With the goal of gaining a few dB’s on the SPL meter I set out to improve upon the box I have had for the last six years. Amongst other aspects, the new design will include a higher tuning frequency, birch wood, and glue instead of screws to hold it together.
Loaded up with a 4×8 sheet of Russian Birch 18mm 13ply for a new box.
This is my set-up for cutting the wood. I clamp a 5ft piece of 1×2 aluminum angle as a straight edge, then outfit my saw with a 40 tooth blade. I then employed an old cabinet making trick, and used carpet tape to adhere a piece of whiteboard (any hardwood will do), then plunged through to create a zero clearance cut. This virtually eliminates any tear-out that normally comes with sawing plywood.
See what I mean…
This is some pretty wood grain.
Using my home brewed circle jig.
I decided to not use any screws on this box, putting my trust in the glue.
I already had a few clamps, but I needed a bunch more. So I went to Harbor Freight and grabbed a mix of clamps. After all was said and done, only two clamps broke (the plastic pistol grip kind).
Although it may seem sunny, it was a tad nippy and I used a thermometer to keep an eye on the temps to make sure I was within a good curing range for the glue.
Some internal bracing and 45′s in the corners.
I moved the operation inside to finish up the box because it was getting too cold.
Using some aluminum shims, I ensured a perfect 3 5/8″ port width.
After using my router to round over all the edges I glued on some feet, and cut some reliefs to tuck the vinyl into.
I started with a mahogany stain, then moved onto eight coats of an exterior high gloss polyurethane. I did some sanding about every 3 coats.
Working towards a mirror finish, I wet sanded the poly all the way up to 1500 grit. I then worked the surface with a 3M rubbing compound following it up with a marine grade wax. You can see a pretty good reflection of the scissors on the left.
After gluing the vinyl, and using a bone tool to tuck it in for a nice edge.
I ended up flaring the port like this because of a miscut and a little extra internal volume. In the end, I think it looks pretty sweet displaying the wood grain like this while also reducing the air velocity at the mouth of the port.
All in all, the box is tuned to ~38hz with ~2.1 cuft of space after port, driver, & bracing displacements.