How to Build a Stereo Cooler Part II
I decided to take the next step and install a receiver in my cooler so that I can control the audio from outside the cooler without having to get inside and mess with my iPod. I chose the Pyle PL98M4 for $100 as my receiver, mostly because I knew that I wanted to play mp3 from a card rather than CDs, and the Pyle unit is “mechless” in that it doesn’t have any moving parts. This should make it more reliable and eliminate the risk of water penetrating a CD slot. I was disappointed that the unit does not have an REM output that would allow me to turn the amplifier on and off from outside, but otherwise it’s a good unit and the LCD display is convenient.
I’m using the RCA outputs and not the built in amplifier because I already have the 400W Jensen unit. I don’t know whether the receiver’s amplifier draws the same current if no speakers are connected, so I’m a little concerned that it will mean less battery life overall, does anyone know? If it is drawing lots of current then in a future project I will install more speakers – we might as well use the juice rather than waste it!
To protect the receiver from water, I purchased a universal splash guard. It’s not water proof, but should be good enough to protect the unit from a brief dunking if the worst comes to the worst on the river. I had to install it on the back of the cooler due to lack of space on the front. The water resistant seal provided provides a convenient template for cutting into the cooler.
Having done this a few times now, the best technique I’ve found so far to remove the foam is to cut a grid pattern, then pry out the foam in cubes. Once you’ve got most of the foam out, you can simply cut through the inner panel from the outside. You need to make the hole on the inside about 3/4 of an inch larger on the top side to accommodate the lid of the splash guard. A sanding block comes in handy for smoothing and shaping the foam.
The receiver comes with a caddy that you’re supposed to fix into your car and then the receiver can slide into it easily. Push the caddy in from the font and then fold the metal flaps out to grab the body of the splash guard. Given that we’re putting it into a cooler there’s not much support for the caddy, but fortunately we can use the splash guard itself to secure the whole apparatus to the cooler.
Don’t try to install the splash guard and caddy with the receiver already in it, it would be much more difficult.
This is the view from the inside. I used the nuts and bolts provided with the splash guard and washers to secure it to the panel. I marked and drilled small holes in the panel to slip the bolts through, and cut out foam to get at the nuts from the inside to hold them while I tightened. I would not do it the same way again – it was a major hassle fitting and tightening the nuts. Instead, I would buy longer 3″ bolts, long enough to pass through the entire wall of the cooler. Then it would be easy to just drill through the entire cooler wall and secure cleanly on the inside.
Now to wiring. I already have an amplifier hooked up, but if you’re using just the receiver for amplification then you can use the appropriate steps from my initial post on building an ice chest stereo to set up and wire the speakers, switch, and power supply. As I said before, there is no REM wire to control the amp, so we’ll need to continue to rely on the switch to power the system on and off. It’s important that we can turn off both the receiver and amp at the same time, because they’ll quickly draw down the battery if left on even with no music playing.
The instructions provided with the Pyle receiver were completely worthless – the only useful information is in the wiring diagram printed on the unit itself (see above). I have no idea what “Memory B+” means, but a little testing showed that this is the +12V power line that drives the unit. “Ignition Switch” is the signal line that triggers the unit to turn on. We need +12V on both these lines, but the real current is drawn on the confusingly named Memory B+ (can anyone explain what this means?) [Edit: Jacob F pointed out that Memory B+ is most likely to keep the clock and settings alive and that Ignition powers the receiver - he's almost certainly right]
The solution is to put the Ignition Memory B+ line on the same circuit as the REM switch. We also need to connect power, so I opted to crowd everything on the amp connectors, doubling up the +12V and GND. This looks messy, but is screwed down tight and secure. Both the amp and the receiver are at +12V, but the switch simultaneously gates power to the receiver ignition and amp REM lines keeping them on or off together.
I also took the opportunity to secure the switch to the side of the cooler. I used a metal strip that happened to come with the receiver, with a nut and bolt and wood screws. I used 3 screws just to be sure because the plastic wall is flimsy.
And here is the finished result.
The Pyle receiver will accept SD and MCC flash RAM loaded with MP3s, and allows you to navigate through one level of folders. I was disappointed that it didn’t handle the track names better when browsing for music, but I usually just listen to playlists on the river anyway, occassionally skipping through tracks, so it isn’t a major problem.
Well that’s another afternoon project completed successfully! Next time I might add some smaller speakers to the front of the cooler to get more of a “surround sound” and take advantage of the additional amplification in the receiver. Comments and feedback are welcome as always!