Question About Cardboard Tube Traps

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Question About Cardboard Tube Traps

Postby toner » Mon Feb 14, 2005 7:16 am

Hi, I am thinking about making some cardboard type tube traps from the construction tube concrete type forms. I plan on using them in my home recording studio. Basically, I am wondering how they will work if I glue 1" rigid pipe fiberglass insulation to the inside of the 12" tube.  Would they work better to stuff the tubes full  with the fluffy type fiberglass insulation?
My reason for hoping to use the cardboard type tubes is so that I can mount them on stands with feet so that they are portable.  They would be 4' tubes and the stands would make them 5-6' overall height. If the rigid cardboard material on the outside is a bad idea then I will have to design them without it. Also I plan to wrap them in fabric. Any Ideas or suggestions?
Thanks,
Bill
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Postby toner » Mon Feb 14, 2005 7:21 am

I meant to add that I plan on sealing the ends of the tubes with plywood or some other material.
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Postby Eric.Desart » Mon Feb 14, 2005 8:36 am

Hello Bill

Welcome to the group.

Have a look in this thread:
http://forum.studiotips.com/viewtopic.php?p=7599

Bob Golds entered a very nice link explaining those things.
http://web.archive.org/web/200108030528 ... mTubes.asp
Only take into account that the way they (Bob's link) define the lenght of the tubes for the tangential modes is complete nonsense.
I wrote those guys after Bob started this thread to tell them gently, but as so often they never replied.
On the net it seems often more important to show nice and impressive than accurate things.  Sense of responsibility versus site visitors is completely subordinate.

By definition such a tube works as a 1/4 wave silencer.
The way they define the first order tangential (and higher) by relating the 1/4 wavelength with 50% of the diagonal of the room is wrong.
Since they didn't reply when I informed them, I don't take those guys serious anymore, no matter how nice those animations look.

Without absorption inside those tubes, this are very narrowband devices.
Adding wool in it will broaden the bandwidth but will diminish the efficiency of the absorber significantly (depends of amount of absorption). Compare it with putting absorption in a windwood instrument, you block the resonance from building up.

    Some Fun:
    One could make them also with both sides open, then one could make them shorter since it become 1/2 wave silencers.
    There is only one annoying problem: both sides must be excited in inverse phase, that should even increase efficiency.
    If both sides are excited in phase, the thing won't do a thing.
    So that should become a matter of playing with very exact positioning in the modal pattern in a room.
    This is more theory than practical, but should be fun to experiment with.
    The idea: http://www.physicsclassroom.com/Class/sound/u11l5c.html
My advice:
Use them without wool but only to solve ennoying remaining problems.
Those things are very easy to tune.

Martin Walker from SOS (technical editor, reviewer) told he used such things without wool, but found them having low rendement. It were those he tested:
http://absolute.users.netlink.co.uk/Rats.html

I think a better approach is the corner absorption to start with as found in the FAQ.
Use those 1/4 wave silencers if needed to solve specific problems.

But that's my personal vision, you decide.
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Postby toner » Tue Feb 15, 2005 1:31 am

Eric,
Thanks for the welcome, advice and the links! I guess the rigid pipe (tube shape) insulation would work better by itself rather than inside of of the cardboard tube. I just purchased the pipe insulation a couple days ago and havn't looked at it close enough to see if it is strong enough to support itself and a stand. I have some tripod type micrphone stands that I plan to mount thruogh the center attached to the end caps.
Thanks!
Bill
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Postby Eric.Desart » Tue Feb 15, 2005 6:38 am

Hi Bill,

They will work, but as per a different principle as per the ASC Tube Trabs.
http://www.acousticsciences.com/tubetrap.htm

DIY projects:
http://www.teresaudio.com/haven/home.html
http://www.teresaudio.com/haven/traps/traps.html
http://dougploss.com/tubetrap_diy.htm
http://www.geocities.com/jonrisch/basstrap.htm

Some additional info:
http://www.audioasylum.com/audio/tweaks ... 77809.html
http://www.geocities.com/jonrisch/a1.htm


In general:
The position of the traps, whether it are tube traps or the FAQ type traps is very defining.
Put in the corners they perform MUCH better in the low frequencies and better overall.
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Eric.Desart
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