Skyline Diffuser / Wall Art General Woodworking

Tastes can change over time, as do needs. When I started building the project that these blocks were made for, I wanted a big, thick, Gothic looking butcher block table for my kitchen. As the four years that passed between starting this and today wound down, I found that I no longer wanted that. Instead, I would like something much different – more modern looking and bigger, with storage underneath, since my kitchen as built is larger than I initially envisioned.
So, what to do with the parts? Roughly 120 – 2x4x10″ blocks cut out from the old wall studs removed from the house during the renovation. I considered a few different things, but was limited by the length of the parts. Since I had just finished the desk for my new office, I thought an excellent way to cut my losses on these was to build what’s known as a skyline diffuser. These are primarily made to act as sound treatment (to reduce reverberation in a room), but besides that (and more important in my view) is that they look exceedingly cool.

The blocks were moved around several times during the renovation of my house, and each time i cursed making them in the the first place. The last resting place was stacked up on my shelving in the basement, where they’ve been for nearly a year:

how to make a skyline diffuser

The first step was to cut the blocks into pieces that were exactly 1-1/2″ square. Getting them exactly the same size was important, since it won’t go together properly if there’s variation in the thickness.

After they were cut to size, I sanded them thoroughly with my belt sander and my random orbit sander. Again, I needed to be careful not to sand them unevenly, or that would mess up the fit.
When they were all smooth on the sides, I cut them down into three lengths – 6″, 4″ and 2″. Then more sanding, the ends of each block that faces outwards:

how to make a skyline diffuser

That’s what defines this project – the hours of sanding. When you look at the finished result, it’s tempting to say it would be a snap and only take a few hours to build. Wrong! Not if you actually want it to be smooth and look good, that is..

Assembly next, and I set up my folding saw horses in my shop and placed a door on top. The door is strong and lightweight, and will stay flat. I also covered that with a piece of drywall, just in case any glue squeezed out.
Basically, I had to lay the blocks out in a random pattern, but try to use the same number of each size
in each row:

how to make a skyline diffuser

I used polyurethane construction adhesive to glue the blocks to each other in an end grain cutting board style, rather than gluing them down to a plywood backer. Using a backer would likely be a mistake for one this big, due to seasonal expansion / contraction of the solid wood blocks. That movement could make the assembly change from flat to cupped.

Again, it seemed like putting this together would be a snap, but it took the better part of a full day and nearly a full tube of construction adhesive. I left it to dry overnight, then flipped it over and routed the slot for the French cleat that would mount it on the wall:

how to make a skyline diffuser

The top of the slot is cut with a dovetail bit to create an angle for the angled cleat to lock into, and you can see this happening in the video at the bottom of this page.

I was able to hit my target size of 18″ high and 60″ long, but just barely. I had no blocks to spare:

how to make a skyline diffuser

With it finished with several coats of water based polyurethane and mounted up on the wall in my office, it does look very nest indeed. I doesn’t do a whole lot for the sound in the room, but every little bit does make a difference:

how to make a skyline diffuser

The build video:

I made a video showing how I finished it and mounted it on the wall: