tube trap idea

[doulos]

ok interesting idea want to know your thoughts. I'm thinking of making some traps from stuff found at home depot cause it's what i have to work with. They have these 12 inch diameter 4 feet tall concete tube forms there. they seem to be made out of cardboard I was planning on stuffing them full of regular r-30 insulation and sealing them with some foam or something so it doesn't come out. R-30 is 9.5 inches thick unfaced so was thinking of doubling it so thats 19 inches rolled and compressed into a 12 inch diameter or am I wasting material by going that much thicker? cause 12 inches should give me a absorbion below 125hz and since it's 4 feet tall I should be able to make them floor to celing with 2 per corner and still be able to close my closet and main door to get in the room. I know the issue is in the size not being very large, but I should be able to get away with just making more of these absorbers and it will work no?

basiclly is there any reason this won't work? if i need more absorbtion I can always make panel traps in the middle of the walls but the corners need to be smaller so I can still open the doors any thoughts?

[braden_]

http://homerecording.com/bbs/showthread.php?t=279743

[doulos]

i didnt ask if it was less effetive i asked if it would work

its going to be less effective do to surfae area i alredy knew that but if i make enough of them will it work?

[braden_]

it will do something. whether it will be a night and day difference, i'm not sure. personally i'm holding off until i can get 703 or knauf. i don't want to waste any money on cutting corners and end up regretting it later. it seems like you're picking the first two options on your signature. =)

[RICK FITZPATRICK]

basiclly is there any reason this won't work?

That depends on your definition of "work".

I'm thinking of making some traps from stuff found at home depot cause it's what i have to work with.

If you are referring to "bass" traps...yes, there IS a reason why they won't work. Its very simple.
1. There is no access to the face of the fiberglass. Most molecular velocity is reflected by the rigid shell. What is absorbed THROUGH the shell MAY be absorbed SOMEWHAT by the compressed fiberglass. However, the density of this fiberglass is nowhere near that of manufactured rigid fiberglass. Absorption occurs because of this density. Gas flow is restricted through the INTERSTICES of the fibers, which causes FRICTION. This friction is the procees that makes "absorption" occur.
2. Low frequencys will simply defract around them as their wavelengths are MUCH longer than the diameter of the shell. You may achieve a modicum of diffusion of those frequencys whose wavelengths are SMALLER than the diameter of the shell. However, this has no bearing on the success of these units as "bass traps".

REAL Tube Traps, as manufactured by Acoustic Sciences Corp. are built of EXPENSIVE 4"thick 12-16" diameteter rings of OC703, which are glued together to form a "tube". 3/4"thick MDF discs are then glued to the ends. This assembly is then wrapped with a rigid wire screen, which is staple to the ends. A strechable fabric "tube" is then pulled over the assembly, stapled to the ends, and then FINISH ends are fastened...voila.. a tube trap. I've personally visited their factory and was allowed to view them building one.

I'd submit, you a gambling with your time and money. . Is the results worth the effort and expense? I would submit...no.

I WOULD suggest..if anything, cut a couple of MDF/Plywood discs at your chosen diameter. Form a rigid wire screen "tube" with a diameter the same as the discs with the length as tall as the screen is wide. Slip one disc into the end of the wire tube and fasten it with whatever you have. Fill this tube with your R? fiberglass and compress till you no longer can compress any more into it. Slip the other end in and fasten it. Then take a piece of STRETCHABLE fabric with a length 4" longer than the tube and a width equal to the circumference of the tube plus 2". Fold this fabric OUTSIDE IN, and sew the length, leaving about 1 1/4" of fabric past the sewing line. Once sewed, turn this INSIDE OUT, and stretch over the tube. Now you should have about 2" of material to bend over the top edge of the discs and staple it. Cut a couple more discs about a 1/2" or 1" bigger, or even the same size. Prefinish these and then fasten to the ends. VOILA! A tube trap that may actually do something.

