Acoustic Treatment

Absorption Panels

I've been living in rented apartments with small bedrooms for a while and the acoustics of my music spaces has always been terrible, so I finally decided to address it with absorption panels and quadratic residue diffuser (QRD) panels.

I started with the absorption panels in the summer of 2021. Being close to home was helpful because Pops has a (messy) shop full of tools and his years of experience. The design I settled on was fairly simple, but a priority for me was for the absorption panels to not be one-sided so that I could eventually make some stands for them so that they could be freestanding for use as gobos. It would be a butt-joint frame with dowels for added strength, as well as some corner cleats on the inside for rigidity. I have no worries about these panels falling apart.

I went with 5x 2' x 4' panels, 4 of which were 2" deep, the last one 4" deep for use as a bass trap. This isn't really enough for treating a big space, but it's definitely better than nothing, and works fine for a small room or as gobos, as you can see at the end.

So we started cutting out the frame on the table saw, and wound up having to replace the blade for a newer and finer-toothed blade to prevent tearout, because I wanted to the wood to be visible and pretty.

After cutting out the frames, we marked the ends for drilling the dowel holes,

Using the dowel jog to drill the holes is super helpful to keep the drill straight and true, because you obviously can't fit this stock standing up on a drill press.

We did however use the drill press for the opposite joint. We used the painter's tape as a depth marker to make sure we didn't blow out the other side of the wood.

Unfortunately, I didn't get more pictures of the absorption panel process because it was a lot of work and I just wanted to get it done. After assembling the frames with glued dowels and corner cleats, I coated the frame in a clear water-based Polycrylic. I really like the look of it. I then cut rock wool to size and wrapped it in a fine mesh intended for installation in screen doors just to help keep cancer-causing particulate from entering the air, then wrapped that in a black burlap, which is one of the cheapest fabrics you can find, but also looks pretty good for this application.

QRD Panels

I have always wanted some diffusion panels to address flutter echo in the rented spaces my studio has inhabited, but that wasn't necessarily ever enough motivation. So when I my sound art installation (using acoustic treatment as a creative element) proposal was accepted, I finally had my motivation.

Having a constrained budget, I wanted to ensure minimal material waste, as well as minimize weight because these panels were going to hang from the ceiling in the installation. I found a video which utilized a different construction style, eliminating the need for a large percentage of the material by eliminating the backing plane as well as shortening each well fin to match its maximum depth. This method of construction saves a lot on material cost, but takes a little more planning to put it together.

I began by using a QRD calculator (QRDude) to find some dimensions that would diffuse within a useful frequency range without making the panels too big. I don't actually remember my target frequency, but I believe it was somewhere between 200Hz and 800Hz.

Armed with all the dimensions QRDude gives, I did a mock-up in Sketchup in order to figure out how to assemble them, just making sure I would be able to get my nailgun in where I need to by number the order in which to join each piece.

After that, I found an app called CutList Optimizer, which takes the dimensions of all the pieces you need and gives you the most efficient method of cutting them from whatever stock you have. Then I just had to glue and screw them. I forwent sanding as people wouldn't be touching these.

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