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DIY Acoustic Treatment: Gobo, part 3 March 20, 2009

Posted by ConnorSmith in : Acoustics, Project Studio, Studio Setup , trackback

Filling it up!

So at the end of the last post, I had built the inner frame and attached the plywood backing.  Next up is the two layers of 5/8″ drywall.

Unfortunately, I forgot to grab my camera until after the drywall (and insulation support braces) were already in… Cut out two pieces of drywall (one will be ~2’x4′ and one will be ~2’x2′).  Lay down a bit of construction adhesive (I used PL400) and press the drywall on top of the plywood.  (Repeat for the second layer).

Then I caulked the edges (again, acoustic caulk is the best, but Alex Plus will work on a budget) and used a few 1″ drywall screws to better connect the two layers of drywall.  I would suggest leaving the box as I have positioned here (this side up, flat on its back) while the caulk sets.  This will allow gravity to pull it down into the seams a bit more.

(In these pictures, you will already see the wood cross braces, which I will discuss next… sorry)

Next, I need to install the wood cross pieces that will help keep the air gap between the 703 and the drywall (as well as provide additional structure and support).

I used a T square to measure down 4″ from the top of the frame (since I know that I will be putting 4″ of 703).  I cut five ~24″ pieces of 1×2.  Measure across the box for each of these pieces!  Wood is not an exact science, so there will be slight variations. I spaced them out evenly (3 in the big section, 2 in the small) and attached with a bit of wood glue and a screw on each side.  Just make sure that the top edge of the brace doesn’t go above 4″ down from the top so you have enough room for the insulation.

Now in the next picture, notice how the cross braces are not laying on the drywall.  They are only attached to the sides of the frame.

After the cross braces are in, it should be a breeze to just drop the 4″ of 703 in.  The large section of the gobo should fit two pieces exactly if you build the frame correctly.  For the top half, just carefully slice one piece in half with a razor (I used my level as a straight edge).

Ok – now all the insulation is in.  Time to wrap it with fabric.  There are a lot of options for fabric, a lot of which can be decided merely by budget.  Guildford of Maine fabric is probably the ideal fabric.  Unfortunately its 4-6x more $$ per yard than other average fabric.  If you have the cash, get that.  You can also go with a burlap or muslin covering.  I went with something a little different.  I grabbed some fairly low thread count cotton/synthetic blend that had a little stretch to it.  I did almost get chased out of JoAnn fabric because I was taking dozens of fabrics and blowing through them… which didn’t make the sales lady that happy.  This fabric passed plenty of air but seemed like it could take abuse.

Now – one thing this fabric is missing – anti-flammability.  If you don’t treat this fabric, your gobo could become a giant match in a split second.  Unless your fabric is pretreated, just grab a can of fabric fire retardant and spray it down.

2.5 yards will cover your gobo.

Covering these with fabric is a bit of an art form, and you will get better at it with practice.  I chose to lay the fabric down over the box and staple the top side completely across.  This will give me something to pull on as I (slightly) stretch the fabric around.  Note – I did give the frame a very light sanding job beforehand, in hope that no sharp edges would damage the fabric. After you get one side stapled, its a matter of working your way down opposite sides, pulling out any wrinkles as you go.  I put a lot of staples in, in somewhat of a random fashion.  Since I am soon going to be covering these staples with wood, I thought spreading them out would help defeat any tilt that might be imparted (and it did).  As I got more staples in, I just cut away the extra with a knife/scissors.

In the next post, I’ll show you the outer frame and the base. (aka the finish line)


The Studio Files


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