[stevenkelby]

Hello all,

I'm just posting for some expert advice before I start buying things for treatment.

I'm finally ready to do something about my room, it's only a temporary room as I plan to build a dedicated room in the next 12 months approx.

The room has doors/openings, furniture etc in places that make normal panels impractical. My first reflection points are an opening to the dining room and a huge lounge suite.

My room is 16ft long x 13ft wide and 10ft tall.

My speakers are Omega Superhemp Alnico single drivers, and dual Deep Hemp subs.

Listening position:



Front:



Dogs:



 

Here is a thread on my speakers:

http://www.audiocircle.com/index.php?topic=56815.0

I have read most posts in this forum for the last year and all of Ethan and Bryan's sites, thank a LOT guys 

As I'm in Australia and panels cost more to ship than buy, I am going to DIY. I'm confident I can do a good job but it will take a while probably a coupe months til I'm done.

My plan is to make 4 tri corners (walls/ceiling obviously), and that will be it for this room. I can use them in a future room.

I can take as much space as I want, I try to discuss WAF but get a desultory response so am going for it. My motto is "Ask forgiveness, not permission!"

I plan to make my tri corners to have sides 4ft long, about as big as I can go, to get the most surface area and absorption presumably.

I'm guessing bigger is better?

My main questions regard construction.

I plan to find some fiberglass insulation but being in Australia we don't have the same stuff you guys do so it's hard to know exactly what to get. I plan to just find the heaviest, densest stuff I can find?

I kind of thought, 4" thick, and I'll chamfer the edges to sit flush-ish with the wall/ceiling.

I'm not sure how to construct them for mounting etc though, I thought about using a piece of masonite or thin MDF as a backing, on the inside of the corner, sitting my cut insulation on that and wrapping with fabric, then just stapling the fabric to the board.

That would mean the sharp corners of fiberglass, where it meets the walls/ceiling, would probably get squashed/rounded if I pull the fabric tight. Not sure as I never played with this stuff before.

It would also mean some careful cutting to get the right size and shape of fiberglass.

For fabric I had thought of using calico but will try to find something suitable when the time comes.

How acoustically transparent does it need to be?

To mount I planned to put a big solid eye hook/loop in the center of the back of the board, and the same in the ceiling, near the corner, then tie elastic to the loop on the back of the panel, thread it through the loop on the roof and heave away to raise the panel, then tie it off to a small hook on the back of the panel, near the bottom corner point.

Or should the panels be mounted slightly out from the walls/ceiling?

Does any of that make sense?

Am I on the right track or should the panels have a hard face?

Any advice much appreciated.

Thanks,

Steve

[bpape]

4' sides is going to be huge.  While there certainly be more surface area for absorbtion, there will be little additional extension gained by doing it.  If you want to go deep into the bottom end, you'll want 6" of thickness for the panels in the corners.  Also, do not under any circumstances put a hard back on it.  You'll lose a lot of extension from the gap behind.

Bryan

[stevenkelby]

Good stuff, thanks for the quick reply Brian.

No backing at all then, just a thin frame, from 1" wide slats maybe?

I can easily go 6" deep, is it worth filling the whole corner with fiberglass, or is 6" optimum?

Of course due to the angle cut into the fiberglass, there will be some of every thickness from 6" down to zero, with probably only a small patch that is actually 6" deep.

I may go slightly less than 4', that's just my maximum and if there is no harm in making them 4', and possibly some good, I'll do it.

I would like to use them in my next room, which will be big, at least  30' long, 18' wide and unlimited height. Yet to be planned accurately but I have the space.

Bryan, should the panels be mounted flush with the walls/ceiling or with a gap around the edges?

Thanks,

Steve

[bpape]

The more the merrier with thickness.  If you build them as full 'chunks', then you can do more of a backing as it will be in the same place as the wall instead of away from it.

As for mounting, for this particular application, it really doesn't matter other than aesthetically.

Bryan

[stevenkelby]

I see, so it would be best to build something like a pyramid in slices of fiberglass, like this, only with 3 sides and without words written all over it  :



I'll have a think about how to make something like that, cover it with fabric and mount it.

Thanks,

Steve

[bpape]

If you have access to a BIG bandsaw, you can just build a cube and then slice it diagonally.

Other than that, it's just a trig problem with compound angles.

Bryan

[stevenkelby]

That's a great idea, would have to be a big one alright.

Maybe I'll take a trip to here:



 

I'll work something out along those lines though, if you think it would give a better result than just a 6" thick panel. I might as well make the most of it, can't use the inside of the corner for storage space.

Going to be a big job.

[rajacat]

 Just cut the fiberglass into right triangular pieces and stack them floor to ceiling. Then cut on the tablesaw two strips of wood that would stretch floor to ceiling with the appropriate angles that will present a flush surface for the installation of a light  frame that would support acoustically transparent fabric. Hopefully, there would be some studs in the perfect location to nail or screw the wooden strips. Then just use heavy duty Velcro to attach the frame to the wood strips.

The frame could be easily removed and the strips just unscrewed so that the whole contraption (pardon the pun) could be moved to another location with a minimum of fuss.

-Roy

[ebag4]

The more the merrier with thickness. 

