Question about Gobo insulation

[jwl]

JWL, with your experience with these gobos, how useful have you found them for isolation? I plan to use them as room dividers and I'm hoping to get a decent degree of isolation from one side to the other so I can limit the bleed to the mics on each respective side.

These gobos, along with the 6 broadband absorbers I built, changed everything in my recording reality.

I'm still trying to figure out my space, but I needed something quick and dirty so I built these. I also put some insulation in the ceiling joists. I have a 15'x17' corner of an unfinished basement, 2 concrete walls and 2 unfinished sheetrock/framing walls with no doors. So really, sonically, the entire basement contributes to the sound.

When recording basic tracks, I put the gobos around the drum kit, with the drum kit under one of the insulated spots in the ceiling. I then put the singer outside the unfinished room, on the other side of hte basement, singing into a futon mattress. In the drum overheads, you can just barely make out the vocals, if you seriously crank the gains.

I was pleasantly surprised, borderline shocked, on how well they worked for quick and dirty isolation. You won't achieve 100% isolation, but using these gobos and careful mic placement you can get very good results.

They also do a great job doubling as side wall absorbers to create a RFZ for mixing in this room.

[jwl]

I wanted to post a bit of my layman's understanding of the theory between these gobos and bass absorption, and ask a question I've been thinking about since shortly after I built the gobos. I want the gobos to absorb as much low end as possible, while recognizing the fact that gobos are not bass traps.

In theory, the gobos should absorb all sound at which the wavelength of the sound is smaller than the size of the gobo. The gobo is 2' wide, so IIRC that means everything under about 600Hz-ish will simply diffract around the gobos.

However, in a situation with more than one gobo stuck together, it seems that you must account for the total width of the gobos that are together. Observationally, this seems to be true, but I'm not sure about the theory here yet.

One thing I've considered; I wonder what would happen if I were to use, say, a 3" holesaw, and cut holes in the sides of the gobos, in the airspace between the cotton and the sheetrock? The air would then be able to pass through and behind the cotton, so it should have a positive effect on the absorbtion. But I'm not sure what that would do to the isolation. If the holes lined up on multiple gobo, would it fully act as one larger absorber?

[MJP]

JWL, it seems like the gobos have really helped you a lot (along with the other treatments). I have no treatment whatsoever yet in my basement, so I am thinking maybe i should build some broadband absorbers first and perhaps some superchunk bass traps in the corners and then the gobos.

The main thing for me is that I'd like to use three 4' wide gobos as a kind of room divider. Obviously not soundproof, since they would not be airtight, but still I'd like to get some decent isolation between the two section of the divided room. Thanks for your input JWL!

[MJP]

I just had a thought for the gobos. Making them 7'5" tall would make them huge and a possible tipping hazard. But what if I made a 6' x 4' (similar to your design except 2 feet wider) gobo and then made "mini gobos" for the tops that would be about 2' tall x 4' wide and would rest atop the 6' tall gobos? Then they would be easier to move and take apart. What do you think of this, JWL?

[MJP]

Here is a rough design for a gobo base with wheels (with drawings).

1x3 panels (24" inches long) would be the "feet" of the gobo. I would use 4 of them evenly spaced which would extend 12" out on the MDF/sheetrock side and 4" on the insulation/fabric side. Then I would mount a 4x4 (4 feet long) across the feet at the very base of the gobo (in red in the drawings). This 4x4 would be there so that wheels can be attached on each side of the gobo (4 wheels in total).

What do you guys think of this base? WOuld it be strong enough to prevent tipping of a 6' high x 4' wide gobo? Or possibly a 7.5' tall x 4' wide gobo?

PS: Drawings are not to scale.

EDIT: I just noticed the pictures are HUGE, I thought I had resized them. I have to go to work now so I'll do that when I return. Sorry!

[jwl]

I think that looks good.... except that the wheels are not on the center of gravity.

The center of gravity of this design is pretty much right where the MDF/sheetrock is, ie, at the edge of the gobo.

So in the bottom drawing, I'd put the wheels out at the edge of the foot slats. I don't think the slats need to extend 4" out the front side. You could attach 2 wheels directly to the bottom of the absorber side of the gobo, and 2 more wheels at the end of the legs. That would probably be more stable.

Again, though, the problem for me with a design like this is that it means you won't be able to put the gobos flush up against the wall. Maybe not a problem for you, but that's a deal breaker in my small studio.

Regarding gobo size, I'd personally err on the side of modular and stack them however you need to. You might consider some sort of fastening system to lock them together....

[MJP]

Good point about the centre of gravity. I will design some plans based on your advice. Thanks!