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Absorbers from Books. Overenthusiastic newbie help (Read 872 times)
Azul Shiva
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Absorbers from Books. Overenthusiastic newbie help
07/14/14 at 21:28:45
 
Hiiii

Whoa its been 5 years ago since I was last active here, been spending too much time with my headphones but Im back on track with speakers.

My budget is somewhat limited, and I intend to invest most of my money into the speakers instead of the room. However since I started to work in a 2nd-handshop selling books, lots of books, and the books that dont sell get thrown away, being several hundred KG every week, I find myself having absolute free access to as many books I want. Instead of spending hundreds if not thousands on room treatment, I thought it would be possible to create everything from.. well, books. This idea got me very enthusiastic also imagening the money Id save. I just hope it could work, however Im clueless and Im hoping for some information.

It is a common thing to put books in a listening room to increase absorbtion but Ive never seen anybody actually try and BUILD Absorbers out of books LOL. I figure nobody is that barbaric to rip apart hundreds of books for the sake of sound nor has access to thousands of books for free.. well, I do. I need help, I have little idea of what Im doing, any valuable information on Sound Absorbance regarding paper would be more then appreciated.

I checked out some theory about acoustics and heres some questions:

Absorption coefficient: Anyones got any clue what frequencies Paper would absorb at what thickness? I found absolutely nothing on the internet. I've learned that an absorber begins to absorb frequencies 10x length of its thickness and reaches peak at 4x. But is there no way to calculate this provided you got the initial values for the material? So a bookshelf with books 15cm deep should peak at 400hz?

Air flow resistance: Books are very dense and heavy, much denser then fiberglass panels and wool and sponge stuff. As far as I know the density increases the absorbtion characteristics, however after a given point, it decreases dramatically also as denser materials absorb higher frequencies due to the loss of friction. Will a book itself absorb decently itself into the lower midrange or is there a need for me to treat it somehow to decrease its density, be creative, sink it in water, watch it crumble as it dries, dunno I guess, lol?

Air gap: 5mm airgaps I've heard should help with lower frequencies. Is there anyway to calculate this? Again, I have no idea what Im doing. Would crumpling up paper inbetween of 2 Books work as an airgap?

Diffusors: No problem in building Diffusion Panels out of wood is there? Except for the cost for the wood.. I estimate around 100-200chf per square metre. Absolute no go for me. So heres an idea:
Solid Book Covers are surprisingly rigid compared to standard carton (carton? cardboard? same thing?), they could serve as frames for absorption panels, since I intend to rip them off anyway, and maybe as well as diffusors. Build an entire diffusor out of thick carton? Does that make any sense? Or will mid frequencies simply pass through the cardboard and the entire Diffusor will work like a miserable absorber? Again, an absoption coefficient for hard carton would be useful.

Next thing Ill ask is how to build a house from books... alright, so..

Uploaded a picture of a recorded impulse. Delay is around 300ms. Maybe if I make progress with absorption Ill upload more ^^

If anyone can help It would be very helpful. First thing Im building with these books anyways is a Sound Barrier for Ambiophonic speaker setup.

Kindest Regards,
Azul
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« Last Edit: 07/14/14 at 21:32:41 by Azul Shiva »  

impulsee.jpg

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Lonely Raven
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #1 - 07/14/14 at 22:06:11
 
As you alluded to, you need airflow through the material in order to get absorption - books don't allow airflow. When the density gets to a certain point, they will simply act as a solid reflector. So unless you run all the books through a shredder and put the resulting streamers into a breathable container, I don't think you'll get an absorber out of books. And even if you did do all that, there isn't enough micro-air pockets for the sound waves to get caught up in like with insulation.

Now, on the diffuser side, I can see this working, but you need to keep in mind, proper diffusion is a mathematical exercise. You can't just stack books with some sort of spacing between them and hope for for positive change. At best the diffusion would be in a very narrow band.

If you're serious about books for diffusers, and you have *lots* of books, you could build a wood frame, and glue the books together at calculated depths to form a 1D diffuser. Easy calculations can be done using QRDude.

http://www.subwoofer-builder.com/qrdude.htm

If you poke around there, some of my projects might still be on his page.

