Boom Box for the Workshop, Tailgating, Etc.

Greetings. This is my first Instructable.

I've grown tired of listening to the radio in my workshop and, as a gearhead, I figured I'd build a relatively portable boom box using an automotive head unit and speakers. After doing a bit of research on web, including Instructables, a Harbor Freight power pack appeared to be the best choice to source a sealed lead acid battery. My music collection spans from CDs to MP3s so an AM/FM receiver with those features would be in the works....

After thinking about the overall concept, I came up with the parts list:

3-in-1 Power Pack PN 62306 (17aH 12VDC battery) - Harbor Freight
Kenwood KDC-125U AM/FM/CD-Receiver with USB - Amazon
Boss Audio SK65 Phantom Skull 400 Watt 6.5" Speaker Component System - Walmart.com
Metra Universal Antenna 44-UL09 - Amazon
Finger Guards (Door Pulls) 3-inch on center - Home Depot
Handle, Audio Cabinet - Speakerhardware.com
Rubber Feet, Audio Cabinet - Speakerhardware.com

Materials

3/4-inch ACX plywood (all from the scrap bin)
Acrylic caulk/sealant, paintable
Joinery biscuits
Wood glue
Assortment of sheet metal and wood screws
Electrical supplies included barrel (crimp) connectors, heat shrink, zip ties.
Sandpaper, painter's tape, paints, & finishes

Tools.... Some of this might be overkill but I have the tools so why not? In addition to common hand tools....

Table saw ........... Delta
Drill driver ............DeWalt
Jigsaw .................Milwaukee
Biscuit cutter .......Porter cable
Plunge Router..... Bosch
Air saw.................Ingersoll-Rand
Orbital sander....... DeWalt
Clamps (various)............swap meet!
Hole saw (for tweeters)....Harbor Freight
Wood and metal files/rasps... Stanley

Step 1: Get a Power Pack!

The first step was to get a power pack. As luck would have it, the latest Harbor Freight mailer included a coupon ... and I picked up another free (with any purchase) 25-foot measuring tape. The power pack has a fully moulded case with a master switch, two 12VDC ports, a USB charger, an LED work light, and of course, the jumper leads to jump start a vehicle.

Got it home and read the instructions. The press-to-test battery charge indicator lit up yellow and the instructions stated that it needed to be charged immediately so that's what I did. ...24 hours later and it was showing a green light. Onward!

Step 2: Hack the Power Pack!

With the master switch off, rest the case on its face and remove a total of eight screws if I recall correctly. This was the time to take reference photographs for future use. After taking some notes, the battery was removed, measured, weighed and set aside. 11 pounds!

Then the hacking began... actually, it was more like careful disassembly and keeping track of the hardware.

Step 3: Determining the Layout and Size & Reusing Most of the Power Pack

I laid out the components on a large piece of cardboard and came up with a cabinet face measuring 23.5 inches wide by 13.5 inches tall. The final depth was driven by the depth of the head unit. If it didn't have a CD player, then it could definitely be constructed shallower. The overall depth (front to rear) is 8 inches.... I used scrap 3/4-ply for the front and back so the interior dimension is 6.5 inches. The height was partially driven by the Metra retractable antenna.

'Sized the front face on the table saw and proceeded to cut out the speaker holes and hole for the receiver sleeve. Filed and sanded them smooth until they fit without being "tight".

At this point I came to the conclusion that this project would use as much of the plastic moulded case so I commenced to cutting with a pneumatic air saw.... Hack, slash, and cut!

The bottom halves of the case became the battery box. The 12VDC power ports were neatly excised and a face plate fabricated from 20g sheet metal. A little bit of five-minute epoxy gets the job done. The control panel was also neatly trimmed out. Yeah, the work light stayed. In fact, I'll tell you a nice surprise about it later...

Then it came time to fit them between the tweeters and head unit. A rough layout and then plunge router sunk the panels into the cabinet face...

Step 4: Installing the Battery Charger & Antenna

The top, bottom, and side panels were sized for the final cabinet dimension. More components to install.

Pictured is the battery charger which is on the upper rear side of the power pack. I cut it out with the air saw and left it "big" to use the case as a mounting plate. Its prongs fold so I cut the hole to the extent of the recess and square it up so the cord can be plugged in. After the photo was taken, the hole's edges were eased with a chamfering bit on the router. The prongs can be left upright and still not project beyond the plywood.

The universal Metra antenna is installed. Using the escutcheon and the angle ball resulted in the top nut unable to thread on the antenna's sleeve due to the thickness of the plywood. Deleting them worked out where only the grommet and top nut was used... The antenna doesn't need to be angled anyways.

Step 5: Preliminary Assembly & Testing

The cabinet was glued together with biscuits using a Porter-Cable biscuit cutter. I used 20s only because I have lots of them. Left clamped to dry over night, the boom box was completely assembled (including the finger guards) and powered up. Works great!

NOTE: One thing I should not have done was to add the two rear panels at this time because while the battery can be removed, it got tight when using screwdrivers, nut drivers, wire strippers, and drilling pilot holes for the crossovers which are on either side of the case. Lesson learned but too late because the panels are glued and biscuited solid! A perforated center panel allows cooling and is easily removed in case I need to get in there.

Then the entire boom box was disassembled for paint...

Step 6: Paint?... Paint! ..... & Final Assembly

What to do? I showed my colleagues at work this little project and received all kinds of suggestions for the exterior finish...... from camouflage, to an SF Giants theme, and DeWalt-like in black and yellow. In the end, this is one project that I didn't want to go "overboard" on like I did with a lawn tractor which got "hot rodded".

I decided to keep it simple with three coats of Rustoleum silver enamel and three satin clear coats of Minwax water-based polyurethane. Then I masked off the upper part between the tweeters, sealed the tape edge with a light brushing of clear, and then applied two light coats of Rustoleum gloss black. Applying clear on the tape edge and letting it dry thoroughly allows the tape to be pulled with a nice crisp edge. The two more thin coats of satin poly.

I took to assembling the boom box at a leisurely pace. I left the battery and and battery box out while reinstalling the components to my left (charger, tweeter, crossover, control panel) then worked on my right (antenna, tweeter, 12VDC power ports, and crossover). Then the rear half of battery box was secured, the battery installed, and then the other half of the battery box screwed to the front half using the OEM screws.... I found a 3-inch wide strap and plastic latch in my miscellaneous parts bin and screwed it to the case so the battery cannot fall out if, for whatever reason, it takes a tumble. Finally, the head unit sleeve and head unit was installed. Wired it up and everything works great. It cranks! The finishing touches were the rubber feet and carrying handle from Speakerhardware.com.

Based on my typical volume level and periodic voltage drawdown measurements, I figure the listening time will be between 20 and 25 hours before it needs to be charged. And in a pinch, it can probably still jump-start a vehicle!

By the way, it's no surprise that the LED worklight can switched on and left on, right?. But depressing the button a second time results in the light flashing "SOS" in Morse code. Ha! It doesn't even state it does that in the owner's manual!

Total Build Time: Over a span of 30 days in my spare time.
Total Cost: $186.67
Total Weight: 37 pounds. Yeah, a bit hefty. Oh well.

....Version 2.0 is in the planning stage and will consist of a TIG-welded aluminum frame, aluminum panels, and a digital media head unit - No CD.

Thanks for reading and viewing.