Homebrewed Music

I built a batch of broadband absorber panels before I recorded my Kaleponi CD. I have 13 panels constructed of 4 inches of OC703 wrapped in burlap. It’s been a while since I built these and I’ve lost track of the cost, but I’ll do better with the next batch, I promise. Here’s a look at what they’ve done for my recording space.

My panel construction is crude compared to a lot of examples I see. I use no frame, relying on the rigidity of the compressed fiberglass to hold itself up. I simply glue together two 2″ panels and fold the burlap around them, then shoot the burlap with glue and hope they hold. They’re not very rugged, not terribly pretty, but they hold together well enough for my needs, they’re easy to maneuver, and do a nice job of improving the sound of the room.

Broadband absorber, quick and dirty style

Hardware Free Mounting

I’m lucky to have 8′ ceilings in my recording space, so the 4′x2′ dimension of the OC703 works great. I can easily shove two panels into a corner and they’ll hold themselves in place. I can place two of them on a wall with a 4″ spacer (like a small cardboard box) behind them and they’ll wedge into the space and stay there.

Here’s a model of Digital Duck Studio with 13 panels installed.

Digital Duck Studio with 13 broadband absorbers installed

and a picture of the business end of the listening setup.

Digital Duck listening position with broadband absorbers

My layout simply follows the advice given so generously by Ethan Winer, concentrating on the corners. The two forward corners are the easy ones, every other vertical corner in the room has some obstruction. The floor to wall corner is the next easy one to cover. The forward traps are out of the way, so I angle them out a bit, nearly 45 degrees straddling the right angle. On the side walls, where space is more valuable and also where we need mid and high damping, I stand the panels up and lean them against the wall at a small angle. They’re tall enough to cover the first reflection points on the side walls, and since they’re not fastened, they’re easy to move if needed.

On the left I have a pair of panels spaced 4″ from the wall, once again following Mr. Winer’s advice.

Mounting of two broadband absorbers using a spacer

These two panels are self-supporting by being wedged against a spacer, a conveniently sized piece of styrofoam. Once again, this arrangement can be altered in minutes.

Room Testing with Room EQ Wizard

Now lets fire up Room EQ Wizard and see if we can measure any improvement with 13 panels. Here are three measurements taken at three different locations, just as we did in the previous post. The first measurement is light blue, taken at the listening position. The second, green, has the mic moved back 1 foot. The third purple graph was taken another foot back.

Three frequency response plots - 40 to 1000 hz

and for comparison here’s the graph from the untreated room:

REW graph 40 to 1000 hz, 3 measurements combined

I’m pleased with the this graph in the area between 100 and 200 hz. In the untreated room measured in our last blog entry each measurement showed a distinctly different dip, right in the low strings of the guitar. The new measurements with the treatment in place may not be flat, but they’re much more consistent between positions which makes getting a good recording a lot less of a headache.

And speaking of recording, here’s a clip with the same mic layout we used in the untreated room.

post2clip1.mp3

or if your prefer, download the clip

Here’s the clip from the last post, in the untreated room.

post1clip1.mp3

or if your prefer, download the clip

To my ear this new clip in the treated room has a tighter stereo image and sounds much more like a studio recording. This recording shows how much the broadband absorbers do to control the early reflections that make a small room sound “cheap” and tinny.

Well, if a little is good, then more is better, and too much is just enough. In the next stage of the panel project I’ll buy some more compressed fiberglass and some more burlap and make a few more panels to try to improve the room a bit more.