Studio Build Part 3 – Building More Broadband Absorbers

In my previous posts I wrote about the planning process for building my acoustic treatment and refining the space and how I installed bass traps in the two available corners of my studio.

In this post I’m going to show you how I built the rest of my broad-band absorbers.

With my trihedral corners covered, The next set of treatment involved absorbing sound in the dihedral corners.  The only ones available to build along were where the ceiling meets the walls.  Following the success of the trihedral corner traps I used a similar design.  I chose to fill the corners with insulation rather than straddle them to maximise the low-end absorption.  As with the upright traps I used Knauf Earthwool RS60.

First I constructed the frames using reclaimed wood from the Newcastle Wood Recycling Centre.  I made them 60 x 60 cm along the wall and ceiling.  This should be large enough to absorb frequencies as low as 80 or even 70hz.  It was also a convenient size to cut the insulation to as it is supplied in blocks of 120cm x 60cm.  The absorber can always be bigger to absorb more low frequencies but at some point you have to leave enough space to actually get into the room…

I added strips of MDF running horizontally along the wall and ceiling to “hold” the insulation in place against the wall.  The MDF turned out to be far to flimsy for the job so I reinforced ti with some 1×1 timbers.  It foiled my plans a bit and made it very hard to get the insulation in.  Suffice to say that it is horrible stuff to work with overhead.  Check out the pictures below to see the frames and insulation.


I constructed a similar frame above my window, except due to the size of the window this one measured only 30cm down the wall and out along the ceiling, meaning that it would not be very effective down at the lower frequencies but help to absorb a lot of the mid and high frequencies.

Window Frame filled End Window Frame FilledThe challenge here was to accommodate the curtain rail.  I planned to make curtains from Kilo surge wool, which as its name suggests is a sort of wool that weighs about 1kg per square metre.  It has excellent acoustic properties (for a piece of fabric) and is commonly used in theatre and studio applications.   The problem with the surge wool is the weight and so I had to fit a heavy duty curtain rail within the frames for the absorber.  Because of the limited space above the window I wanted the absorber to be as big as possible – in order to absorb as many low-frequencies as possible.  This meant cutting gaps into the absorber from which the curtain rail supports would protrude.  The curtain itself was lined with the kilo surge wool covered with a nicer colour poly-cotton as the kilo surge wool is only available in black.


To cover the unsightly insulation and make a more cosy creative environment I used 70/30 poly cotton screens, stretched over lightweight wooden frames and stuck to the front of the absorbers using heavy duty velcro.  The adhesive on the velcro was awful so I ended up using a multi-purpose adhesive and staples to stick the velcro to the frames and screens.  I used Dylon machine dye to dye some white fabric the same colour as my walls.  I would definitely advise against this!  It would have been far easier to buy similar coloured fabric of the correct cotton/polyester mix.  After many washing machine cycles though, I was pleased with the result.

Finished 2 Finished with Screens Window curtains finished

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