Amplifier box - PC Case fans for cooling.

[Kwinnie Bogan]

I've built an amplifier box for car audio, and it's all pretty straightforward and wired up. However, there is the issue of core-of-the-sun temperatures in confined spaces, or more worryingly having my amps overheat and die then catch alight. Especially as they're pretty much bolted to the fuel tank, and are hard to access.

I have decided upon two 120mm PC fans which I hold in my hands right now, to both be at one end of the box and suck cold air through, around the amps, and blow it out. I don't really know how to wire them in, though - and looking up the specs* I would also like to up their flowrate from 37cfm a piece to as much as computerly possible without beginning to suffer.

I've been told to tap them into a power source somewhere, and use the amplifier's trigger wire (that is, the miniscule wire that goes form the radio and carries the current that tells the amplifiers to turn on when I want to listen to the sweet sound of Nile vs Red Army Choir feat. Nina Hagen) to trigger a relay, which will then power/turn on(???) the fans so they run simultaneously with the amp.

They're two 120mm *'ZALMAN' case fans, 12V 0.35A case fans. Only $8 each, too! I would like to know how to wire these puppies up to be less like puppies and more like bad dogs.


Anybody? with some help? How do I make a relay? How do I run the fans, and how do I overclock them without a CPU?




[[Down the line I would also like to add a thermoresistor into the circuitry tuned to the right operating temperatures of the amplifiers (they should run pretty toasty, but not searing) with a 15-20 degree difference between the 'on' trigger and the 'off again' trigger, aaaaaaaand a thermometer with digital readout to put in my cabin, so that I know when shit's getting too hot in there and the cooling aint working. BUt that, can come much much later.]]

[MunkeyQ]

No need for a relay there - they hardly draw any current. Simply wire them in parallel with the amplifier's main power supply...if it were me, I'd just wire them straight from the amplifier's power terminals.

To make them go faster, you need to feed them more voltage, but to be honest, the 14v they're going to be receiving from the battery is fine. Over-volting them shortens their lifespan quite a bit, and in your case you'd need a boost converter to step the voltage up.

If the amplifier does overheat, it's got a thermistor inside which will shut it down until it cools off. Avoids having the thing go with a bang. For better cooling and if they're in a completely enclosed box, it's probably worth taking the lids off the amps to allow for better air circulation. Keep your fingers out though as there's some pretty high voltages inside...some newer one have 70 volt rails, which is enough to give you a nasty jolt.

Bolting the amps to a chunk of metal...maybe making the back of the box out of mild steel...will help greatly with heat dissapation too.

[Kwinnie Bogan]

Alright, that seems more simple too. Thanks for the post Munkey.


I'll see if I can get some copper sheet to 'heatsink' the amps - or even attach some bent copper to draw heat away from them and into the car's body, except that's where I'm grounding them both to (a common point on the underside of the stamped steel parcel shelf).

I've got them mounted only on 16mm MDF right now, and it's pretty schmick so it'd be a shame to go out and spend money on some sheet steel and getting that bent up. Now that you mention it though I do have a shitload of steel sheet and even diamondplate (aka faggotplate) lying around I could use instead..

..but I like the MDF And I was going to cut it to fit the pass-through of the boot flush and then carpet over the lot so it looks factory . And I was planning to put a good 2 inches gap underneath too with some spacers. We'll see what happens there, but steel would also have the benefit of not blocking the shit out of my bass.



EDIT: And I jsut lost a couple fingerprints, picking my hot soldering iron up by the business end without looking.