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My DIY Gobo Signal Splitters (HW)
Old 20th March 2009
  #1
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My DIY Gobo

This gobo is somewhat different than more traditional gobos. I designed it with a few specific intentions. For starters, I wanted gobos that could shape the acoustics of a project studio (so perhaps a "live" and a "dead" side). I knew I wanted them at least 6' tall, so I could put a few together and form a quasi-vocal booth. These are designed to be used in at least pairs (preferably more). The pointy base of the original design was chosen so that I can put multiples together at any angle (up to 90 degrees) without the bases hitting each other and maintaining an "airtight" gap (with the weatherstripping). For the actual build, I took off the point.

Rather than making them collapsible (with the intention of breaking them down and hiding them when not in use), I decided to make them big and (I think) nice looking so that they could stay "out" permanently. Once I build more, I think they will be a permanent fixture in the live room, as I can shape the sound of the room (a bit) depending on who is recording.

The gobo is heavy, but one person can slide it on a hard floor very easily (carpet on the bottom). Two people are needed to pick it up and move it.

Sorry about the discourse - just wanted to get across that I designed these for my own needs (hence some odd choices), but I hope/think other people may find them useful.

If people are interested I'd be more than happy to post any/all details/pictures of the build here. The full build is on my blog (sig), but again, if anyone is interested, I can post everything and more here.

Unfortunately I'm about to fly back to school until summer so I can't build any more of these right now... My plan now is to build 2 window models and two "full" models.

I've attached pics of the original sketchup design and then the finished gobo. I'll start posting the build pics asap.

EDIT: The materials cost under $130, and everything except the 703 can be found at a Lowe's/Home Depot (plus JoAnn Fabrics or similar for fabric)
Attached Thumbnails
My DIY Gobo-new-gobo-2.jpg   My DIY Gobo-new-gobo-1.jpg   My DIY Gobo-new-gobo-3.jpg   My DIY Gobo-dscf0135.jpg   My DIY Gobo-dscf0140.jpg  

Old 20th March 2009
  #2
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Materials

This is everything that I used in the gobo -
  • 3x ten foot, 1x8″ boards
  • 1x eight foot, 1x8″ boards
  • 2x 2x4′, 3/4″ birch plywood boards
  • 1x 2x2′, 3/4″ birch plywood boards
  • 5x 2′ long, 1x2″ boards
  • 1x 4x8′ piece of 5/8″ drywall
  • 3x Owens Corning 703 2″ pieces
  • 2.5 yards of fabric
  • Various tubes of Wood Glue, Construction Adhesive, Caulk (I used Liquid Nails for wood, some acoustic caulk, and PL375 heavy duty construction adhesive)
  • Wood Screws (1.5″)
  • Staples
The 1x8's are for the frames. Its definitely worth digging through the racks to get the straightest pieces possible. I dug all the way to the back of the rack at Lowe's, but ended up getting pretty good pieces of wood.

The plywood is for the backing (4' piece and 2' piece) and the other 4' piece is what you can cut the base out of. I ended up going with the octagonal base rather than the pointy hex of the original design because
A) this thing stands upright without any base and
B) the pointy hex would have had to be cut out of a full sheet (rather than a 1/4 sheet for the octagon)
C) smaller footprint means more room for mic stands etc.

The 1x2's are for the cross braces to support the gap. One 8' piece of drywall will cover both layers (plus a little extra).

Originally I also thought about going with 3 or more layers of drywall rather than an air gap. This turned out to not be a great idea for a few reasons. The biggest reason is that this thing is already pretty darn heavy. Second, I was trying to be pretty conscious of material uses, and you can fit 2 layers on one sheet of drywall. Third, I should theoretically get slightly better low end absorption with the air gap (plus the change in acoustic impedance should help everything).
Old 20th March 2009
  #3
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Thread Starter
Building the inner frame

So first up was building the "inner" frame. This is the meat and potatoes of the gobo. All of the isolation materials go in this frame and it gets wrapped in fabric. The "outer" frame (which goes on much later) only serves to cover the fabric edges and provide a little additional structure.

