Bass Traps from Concrete Tubes

[spindlebox]

I wanted to talk about this here; there was an old thread about this but it was from 2008.

I have it from a good source, a gentleman that worked at Digidesign whom is excellent at studio acoustics.

He recommended I use those cardboard tubes, similar to concrete tubes for bass traps. I have been doing a bit of reading and these things seem to elicit both strong proponents and downright heckling.

Here is an example of the Concrete Tubes: http://www.google.com/imgres?imgurl=...ed=0CDMQ9QEwBQ


My idea is this for construction: I am going to take the tubes and fill them with OC 703. I am going to drill 1" holes evenly over the surface of them. (I think the holes will be important to allow the bass to enter and be absorbed by the 703.) My idea came from this:



I am going to cap the bottoms of them similar to what is described in this thread: DIY Tube Traps

I am then going to cover the outsides of them with black, breathable fabric.

Thoughts?

[PaulP]

You might want to consider drilling the holes in a 'BAD' pattern to add a bit of diffusion.
See this thread : RPG Bad Panel -- Detailed Plans

Paul P

[spindlebox]

Originally Posted by PaulP

You might want to consider drilling the holes in a 'BAD' pattern to add a bit of diffusion.
See this thread : RPG Bad Panel -- Detailed Plans

Paul P

So Paul, firstly thanks for your response, I was very nervous at first trying to figure out how to drill SQUARE holes!! LOL.

What I mostly took from that article was that I should drill a random pattern firstly and secondly that I should drill them 1/2" instead of 1". Does size (in this case) matter?

I would think that the smaller the hole, the more absorption would take place because the sound waves would become more trapped without a way to exit, that and by being absorbed by the 703.

Even with the cardboard tubes being not hard or very reflective, I'm thinking those holes will be necessary.

Am I on the right track?

[PaulP]

Originally Posted by spindlebox

What I mostly took from that article was that I should drill a random pattern firstly and secondly that I should drill them 1/2" instead of 1". Does size (in this case) matter?

The BAD pattern is not random but the result of some mathematics. Simply
drilling holes in a random fashion is supposed to be less effective.

Even with the cardboard tubes being not hard or very reflective, I'm thinking those holes will be necessary.

For (a probably narrow band of) very low frequencies holes probably aren't
necessary as the whole tube will vibrate. At some point they'll become
effective. Smaller holes and wider spacing will reflect more higher frequencies.

Perforation itself can be used to trap bass and a flat panel designed to
work with perforation can be a lot thinner than a panel using absorbant
(see Acoustical Uses for Perforated Metals).

I'm no expert on these matters, I just wanted to point you in what I think
is an interesting direction. You'll have to figure out for yourself if it makes
sense and is worth the trouble.

Paul P

[spindlebox]

Gotcha about the mathematics! It sure is a pretty pattern though!!

Here's a picture that may illustrate as to why I'm considering tube traps, you'll see I have limited space. I could build superchunk bass traps too, and that was my first choice. The narrow band concerns me though. I don't want to go through the effort if it's only going to work with certain frequencies.



Please ignore the unfinished walls, I'm in the process of mudding/taping/painting etc.

Thanks to all!

[PaulP]

I think the tubes will have to be a lot larger for them to have much effect.
You don't have much room so you may be better off with another plan.

An alternative to just standing tubes in the corners, but requires more of a
permanent installation, is to use really big tubes that you cut into sections.
You then install a section straddling a corner and fill the whole thing with
insulation. This gives you a nice big 'poly' diffuser and a bass trap. Like a
regular filled corner trap but with a curved front.

Paul P

[spindlebox]

Originally Posted by PaulP

I think the tubes will have to be a lot larger for them to have much effect.
You don't have much room so you may be better off with another plan.

An alternative to just standing tubes in the corners, but requires more of a
permanent installation, is to use really big tubes that you cut into sections.
You then install a section straddling a corner and fill the whole thing with
insulation. This gives you a nice big 'poly' diffuser and a bass trap. Like a
regular filled corner trap but with a curved front.

Paul P

Yes, that's interesting about the curved front idea. I may just go ahead and do the superchunk idea then, as it will probably work better and I can go right up the entire corner. I will probably do all 4 corners that way. I was just thinking I could fill these up with the 703, drill holes and it would act in a similar manner. However, I just don't know how much these things would resonate, and I think that is an important part of the trap itself?

[PaulP]

Originally Posted by spindlebox

I may just go ahead and do the superchunk idea then, as it will probably work better and I can go right up the entire corner. I will probably do all 4 corners that way. I was just thinking I could fill these up with the 703, drill holes and it would act in a similar manner.

Well it would if it were big enough. A superchunk is a lot bigger than the tubes
in your photo. One nice thing about using freestanding tubes is that they're
easy to move around and you can take them with you when you move.

However, I just don't know how much these things would resonate, and I think that is an important part of the trap itself?

I don't think a panel will resonate much if it's full of holes.

Paul P

[spindlebox]

Originally Posted by PaulP

Well it would if it were big enough. A superchunk is a lot bigger than the tubes
in your photo. One nice thing about using freestanding tubes is that they're
easy to move around and you can take them with you when you move.

