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DIY Acoustic Treatment: Gobo, part 4 March 20, 2009

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

The final installation of the DIY gobo – the outer frame and base

The outer frame serves to cover up the staples/fabric as well as provide some additional structure to this (heavy) gobo.  I opted to NOT use any glue or adhesive when attaching the outer frame or base.  Why?

This way the gobo is serviceable. You can access the fabric and innards just by taking out screws (rather than having to hack through dried glue/adhesive).  The gobo is plenty strong without the outer frame, so screws should do just fine by themselves.  The first time someone puts a mic stand through the front fabric, it won’t ruin the gobo.  You can take it apart in a few minutes, replace the 10$ worth of fabric and be as good as new.  I’m sure these things will take some abuse in the studio (as most equipment must), so I hope it proves to be a good idea.

Ok – so the outer frame is pretty easy.  Measure and cut the wood accordingly (to fit snuggly around everything) and just put on one piece at a time.  I opted to put the top and bottom on first, then the big sides.

Now the outer frame is on. Just a few steps left until a completed gobo.

When putting multiple gobos together, an “airtight” gap between them is ideal.  Since these are designed to be put together at angles (plus the fact that lumber is not always perfectly straight), I needed something plyable to join multiple gobos together.  I found some thin, “D-shaped”, non-porous weatherstripping that I am going to try.  It was approximately 6$ for a pack (which will cover both sides).  There’s no way to really test it until I build another one of these and put them together (plus to see if the stripping can take some abuse), but it looks promising so far.  (This is the only close-up I took of it, sorry).  Its just self-adhesive, and I ran it down both of the “absorptive-side” edges.

Now to get the base on.  First, I had to cut it out of plywood.  Its an octagon.  The center section is the wdth and length of the final base, and the edges come out at 45 degree angles.  I just marked up a piece of wood with a pencil and straight edge and cut it out freehand with a circular saw (rather than busting out a table saw).  If you go slow and are careful, you can get straight and accurate cuts.

Now I also decided to put carpet on the bottom (through the advise of others) so that it would slide on hard floors (as well as help keep the wood in good condition).  I had some scrap carpet around, so I just traced the edges of my base and cut it out with a knife.

Now time to screw the base on and attach the carpet.  Put the gobo on its side, then you can just screw the base right in.  (Again – I chose to not use any adhesive so I can take this thing apart if need be).  I think I used a dozen screws or so just to make sure it was REALLY on there.  For the carpet attachment, I used PL375 (the “heavy duty” construction adhesive).  I loaded it up, especially around the edges, and pushed the carpet on.  After using a somewhat mantis-like position hold on the carpet while it set for a few minutes, I quickly grabbed some extra wood and a bunch of clamps to hold it on while it dried.  I actually just left it like this for about an hour and then flipped the gobo upright (the weight of the gobo will hold the glue in place).  I did this rather than screws or carpet tacks because this is going to get dragged all over wood floors.  A stray end of a nail/screw with a 100 pounds pushing it down could bring HAVOC to floor in seconds.  I’ve been pushing this thing around my garage and the carpet seems to be holding just fine with the glue.

And finally ::drum roll::, the finished gobo!  I need to build another one to really field test it, but from my scientific initial “walk by it and hear what it does” test, I can say that this thing blocks some serious sound.


The Studio Files


1. Hendrik AKA Henny Rock - March 28, 2009

I think that the gobo needs a ladder so you can climb up it for a stage dive. There are so few pieces of furniture in a studio suitable for a stage dive…

2. ConnorSmith - March 28, 2009

It could definitely hold the weight. Its quite a beast.

Hmm – perhaps little struts that stick out the reflective side. It’d be bumpy too. I can use a quadratic residue sequence for the rungs and make it diffusive 🙂

Unfortunately, the last time I heard of a stage dive in a studio (well, more of a stage dive INTO a gobo), it ended with a bent-in-half Korby.

Yes – not a bent grill, bent body, broken capsule… nope. Bent in half!

3. Blair - June 12, 2009


4. Georges Couling - July 26, 2009

hey nice work, i started building two of these today. i was wondering if now that you’ve completed them is there anything you would change in the design? i’m wondering if placing the air gap between the two sheets of drywall instead of between the drywall and 703 would change anything?
would love your thoughts.
thanks for sharing the design.

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