Fall 2009

DIY Room Treatment Devices
Article By Bob Jackson (aka Bob In St. Louis)

Difficulty Level

  Room treatments... Bla! I'd rather build some speakers or buy an amp. How much more boring could you get than by hanging stuff on the walls? I mean come on, room treatments don't have pretty lights, they don't have sexy brushed aluminum face plates, they aren't even shiny. The wife acceptance factor (WAF) for room treatments is generally lower than the six foot tall, two hundred pound set of arrays you've been told "you can't have because they're too big". It's no wonder acoustic room treatments are the last thing most of us worry about.

We've all heard stories of how properly treating our rooms will have sonic benefits beyond what any single piece of equipment will ever achieve. Bla....

Brothers and Sisters, I'm here to tell you what. Get off the fence and stop draggin' your feet. All of the positive words you've heard regarding acoustic panels is correct. A wise man told me, "You got walls -- You got issues". Truer words have not been spoken. So here's the story of how I build several panels for less than $300. And did indeed gain a sonic benefit greater than any other single piece of equipment I've heard.

I bought a bundle of Owens Corning "703" which consists of 12 pieces of 2' x 4' rigid panels that are 2" thick. Before I got too carried away building stuff, I thought I'd scatter the panels around the room to see (hear) what all the rage is about. Besides, at this point in time I'm still a little skeptical about the sonic benefits I'm supposed to be getting by hanging this stuff all over my walls. 

Here are a couple panels at what's called "the first reflection points".

The right wall and rear wall.

And finally, the rear wall.

With the panels scattered in these locations the first thing I noticed was the room had a much greater sense of "quiet". I thought the room was pretty quiet to begin with, but these panels somehow sucked up noise I wasn't aware was even there in the first place. Ok, I'm impressed. After playing a few reference songs I am now sold on the idea of room treatments. All audible frequencies seems to be cleaner and clearer now due to the fact the sound waves aren't bouncing around the room like a balls on a billiard table. Now I see what all the fuss is about. It doesn't take long to realize this is something I should have done a long time ago. You've heard that before, right?

Let Us Get To Work
The goal is to make two panels for the left wall, and four panels for the right wall. All of them will be one panel thick (two inches) of the "703". The right and left asymmetry isn't ideal, but due to the arrangement of the walls, that's the only choice I've got. The rear wall will receive three panels all of which are two panels thick (four inches) to act somewhat as a bass trap.

Of course you could just wrap the panels in burlap fabric and hang them on the walls. Bang, you're finished. It's that simple. But surely you don't want the project to be that easy do you? Let's make things overcomplicated shall we? How about a nice wood frame. That would be good except the sound waves can't enter the sides of the panels thereby decreasing the overall effectiveness. We could drill holes in the wood frame, yea, let's do that.

A person could buy lengths of 1" x 3" inexpensive pine or poplar or what I did, a sheet of 0.75" plywood and cut it in strips. The plywood is less expensive, so let's go that route.

For proper absorption, the panels should be as far from the wall as they are thick. Meaning a two inch thick panel should be two inches form the wall for a total distance of four inches. The science behind "why" escapes me, but has something to do with increasing the overall effectiveness of the panel. A smart guy told me that, so it's good enough for me. The wood frame will be three inches deep. The sound waves should be able to get behind the panel which is why it's not four inches thick, but I didn't want the ugly area behind to be visible so I left a one inch gap between the wall and the wood frame. Using this theory, the rear panel which is four inches thick will have a five inch wood frame and be a few inches from the wall.

Dissecting the sheet of plywood into a couple dozen strips three and five inches wide respectively wasn't too hard using the circular saw guide attachment. If you're building a panel that's 2' x 4', then you need four strips of wood. Two of which are 4' long (that's easy since plywood already comes with that convenient corresponding length). The other two pieces will need to be 25.5" long. The added distance is needed to overlap the four foot length thereby creating a four sided box with internal dimensions of 2' x 4'. Once you've got all the pieces in various lengths, it's time to drill some holes.

For the right and left panels, I put a mark on the frame pieces every 2.5" these will get 1 3/8" hole, leaving enough material in between the holes to retain some strength in the material. The larger, thicker panel for the rear wall will receive 2.5" diameter holes spaced every 3.5".

Using hole saws on a drill press I begin to make holes.
Here are the results.

Of course a sane person might consider this "enough", but it seemed like a good idea to smooth the edges using a round-over bit on a router. All edges and all holes on both sides get the router treatment. I did this mainly to help avoid snagging the fabric material the wood will be covered with or possibly having splinters poke through damaging the fabric. Of course painting or staining the wood would be an option as well. Your significant other will tell you their preference. If you don't believe me, just ask them.

I assembled the rear wall panel first, here's the result.

And the assembled side panels below.

Before I wrap the "703" and the wood frame with the fabric, I did a test fit of the assembly on the wall.

The "703" will be covered with #260-337 gray speaker grill fabric from Parts Express. A quantity of two is less than $14. The side wall panels will be covered in #260-335 black grill fabric, also $14.

To have wrapped the wood frame in the same material would have been the easiest, quickest and cheapest way of finishing this project. But we're not going that route. Instead I got several yards of charcoal gray corduroy fabric from a fabric store. This, I cut in several inch wide strips to wrap the frame in. A staple gun was used to secure the fabric to the wood. Inexpensive 2" steel angle brackets painted flat black will be used to secure the panels to the walls. The panels are not very heavy, but just in case I mounted the brackets where the studs are located. The brackets are only attached at the tops of the panels.

The final result for the rear wall panel

The left wall

And finally, the right wall.

Overall, I couldn't be happier with the results. The audible effects truly are everything you've read about.