Reducing heat around a HT amp

[Paul47]

Well I have taken the plunge and upgraded my HT amp to an Onkyo TX-SR875 amp (prev was Marantz SR4200). I am very happy with the performance, but geez it runs hot.

The cabinet it is in is open sided, but as the Onkyo is larger than the Marantz there is now only 1cm airgap between the top of the amp and the bottom of the shelf above (which holds the plasma, so cannot shift the amp up to that shelf). I am concerned either that the amp will shut down, or else cook the shelf above (approx 30mm MDF I think).

Just went to my local Jaycar store - not much help from the staff there. I was looking at the 12v cross flow fan (discontinued model) or 240v (YX2565). The 12v model moves 32cfm, and the 240v moves 49cfm. Otherwise maybe a square computer fan, but then I would have to build some sort of ducting to channel the air effectively across the top of the amp.

Not being a DIYer, I would prefer to work with 12v (just connect a regulated wall wart I presume).

Is the cross flow fan a reasonable solution?

[Madhatter]

They only vent through the top (no vents on the sides), the fets run pretty much right across the middle of the unit with the transformer sitting in the middle, so a lot of heat is located towards the front of the unit. Even with the fan id probably be trying to make a little extra space in that shelf, can you drop it down in the unit? even if it means cutting through the sides to remove the shelf? mdf is pretty easy to work with. I guess a fan is going to be better than nothing. The SR7002 ive got surprised me with just how hot the thing runs even when its not driving anything, pumps out a huge amount of heat, even with an open cabinet and a good couple inches clearence. I was playing around with some hdmi connections the other day, never realised just how hot it got.

Edited April 21, 2009 by Madhatter

[A9X]

I would find out where the amp modules are in the AVR as these will be the largest source of heat. Then I'd cut a hole for the fan(s) on the shelf supporting the AVR below the amp moldules and place them there. Not optimal, but about as good as you can get.

There are large differences with fans between their flow capabilities and the amount of noise they make. Do some searches for "Behringer fan modification" as the EP2500 amps are popular amongst the HT crowd and there's been a bit of research on high flow, but very quiet fans. I don't recall some of the model numbers, but they were available at Farnell locally for ~ $20 ea.

[Paul47]

Thanks guys for the responses.

Madhatter ... cant remove the shelf unfortunately - the unit is 1500mm wide, and the AVR is sitting on the RHS opening, so I can get air on 3 sides (corners are just round alloy posts). There are some small vents on the side, but mostly on the top as you describe. The unit is definitely hottest at the top front.

Brett ... thanks - I never thought of cutting a hole in the shelf below. There is a cupboard below with a darkened glass door on the front, so fans mounted in the shelf would be hidden from view and probably sound proofed to some extent. I think I can get a router into that gap (would be holding it upside down though - not sure how safe that will be!!!) - I will investigate further !!

Will follow up on the Behringer mod fans also.

[norpus]

I heard the Onkyos do run hotter than most

I agree you should take some measures, as heat will eventually kill the shelflife of any electronics. Projectors and the likes use fairly efficient fans, but typically they are directed across the heat source. I suggest a fan pushing air into the cabinet rather than drawing it out - you can direct the flow better

[Super Mustud]

Paul, you say the cabinet is open sided. What about the back? If it is open, and I guess it must be at least partly, you might be able to mount a fan and bracket there. Is the opening at the back the full size of the shelf?

Whenever I use a cabinet to mount stuff, the first thing I do is make as large an opening in the back as I can. Oh, and then I put casters under the cabinet if not already fitted .

[Paul47]

Hi Mustud,

Yes - the back is fully open, and my original plan was to mount a cross flow fan (approx 200mm wide) under the shelf above at the back (blowing forward across the top of the AVR). But I wasnt sure if the Jaycar fan would move enough air to make it worthwhile - although I guess that anything is better than nothing!

[Paul47]

I heard the Onkyos do run hotter than most

I agree you should take some measures, as heat will eventually kill the shelflife of any electronics. Projectors and the likes use fairly efficient fans, but typically they are directed across the heat source. I suggest a fan pushing air into the cabinet rather than drawing it out - you can direct the flow better

Good points there - thanks Norpus. I was wondering about whether it was better to push the air in or pull it out - guess that's the old suck or blow question oops now i'm going OT.

[Grizzly]

If you plan to mount the fan underneath then definitely work with convection and use it to blow air up through the AVR. Assuming there are vents in the underside of the Onkyo.

[Paul47]

Thanks Bear - when I investigate A9X's idea, I will remember to check for vents underneath !! It would be good to get air flowing up through the chassis.

[Zaphod Beeblebrox]

Thanks Bear - when I investigate A9X's idea, I will remember to check for vents underneath !! It would be good to get air flowing up through the chassis.

