# The Cleatus DeathTRAP sound absorbtion projekt



## Cleatus (Feb 27, 2010)

Do you think this is a viable sound solution?
The Cleatus sound control projekt is started. Got tired of looking around for Owens 703,705- and its expensive. So the Cleat tried to make his own....the story follows....

1. Make a frame (1x6)with inner dimensions that will fit a 2'x4'(approx.) flourescet light grid. (overpriced piece of plastic) plastic not mounted to anythign -yet.









2. I put two leftover strips of 1/2" plywood along the back-









3. I had some leftover carpet padding- I thought it would add a little more "mass" to the "mess". I stapled it in the frame









4. I added some strips on the inside of the box for the grid to lay on.










5. I put in a couple of strip acros the middle for more support for the grid and to hold insulation down.










6. I put the insulation in- I only had R-13 for standard 16" centers, but if you put one whole one, and one half it fits perfect. I put in TWO layers of the stuff.










7. Put on the plastic grid- of course mine was about 1/8" too tight, so I have to loosen things to get it in.










8. I stapled the grid into place with my air stapler- worked ok, but could maybe caulk the edges instead...










9. the completed DeathTRAP... without fabric. Its pretty good at sucking up the sound- have not tried it yet other than getting near it- kinda freaky-deeky not getting echo near it...


----------



## bpape (Sep 14, 2006)

Which side is to be exposed to the room?

The carpet padding won't do much of anything except reflect highs if pointed out toward the room.

The insulation looks like it's back from the face (assuming that side is to be facing the room). You'd get better performance if the insulation came all the way out and any gap was at the rear, close to the wall.

Bryan


----------



## Cleatus (Feb 27, 2010)

carpet padding is against wall- or will be the "back"
next box i may use small mesh chicken wire/rabbit wire for the front, which would put it more up to the edge.


----------



## Cleatus (Feb 27, 2010)

anothe concern is I am not sure what sounds/frequencies its absorbing...


----------



## bpape (Sep 14, 2006)

It will depend on the density and composition of the insulation, how thick it is, how much gap is behind it, etc.

Bryan


----------



## Cleatus (Feb 27, 2010)

well, i can make it more or less dense, and i can leave the back open (no carpet padding) too.
the padding DID deaden the sound of the frame when knocked, but doubt that has any bearing on anything in this application


----------



## bpape (Sep 14, 2006)

What is the initial density? how thick? How deep is the frame?

If it's like standard wall insulation, it's likely about 0.5lb/cu ft. The thicker you are, the more you can tolerate less dense material.

Bryan


----------



## Cleatus (Feb 27, 2010)

regular wall insulation, but i think its more dense as i think "standard" is r-11 and this is r-13
6" depth of box (2x4' outer)

factoring in the grid depth, etc- it probably around 5" actual insulation depth


----------



## bpape (Sep 14, 2006)

The R factor is generally mapped more to thickness. R-13 is 3.5", R-19 is 5.5", R-30 is 11.5"

Can you take a few cubic feet of it (known dimensions without compression) and weigh it? That will tell us exactly what it is.

At 6", I'd like to see at least 1lb/cu ft or maybe a bit more. So, likely doubled up and compressed.

Bryan


----------



## Cleatus (Feb 27, 2010)

i should be able to weigh it- but will have to do it later....


----------



## Cleatus (Feb 27, 2010)

so if i build boxes- say with Roxul 2 or 4" i would want the rox up front and leave a open space between the wall and rox? is there a minimum gap?


----------



## bpape (Sep 14, 2006)

That's correct. The more gap, the deeper it will reach into the bass. Rule of thumb - max gap behind is equal to the thickness of the absorbing layer. So, 2" panel, 2" max gap behind.

Bryan


----------



## Cleatus (Feb 27, 2010)

Can you explainn what is happeing in that two inches of space? I am very curious on WHY this works. Also your cutout pattern for 705 picture...not sure of the story behind this- you making soem sort of pyramid traps?
sorry if too curious...Kinda the same reason I watch Alton Brown cook- he tell us WHY something is doing (cooking) the way it is- with science. Make creating future stuff much eaisier.


----------



## bpape (Sep 14, 2006)

The cut pattern is to make solid, chunk style triangular absorbers. The triangles are just stacked in a corner and covered with cloth over slats that hold them to the wall.

The gap behind pushes the leading edge of the absorber out farther from the boundary, closer to the 1/4 wavelength of lower frequencies.

Bryan


----------



## Cleatus (Feb 27, 2010)

Is the 1/4 wavelength important? Why not 1/2 or full wavelength? Or are we then just splitting hairs and making a "box" way too big/deep?


----------



## bpape (Sep 14, 2006)

1/4 wave is the theoretical optimum. More is not that much better. We're really not even getting close, just doing the best we can. When you figure a 20Hz wavelength is about 25' long, don't think you're going to go for 6 FOOT thick absorbers 

Bryan


----------

