the idle/low-power mode, even in the case of an NU6000 that drives a load that dips to 3ohm/ch in places.
I've had an NU3000 spin up to a point where it was sounding like a jet engine. That was 4x 8ohm (which actually get to 5.5ohm in places) subwoofers on one channel, playing LF sine tones up to clipping the amplifier. The amp overheated and shut down after a while, but recovered a few minutes later.
Chris
That was my thought, too.
I think these amps have a very simple cooling strategy - pump lots of air through the chassis, relying on volume of air flow rather than directing it to specific places.
Therefore, I think the direction of airflow won't make a whole lot of difference as the amp itself doesn't appear to be temperature zoned (ie, caps and DSP in the cool air flow, then heatsinks, then exhaust). Everything's just in a box with a whole load of air moving through.
Now that festival season has cooled off, I think it's time to open everything up for a clean out. Thanks for the reminder.
In PA use, I don't think I've ever known the fans speed up from the idle/low-power mode, even in the case of an NU6000 that drives a load that dips to 3ohm/ch in places.
I've had an NU3000 spin up to a point where it was sounding like a jet engine. That was 4x 8ohm (which actually get to 5.5ohm in places) subwoofers on one channel, playing LF sine tones up to clipping the amplifier. The amp overheated and shut down after a while, but recovered a few minutes later.
Chris
If you are concerned at all about the reliability then I suggest setting up the amp by itself and running it hard for a while -in stock configuration.
Run it long and hard so any components that have heating concerns are good and hot. Stop, shut-down, pull cover quickly and measure temps throughout the chassis using one of those laser IR thermometers.
Then flip the fan, perform the same burn-in procedure, pull the cover quickly and measure the same spots again. If there are major differences hotter then perhaps re-evaluate your choice of amps (and trade for some used QSC's or something)
Also consider,
If all your amps are drawing air from the rear and exhausting out of the front then fill the entire rear of the rack with vent panels containing filter foam. Then every amp is only drawing from pre-filtered air and the rack's rear surface is large enough that the air velocity there is much lower so filters at that location will last longer between cleanings. Your amps would almost never need cleaning themselves.
I have done this on installs and the amps still look new after years of service
Run it long and hard so any components that have heating concerns are good and hot. Stop, shut-down, pull cover quickly and measure temps throughout the chassis using one of those laser IR thermometers.
Then flip the fan, perform the same burn-in procedure, pull the cover quickly and measure the same spots again. If there are major differences hotter then perhaps re-evaluate your choice of amps (and trade for some used QSC's or something)
Also consider,
If all your amps are drawing air from the rear and exhausting out of the front then fill the entire rear of the rack with vent panels containing filter foam. Then every amp is only drawing from pre-filtered air and the rack's rear surface is large enough that the air velocity there is much lower so filters at that location will last longer between cleanings. Your amps would almost never need cleaning themselves.
I have done this on installs and the amps still look new after years of service
The iNukes are pretty good for the price. It'd need something like a PLD4.5 to keep up with an NU4-6000.
I'll likely move across to Powersoft for monitors (as I am doing with the main speakers) once budget allows, but for now the 4-channel iNukes (and newer NX amps) are good value for money.
Interesting idea about the filter foam across the back of the rack. Would stretched fabric work as well?
We're looking at a fairly compact rack, in the 4 to 6U range.
Chris
I wasn't disparaging the NU amps due to quality or output, but referred to QSC simply as an example of a brand that every available model has rear to front active venting. I use a Middle Atlantic product for my rack rear filters
Filter Panel, 3 RU | Middle Atlantic
It goes over top of an existing vent or fan panel and can be attached with thumbscrews for easy cleaning. (For larger racks I have fabricated my own that uses standard furnace filters)
Filter Panel, 3 RU | Middle Atlantic
It goes over top of an existing vent or fan panel and can be attached with thumbscrews for easy cleaning. (For larger racks I have fabricated my own that uses standard furnace filters)
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