5 Speaker Car Head Unit Boombox

I built this 20+ pound monstrosity in 2005 for my Mother who was working in a noisy industrial environment and needed some audio umph to enjoy her tunes. I had built a couple of boxy rectilinear 80's style portables to wrap old car stereos and speakers in before and wanted to design something more sleek and sophisticated. I also wanted to incorporate some beefy industrial utilitarian elements hence the expanded metal grills, exposed screws, and unfilled brad holes.

Alas I only have a few poor quality photos of this build that don't show all of the construction details but I shall endeavor to describe the process. UPDATE: I was able to get some fresh photo's showing more details! 

Specifications

Cabinet Dimensions

• Length= 24"
• Height= 10"
• Depth= 11.5"

Electronics

• Pyle PLCDS200 AM/FM CD Cassette 50W X 4 Channel Head Unit
• 2X 5.5" Goldwood Woofers
• 2X 1" Dome Tweeters
• 1X 6.5" Dual Voice Coil Subwoofer
• 120VAC to 12VDC 9A Switching Power Supply

Materials
Cabinet
1 - 8' 1 X 12 Pine
1 - 4' X 4' X 1/4" Pine Plywood
1 - 5/8" Hardwood Dowel
Wood Screws
Brads
Wood Glue
4- Cabinet Feet
3 - Port Rings
Electronics
Car Head Unit
2 - 5" to 6" Woofers
2 - 1" Dome Tweeters
1 - 6.5" Dual Voice Coil Subwoofer
1 - 120VAC to 12VDC XA Switching Power Supply
Speaker Wire
2 - 6" Expanded Metal Speaker Grills
1 - Telescoping Antenna

Tools
Table Saw
Router & Bits
Drill & Bits
Pneumatic Brad Nailer & Air Compressor
Jigsaw
Tape Measure
Pencil
Sand Paper

  1. Crosscut two 24" lengths of 1 X 12.
  2. Choose the straightest long edge to ride against the rip fence and rip the 24" blanks down to 10" in width.
  3. Measure for component placement then draw the layout on the front plate and determine the location for the 2 cabinet partitions.
  4. Measure for speaker port & access panel placement then draw the layout on the back panel, then transfer the partition locations.
  5. Butt the bottom edges of the front & back plate together with the inside facing up making sure the ends are flush. Using a router equiped with a 3/4" straight cutting bit & a straight edge guide clamped to the blanks mill 1/4" deep dados to accept the partitions on the inside of the plates.
  6. Layout the radius on the ends of both plates then use your router equiped with a straight cutting bit and a circle cutting plate to cut the radii in successively deepening passes until cutting through. Using this same router set up cut the holes in the front plate for the 5.5" speakers.
  7. Using your router equipped with a rabetting bit with guide bearing rabbet the radiused ends on both plates on the inside to accept the bent plywood panels. Using this same router set up mill appropriate recesses around the speaker holes to accept the speaker flanges. Also with this set up mill the recess for the access panel in the back plate.
  8. Using your router equipped with a 3/8" radius round over bit with guide bearing round over the outside corner of both plates.
  9. Cut the opening for the head unit in the front plate using a jigsaw.
  10. Use a drill equipped with an appropriate bit or holesaw to make the holes for the tweeters. Use this set up to make the holes in the back plate for the speaker ports.

I added a small recessed panel between the tweeters that I had planned to install a headphone jack and other goodies in, but as you see the panel is blank.

  1. Determine the desired finished outside depth of the cabinet, subtract 1" from this measurement and crosscut 2 blanks from the 1 X 12 stock.
  2. Rip both blanks to 10" in width.
  3. Measure for and machine appropriate dados and rabbets in the partitions to accept the bent plywood ends and bottom panel.
  4. Assemble the chassis by fastening the front & back plates, and partitions together using glue and brads.

Cut the Panels  

  1. Use a sewing tape measure that can conform to curves measure from rabbet around the radius to rabbet for the length of the bent plywood panels. Cut 2 panels of 1/4" plywood this length by the depth of the speaker compartment openings rabbet to rabbet.
  2.  To allow the plywood panels to bend cut kerfs on the inside every 1/2" at least 1/8" deep perpendicular to the radius.

Bend and Fasten the Panels

Successfully bending the panels can be challenging, here's what worked for me. Prepare the panels prior to fastening them to the chassis by thoroughly wetting the outside surface with water and let it soak in for a few minutes. This helps make the wood more supple and flexible. Apply glue in the rabbets that accept the panel. Insert one end of the panel into it's rabbet and brad that edge in. Start slowly forming the panel into the radius rabbets bradding as you go. If there's allot of resistance or you here cracking sounds rewet the surface.

I installed the sub inside the center compartment underneath the head unit firing down through a port in the bottom panel. I built an appropriate sub-assembly and enclusure with pine cleats and 1/4" plywood.

Note. The cone of the sub that I used sags a little due to gravity which allows the voice coil to overextend when driven hard causing some distortion.

Recessed Vented Top Panel

I wanted a recess at the top to fold the handle into and decided it would be aesthetically pleasing and electrically beneficial to vent this panel. Measure the opening and decide on a gap pattern then cut appropriate strips of 1/4" plywood and glue and brad them at both ends to pine cleats pre-drilled with screw holes to attach the panel to the chassis. I also glued a piece of speaker grill fabric to the inside of the panel.

Bottom Panel

Cut a 1/4" plywood panel to fit and drill an appropriate subwoofer port hole then pre-drill screw holes for mounting.

Back Panel

Cut a 1/4" plywood panel to fit then pre-drill screw holes for mounting.

Folding Top Handle

Make the handle from an appropriate length piece of hardwood dowel fastened with screws to 2 strips of scrap hardwood counterbored to accept the dowel.

Finding the cabinets loaded center of balance is tricky. I initially attached the handle at the midpoint from front to back only to realize after the cabinet was loaded, that the front would tip down when being carried by the handle because most of the weight is toward the front. Your handle will need to be attached offcenter toward the front, it will take some trial and error to find the sweetspot. Once I did I installed 1/4 - 20 threaded inserts in the partitions and through bolted the handle.

I recommend lightly sanding all exterior surfaces prior to finishing and then tacking off the dust. I used a rag to apply a couple coats of danish oil, followed by 2 coats of satin polyurethane.

  1. Insert the head unit and fasten it.
  2. Choose an appropriate placement for the power supply in the center compartment and fasten it.
  3. Drill appropriate holes to pass the power cord, and speaker wires through.
  4. Following the wiring diagrams that came with your components, wire evrything securely soldering, nutting, or crimping the connections together then use ties to neatly route them.
  5. Fasten the speakers.
  6. Install the expanded metal speaker grills, and the top, bottom and back panels.
  7. Install the cabinet feet.
  8. Install the speaker port rings.
  9. Install the radio antenna.

Note. I connected both the left and right outputs of the rear channel to the dual voice coil subwoofer. The tweeters are connected in parallel with the front channel woofers through a simple inductor & capacitor crossover network. Also I insulated all of the the speaker compartments with poly fill.

Final Thoughts

This thing sounds great and has some serious window rattling power for an um....semi portable jambox. Unfortunately the CD player and cassette deck failed due to a combination of poor manufacturing and exposure to a volitile environment. The radio and amp still function and it works well with an external input.