# Amp + EQ in spare tire well, fan(s) needed?



## jperryss (Mar 15, 2006)

Hi all,
Just tossing around the idea of pulling the spare tire/jack and mounting my amp and DQX on a simple flat MDF panel in the spare tire well.

(Yes, I have AAA and rarely travel beyond 20 miles from my house. )

Anyway, I took some measurements today..

Tire well: 7" deep, 24" wide, 21" long
Amp: 20" long, 10" wide
EQ: 10" long, 6" wide

Here's a crude drawing of the tire well area, which shows how I plan to set everything up. Amp is in blue, EQ is in yellow, and the black circle is the mount for the tire itself, which I plan to use as one of the mounts that'll hold the MDF panel in place (it's very short, only 1.5" or so from the floor of the tire well).










Of course my main concern is heat dissipation from the amp itself, I don't believe the EQ gives off much heat.

Based on my measurements, the amp will have about 1.5" of space on three sides (between the amp and sides of the trunk well) and about 4-5" between the amp and EQ. The amp will have about 4" vertical airspace between the top of the amp and the carpeted lid above.

The carpeted lid has a 1" x 3" 'vent' in one corner (it's there so fingers can be inserted to lift the lid, but it'll also serve as a vent). If I were to run a fan, I could put it on the opposite end of the lid to either pull the warm air out of the well, or force cooler air into the well. However I'm going for a 'stealth' look and not sure I could do the fan portion correctly.

I've definitely mounted amps with less airspace around them, but it's always been vertically (usually between a sub box and a back seat).

Am I asking for trouble by trying this without at least one fan?

Thanks.


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## sqshoestring (Jun 19, 2007)

I would put a fan on or at the amp, better to vent the area but you will have to try it and see. Some air movement will help cool the amp even if warm air. How cheap are the outdoor thermometers? Could toss one in there and monitor it lol. Depending on the car, you might be able to hack a hole in the side and back into the quarter panel, put a tube/hose, use that to vent it, just a crazy idea but that is how you end up with cool stuff.


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## jperryss (Mar 15, 2006)

Will a typical amp just shut down if it's running too hot? I'd like to try it without the fan first, but I don't want to worry about permanent damage to it because of heat.

Amp is a USAmps AX5600 BTW.


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## sqshoestring (Jun 19, 2007)

Most amps will, but heat is not good for them. A slow speed case fan for a PC is really cheap and makes no noise, that is what I use. A class D will run much cooler, it will not get hot unless you work it hard.


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## eviling (Apr 14, 2010)

jperryss said:


> Will a typical amp just shut down if it's running too hot? I'd like to try it without the fan first, but I don't want to worry about permanent damage to it because of heat.
> 
> Amp is a USAmps AX5600 BTW.


for the most part...YES, i had that very problem many years ago when i first got into car audio where i kept over heating amps, went through kicker, mtx, eclipse. eclipse was the winner, ran very hot, but the heat rails on the body worked very efficient and it never over heated...now i use alpine, they don;'t over heat, but my pdx 1.1000 gets extreamly hot..hot enough to not be able to hold your hand on it for several seconds >_< sitll working on that problem my self tehe. 
but if it doesnt turn it's self off...something WILL burn up, had a kenwood that over heated with out me knowing...blew it's self and some how took down my sub with it... fortunately they were both very cheap parts :|


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## jperryss (Mar 15, 2006)

Guess I should just plan on installing a fan. Thanks for the advice folks.


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## sqshoestring (Jun 19, 2007)

The things that blow often are the high power parts, the power supply mosfets and the outputs...the things clamped to the sink. It is the nature of those transistors that they can handle less power the hotter they are. They all come with a datasheet showing once they exceed 25C (77F) their power handling drops more and more with more heat. It depends on how much extra room the amp maker left and how hard you are running it, and when it shuts off. Also repeated use like that will reduce its lifespan. I would say a good install accounts for cooling needs, but I don't know your situation or typical use, and not wanting to come down on you...you can do whatever you want with your amp. If you never hammer it for a long period of time it might never get hot, hard to say, but a lot of people with installs like that don't push them and say sure it works fine...

Just a fan inside there will help, I would never do an enclosed amp without one unless it had its own. Even warm air will cool a hot amp just not as well.


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## GlasSman (Nov 14, 2006)

Stick one of those small thermometers in there and find out how hot things get.

Even a hidden *80 mm computer fan *placed under the amp would cool the temps in that amp.

Just cut out a spot in the middle of the mounting location......raise the amp off the board 1/2" and you're good.

Your rack isn't enclosed so it's not critical the air flow is on the heatsink fins.....though that would be the best choice for optimum cooling.