I don't think a panel will resonate much if it's full of holes.

Paul P

Amen to both.
I just wonder how the bass would penetrate the cardboard, or if I should just cap the ends and leave it hollow? That may be the ticket!

LOL: "I'M SO CONFUSED!!"

[Ethan Winer]

Originally Posted by spindlebox

He recommended I use those cardboard tubes, similar to concrete tubes for bass traps. I have been doing a bit of reading and these things seem to elicit both strong proponents and downright heckling.

There are two potential problems with cardboard tubes. The main problem is most tubes I see are simply too small, as Paul said. If a tube is 18 to 20 inches in diameter or more, then it will be big enough. But most tube plans I see are 10 inches or even less.

Another possible problem is the thickness of the cardboard. Cardboard around insulation is good, but it has to be thin and not dense. Corrugated cardboard is usually okay, but the concrete tubes I've seen are pretty thick and rigid.

I am going to cap the bottoms of them similar to what is described in this thread:

Don't waste your time. A tube shaped trap will work better if the ends are open because that adds more absorbing surface.

--Ethan

________________
The Acoustic Treatment Experts

[spindlebox]

Originally Posted by Ethan Winer

There are two potential problems with cardboard tubes. The main problem is most tubes I see are simply too small, as Paul said. If a tube is 18 to 20 inches in diameter or more, then it will be big enough. But most tube plans I see are 10 inches or even less.

Another possible problem is the thickness of the cardboard. Cardboard around insulation is good, but it has to be thin and not dense. Corrugated cardboard is usually okay, but the concrete tubes I've seen are pretty thick and rigid.

Don't waste your time. A tube shaped trap will work better if the ends are open because that adds more absorbing surface.

--Ethan



________________
The Acoustic Treatment Experts

Ethan,
Thanks for your input!! I value your advice. However, I'm still a little confused.

Firstly, my picture above, you're saying those would be too small? As you can see, I have space limitations.

What would you do in that situation? (PS, that is the wall behind my listening position)

Perhaps suspending those tubes from the ceiling, so they're slighlty away from the wall would help?

LOL. See what I've done to myself?!

[Ethan Winer]

Originally Posted by spindlebox

Firstly, my picture above, you're saying those would be too small? As you can see, I have space limitations.

Yes, those look way too small. Pull your couch forward six inches and then you'll have room for 24-inch wide panels. Even if the panels are not exactly 45 degrees, just having the additional width will absorb, I'll guess, 4 times more bass than the tubes you have now.

Then put more panels in as many wall-ceiling corners as you can manage.

--Ethan

________________
The Acoustic Treatment Experts

[spindlebox]

Originally Posted by Ethan Winer

Yes, those look way too small. Pull your couch forward six inches and then you'll have room for 24-inch wide panels. Even if the panels are not exactly 45 degrees, just having the additional width will absorb, I'll guess, 4 times more bass than the tubes you have now.

Then put more panels in as many wall-ceiling corners as you can manage.

--Ethan

________________
The Acoustic Treatment Experts

WOW, OK then, it's back to plan A and the superchunk idea. Either that or just acoustic panels over the 90-degree corners as you mention.

THANKS!!!!

[avare]

Originally Posted by Ethan Winer

There are two potential problems with cardboard tubes. The main problem is most tubes I see are simply too small, as Paul said. If a tube is 18 to 20 inches in diameter or more, then it will be big enough. But most tube plans I see are 10 inches or even less.

Another possible problem is the thickness of the cardboard. Cardboard around insulation is good, but it has to be thin and not dense. Corrugated cardboard is usually okay, but the concrete tubes I've seen are pretty thick and rigid.

??? to both statements. Please explain both.

Andre

[DanDan]

I reckon a SuperChunk intruding into the room equal to the tubes will contain much much more fibre, with a greater average depth. I would also suggest that it is easier to construct and looks neater. Here's a genius construct. There is more to it than immediately obvious. Genius I say :-)
Corner Traps finally finished! - Home Theater Forum and Systems - HomeTheaterShack.com
DD

[SAC]

Just a quick comment...

Tube traps are typically tuned Helmholtz resonators.

The discussion thus far has treated them as some sort of passive trap essentially 'equivalent' to a porous trap only inside a tube with 'holes' being drilled in them (?).

As Helmholtz resonators, they can work. As the proposed design is described, I will admit to having no idea regarding exactly what the 'method behind the madness' is to the design.

[DanDan]

Indeed, we are gently talking him in off the ledge. Into the warm soft embrace of a big fluffy SuperChunk :-)
DD

[Ethan Winer]

Originally Posted by avare

??? to both statements. Please explain both.

Yes sir!

A bass trap that's 8 inches in diameter will not absorb as much as a 24-inch wide panel simply because there's too little absorbing surface.

A bass trap made by stuffing insulation into very thick cardboard won't absorb much either because the cardboard reflects. The thicker and denser the cardboard, the lower in frequency it reflects to. The cardboard I've seen for pouring cement into is pretty thick and rigid.

--Ethan

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