Few said:
Anyone who has ever had to get rid of some old car tires knows that you have to pay to have them taken away. Seems that you should be able to get as many old tires as you want free. The next problem is how to shred them. You'd need a very powerful grider
If you need small amount of recycled tire already processed try the people who supply playground equipment. The mats they place under jungle gyms and the like are tire-recycles. You can buy this either as solid mat or in liquid form that can be molded
Also sometimes instead of mulch they use shredded and painted tires. The stuff feels really bouncy and easy on your feet. I have no idea where you can buy it though - I was thinking about getting some for the yard painted brown instead of the blue they use at our park.
Cal: I wouldn't want to try to apply any sort of blade to this concoction; it's mostly coarse sand. I think the most practical application is to pour the stuff into a mold or other form that determines the final shape. I actually see that as an advantage, though. You could make a mold out of easy to work with materials (extruded polystyrene, stretched fabric reinforced with resin, soft wood, whatever...) and then pour in the polyurethane and sand. As a bonus, for two identical speakers you only have to carefully make one mold. You get two carefully crafted identical speakers from the effort required to get one mold right.
Trusound: Love those shapes!
ChrisA and Key: I had similar thoughts about the easy availability of shredded rubber. It just wasn't as easy to find as I assumed it would be when I actually looked for it (this was a year or two ago). I'm not sure I'm up for shredding my own rubber, but if anyone digs up a source of cheap shredded rubber, please share. I could imagine forming a speaker baffle with a hard external surface made of polyurethane and sand, and adding rubber to the mix for some of the inner portions of the wall. The texture formed by the polyurethane and sand mixture is actually quite attractive, and the smoothness is dictated by the surface of whatever you use as a mold. In other words, you could get away with little or no finishing after popping the thing out of the mold as long as you like the natural look of the material. If not, ChrisA's prescription sounds like the way to go.
Dave: I agree there's a lot of background material on perception to wade through before making a fully informed decision. I remain swayed by Andy Payor's approach with his Rockport cabinets--very stiff, very heavy, and very dead--but I acknowledge that there are widely acclaimed examples of other approaches to the cabinet resonance problem.
Few
Trusound: Love those shapes!
ChrisA and Key: I had similar thoughts about the easy availability of shredded rubber. It just wasn't as easy to find as I assumed it would be when I actually looked for it (this was a year or two ago). I'm not sure I'm up for shredding my own rubber, but if anyone digs up a source of cheap shredded rubber, please share. I could imagine forming a speaker baffle with a hard external surface made of polyurethane and sand, and adding rubber to the mix for some of the inner portions of the wall. The texture formed by the polyurethane and sand mixture is actually quite attractive, and the smoothness is dictated by the surface of whatever you use as a mold. In other words, you could get away with little or no finishing after popping the thing out of the mold as long as you like the natural look of the material. If not, ChrisA's prescription sounds like the way to go.
Dave: I agree there's a lot of background material on perception to wade through before making a fully informed decision. I remain swayed by Andy Payor's approach with his Rockport cabinets--very stiff, very heavy, and very dead--but I acknowledge that there are widely acclaimed examples of other approaches to the cabinet resonance problem.
Few
You can get the recycled rubber at Lowe's.
http://www.lowes.com/lowes/lkn?action=productDetail&productId=83288-23132-10030&lpage=none
Enjoy,
Dan
http://www.lowes.com/lowes/lkn?action=productDetail&productId=83288-23132-10030&lpage=none
Enjoy,
Dan
Ah ha! We didn't have a local Lowe's the last time I searched for the shredded rubber. Many thanks.
Few
Few
ChrisA said:
In the UK they use shredded tyres to mix with sand etc. to make an artificial surface for horse-training manages. These people may well share a source or even sell you a reasonable amount for little money. Incidentally the pieces are about 1/2" or thereabouts.
Thanks for the thread. I have been wanting to use sand/resin for dampening but it seems to be much more effective at certain frequency in relation to the particle size.
