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Author Topic: Sound absorption on the cheap  (Read 11819 times)

Randy Pence

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Re: Sound absorption on the cheap
« Reply #20 on: December 09, 2008, 05:37:29 pm »

Does this mean you won't plug in a power cable because someone could slice off the end and electrocute themselves?

Fire, like tools of power, and electricity, is something to respect, not fear.  Testing flammability is also very easy.  A flame (such as from a lighter) on treated material will immediately extinguish once the flame is removed.  The fire marshall can pick out any spot they want and light up.
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Art Welter

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Re: Sound absorption on the cheap
« Reply #21 on: December 09, 2008, 10:25:42 pm »

John,

I normally use a router for repeatability, but in the case of making these arcs, using a band saw was faster and saved quite a bit of material.

The OP wanted cheap, so Baltic Birch was out, and in this application, flexible is actually better so cheap and cheerful is good.

If I would have known about the large diameter Sonotubes at the time I did this work, would have used it, it would have been cheaper and easier than the plywood “wings”.

Art
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Chad Johnson

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Re: Sound absorption on the cheap
« Reply #22 on: December 10, 2008, 12:25:07 am »

Here's a pic of a room I did with large polycylindrical diffusors and tectum panels in between. The diffusors are good for mid and high band diffusion and low band absorption. Tectum is used with large air space in corners for more bass absorption. The tectum wall panels can be painted and are fire rated. They are fired out from the wall 2" and Roxul is used in the air space behind, they are very effective broad band absorbers.

index.php/fa/19548/0/

Edit: There's also suspended ceiling tile over the stage area and interspersed throughout the performance area.  RT 60 was taken from 8.9 down to around 2.6.
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Brad Ferguson

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Re: Sound absorption on the cheap
« Reply #23 on: December 10, 2008, 02:22:34 am »

Thanks for all the suggestions, guys!  I knew I could count on the big brains on this board to help me out.

I'm not too worried about absorbing LF information - the big problem is basically snare drums ringing way too loudly off the stage.

I'm sourcing some 703, and I'm going to basically cover some ply with it, and some material.  Should be cheap enough, and I have some lines on some fire resistant material.

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drewgandy

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Re: Sound absorption on the cheap
« Reply #24 on: December 10, 2008, 08:29:43 am »

Brad Ferguson wrote on Wed, 10 December 2008 01:22

Thanks for all the suggestions, guys!  I knew I could count on the big brains on this board to help me out.

I'm not too worried about absorbing LF information - the big problem is basically snare drums ringing way too loudly off the stage.

I'm sourcing some 703, and I'm going to basically cover some ply with it, and some material.  Should be cheap enough, and I have some lines on some fire resistant material.




I don't think its been mentioned yet that many fabrics can be treated for flame resistance.  http://www.rosebrand.com/category16/flame-retardant.aspx
You would have to weigh out the costs of buying pre-treated (and inherently flame resistant) or buying something cheaper and treating yourself. And of course, a call to the fire marshall about regulations and how they want you to document this stuff would be a good idea.  

Also, years ago I found that mineral fiber was cheaper and offered similar performance (actually slightly better performance) to 703.  I understand the idea to use plywood as a backer but you may also consider cutting out the "center" of the ply in order to take some advantage of the spacing from a boundary.  The idea is that you leave the perimeter as a surface  to staple the fabric to and to use for effective mounting but sound can still pass through most of the panel to the boundary behind.  2 inch material spaced 2 inches from a wall offers almost as much absorption as 4 inch material fastened directly to a wall.  For most of my applications, I've found that 1.5 inch material spaced 1.5 - 2 inches from a wall is the best performance/vs dollar option unless you are really trying to absorb bass.  There is a lot to consider acoustically and in some cases overthinking it may not be worth it. Just getting some material up and seeing how it affects things....

drew
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John Halliburton

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Re: Sound absorption on the cheap
« Reply #25 on: December 10, 2008, 10:09:16 am »

Art Welter wrote on Tue, 09 December 2008 21:25

John,

I normally use a router for repeatability, but in the case of making these arcs, using a band saw was faster and saved quite a bit of material.

The OP wanted cheap, so Baltic Birch was out, and in this application, flexible is actually better so cheap and cheerful is good.

If I would have known about the large diameter Sonotubes at the time I did this work, would have used it, it would have been cheaper and easier than the plywood “wings”.

Art


Agreed, I think I was trying to convey that technique can vary according to comfort level/familiarity with certain tools, along with what you have available.  Since I tend to have more Baltic Birch plywood scrap around v. lumber, and use a router a lot, that's just how I'd consider doing the job.  I'm certainly not against the jigsaw, I've owned one of the great Bosch(EV?) units for many years.
I've been tossing around building some of these diffusers for many years, to take down to the venue I do a lot of work at. This has been another informative thread on the subject, especially for sourcing out absorption materials.

Best regards,

John
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Brad Weber

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Re: Sound absorption on the cheap
« Reply #26 on: December 10, 2008, 10:18:24 am »

The problem with most homemade solutions is that the performance is unknown, you cannot perform any accurate prediction or analysis with them.  As a result, recommendations for homemade treatments are typically based on providing an undefined change rather than a specific change or result.  This does not diminish the potential value of them but it does mean that one often can't predict the results or plan on obtaining any specific improvement or result where that may be desired.  Probably not an issue in this particular application but more often a factor in some other applications.

Since some of you seem to have more familiarity with using Sonotube, are you aware of any actual performance testing or published data?  Has anyone confirmed that they are approved for use in public spaces?  Does anyone else wonder why Sonotube does not seem to mention or promote this use?
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Brad Weber
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Tim McCulloch

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Re: Sound absorption on the cheap
« Reply #27 on: December 10, 2008, 11:59:16 am »

It's been a long time since I've used Sonotube for anything... but 20 years ago it was wax-impregnated cardboard.  I suspect it would not meet smoke density or fuel contribution criteria for use in wall coverings.  I'm not sure if untreated plywood would, either.

That said, as long as they weren't attached to the walls (permanent installation) or used to delineate work spaces (like office cubicles), they *might* not get a second look from the fire marshal.  I could be wrong...

A big part of the reason architectural finishes cost big $$ is to pay for the testing & certification of prototypes and continued QC for produced goods.

Tim "safety is GOOD" Mc
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Jamin Lynch

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Re: Sound absorption on the cheap
« Reply #28 on: December 10, 2008, 01:08:55 pm »

Check out Perdue Acoustics. You may think their panels are expensive, but they are so efficient you need far less than most other panels which makes the over all cost less. Plus they have a wide variety of sizes, colors, and models to choose from.

I just finished a job using their panels and they far acceded what I was expecting.
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Rick Powell

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Re: Sound absorption on the cheap
« Reply #29 on: December 10, 2008, 09:37:04 pm »

ATS's site as I linked to above, shows the test results of their 703/fabric solution.  A homemade version of the same could be expected to have similar results - it's not rocket science to build these things, and the material has consistent and well known properties.
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Rick Powell
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