Part 3: The DIY Route: Building Treatment

For my space, I built four mid-high absorbers and a pair of bass traps for the back wall. Due to construction limitations (One of my reflection points is ON our painstakingly stained entry door), and personal aesthetic limitations (Mrs. Gremlin wasn’t thrilled about putting panels on the ceiling) I’ve compromised in the placement and number of my panels.

Building Mid-High Absorbers:

The construction of these puppies is pretty straightforward.

Ingredients:

• 2″x2’x4′ Owens Corning 703 backless fiberglass panels.
• 2″ (nominal) lumber
• Backing fabric
• Your choice of acoustically transparent wrapping fabric
• Screws or nails for joining the frames
• Staples
• Wall hangers
• Picture hanging wire

Required tools:

• A saw
• Gloves for handling fiberglass panels
• Drill or hammer for making the frames
• Staple Gun

Safety note: Insulation fibers can do serious damage to your eyes, skin and lungs. Wear proper eye protection, gloves and a respirator when working with this stuff.

 

A Word on Acoustic Fabric:
Fabric is the one part of these devices that can provide aesthetic value to your space. There are tons of options that will work fine. Some people even print movie posters onto fabric to really spice things up! The only requirement is that sound be able to pass easily through the surface of the fabric without reflecting back. The classic way to test this is to hold the fabric over your mouth, exhale, and see if you can easily feel your breath move through it.

 

The build process is pretty easy if you’ve ever DIY’ed everything. Even if you haven’t you should be able to follow these steps and get a decent result.

If you haven’t bought exactly 2″ lumber, you need to use a table saw to cut all the lumber down to width. Those without a garage full of tools can pay a small fee to have all these cuts made for you at a Home Depot or Lowes.

My stack of assembled frames

Next, cut your horizontal pieces to 24″ wide, and your verticals to about 49-1/2″ (these should be 48″ plus the width of two of your boards).

Lumber laid out for assembly

Lay the lumber on a flat surface (a spare plywood sheet or a leveled garage floor work well). Affix the sides to the tops and bottoms, so that the fiberglass panel can be stuffed in, with its sides covered. I used a Kreg Jig with pocket screws for a quick and sturdy result, but nails will work too.

If you end up with rough corners, run a sanding block along them to even them out. You can also wrap them with some electrical or duct tape if you don’t mind creating a slight ridge.

Before you insert the fiberglass, you need to staple backing fabric to the back side of the frame. Whichever side of the frame was pressed against the flat surface during assembly should be used as the back (As it has to hang flat on the wall). You can technically use the same fabric for the front and back, but unless you score a deal on fabric, it tends to be more cost effective to buy cheapo fabric (or even an old bedsheet) for the back.

Using scissors, cut the fabric to roughly 25″x49.” Spread the fabric over the back of the frame, and staple it into place, affixing at opposite edges at a time to ensure you stretch the fabric evenly across the surface.

With the back secure, slip your fiberglass panel into the frame, pressing it gently so it ends up even with the frame edges on all sides.

Finally, cut your fabric for the fronts. I made these pieces WAY oversized initially, as its easy to cut off any excess later on.

Carefully place the panel onto the fabric face-down, then pull the fabric around the sides of the panel, and staple it in place on the backside. Again, take your time, pulling the fabric taught as you go. I folded the corners for a clean result. If you have a lot of excess that might impede the panel hanging flat on the wall, go ahead and snip it off with scissors.

Finally, screw two wall hangers into the pack panels. I placed mine about 8 inches down from the top. Pull a length of picture hanging wire through the two loops, and wrap it over on itself until it can withstand a solid tug.

Hang and enjoy!

 

Building Semi-Permanent Corner Bass Traps:

The principals of bass traps are very similar to the above absorbers. The big difference is thickness. Bass frequencies are far too large to be significantly absorbed by a 2″ panel. As a result, bass traps tend to be 12+ inches deep (really the deeper the better). They’re also almost always triangular for corner placement as this positioning allows them to absorb quite a bit more bass energy.

In my case, my room and personal circumstances only allowed for two traps in the back corners of the room. Rather than build a full triangular frame, I opted to permanently install the base trap into the wall in stages.