I ran across a some articles that used micro clay mixed in resulting in a possible wider frequency damping. Here is a link if interested
antivibration performance of nanoclay-modified PU/PEL blends system
I find it interesting that to some extent dampening frequencys are tunable in these kinds of compounds. It would be fun to play with. Useful is another matter unless you prefer to work with fiberglass and such like me.
I ran across a some articles that used micro clay mixed in resulting in a possible wider frequency damping. Here is a link if interested
antivibration performance of nanoclay-modified PU/PEL blends system
I find it interesting that to some extent dampening frequencys are tunable in these kinds of compounds. It would be fun to play with. Useful is another matter unless you prefer to work with fiberglass and such like me.
Thanks Brianco, I was envisioning something closer to rubber crumbs rather than pieces as large as 1/2", but I appreciate the suggestion.
That's an interesting article, Smoken Joe; thanks. I wish it had the figures, but it's useful nonetheless. Too bad I don't have access to materials testing equipment of the type that seems to be designed for this sort of work. Another DIY project? 🙄 Maybe I could come up with a less than quantitative but still useful test. On the other hand, I'll never finish my speakers if I get too distracted by this subproject. Man, this site can be a bad influence.
BTW, I've been working with fiberglass for speakers as well lately. Non-wood based materials really broaden the spectrum of what's possible. I like the idea of incorporating curves whose radii exceed those I can tackle with MDF and a router. I also have to admit I find the whole materials game fascinating, whether or not it has anything to do with audio.
Few
That's an interesting article, Smoken Joe; thanks. I wish it had the figures, but it's useful nonetheless. Too bad I don't have access to materials testing equipment of the type that seems to be designed for this sort of work. Another DIY project? 🙄 Maybe I could come up with a less than quantitative but still useful test. On the other hand, I'll never finish my speakers if I get too distracted by this subproject. Man, this site can be a bad influence.
BTW, I've been working with fiberglass for speakers as well lately. Non-wood based materials really broaden the spectrum of what's possible. I like the idea of incorporating curves whose radii exceed those I can tackle with MDF and a router. I also have to admit I find the whole materials game fascinating, whether or not it has anything to do with audio.
Few
FEW
I was meaning that these horse people may pass you on to their suppliers who may well have a variety of choice.
Good luck.
I was meaning that these horse people may pass you on to their suppliers who may well have a variety of choice.
Good luck.
Few you would be surprised how simple it is.
Basically they got some clay mixed it with anti foaming chemical then dried it out in an oven and mixed it in resin. You dont need to know the chemistry just trial and error to get the best result. You are using resin or glue anyway you might be able to better absorb noise with a little trial and error.
They used Smectite clay you can get in some herbal stores (they use it to treat diarrhea) but lots of water absorbing compounds could work. Clay is cheap and wont hurt strength that is why they used that.
You could skip the anti foaming agent if you dont need to support heavy equipment with it. The bubbles could actually help absorb vibration.
You can measure vibration with the old knuckle test on a painted piece of wood or if you want to get technical you can test with the same software people normally use to test speakers.
If you want to go all out use one cheap or damage speaker directly on a painted board and another hooked up like a mike to the other side of a board or sheet of metal.
Basically they got some clay mixed it with anti foaming chemical then dried it out in an oven and mixed it in resin. You dont need to know the chemistry just trial and error to get the best result. You are using resin or glue anyway you might be able to better absorb noise with a little trial and error.
They used Smectite clay you can get in some herbal stores (they use it to treat diarrhea) but lots of water absorbing compounds could work. Clay is cheap and wont hurt strength that is why they used that.
You could skip the anti foaming agent if you dont need to support heavy equipment with it. The bubbles could actually help absorb vibration.
You can measure vibration with the old knuckle test on a painted piece of wood or if you want to get technical you can test with the same software people normally use to test speakers.