I would highly recommend laying the plywood pieces (that will comprise the "reflective side") down on the ground and building around them. Although they are sold as 2x4' and 2x2' pieces, they aren't actually those dimensions... but close. Lay them down and measure, cut the wood accordingly. I didn't actually screw/glue the plywood into the frame until after the frame was complete.

There are 2 long side pieces and 3 short (top, bottom, and "middle") pieces. I chose to run the long pieces along the entire outside edge, leaving all three short pieces ~24" in length (rather than extending the top and bottom pieces another 1.5"). This also let me cut all three short pieces at the same time, which kept everything very consistent.

Liquid nails for wood, a few screws, and some clamping later... It actually went together really easily. Then I flipped the frame on its side and glued/screwed the plywood pieces in (followed by caulking the inner edges for a tight seal). I ended up using a lot of screws and wood glue, since these plywood pieces (depending on how the gobo is positioned) may have to take the brunt of the weight of the "innards".
Attached Thumbnails
My DIY Gobo-dscf0087.jpg   My DIY Gobo-dscf0088.jpg   My DIY Gobo-dscf0089.jpg   My DIY Gobo-dscf0091.jpg  
Old 20th March 2009
  #4
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Thread Starter
Fill it up!

So now to fill the frame!

Unfortunately, I forgot to grab my camera as I was putting drywall in (and the spacers in for that matter...). I used 5/8" fire rated drywall.

Luckily its not too hard - Just measure to double check (although it should be darn near 2x4' and 2x2') and cut some pieces out. Drop them in. I used construction adhesive to get them in the box (hoping that not screwing it into the plywood might give one less path for sound to travel through), but I did screw the pieces of drywall together with short screws.

After each layer, I caulked the edges for a tight seal. Its worth letting these dry on its back (as pictured). This way the extra caulk/glue will get sucked down into the cracks by our friend gravity for even better coverage.

Now, for the cross pieces -
I knew that I wanted 4" of 703 to fill the top out. I took a T-square and measured 4" (actually 4" and 1/16 just in case) down from the frame on all the sides and marked it with a pencil.

Then I cut 1x2" pieces to length to go across (all about 24"), put some wood glue on the ends, and lined the top up with my 4" marking around the edge. Glue+one screw through the side, and these guys are in. I watched them as they setup, because they had a tendency to just slightly rotate. Watch that - so that the 703 fits snugly.

You may notice that some of my cross braces are not all 1x2" pieces etc... I actually forgot to get enough of them, so I used scraps I had laying around etc. Its much easier to spend 1$/piece to get small 1x2"
Attached Thumbnails
My DIY Gobo-dscf0108.jpg   My DIY Gobo-dscf0109.jpg   My DIY Gobo-dscf0110.jpg   My DIY Gobo-dscf0111.jpg  
Old 20th March 2009
  #5
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Thread Starter
703+fabric

The four inches 703 is really easy to get in, assuming your wood was cooperative.

Luckily for me, the pieces dropped in perfectly to the 2x4' section. They were just snug enough to not fall out, but didn't require any cutting. For the 2x2 section, just cut a piece in half and drop it in.

The fabric leaves a lot of options. I say Guilford of Maine is best, but too pricey for me for the prototype here. I went to JoAnn fabrics to search for a substitute. After being yelled at for walking around the store and blowing through a bunch of fabric... I found a low thread count cotton/synthetic blend that let a lot of air through (more than burlap or muslin). It was also on sale. I went with it.

Now - one thing this fabric is NOT is fire-******ent. In fact, there's a warning on it that says it does not adhere to the flammability standards for children's sleepwear...hah. So I gave it a spray with flame ******ant to hopefully give it a fighting chance.

Anyone who's stretched fabric over panels knows it can be a pain, but there is an art to it which makes it easier. I started by stapling the top completely, and then working my way down the sides. As I made my way through, I cut the excess fabric off with a razor. (I don't care what it looks like, it will be covered). I just made sure that it was tight, with no wrinkles. As a side note - I did give the inside frame a quick sand (fine paper) to prevent the fabric from ripping or weakening over a sharp edge. After it was on, I went back with a hammer and pounded each staple in all the way so that the outer frame would attach flush.
Attached Thumbnails
My DIY Gobo-dscf0112.jpg   My DIY Gobo-dscf0113.jpg   My DIY Gobo-dscf0114.jpg   My DIY Gobo-dscf0115.jpg   My DIY Gobo-dscf0116.jpg  

My DIY Gobo-dscf0119.jpg  
Old 20th March 2009
  #6
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Thread Starter
Finishing it up

Now just for the outer frame and base -

The outer frame is similar to the inner frame, just slightly bigger and without a center piece.