Required Materials:

• 1/2″ plywood (optionally stain grade cherry or other hardwood)
• 3/4″x2″x48″ strips
• 3/4x3x~18″ strips
• Pocket screws
• Wrapping fabric
• Rockwool Safe N’ Sound Acoustic Batting
• L brackets and drywall screws/hangers
• Nails

Required Materials:

• Table saw
• Utility Knife or spare electric carving knife
• Drill
• Staple Gun
• Scissors
• Air compressor and nail gun (optional)

I started by taking some scrap cherry plywood I had, and cutting them into 12x12x~17 triangles. I used scrap pine ply for the bottom pieces.

Mounted bottom of trap

Next, I screwed L brackets upside/down into the wall, so that the bottom triangle could be supported by the bracket and also sit flush against the wall. Secure to the brackets with screws (Note: I screwed up on this part, not factoring that I lacked clearance underneath the bottom boards to insert screws from below. A clean solution to this issue would be to use bolts, but I opted to recut the bottom triangles slightly smaller and flip the L brackets back upright, securing from above).

Next, repeat this mounting process for the top triangle. I test fit the top plywood, then stained it before affixing it in place.

The front edge of the stained top is covered by front of the trap

From here, we proceed into the messy part. The core of the bass trap is a stack of Rockwool triangles that fill the space and provide the sound absorption. These come in rectangular batts that need to be cut to shape.

It’s critical that these triangles be stacked freely, without being compressed by the front cover of the trap, or between the top and bottoms. As a result, I undersized them to ensure they would comfortably fit the space.

My acoustic triangles being stacked into place.

To aid in the cutting process, I cut some spare plywood into a template that was about a 1/4 inch shorter on both sides that would touch the wall. You could undersize them even more if you’re building a larger trap.

Safety note (AGAIN): Insulation fibers can do serious damage to your eyes, skin and lungs. Wear proper eye protection, gloves and a respirator when working with this stuff.

To cut, place the template over the batt on a flat surface, then use a sharp utility knife to score and slice through the batt. It usually takes a couple of strokes per edge. If you’re looking for a shortcut, some people recommend using an electric carving knife (thanksgiving turkey style) to slice the batts more easily, but be prepared to get a new blade afterwards).

Once you’ve cut a LOT of triangles, carefully stack them in place between the top and bottom mounted plywood triangles. You’ll likely have a little empty space at the top. That’s okay.

It’s time to build front frames to keep the fiberglass in place and provide a decorative finish.

I used a table saw to cut angles into the side pieces of my frames. Feel free to cut a somewhat narrow angle. All that matters is that the frame edges sit flush against the wall; they don’t have to match perfectly.

As with the mid-high absorber frames, assemble these on a flat surface. This time we’re placing all the wood flat on the table. I used pocket screws and my kreg jig to secure the top pieces to the sides; you could also use metal joiner brackets in a pinch.

With the frames assembled, it’s once again time to wrap in acoustically transparent fabric. I used the same fabric for the bass traps and my mid-high absorbers. The wrapping process is the same. Pull tight… staple… repeat.

Finally, press the frames into place, using a nail gun (or standard nails and a hammer) to secure the frames into the wall. Be sure to hold the frame flush with the top plywood, to cover the raw edges of the plywood piece.

Repeat for as many bass traps as you have room for!

Putting it all together:

Go forth and enjoy your new creations! As you place these panels, take your time to experiment.

Ultimately, whatever sounds best to your ears is what you should stick with!

If you’ve bought a measurement microphone, take measurements with and without your panels to see what they’re doing. Try moving the panels into different positions and compare the sound of your system. Ultimately, whatever sounds best to your ears is what you should stick with! If you look at my graphs, you can still see lots of hypothetical issues, but I placed to taste within the limits of what I could correct, and I’d advise you to do the same.

Thanks for reading, as always. If you found this information useful, please consider using this site’s product links. Your purchases may earn ByteGremlin a small commission, and it doesn’t cost you a dime.

If you enjoyed this write up, feel free to share this post, or drop a comment below!