Bryan,
I have read that it is best to have an air space behind the absorbtion.  Do you feel that a 6" corner trap that has air space behind it would be better or worse than a triangle that would fill the entire corner assuming the face area of both solutions is equal?

Thanks,
Ed

[bpape]

Just cut the fiberglass into right triangular pieces and stack them floor to ceiling. Then cut on the tablesaw two strips of wood that would stretch floor to ceiling with the appropriate angles that will present a flush surface for the installation of a light  frame that would support acoustically transparent fabric. Hopefully, there would be some studs in the perfect location to nail or screw the wooden strips. Then just use heavy duty Velcro to attach the frame to the wood strips.

The frame could be easily removed and the strips just unscrewed so that the whole contraption (pardon the pun) could be moved to another location with a minimum of fuss.

-Roy

For a full floor to ceiling corner absorber, that's absolutely the easiest way to go.  I think he's wanting just a triangle that straddles the upper tri-corner.

Bryan

[bpape]

The more the merrier with thickness. 

Bryan,
I have read that it is best to have an air space behind the absorbtion.  Do you feel that a 6" corner trap that has air space behind it would be better or worse than a triangle that would fill the entire corner assuming the face area of both solutions is equal?

Thanks,
Ed

A panel with an air gap behind it is superior to the same thickness of panel flat on the wall.  A solid chunk is superior to both.

So, in reverse order of performance in the low end:

2" flat on the wall
2" with 2" gap
4" flat on the wall

Bryan

[ebag4]

Thanks for the additional info Bryan.

Best,
Ed

[stevenkelby]

Yeah I can't do floor to ceiling, doors and shelves in the way.

I will go for enormous solid corner blocks.

Two questions now:

1. Should I just buy the heaviest, most dense fiberglass insulation I can find, or is there more to it than that?

2. Any ideas how to mount these big blocks of stuff? SHould I try making a "framme" from slats of wood or something?

Thanks again for all the help.

 

Steve

[bpape]

Framing is going to be required.

When doing a chunk style like this with good thickness, you don't need a high density product.  3lb/cu ft will be just fine.

Bryan

[stevenkelby]

Cool.

What about the fabric for covering them? Is that critical or can it be just any cheap thing that looks acceptable? Does it have to be acoustically transparent? Or does it make no difference?

Thanks,

Steve

[whubbard]

Steve,

According to research done by others, I would cover with polyester batting, then cover with burlap. That is what I will be doing with my DIY traps.

-West

[bpape]

It really depends on the desired results. If you want them to be full range, then using poly (only as a 2nd layer to prevent any fiberglass shedding) and covering with pretty much anything that's halfway soft and open will be fine.

If you want broadband bass with minimal high frequency absorption, then face the fiberglass with something like FSK or a heavy kraft paper (bond with spray adhesive) and then cover with a pretty open weave cloth to avoid high frequency absorption from either the fiberglass or the cloth.

Bryan

[stevenkelby]

I guess full range would be better but I suppose it's impossible for you to know without hearing or measuring my room first.

I like the idea of full range anyway, surely generally better for the sound if I remove as much reflection from the corners as possible. Should also help kill the room in general, making it quieter for conversation etc, which I like.

you can just build a cube and then slice it diagonally.

I just thought about this and don't think it will work. It would give a 4 pointed pyramid, leaving a flat section on the bottom. If I cut 2 tri corners out of a cube, I would end up with a big thick slice left over, the middle of the cube.

I'll figure it out.

[bpape]

Doh!   You're right - not sure what I was thinking.  Was thinking more on the line of the floor to ceiling thing but shorter.

Bryan

[stevenkelby]

OK had a think about it and made a model from some business cards. A cube will work, giving 4 tri corners, and an equilateral triangle.

I took some pics, "filling in" the pieces so it looks solid.

My cube showing cut lines:



The two top tri corners removed:



Front one removed:



Leaving the back one and the center triangle:



The five pieces. The center pyramid can go in the bin/upside down on the ceiling/on a coffee table/on my head like a hat:



The dimensions would be 2ft sides to my "cube" giving 3 ft sides to my tri corners, facing the room:



I found a local product apparently identical to the 703 here:

http://www.owenscorning.eu/docs/products/700series_DataSheet.pdf

It is fiberglass 48kg/m³. Comes in 50mm thick pieces, 2400 x 1200. So if I get 3 pieces (a full "pack", $210 AUD) I can cut them in half, giving 6 pieces. Each piece I cut in quarters, giving 24 pieces, each 600 x 600 (2ft x 2ft).

As they're 50mm thick, stacking 12 of them up will be 600mm high so I get 2 cubes, enough for 2 rooms, or floor and ceiling tri-corners in 1 room, but not this room, no space for anything but ceiling/wall corners.

I plan to glue the layers together but don't know what to use, maybe spray on contact adhesive? Spay both pieces, let set for 10 minutes and stick together? I don't know what will work best.

I will draw on my cube(s) along the cut lines and slice through by eye using a katana sword, or something Maybe a big enough serrated bread knife? Thoughts?

I may frame them with rt angle pieces of aluminum or plastic all the way along every rt angle edge (3 per piece), riveted together or something. For the edges on the front of the panel, I don't know how to frame them but will figure it out.

Then cover the front with 2" batting and burlap or calico/muslin cloth.

Any thoughts?

Thanks,

Steve