While this is a project that is specific to those of us that make videos in our shops and want to reduce the amount of reverb (echo), the method used here can also be applied to a home theater or other space that has bad acoustics. This article covers how I made the panels and this video shows how they were installed:

The main part of the system is this fiberglass insulation:

It is just regular house insulation for 2×6 walls, about 6″ thick. I’m using this because it is what I had on hand, but a denser product like mineral wool (Roxul) would probably give better results. As this is more of an experiment than a set method for doing this, I have the option of changing the fill material later to see if that makes a notable difference.
There are five pieces because I want to make five panels that are 24″ x 48″ and about 7″ thick. Thicker panels will work well with lower frequency reverb.

These panels are simple low frequency absorbers, which are different from bass traps. Bass traps typically have a hard, thin panel to close in the bottom and are mounted below the ceiling. This space allows reflected sound to enter the trap from above and bounce around inside, using up the sound energy. Since this is a workshop, my thinking was that this type will eventually fill with dust. They are also a bit more difficult to make and more expensive.

These panels will be mounted on the ceiling of my shop, so a frame is needed to house the fiberglass. Again, since this is just an experiment, I wanted to keep it as low cost as possible, but still do the project correctly. To this end, I used 7/16″ OSB to make the parts for the frames:

Side panels are 7″ x 48″ and I’ve attached blocks at the ends to connect the end panels. The cleats in the middle are there to screw on the cover.

The end panels are 7″ x 24″ with a cleat attached to mount the frame on the ceiling:

All five assembled and stacked up to let the glue dry.

To make the covers, another frame is needed and this will be covered with fabric. OSB is cut into strips and a groove cut on the inside edge:

The ends of the shorter strips also have a groove, and this is to connect the parts with a spline.

The splines are cut from 1/2″ plywood so that the grain direction is across the joint:

Solid wood could also be used for these splines, but the grain has to run across the joint, or it will not be strong enough. Originally I was going to use biscuits, but thought it would be interesting to do it this way.

Gluing up the frames for the covers is simply a matter of getting some glue into the grooves and slipping in the splines:

When they are all assembled, I set them on top of the frames to dry. I didn’t use any clamps, as the splines fit tightly in the grooves and that will hold them together while the glue dries.

Here’s a closer look at the splined joints:

This is probably the most effective way to do this and really didn’t take long. Using solid wood or better plywood for the frame with half lap joints is another option, as is using thicker material and screws.

The panels need to be covered with fabric and the best material for this is a canvas drop cloth:

The one I bought is 9′ x 13′ and was around $20.

I cut it in half and then cut one half into five pieces. The other half can be used for something else, maybe more of these panels. To attach the fabric to the frame, I’m just using hot melt glue:

I start at the ends, stretching it tight, and then do the sides. Staples could also be used, but the OSB is pretty hard to drive them into.

The first cover completed. I put regular wood glue on the supports in the middle to hold the cloth on:

To help keep the material from unravelling, I soaked glue into the cloth where I’ll drill the screw holes.

The final step is to paint the canvas with water based primer. This serves two purposes – it helps prevent the cloth from sagging, and makes the material a bit more reflective of higher frequencies. Killing the high frequencies will make the room sound too “dead”, so that should be avoided:

I also gave the frames a coat of primer to make them look a bit better.

To mount the frames on the ceiling, I’ll be using four 2″ wood screws that are driven into plastic anchor plugs. To mark the locations for the plugs, I drove the screws in so that they project up slightly. I can the position the frame on the ceiling, push it up and the screws will make easy to see marks in the drywall:

Since the panels are light, the four plugs will easily hold them firmly on the ceiling.

The plugs installed. A note on driving these: drill a 1/4″ hole first, then screw the plug in without holding the sharp edges. I made the mistake of doing that a few years back, and had some deep cuts on my finger and thumb to bother me for a week afterwards.

With the anchors installed, mounting the panel frame is just a matter of lining up the screws with the plugs and driving them home.

The covers need holes drilled for the screws that hold them up, and that where the glue trick comes in. A 1/8″ hole is drilled easily through without snagging the cloth:

Doing it solo can be difficult and to help hold the cover up on one end, I made a simple bracket that is screwed on temporarily:

All five fully installed. The random pattern is intentional and was determined by placing the pieces of insulation on the floor beforehand to listen for the best locations.

In conclusion I’ll say that the improvement was a bit smaller than I expected, but there was a significant difference, especially in certain areas of the shop. As I get more things on the walls the audio problems will diminish, and as noted on page one, I can change the fill material to a denser insulation to see if it makes an improvement. Also, I can always make and add more panels to the ceiling.

January 2015 Update

After ‘living with’ the treatment for nearly three months, I decided to try something different. I knew that the reason why it wasn’t as effective as I need it to be was due to not using enough panels in the first place, but I also didn’t want to go to the trouble of making more of them. Also, the random placement on the ceiling was good in theory (non-parallel surfaces, placed where most effective), but made it difficult to add more.
I had been thinking about it off and on, and had come up with a much simpler way to cover a major part of the ceiling quickly, using just a single canvas drop cloth to contain the fiberglass.

First, I took everything down again:

I did some measurements and figured out where I would need to place it, and stapled the first edge in place. This is 30″ from the wall. Since my shop is 13′ wide, positioning it 30″ from the walls left 8′ in the middle. The drop cloth is 9′ x 12′, but the actual width is 8′-6″, so I had 6″ slack to put the insulation:

The fiberglass batts are about 44′ long and fit in two rows. When the first half was done, it was drooping quite a lot in the middle, so I drove long screws with washers to act as buttons (like the back of a chair or couch) to pull it up.
The cloth is just stapled up to the drywall ceiling all the way around. If I want to change this arrangement at some time in the future, I can just pull it down with minimal damage.

With the main absorber done and working well, I thought I would reuse the covers from the panels for corner treatment. I stapled on a piece of insulation:

And just screwed it into the corner using long drywall screws. These will be effective absorbers, but also reflect much of the higher frequencies from the painted canvas.

To cover the ends, I made triangular pieces and hot glued more drop cloth on:

Really cleans up the appearance.

Finished:

Now THIS is effective, 100% effective. It has killed the reverb completely, but I still have good higher frequency definition. Or, those are my early impressions, at least. There are ways to reduce the higher frequency absorption that I may try, like replacing the screwed in ‘buttons’ with strips of 1/4″ plywood about 20″ wide and 8′ long. These will turn the absorber into more of a typical ‘trap’, where the lower frequencies will reflect between the ceiling and plywood.

At some point in the future, I may make ‘real’ acoustic panels, but that would be more of an interesting thing to do, as opposed to an actual necessity. In the meantime, mission accomplished: I can now use the microphones that are in my camera for the videos that I make.

I made a video showing the installation and quickly demonstrating how effective the treatment was:

A great resourse for factual details on acoustic treatment is Ethan Winer’s article on building bass traps and his website in general.