Just measure, cut, and screw.
(Important) I would suggest NOT using any glue/adhesive for the outer frame. Just screw it on. This allows the gobo to be serviceable. If someone puts an elbow through the front (ripping the fabric, damaging the insulation, etc), you just need to take out some screws (and NOT hack through glue) and fix the problem, rather than leaving a nasty looking/broken gobo around with no way to easily repair it.

EDIT: I also gave the outer frame a super quick sand with med/fine paper. This was an attempt to prevent splinters and cuts during daily use. Nothing major, just a few passes will tame any bad edges.

The base piece is cut with a circular saw out of the 2x4' piece of plywood. I measured (and marked) for the length/width of the outer frame base. Then from the corners, I made 45 degree angles inward. This will allow gobos to be placed right next to each other at any angle (up to 90 degrees) without their feet getting in the way of each other. Like the outer frame, I would suggest just screwing the base on for ease of service. I used a bunch of screws to make sure it could take the abuse of moving around.

For ease of sliding on wood floors (thanks Prof. Case for the idea!) I cut a piece of carpet for the bottom. I attached it with heavy duty construction adhesive (PL375) and clamped it down with some scraps. Eventually, once it dried a bit, I just flipped the gobo upright so the weight would keep the carpet flat and attached as it dried.

Finally, I ran some inexpensive ($6 per pack, which does both sides) D-shaped, non-porous weatherstripping down each side. This should help give a better seal when putting multiple gobos together. I hope it can take the slight abuse of gobos bumping into each other - I'll only be able to tell when I'm home in May and can build more of these. Ideally I'd go with a bigger (likely 1") strip of Neoprene down the side, but that would almost double the cost of the gobo...

Done!

I think one of the big successes of the design is that it doesn't take long to build. I tried to use standard sizes of everything with as few cuts as possible. Other than the base, the plywood doesn't need cuts, the insulation needs one cut, etc...


This summer I'll put these guys through the paces to see how they perform. So far they seem like they work very well.

The finished pics (both sides) are in the first post of the thread
Attached Thumbnails
My DIY Gobo-dscf0123.jpg   My DIY Gobo-dscf0124.jpg   My DIY Gobo-dscf0125.jpg   My DIY Gobo-dscf0127.jpg   My DIY Gobo-dscf0130.jpg  

My DIY Gobo-dscf0131.jpg   My DIY Gobo-dscf0133.jpg  
Old 26th July 2009
  #7
Gear interested
 

Could you pack R13 in the box tightly instead of using OC 703?
Old 28th July 2009
  #8
Gear interested
 

Super heavy!

Just made one of these, only mine is 4 foot instead of 6. Even the 4 foot version needs 2 people to move it, so keep that in mind. BUT, it does do a good job and looks good.

Great plan though.

Matt
Old 18th February 2010
  #9
I might try to make a few of these, but on caster.
Old 27th February 2010
  #10
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apadua's Avatar
 

why did you seal up the back with a layer of plywood?
Old 2nd March 2010
  #11
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@apadua
For better isolation you need mass. Fuzz alone won't make much of a gobo. I chose to go with plywood+drywall.
Old 2nd March 2010
  #12
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That can't be heavy enough! Put a wooden PRD on the other side... j/k!

Looks great!
Old 2nd March 2010
  #13
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Quote:
Originally Posted by guitarwes View Post
That can't be heavy enough! Put a wooden PRD on the other side... j/k!

Looks great!
Hah thanks.

They are pretty darn massive, but I can safely move them myself on either carpet or wood flooring by myself (the carpet of course requiring more effort). ...and a body-builder I am not

I have some at my place, and have built them at a few others. Everyone including myself (although I am a little biased...) seems to like them and says they work well for their needs. These are especially cool in one or two room project studios where variable acoustics are important. (i.e. setting up the back wall with thick absorption for mix time, blocking off a guitarist/vocalist, vocal "booth", etc.)
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