I could absolutely see functional and conversation starting diffusers out of books if you follow the math.

P.S. I'm glad your measuring! That's step 1!
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« Last Edit: 07/14/14 at 22:06:32 by Lonely Raven »  
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Archie
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #2 - 07/15/14 at 01:28:26
 
What about getting Radial Speakers?  Steve says they get around the room treatment issue.
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Lonely Raven
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #3 - 07/15/14 at 02:21:18
 

That's not exactly true. They help make the room less of an issue for imaging; nothing but true room treatment (and proper design) fixes a room.

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marky
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #4 - 07/15/14 at 17:22:55
 
Dragging my mind away from in house library sound systems it could be just a case of lots of bookshelves and randomly stacking them as normal except pushing them all back against the wall so sll the different depths of books make them offer a  stepped surface which could be taken further by jutting some out, and leaving a gap between each one. Cant say I`d be enamoured but then my absobers might look better if they were covered in acoustic material with book prints on them.
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Azul Shiva
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #5 - 07/15/14 at 18:38:32
 
Hi

Thanks alot for your reply. I will post feedback on how the build worked on the weekend.
On the website of QRD they have stated that covering a diffuser with cloth will lower its effectiveness. I dont see how a 1mm thin sheet (or maybe a flynet) should reflect or absorb or refract anything, not like some additional absorbtion or refraction is a problem or am I wrong? Cos 1 things for sure, Im staring at my pile of books and as I think about how I shall proceed creating frames and fins out of solid book covers, especially if they are meant to cover huge surfaces of my walls, these diffusors will look ugly beyond your imagination to say the very least. Very least thing I could do is wrap every piece of cardboard up in white paper..
I wanna put  cloth across the things and make neat looking cute little white boxes hanging innocently on the wall. Is there really something wrong with that?
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Azul Shiva
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Re: Absorbers from Books. Overenthusiastic newbie help
Reply #6 - 07/16/14 at 16:52:26
 
"Notably, Fujiwara
and Miyajima26 measured absorption coefficients ranging from 0.3 to 1, and
Commins, Auletta and Suner 27 measured coefficients peaking at about 0.5. These
high absorption coefficients are in marked contrast to random incidence absorption
coefficients measured on commercial samples28. The contradiction can probably
be explained by construction quality; Fujiwara29 later publication showed that the
excessive absorption seen in his earlier publication was caused by poor
construction.

Provided Schroeder diffusers are well sealed and made from non-absorbing
material, there is no reason why absorption should be excessive. However, it is
very important that the surfaces are not covered, because excess absorption then
occurs due to high particle velocity near the well entrances.
" QUOTE FROM http://www.rpginc.com/

I would understand if the diffusor would instead absorb the frequencies that it should diffuse, but a sheet of cloth over them would rather absorb the very high 5khz+ frequencies. From what I read frequencies that range above the effective diffusing range of a diffuser will get simply reflected. Building the thing out of paper/cardboard would probably make more of an absorbby diffuser eh? I don't understand the problem with high frequency absorbtion within a diffusor.
Damn if it were up to my logic id say absorb everything with the diffuser thats above its diffusing range by putting lil absorbers in every well, and why in theory might even put a basstrap behind it.

I've realized that diffusion theory is more intuitive and expertimentive than it is calculated and measured. I'm worried that some information regarding Diffusers designed to be in Concert halls where the absorbtion is NOT wanted is flowing to diffusers meant to chill in listening rooms and people with stereo systems pick up this information without questioning it and then just build stuff and spread the word. It doesnt make any sense to me, but if you can prove me wrong, please do Cheesy

Also the soundstage of an ambiophonic system greatly benefits from a nearly dead room in the high frequency range. Low mid frequencies will not be as accurate (also since the sound barrier lets some of these through) however, as long as the instruments are human, the brain will link the lows with the mids and the highs in the soundstage. At least this is something Ralph Glasgal told me, but makes good sense to me Cheesy

forgiv me my teribbel speling and gramar

regards
azul
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« Last Edit: 07/16/14 at 16:53:56 by Azul Shiva »  

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