Friday, February 23, 2007

ProAC 2.5 Clone Project - Part 4

Putting the speakers together

Continuing from the last article. Once you've installed the crossover module into the bottom of each speaker cabinet, it's time to glue the rear panel to close the speaker cabinet. Next, use the sander to sand flush all the seams. Fill any gaps with wood fillers. Clean all surfaces from dust with a damp towel/rag prior to applying the wood veneer.

Applying Wood Veneer

Parts and tools needed
  • Wood Veneer
  • Contact cement
  • Router with a straight bit (for trimming excess)
  • Roller pin
Here are the steps applying wood veneer. Apply to the side first, then the front.
  1. Cut the veneer to size. I added 1/2 inch to each edge.
  2. Apply contact cement to the back of the veneer and the speaker cabinet surface. I used a 3" roller designed to apply contact cement.
  3. Wait for the contact to dry. I waited 25 minutes for mine. Depending of the contact cement you're using, the drying time varies based on the manufacturer or the humility. Read the label.
  4. Before you apply the veneer to the speaker cabinet, a word of warning. Once the veneer and the speaker touch, it's final. The saying "That is all she wrote" applies here. So make sure everything align correctly before you apply the veneer. A good tip I read in a forum for applying contact cement surfaces is to wrap wax paper around sticks, put them on the surface, lay the veneer on top of these sticks. This will give a better way to align the veneer properly. Once you're satisfied with the alignment, simply slide the sticks out one by one.
  5. Use the roller pin on the veneer. Start from the middle and roll it out to the edges. Make sure there aren't any trapped air bubbles.
  6. Trim the edge excess with the router.
Repeat the above steps for all the surfaces. The toughest part to trim the excess off those circular speaker holes with the bevel. You need to trim the bevel edge with the utility knife.

Sand all the veneer surfaces with an orbital sander. I started with a 150 grit and ended with a 220 grit sandpaper. I chose to finish the veneer with clear shellac from Zinsser. Here are the steps I took to finish the veneer.
  1. First coat, apply liberally amount of shellac with a brush
  2. Wait for it to dry (1 hour or so)
  3. Hand sand with a 220 grit sandpaper.
  4. Clean the surfaces with a damp towel.
  5. Apply the second coat of shellac
  6. Wait for it to dry. It takes much longer for the second coat. I left it dry over night.
  7. Lightly sand with 220 grit sandpaper.
  8. Clean the surfaces with a damp towel.
  9. Repeat the step 5 and 6 for the 3rd coat
  10. Again, wait for the shellac to dry. Left it dry over night.
  11. Lightly sand with 220 or higher grit sandpaper. The finer the better.
  12. Clean the surfaces with a damp towel.
  13. Repeat the 4th coat as you would the 3rd coat. I was planning to put on 4 coats of shellac.
  14. For the final coat sanding, I used "9999" steel wood, make sure it said "9999" on the label. After this sanding, you should a piano finish.

This is after 4 coats of Shellac

The more layer of shellac you apply the better the finish will look. Of course you can choose whatever technique on finishing you desire.

Building the Plinth
  • Cut 2 pieces of 3/4" MDF to size. 1" from all the edges of my speakers. I glued them together to create a 1-1/2" thick plinth.
  • Round the top edges with a 1/2" router bit.
  • Painted the Plinth glossy black with a spray can.
  • Glue it to the bottom of the speaker cabinet.

This project may look daunting but once you're committed and get going. It's not as tough as you think. I enjoy working on this project immensely and now I'm still reaping the reward for the work I've done. Now that I've built a pair of loudspeakers, I'm thinking of building a subwoofer next.

Tuesday, February 6, 2007

ProAC 2.5 Clone Project - Part 3


After you've put together your speaker box together (except the rear panel), you're ready to build your crossover module. I built mine based on this diagram.I followed the optional notch filter using the 1.5 Ohm and 5.6 Ohm resistors. I used an extra piece of laminated flooring cut to size to fit at the bottom of the speaker.

Top View

Bottom View

After testing the crossover module to make sure it works, it's glued to the bottom of the speakers cabinet. Also, it is a good time to label the speaker wires prior closing the back panel.
Glue the rear panel to close the cabinet. In the last article, we'll apply the maple veneer, finishes build the plinth and install the speaker drivers.