I love to tube the river in the summer, but what’s a hot Texas day, beautiful countryside, and cold beer without good music?  It’s possible to buy floating or waterproof radios, most of which double as coolers, but I have never found one that actually generates serious volume. Worse, central Texas rivers are often in deep canyons, with little or no radio reception. I had seen people on the river with what appeared to be standard chest coolers that had been custom fitted for audio, but I couldn’t find anyone online that made them or even any information about how to do it. So, I embarked on a project to make my own Stereo Cooler, and what follows may be the first Internet Guide on how to build one. As a standard disclaimer, if you try to modify a cooler using this information, you agree that I’m not responsible for any injury – use at your own risk!

Things you will need:

• A medium to large size cooler with (very important) a latch on the lid – $30 from Walmart or Academy Sports
• Amplifier installation kit 8 or 10 gauge – $35 from Best Buy, or $20 online
• Waterproof Marine Speakers – $60 online
• 2 channel car amplifier – $50 for 400W Jensen online
• Medium sized 12 volt battery, e.g. for a riding mower – $20 at Home Depot (try to get a sealed one)
• Ratchet tie downs for roof rack – I bought Good Year Tie Downs at Sam’s Club for $20, but probably any kind will do
• RCA to headphone adaptor or cable – You can buy these at Radio Shack or Best Buy; they cost a couple of bucks and look like this
• An electric switch – $3 from Radio Shack or Fry’s, don’t worry overly about A/C vs. DC or the voltage, it’s for a signal line only
• Tools: Exacto knife or box cutter, wire stripper, screwdrivers, pliers, hack saw blade

Note that I built my cooler to support an iPod, so I bought an Otterbox Waterproof Case at Amazon for $40, but you might decide to go without this added protection. Total cost, assuming you already have tools is $200.

First, you need to set up your amplifier. There are a variety of marine amplifiers available, but they’re build to withstand salty air and are not really waterproof.  I opted to go for a cheap car amplifier so that if it’s lost in the river it can be replaced cheaply. I’m not an expert on audio, but at the low end of audio you don’t really need to think overly hard about matching speakers omhs with amplifiers, etc. Audiophiles might look down their noses at the Jensen and Clarions I used, but they’re solid, cheap, and do the job. Believe me, they are a LOT louder than they appear for their size and price.

You can see the amp hookups below. +12V goes to the battery positive terminal, GND goes to negative. REM stands for REMote terminal, and typically connects to the “head unit” in your car that has the radio, CD player, controls etc. I chose not to use a head unit for this first project to keep things simple, but we need to be able to turn the amp on and off, so the way to do this is to connect the REM to +12V with a switch inbetween. My amplifier installation kit came with a thin REM wire, and the switch I bought has three settings, and I connected the REM wire to the middle position. This means that the amp is on when the switch is in the middle, but off when to either side, meaning that you don’t have to see the lights on the amp itself to know if it’s on or off. The skirt around the switch is just some heat shrink plastic, it’s probably optional. Note that you can click on the images to see more detail.

Once you have the amplifier hooked up and calibrated (read the amplifier instructions for this), it’s time to start cutting up the cooler. Conveniently, a CD works as a template. Draw the template and cut using a box cutter. It’s very important to not cut the holes too large,  they don’t need to be very big we can adjust them later.

Scraping out the foam insulation is messy, so have a dust buster handy. Once you have it scraped clean, cut the inside holes. These can be smaller, and rougher since they won’t be seen. I finished it with sand paper for a smoother look.

Check the speakers for fit, and use a knife or pen to mark the cooler surface where the screw holes on the speakers line up.

The speakers should come with panel clips that will help to securely clamp the speakers to the thin surface of the cooler. Use the clips as a template to cut out rectangular notches large enough so that the hole in the clip lines up with the marks you made on the cooler.

Now you can fit the speakers and secure with the screws provided. The Clarion speakers I purchased have a sticky, waterproof seal on the back, but you could put caulk around the edges for additional water protection if necessary.

Now we turn to the guts of the stereo and the power supply. It’s very important that everything inside the cooler be secured, especially the battery which is very heavy. If the cooler tips over in the water, a loose battery would break the latch and rip everything out of the cooler, and even if the cooler stayed closed it would probably damage the other contents – don’t take a chance on this. I thought about a variety of ways to secure the battery, then came up with the idea of strapping it to the wall of the cooler using a ratchet. This way, it will be tight but can also be removed easily for recharging or replacement. Ratchet tie downs usually come in two pieces with hooks, so we’ll need to modify it into a single loop.

Cut the strap completely off the ratchet, cut off the hook from the other strap, and cut it down to a length that can wrap around the battery and still leave 10 or 12 inches.

Now we have to fix the strap to the ratchet, I used my wifes machine to sew it together, but you could probably use a strong glue or staples if you don’t have a machine.

Cut two narrow slots in the side of the cooler, one above the other, and use a hacksaw blade or something similar to push the strap from the top to the bottom, making sure that the ratchet will be facing the right way up.

Pull it through the bottom slot with pliers, this is much easier than I thought it would be. Apply duct tape around the edges of the slots so that the thin wall of the cooler doesn’t tear.

Now position the battery and strap it in. If you’ve positioned the slots correctly, you shouldn’t have to worry about overtightening. This battery is going nowhere!

That’s the hard part done, now all we need to do it screw down the amplifier into the bottom of your cooler, or onto the side if you have a smaller cooler, and we’re pretty much done. Attach the amplifier switch to the side of the cooler using screws or strong tape and use plastic ties to tidy up the various cables.

The finished cooler. Maybe if I was doing it again I would get a different colored cooler or speaker covers to stand out a little, but its innocuous look belies the power that is inside. With the 400W Jensen and Clarions, the volume easily went so high as to be uncomfortable to the ears! I also found that the system had plenty of bass. It probably would be effective to use a 4-channel amp and add in a bridged sub-woofer, but something about the cavity of the cooler itself seems to generate a strong low end kick. It’s very noticable when closed vs. open.

The cooler is great for floating the river and outdoor parties, and although I’ve never had the battery run out on me yet I figure it has at least 8 hours of continuous play before needing a recharge – enough for a really long float! My only complaint about it is that the sound is very directional. If I were doing it again I’d maybe put one speaker on each side of the cooler, or perhaps even on the lid.

Finally and I hope I don’t even have to say this, but don’t put ice or liquids in the cooler! I’ll occassionally keep items that need to be kept dry in there, but the insides are not liquid-friendly so keep your drinks in a different cooler.

I hope you enjoyed this post, comments and questions are welcome!

Keith

This is a personal blog by Keith Sibson. Here I’ll post about projects I’m working on or things that interest me – nothing too controversial I hope.

Keith