DYI Project: Sound absorption panels

After wanting sound absorption panels for a long time (years!), I finally got the opportunity to build a couple to place on the wall behind my studio monitors. So, here's my recipe for 8 absorption panels, with a total size of 615 * 1195 * 70 mm each. I do apologize for the blurry and dark pictures... still getting to know my new camera! ;)

I choose to build the panels using flax(linseed) insulation panels instead of fiberglass or rockwool, as the latter are not that environmental friendly, safe to handle or healthy to have in a living room.

For the flax insulation panels, I found these absorption coefficient values, stated by the manufacturer (not verified):

	125Hz	250Hz	500Hz	1000Hz	2000Hz	4000Hz
50mm	0,2	0,45	0,70	0,80	0,90	0,95
100mm	0,65	0,75	0,75	0,85	0,90	0,95
150mm	0,80	0,90	0,90	0,90	0,90	1,0

What you need for the job:

• 8 insulation panels
• Flax panels, 70 * 565 * 1170 mm.
• 7-8 pieces of wooden boards 28 * 70 * 4200
• Depending on available board length at the warehouse, do the math about length and best cutting measurements. (I bought 8 of these boards)
• a Mitre saw
• Screws 4,0 * 50 mm
• Staple gun and 6 mm staples
• Bigger staples for hanger wire mounting
• Hanger wire
• Some nice pieces of cloth
• Electric drill 
• Electric screw driver

The must-have tools, besides electric drill and screwdriver.

I measured the insulation panels and they were actually 1140 mm tall and not 1170 mm as specified! The width was correct though.

To get a good fit inside the frame, I subtracted 10 mm in both X and Y dimensions.
I cut the boards in 45 degree angles, so the tall sides were 1186 mm on the 'outside' (1130 mm 'inside') and  the short sides were cut in 616 mm on the 'outside' (560 mm 'inside').

Not cutting audio this time.

I pre-drilled holes for the screws, to minimize risk of wood cracking, put some wood glue in between and put 1 screw in the middle from one side, and 2 from the other side. This way the frame gets really sturdy.

Use a previously built frame to support building of others.

Three screws per corner. Start with the single screw, but do not tighten it until the other two screws are in place. This to prevent misalignment.

Some pieces of wood looked like this, or worse. Face those pieces to the inside of the frame.

The panel fitting nicely into the frame!

Did some weight reduction on one of the frames.

Depending on the cloth pattern I used different methods to cover the back side. The one in the picture above was clearly the best option ('the double wrap'). The other method was to cut out a single sheet as big as the back side, and staple it in place before putting in the insulation piece in and mounting the main cloth.

Cutting the cloth this way made it simpler to get a nice fold in the corners. Begin win the backside corner, making a 45º fold pretty much aligned with the wood cuts. Then stretch the cloth from the middle of the short side outwards, and then finally stretching the cloth from the front side corner to get a tight fit with no slop.

A neat and tight corner.

I placed the hanger staples at 23 cm from the top.

Stretch the wire between the staples, pinch it in place with the hammer, and tie a small knot at each end.

The wire will flex a certain amount, giving 16 cm to the top when supporting it's own weight, making it an easy task to place the wall hook and get all panels at the same height.

The final result! Looks pretty good, and a lot of room reflections are gone. Next mission is to find a fitting carpet to place on the floor to get rid of a bit vertical reflections. Much more could be done to the room, but remember... this is still our living room! :D

A big thanks to my friend Tobias for driving to and from the hardware store,  and building the first panel!

Kisses to my pregnant girlfriend for putting up with my audiophilia!

I hope you found this post useful!