DIY Project Review
 

Pyramid Powered Isobaric Subwoofer

Part VI

April, 2006

Kevin Lichterman

 

Making it Pretty

Well most of the box is now assembled. If you're anything like me, not all the MDF joints will line up perfectly. This is likely a reflection of my own skill. In order to get nice smooth seams and to add an extra air leak seal to each joint, I used Durhams Wood Putty. Durhams is a powder filler - just add a little water and presto you get a paste that you can spread onto the box seams with a putty knife. After drying to a rock hard finish, the area can be sanded smooth for a nice tight seam, flat surfaces and sharp corners. When covered by a veneer, you don't know it's there.

49. Mix up a small amount of the Durhams Wood putty and apply a thin coat (just like plastering a wall) to the box, paying special attention to the seams. Apply enough coats to cover all box imperfections allowing time for the putty to dry between coats.

Tip: Even if a seam 'looks ok', still apply a coat of the putty. The putty will act as another leak sealer.

Tip: Mix the putty in small batches - it dries quickly.

50. Once the putty is dry, sand the box until smooth.

Applying the Veneer

Now we're really getting close, so let's make this thing looks like it has a fine wood construction.

51. Note the EXACT location of all the holes for speaker or port connections since we'll be covering them up with veneer. Especially the top ports and the bottom spike feet.

Tip: Use a pencil and a sheet of paper to take a rubbing (negative imprint) of the location in addition to the measured dimensions so you have a template to work with.

52. Cut a sheet of veneer to roughly the size of the panel to be veneered.
53. Using the spray adhesive, attach the veneer to the back panel and allow it to dry.

Tip: The goal in applying the veneer to any panel is to have a smooth surface. The best way I found to accomplish this is to apply the veneer starting at one edge and then use a veneer roller to work that edge from one side to another, eliminating air packets along the way. After it is in place, to prevent the veneer from lifting, I place another flat board over the panel and place heavy weights on it to keep pressure on the veneer until it is dry.

Tip: Apply glue to both veneer and panel before putting the veneer on the panel.

Tip: Overlap each edge of the panel with the veneer; it's better to cut off the excess than to end up short.

Tip: Practice with some scrap before you work on your final box.

Tip: Plan how you want the grain of the box to look for each panel and mark the veneer's destination before you start gluing, so the finish product looks as good as it can. For example, pick an attractive grain for the box front and for adjoining sides try to line up the grain orientation. Save the ugliest for the bottom.

54. Once the veneer dries, use a cautious hand and a new sharp razor blade to trim excess veneer from the sides of the panel.

55. Repeat the veneer application process for each side. Make sure to allow each side to dry before applying the next.

Tip: The top panel is the most awkward to install. First, two 2" holes must be cut to match the two ports installing the veneer. Next, the tops of the ports must be removed WITHOUT dropping the bottom portion of the ports into the box, so do this with box on its side. With the top flares removed, the veneer is slipped over the ports. With the veneer in place, glue the two top flares onto each port and allow the glue to dry. Be careful not to drip glue onto the veneer! Finally, glue down the veneer. I'd suggest doing the bottom first then the top and finally the sides.

Tip: For the back panel only, cut a hole EXACTLY this size of the WBT binding posts to allow them to pass through the veneer.

Tip: Be careful moving this around and place it on something clean - the veneer is fragile!

56. Using the measurement you made earlier, cut or drill out all the screw holes, speaker cutouts, and port cutouts throughout the box.

57. Lightly sand the veneer.

Tip: Be careful around the edges and do not oversand. The veneer is very thin and can quite easily be sanded through.

Finishing

Getting excited, you're really close to done now! It's time to bring out that grain by staining and sealing the box and really make the project yours by picking out the color scheme - or just use mine.

58. Apply the stain of your choice to the box according the manufacturer's directions and allow stain to dry.

59. Permanently connect the two 2" ports into the box using the round black head screws.

60. Following the directions on the can, apply two coats of the polyurethane to the bottom of the box allowing each coat to dry completely before applying the next.

61. Install the spike feet to the box using directions provided and stand the box up.

62. With the box vertical, work from the top down applying 2-3 coats of polyurethane to the entire box.

Tip: Use spray-on polyurethane around the ports of the box being sure to get some of the product down the throat of each port. The glossy ports really are a nice touch.

Tip: Thin coats are best, thicker coats have a tendency to run.

Tip: Lightly sanding with a very fine sandpaper, or 6X steel wool, can enhance the smoothness of the finish.

Tip: Use a tack cloth to remove all dust before applying any finish.

Tip: Don't sit on a wet speaker!

63. Let things thoroughly dry before handling.

Click Here to Go to Part VII.

© Copyright 2006 Secrets of Home Theater & High Fidelity

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