Speaker Cubes -a hifi upgrade to your TV

Projectors and flat screen TVs are pretty cool, but the horrible speakers built into them are only cool if you really hate your ears. In this small project I build a pair of self-powered speakers that can connect to anything, and make a great upgrade for a TV.

Materials

• 2'×4' sheet of particle board
• 2'×4' sheet of thin lauan plywood
• Wood glue
• About ½ yard of sheer nylon fabric
• Two 5" speakers
• Panasonic AN17147 amplifier IC (or equivalent) and associated components

Cabinet Construction

Start by laminating the plywood onto the particle board with wood glue, weight it down and let it set overnight. Cut your new composite board crosswise into several strips 6.5" wide. For this next part, it really helps if you have a table saw. Set your saw's rip fence to 6.5" and set the blade at a 45° angle. Cut your strips into eight 6.5" squares, with bevels on three of four sides. This takes care of all four walls of both of your cabinets. Cut two more 6.5" squares with a 45° bevel on all four sides, this will be the back panel of the cabinet. Assemble the five parts of the cabinet with a liberal application of wood glue and clamp it together overnight, or use a few small finishing nails to hold everything in place until the glue sets up. Wipe off any excess glue with a damp sponge immediately, especially if you're going to stain the cabinet, since stain won't absorb into wood glue. You should now have a nice box with an open front.

Now we need a front panel. Take a small piece of unlaminated particle board and cut it into a 6.5" square. Use a table saw or router to give the panel a decorative edge. I used a 45° chamfer, but a roundover will work here as well. If your speakers came with a template, tape it to the dead center of the panel and cut out the opening with a jigsaw.If you don't have a template, you can use aluminum foil to make one, take an impression of the front of the speaker with the foil and use it to cut out a hole the same size as your speaker's face, sans mounting flange. Use a router with a roundover or chamfer bit on the front of the opening, this is mainly a cosmetic thing, since the hole will show through the fabric covering unless it has smooth edges. When you're done, paint it black with acrylic paint, so that it won't show through the fabric grille cloth.

Stretch the fabric around the front panel and staple it in back. Start with the corners, then put staples all the way around the outer edge. Fasten your speaker to the inside of the front panel with at least four ½" screws. Now that the front panel's finished, we're going back to the rest of the cabinet. Fill any gaps in the corners or nail holes with wood putty. Sand everything with 80 grit sandpaper, followed by 120 grit sandpaper, followed by 220 grit sandpaper. I painted mine with a coat of Rustoleum Metallic black, but you can use an oil based wood stain instead. Finish up with three topcoats of lacquer, giving each coat a rubdown with #0000 steel wool once it dries. Once everything's finished, drill a 1.5" hole in the exact center of the back of both cabinets, this is the bass port. Round the edges with a router, if you have one handy. Drill a small ¼" hole near the bottom of one of the cabinets and slip a cable terminated with an RCA jack through the hole, and secure it with an electrician's knot. Solder the speaker to this cable, and glue the front panel on with a liberal dose of hot glue. Your passive speaker is now finished, so set it aside for now.

Electronics Construction

The other speaker will contain the amplifier, so we'll have to get more elaborate here. Drill a 1" hole at the middle at the bottom of the cabinetfor the volume control and external speaker connector, then drill a ¼" hole on each side at the bottom of the cabinet. Slip a power cord through one hole, and an audio cable terminated with your plug of choice (RCA plugs, or a headphone plug) through the other one. Secure both with a knot. Solder the power cord to the fuse holder, and the fuse holder to the power transformer, and mount them both to the inside of the cabinet out of the way of the speaker. Skip this part if you want to use an external wall-wart power supply.

Build the amp board according to this schematic, and solder stranded leads about 8" long to the audio inputs and outputs. I built my amp point-to-point on perf board, which is available at Radio Shack for a small price. Cut a thin sheet of plastic or sheet metal about 2"×3" and drill two holes, one for the volume control and one for the connector for speaker 2. After you've soldered the proper leads to the volume control and speaker connector, mount the little mini board on the back of the cabinet with a few wood screws. Mount the board somewhere inside the cabinet where it won't be touching the speaker, I used plastic spacers and some hot glue. Now all you have to do is solder the leads to the speaker, and glue the front to this cabinet the same way you did the last one.

Conclusion

Overall, I'm really pleased with these little speakers. It only took me about a day to build these, and cost me about $10 for the wood. Everything else I already had on hand. If you'd like to build a set for yourself and need to buy the materials, take a look at my resources page for a list of trustworthy suppliers. All of the parts should come to less than $35 or so.

These are no substitute for a real stereo, of course, but they're an order of magnitude better than the speakers in my TV, with plenty of bass and a much more fluid sound. Being as small as they are, they're also quite portable, and since they're self powered you can plug anything into them, CD player, satellite receiver, tape deck, MP3 player, whatever you have. You can even listen to the music channels without having to turn the TV on. If you liked this project, you may also like my Cirrus Logic hi-fi DAC and my homemade computer speakers.

Gallery

The back of the finished cabinet. You can really see the metallic sparkle here.	Another view of the assembled cabinet.	This is the front panel after I machined and painted it. Note the chamfered edge around the  opening.
These are the little full-range drivers I used.	I've mounted the drivers to the front baffles with small wood screws.	This is how you attach the fabric to the front baffles.
Front of the fabric covered baffle.	A view inside the cabinet. The power transformer is at top right, the fuse holder is at the bottom, and barely visisble to the left is the volume control.	Another view inside the cabinet with the amp board installed.
The finished product sitting next to the TV in my office. Yes, I have an orange room in my house. Who doesn't?!	This is the back of the active speaker, showing the volume control and connector for the other speaker.