gobos?

[elan]

how do you build a gobos 24x48x4 bass trap?

i already have the bass trap i need to build some gobos

[Disjointed]

well, its my understanding...
you take your bass trap,
dont mount it to the wall,
set it standing in your room somewhere..
and you now have a gobo


gl

[Weasel9992]

Originally Posted by elan

how do you build a gobos 24x48x4 bass trap?

i already have the bass trap i need to build some gobos

What the previous poster said is pretty much right...a gobo would generally be more like 6'Wx6'Hx6"D. It's supposed to emulate in some way what a more solid boundary layer would do in terms of separation, without the reflective effects. It's also intended to be mobile so that you can change the acoustic characteristics of a room, especially a larger one.

Frank

[nosebleedaudio]

4' by 4' is more common.
Have made them from 3' to 4' and have put plexiglas on top if needed.
No rules, what ever is needed....Depth from 4" to 8", one of two sided, again what ever is needed...

[elan]

i mean what do you use as stand?

[Weasel9992]

Originally Posted by elan

i mean what do you use as stand?

The frames are 6"-8" thick...no stand needed. You can buy or make dollies for them as well (dollies are stands with wheels).

Frank

[nosebleedaudio]

Have built most out of 1 by 8 pine with a 1 by 3 on the bottom for legs, and mount wheels on the bottom of those.
You want the bottom (leg part) to be wider than the main frame for stability.

[elan]

thanks!

[Disjointed]

my gobos are 5.5" thick 4' x4' and are stable enough to not need any additional support


gl

[jwl]

Just to be clear, a broadband absorber is NOT a gobo. A gobo is something that will block sound; whereas a broadband absorber (or a velocity absorber) depends on sound passing through it to be effective.

It's a subtle distinction, and sometimes moveable broadband absorbers are preferable to gobos.

But if you want a gobo, then there should be a barrier (such as a layer of MDF or sheetrock or something) in there somewhere. You can make them reversible, with a reflective surface on one side and an absorptive surface on the other, or put the barrier in the center with a thinner layer of absorption on each side.

The size of the gobo will determine its performance; any sound with a wavelength longer than the size of the gobo will simply diffract around the gobo. Whereas a sound with a shorter wavelength than the size of the gobo will be reflected and/or absorbed (depending on which side of the gobo is facing in).

[elan]

i will use them at the reflection points at my left and right, so i need them absorber.. so why not broadband

[nosebleedaudio]

The size of the gobo will determine its performance; any sound with a wavelength longer than the size of the gobo will simply diffract around the gobo. Whereas a sound with a shorter wavelength than the size of the gobo will be reflected and/or absorbed (depending on which side of the gobo is facing in).[/QUOTE]

The closer you are the better the isolation, I mean a few feet away is max in my book, if its a gtr amp as close as possible. 15 to 30db of isolation is typical, the treatment of the walls and ceiling in that area makes a big difference as well.

[elan]

nosebleed how do you use gobos?
which is your size?

[RedWallStudio]

My gobos are 3 foot wide x 5 foot high. The sides are 1 x 4 pine that extends an extra foot (6 feet tall overall) and act as legs. Then I bought these big T brackets at Home Depot (get them where the Deck Building hardware is) and I attached the T to the bottom, so it acts like a stand. They work fantastic and only cost a couple bucks each.thumbsup

[nosebleedaudio]

Originally Posted by elan

nosebleed how do you use gobos?
which is your size?

How?
Like everyone else I guess...
Size?

[elan]

how.... in which positions

size.. you have talked about the gobos size, that biggest is the size the better the response.. so which is the size of your gobos?

[nosebleedaudio]

Originally Posted by elan

how.... in which positions
Depends on what and why, in a U shape (3 Gobos)around an amp for example.

size.. you have talked about the gobos size, that biggest is the size the better the response.. so which is the size of your gobos?

For most a 4' by 4' is common like I stated above, for a 2 voice (2 people facing each other) thing a 4' tall with a 2' plexiglass top for visual contact works very well.
All depends..
Note: I must not be using the "Quote" feature right...
.

[elan]

ok ma to absorb the early reflection in the left and right point (to the listening position) the plexiglas i think is a nonsense ... don't you think?

i have to absorb not to reflect

[nosebleedaudio]

Here's a pic of the one with a plexiglass top.

[nosebleedaudio]

Originally Posted by elan

ok ma to absorb the early reflection in the left and right point (to the listening position) the plexiglas i think is a nonsense ... don't you think?

i have to absorb not to reflect

No, depends on use...

[Weasel9992]

That's a nice lookin' gobo, Keith.

Frank

[elan]

it is full of rockwool covered with a foam? like auralex wedge? 1 inch thick?

[nosebleedaudio]

Originally Posted by elan

it is full of rockwool covered with a foam? like auralex wedge? 1 inch thick?

I normally use 703, that one I used 3" Auralex, what I had on hand at the time...

[elan]

3?? seems much more thin..

could you explain me better the plexiglass use in this case? i don't understand which are the benefits for absorption

[nosebleedaudio]

Originally Posted by elan

3?? seems much more thin..

could you explain me better the plexiglass use in this case? i don't understand which are the benefits for absorption

Isolation.. that's what a Gobo is used for, isolation.
Plexiglass provides visual cues.

[elan]

in my case i don't need the gobos for insulation.. i need them to improve the acoustic, the early reflections..

so i don't need the plexiglass.. right?

[nosebleedaudio]

Originally Posted by elan

in my case i don't need the gobos for insulation.. i need them to improve the acoustic, the early reflections..

so i don't need the plexiglass.. right?

Right, I ONLY mentioned the Plexiglass as a another way to Isolate and still see.
If it does not apply to your situation then dont worry about it..

[elan]

thanks, sorry but i wasn't sure about the use of plexiglass

no i've understood

thanks!

so maybe just rockwool and wedge 3 inch or 4 inch

[Jax]

Originally Posted by jwl

The size of the gobo will determine its performance; any sound with a wavelength longer than the size of the gobo will simply diffract around the gobo. Whereas a sound with a shorter wavelength than the size of the gobo will be reflected and/or absorbed (depending on which side of the gobo is facing in).

I think the density of a gobo also determines if a wavelength can pass through it or not. Am I right? Lower frequency waves will more easily pass through a 1/2" sheet of plywood than a 1/2" slab of granite. Or will the low freq. waves be reflected back?

Of course, a big rock gobo would be difficult and expensive to build. I'm just sayin'.

Maybe a couple 1/2" MDF boards would be a good idea because they're very heavy, although you'd need a really strong structure for them. Would MDF work better than a couple thick sheets of plywood?

[nosebleedaudio]

In my opinion a over heavy Gobo is a waste, a small percent of sound will still reflect off ceiling, walls ect and make their way back to the mic your trying to isolate.