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## jperryss (Mar 15, 2006)

Thanks guys.



GlasSman said:


> Even a hidden *80 mm computer fan *placed under the amp would cool the temps in that amp.
> 
> Just cut out a spot in the middle of the mounting location......raise the amp off the board 1/2" and you're good.


Yes it might help a bit and would definitely be the easiest way, but my concern is that it'll be the same air (for the most part) floating around in there. But you're right. It'll at least circulate the air a bit in that area, and stop the hottest air from hovering around the heatsinks and the top of the amp.

Would be neat to make a small hole in the floor to pull outside air in and push it right up under the amp, but that'd be overkill and I'm not ready to go that far, heh.

What'd be slick actually would be to put the fan in the lid (my original idea) and have that air piped under the amp and through a hole right under the raised amp (your idea). Hell, I could mount the fan right under the amp like you suggested, and make a tube (dryer hose LOL) from there to a vent in the spare tire lid. That'd pull air in from the large trunk area, force it under the amp, and just vent out through the stock hole in the lid. The edges probably aren't airtight anyway, but it doesn't really matter how the warm air leaves I guess.

Hmm...


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## jperryss (Mar 15, 2006)

So I actually gave this some more thought last night and today...

I could make the amp rack out of two pieces of MDF (top and bottom). Mount the amp and EQ on the bottom panel, use the other panel as a lid for the whole thing, with maybe 4" between the top and bottom. I could then mount two fans at the amp end, blowing air across the top of the amp (as was recommended above) and pushing it out to the other side (no fans there, I'll probably just leave it open). The sides of the rack would be sealed off with MDF also, forcing the air from the fans all the way across the amp and EQ, then out the other side.

Then put the whole thing under the spare tire lid, then leave the lid in place for cosmetic purposes (stock look). I'd have to make a good-sized vent at the end where the fans are 'pushing' into the amp rack, to make sure they're always grabbing cooler air from the trunk. The warm air being pushed from the amp could exit out the other end of the rack and through the other end of the spare tire lid.

Stupid idea? Any glaring issues that aren't coming to mind for me? I could, instead of making a top lid, design the bottom panel with dividers to direct the air appropriately and seal with the factory lid, but I think it'll be much easier to pull off this way.

I'm actually looking forward to this, should be a fun little project.

Thanks!


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## jperryss (Mar 15, 2006)

Quick mock-up in case anyone cares. 

Fans are in red on the 'bottom' pic, brown border indicates where the two panels will be side-walled to block airflow in that direction. The idea is basically an MDF 'box' with cutouts and fans to assist airflow. The trick will be making sure that all the cool air pulls in from the upper-end of the 'box' (from the vent into the trunk) and all the warm air exits at the opposite end (through the other vent into the trunk). The box will be secured to the spare tire mount, and the height of the box will probably be just high enough to meet with the lid, so that it doesn't flex downward if weight is applied to it. Two decent 120mm fans should do the job nicely (and quietly). Everything should look 100% stock when finished, except for the input vent I need to make in the lid. Still thinking of a clean way to do that part.


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## sqshoestring (Jun 19, 2007)

Looks good to me.


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## jperryss (Mar 15, 2006)

Thanks again for the help, SQSS and others.

Picked up some 3/4" MDF and made the floor of the rack today. Once in place and secured, I realized that I probably won't have a lot of room for the top panel underneath the stock lid. So the new plan is to cut a vent in the stock lid and mount a single fan directly under it. This will be at the opposite end of the stock cutout so that air can be forced across the rack and exit at the opposite side. The 1-2" of clearance between the top of the amp and the lid should allow for good airflow across the amp fins. Just need to figure out how to make that fan/vent look clean and not out-of-place.

I'm pretty happy with the fit. It's very secure using just the tire mount as the edges of the panel are snug against the sides of the tire well, and I'll have space for my gear and both distribution blocks. Maybe for once I'll actually try to do a neat job of the wiring.


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## jperryss (Mar 15, 2006)

In case anyone's still following along, the rack itself is pretty much finished. 










The fused DB needs to be moved slightly, somehow I goofed that part up, the hole is slightly to the right from vertical. The second hole is for the 12v relay wiring, haven't done that part yet but it'll be mounted right next to the DB. 

The current idea is to incorporate a fan into the spare tire lid. I need to accommodate the fan and add some support to the lid that is lost without having the spare tire and jack directly under the lid. So I will be adding an MDF 'brace' across the bottom of the lid, probably 1/2" thick and about 5" wide. It should sit perfectly inside two pairs of grooves on the floor of the trunk. I can then mount the fan in that brace, on the left side, to pull air into the tire well and out of the vent on the opposite side.


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