Check your instruction manual. What does it say about adequate cooling for your amp?

1cm clearance is hopelessly inadequate. Your best option may be to make a cover for the rear of the cabinet and whack a couple of 120mm (don't even THINK of using smaller fans) fans to suck the hot air out. Naturally, the best option is to use convection, but, I'm afraid, you've failed to plan for that.

[Paul47]

Check your instruction manual. What does it say about adequate cooling for your amp?

1cm clearance is hopelessly inadequate. Your best option may be to make a cover for the rear of the cabinet and whack a couple of 120mm (don't even THINK of using smaller fans) fans to suck the hot air out. Naturally, the best option is to use convection, but, I'm afraid, you've failed to plan for that.

Thanks ZB - cant really argue with your comment re lack of planning !! I didnt intend to buy this model, but got a bit carried away with some extra features & a good price, and didnt consider the size. So now I have to live with my decision, and thats why I have asked for help.

The instruction manual says 20cm above and 10 cm each side. The sides are no problem, just the top (of course thats the hottest part ). Thanks also for suggesting the min fan size - that helps considerably, and saves me wasting money on trial & error (since I would have started much smaller!!).

Back to my local Jaycar tomorrow !!

[Zaphod Beeblebrox]

Thanks ZB - cant really argue with your comment re lack of planning !! I didnt intend to buy this model, but got a bit carried away with some extra features & a good price, and didnt consider the size. So now I have to live with my decision, and thats why I have asked for help.

The instruction manual says 20cm above and 10 cm each side. The sides are no problem, just the top (of course thats the hottest part ). Thanks also for suggesting the min fan size - that helps considerably, and saves me wasting money on trial & error (since I would have started much smaller!!).

Back to my local Jaycar tomorrow !!

No problems. The 20cm figure is very important. Clearly the manufacturer wants you to have LOTS of cooling. Make sure you do just that. The distributor will be well within their right to refuse any warranty claims, if they find that the amplifier has not received adequate cooling. It is very easy to spot such things.

Please take note of my comment re. the fans in the rear of the cabinet. Make sure it is reasonably well sealed, so that cooling air can be drawn through the front.

Frankly, I think you're in big trouble. 1cm clearance is seriously deficient.

Edited April 22, 2009 by Zaphod Beeblebrox
Brain fart

[A9X]

FYI, Behringer mods.

http://www.hometheatershack.com/forums/diy-subwoofers/3658-quieter-fan-mod-behringer-ep2500.html

http://www.htguide.com/forum/showthread.php4?t=19024

http://forums.audioholics.com/forums/showthread.php?t=45137

A fan on a plate at the rear isn't going to go a lot as the air is going to come from the path of least resistance, which will not be through the amp but around it.

[A9X]

Perhaps I am just too big a nerd.

[emesbee]

If the manufacturer says it requires 20cm, but you only have 1cm available, then it does sound like a potentially serious problem. I'm afraid the only solution might be to move the amp outside the cabinet to a location where it has unrestricted airflow.

By the way, did you have a similar heat build-up problem with your Marantz? I have a Marantz SR6200, and I find that heat build-up is not a problem with it. It gets warm, but not excessively hot. I also have it located on the top shelf of a built-in unit with nothing above it, so it has plenty of space for heat dissipation.

[Paul47]

If the manufacturer says it requires 20cm, but you only have 1cm available, then it does sound like a potentially serious problem. I'm afraid the only solution might be to move the amp outside the cabinet to a location where it has unrestricted airflow.

By the way, did you have a similar heat build-up problem with your Marantz? I have a Marantz SR6200, and I find that heat build-up is not a problem with it. It gets warm, but not excessively hot. I also have it located on the top shelf of a built-in unit with nothing above it, so it has plenty of space for heat dissipation.

The top shelf on this unit is 1500w, and is home to a 50" plasma, so no room there for the AVR. The Marantz had an extra 2 cms gap, and didnt ever run too hot. I am considering what other options I have, but none are likely to be visually acceptable to SWMBO, or in practical range of the remote control.

So far I am making sure that the kids switch the AVR off after use, and we dont tend to play anything at high volume, so the temperature is ok at the moment. Mostly just tv/foxtel and the occasional DVD. But longer term I need to resolve this somehow, since clearly it will potentially shorten the life of the AVR. Having used this for a week or so, I am now not so concerned about the fire risk, but it may damage the cabinet also.

Does anyone know what a safe working temperature is for this type of equipment?. I can keep a small thermometer nearby and check the temp after it has been on for a while. So far it doesnt get hot enough to burn skin - is that a reasonable test? (Of course I understand that the eqpt life issue occurs at lower temps that this).