Furthermore, you COULD cut those cardboard forms in half...lengthwise, and form you discs and screen to the same diameter. Staple one of the discs to the HALF ROUND tubes, wrap wire around this assembly, stuff, fasten the other end and cover with fabric and finish ends. Place in a corner allowing about 4" of airgap to the corner, with the the FACE of the half round cardboard to the room. Reflections off the corner(low frequencies terminate in corners, will now go THROUGH the fiberglass, and then be reflected again via the cardboard halfround back through the fiberglass...again, and again.(At least thats the theory! Have fun and good luck.
fitZ

[Ethan Winer]

Originally Posted by RICK FITZPATRICK

REAL Tube Traps, as manufactured by Acoustic Sciences Corp. are built of EXPENSIVE 4"thick 12-16" diameteter rings of OC703, which are glued together to form a "tube".

The tube traps I've taken apart use 1-inch thick 703.

--Ethan

[doulos]

If you are referring to "bass" traps...yes, there IS a reason why they won't work. Its very simple.

1. There is no access to the face of the fiberglass Most molecular velocity is reflected by the rigid shell

are you serriously saying 1/8 inch thick cardboard will stop bass waves from reaching the fiberglass?


What is absorbed THROUGH the shell MAY be absorbed SOMEWHAT by the compressed fiberglass. However, the density of this fiberglass is nowhere near that of manufactured rigid fiberglass

thats why I'm not using 4 inches thick I'm using up to 19 compressed to 12 and 12 inches uncompressed r-19 is proven to 100% absorb 125hz

2. Low frequencys will simply defract around them as their wavelengths are MUCH longer than the diameter of the shell. You may achieve a modicum of diffusion of those frequencys whose wavelengths are SMALLER than the diameter of the shell. However, this has no bearing on the success of these units as "bass traps".

then why does the same said company sell 9 inch and 12 inch tubes? if the surfae are of 20 is the only one worth using for broad band absorbtion?

I'd submit, you a gambling with your time and money

money spent 20 dollars per trap max and time spent to stuff a 12 inch diameter 4 foot tube um 30 mins? maybe an hr?


ok lets simplify this with facts

fact 1 if I buy 50 dollars in fiberglass for each corner an stack them floor to celing in the bags they will work very well for bass traps faced or unfaced it doesn't matter for low end absorbtion r value doesnt matter much either

fact 2 12 inches of r 19 will absorb down to 125hz 100%

so now your saying if I take the r19 out of plastic and stuff it in a 1/8 inch thick cadboard tube I lose a large percentage of it's absorbtion ability in the low end cause it will defuse the low frequencies? I know I will lose some surface area, but I asumed that could be made up by adding more traps if each trap can and will aborb down to 125hz

how am i wrong on this?

[RICK FITZPATRICK]

The tube traps I've taken apart use 1-inch thick 703.

In which direction? If memory serves me, the ring looked 4" long and had a wall thickness about 2". Maybe they had glued some together already, but they looked like this.




So Ethan, tearing apart competetors products huh? Ok, what would you say regarding my reply to doulos. Your the expert. Am I wrong?

[Ethan Winer]

1) Thin soft cardboard passes bass well enough, but thick rigid cardboard reflects. It's not a hard cutoff, and how much bass gets through depends on the frequency and the cardboard's makeup. The concrete forms I've seen are pretty thick and rigid.

2) The tube trap I took apart had 1-inch thick rigid fiberglass wrapped into a tube shape behind the fabric. So the walls were only 1 inch thick.

--Ethan

[RICK FITZPATRICK]

The concrete forms I've seen are pretty thick and rigid.

Thats exactly what I was thinking. Big difference between a vinyl covering over a roll of batt insulation, and a rigid cardboard tube.


Speaking of vinyl. When I visited Acoustic Sciences Inc., I saw them wrapping the 703 rings with a perforated clear vinyl. This was to create a diffuser as well. Kinda like this. I expanded the vinyl for illustration purposes. Its actually wrapped around the metal screen. Anyway, heres a few illustrations. The one with a Half round is only a suggestion. And the vinyl wrapped 703 is illustrated out of the cage.



btw Ethan, if you ever need some illustration work...let me know(I know, I'm spamming)