[Paul47]

FYI, Behringer mods.

http://www.hometheatershack.com/forums/diy-subwoofers/3658-quieter-fan-mod-behringer-ep2500.html

http://www.htguide.com/forum/showthread.php4?t=19024

http://forums.audioholics.com/forums/showthread.php?t=45137

A fan on a plate at the rear isn't going to go a lot as the air is going to come from the path of least resistance, which will not be through the amp but around it.

Thanks Brett - I will read these later tonight.

If I can block the air coming from the sides (ie make the plate |_____| shaped) with the fans across the back, would this channel enough air across the top, since that is where the heat is? Hope that makes sense !! I would have to mount the fans at the top of the plate to maximise the draw over the top of the AVR. Maybe even block some of the air from the top sides to pull as much as possible from the front.

[Paul47]

I purchased a 12v 120mm fan from Jaycar, and after some experimentation found that blowing air onto the back plate from an angle has made a massive difference. The whole case is much cooler - you would hardly know that the AVR is even switched on. My wife actually complained that she could feel the draft from her seat approx 4 metres away!!

Apparently the video processing unit is in the top right back corner - I found this was the hottest part of the case, so the fan direction ensures good flow across this part of the case.

Next step - well this fan is a bit too noisy, so I will try some of A9X's suggested fans - maybe 2x80mm will be enough if positioned correctly. I will check the airflow specs, and build some form of cowling to raise the fans to the max height under the shelf. Then I will try to connect the plug pack to the AVR's AC outlet so that the fans switch off when the unit is not in use. Would like to add a thermostat switch but at the moment that is beyond my DIY capability.

So in summary the heat issue is now under control & the risk is considerably reduced - just need to reduce the noise while maintaining the airflow.

Thanks to everyone who added their 2c worth - I appreciate the help SNA is a great place, especially for novices like me !!

[FAPOS]

just need to reduce the noise while maintaining the airflow.

Get yourself a universal (or whatever its called) plugpack - the one where you can adjust the voltages from 12V down to 3V... that way you can run the fans at lower voltages & hence speed and it'll be quieter. Find the required voltage to keep things comfortably cool by by starting at as low a voltage as the fans will operate with, then move up one at a time until satisfied with its effect. Move the same amount of air quieter by adding more fans running at lower voltages!

I run a 12cm 12V fan in the back of my cabinet to circulate a bit of air around a Rotel 1075 poweramp... has about an inch either side and 2 above it - recomendation is 4" all around. The amp still heats up, though not any more than it did out of the cabinet, though the actual cabinet itself above the unit no longer heats up as it once did... so i can assume its effectively moving the heated air.

Mine is just running off one of the 12V triggers on my AVR, and has a 3 speed switch built in... ive found that the lowest setting does the job and is almost silent - mid & high i can notice. I dont like running it off the 12V trigger though so i might rig up an external trigger/power supply with an SS relay & selectable transformer (& some dodgy wiring)!

[Paul47]

Thanks fapos - good idea about the universal plugpack. I may have one somewhere around the house.

I am now running the 12v plugpack directly off the AC outlet on the back of the amp - this means that it automatically switches off when the amp goes off. It was a european outlet, so just added an aussie adapter & all works sweet.

[sfreak]

Hello Paul,

In regards to quiet fans the like, best look at Noctua and Nexus fans. Both 80, 92 and 120mm sizes all work great. Very quiet/borderline silent fans that do move a bit of air.

Nexus http://www.pccasegear.com/index.php?main_page=product_info&cPath=9_202&products_id=4561 Used to be 80mm and 92mm sizes too.... Don't seem to stock them anymore.

And Noctua http://www.pccasegear.com/index.php?main_page=index&cPath=9_413 Pretty much what I use these days when I want a silent computer. Bit more expensive than most generic fans, but you do get what you pay for, and that is a great product.

Whether run at 12V or usually silent somewhere around ~7-9V but if thats the case, best to check the airflow. And you would need something to control the voltage too if your plugpack doesn't.

[FAPOS]

In regards to quiet fans the like, best look at Noctua and Nexus fans. Both 80, 92 and 120mm sizes all work great. Very quiet/borderline silent fans that do move a bit of air.

Which one would you consider better - as in moves the most air the quietest??

I want to add another to mine, though im thinking two of what i have, standard 120mm antec case fans, even at 7V, would be noticeable.

[sfreak]

120mm Noctua S12 best for noise to airflow ratio with low air restrictions (Ie. Not tight CPU heatsink fins etc). Got 3 going about 40cm from my ear atm, all running 12V and with a muffled exhaust setup and can't hear them at all.

[FAPOS]

Cheers mate, i think im sold on them!

The others are $7 cheaper is all... im a bit of a tight ass.

Can get them locally too, saves the $14 they want for postage!