If you want to go all out use one cheap or damage speaker directly on a painted board and another hooked up like a mike to the other side of a board or sheet of metal.
Smoken Joe said:
I was thinking the other day that if you REALLY wanted to get crazy with measuring cabinet resonance the way to do it would be to get one of those 'sound exciter' transducer things (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-375) and attach it to a board, then instead of a microphone use a piezoelectric pickup like you'd have in an electric/acoustic guitar and use that to directly measure vibrations in the board.
With that type of setup I would think you'd be able to get some extremely accurate results.
Not a bad idea! You could use one to excite, the other to pick up. But you might not get much LF.
I think I have pair stashed away somewhere....
I think I have pair stashed away somewhere....
I've used the piezo disk from a buzzer as an accelerometer before, and it can be made to work quite well. I've just never looked into calibrating it or evaluating its bandwidth. I usually add a bit of intertial mass to the center of the piezo disk (just stick a coin or steel nut to it). If the signal is large you can see it directly with an oscilloscope. Otherwise I use a one op amp preamplifier to beef it up. If I get inspired/distracted, I may actually pursue this approach, but I'm still trying to keep my main focus on building my speakers.
I have a lead on some rubber crumbs, thanks to the generosity of one of our diyAudio comrades, so if I come up with a sand/rubber/polyurethane mix that seems interesting I could try to make up two test pieces with the same dimensions, one with rubber and one without, and try to measure their vibrational behavior. It still won't be calibrated, but it would likely be useful as a way to measure the two materials' relative behaviors. I could get fancy with an "exciter" but might start by just dropping a steel ball onto the test piece from a consistent height. I suppose that even with an inconsistent excitation I could still get some sense of the Q just be seeing how many cycles it takes the vibration to die away. The results should be independent of the amplitude of the original excitation, at least to a first approximation.
But I'm supposed to be focusing on my speakers! Focus...Focus...
Few
I have a lead on some rubber crumbs, thanks to the generosity of one of our diyAudio comrades, so if I come up with a sand/rubber/polyurethane mix that seems interesting I could try to make up two test pieces with the same dimensions, one with rubber and one without, and try to measure their vibrational behavior. It still won't be calibrated, but it would likely be useful as a way to measure the two materials' relative behaviors. I could get fancy with an "exciter" but might start by just dropping a steel ball onto the test piece from a consistent height. I suppose that even with an inconsistent excitation I could still get some sense of the Q just be seeing how many cycles it takes the vibration to die away. The results should be independent of the amplitude of the original excitation, at least to a first approximation.
But I'm supposed to be focusing on my speakers! Focus...Focus...
Few
Due to the generosity of one of our fellow diyAudio members I received some rubber crumbs to play with. They are quite fine--smaller average size than I was expecting.
I haven't yet conducted a quantitative test because life keeps getting in the way, but I did repeat my previous very coarse test, this time with rubber instead of sand, so that I wouldn't feel so guilty about not making faster progress. At first I thought the results were very similar to the sand composite because I was surprised by how hard the rubber crumb/polyurethane combination was. But, when I did a head-to-head comparison there's a pronounced difference between their responses to the "smack it on a concrete wall" test. The sand composite sounds almost like a rock when struck but the rubber crumb composite clearly sounds less hard---if that makes any sense.
I have to admit this mushy description of how things sound, without any quantified measurements, really runs counter to my preferred mode of operation, but until I can complete my more quantitative test I'm afraid it's the best I can offer.
Here's my tentative plan for a more quantitative approach: I plan to make tuning forks out of several different materials (mdf, polyurethane/sand, polyurethane/rubber crumb), but with the same dimensions, and compare their resonance frequencies and quality factors (Qs). I want to use tuning forks because I want to make the Q values as high as possible so that I can make the most reliable measurements. I'll probably stick piezo disks to the tines of the forks as accelerometers and then digitize the forks' responses after I somehow get them vibrating. I don't think it'll be crucial that I make the stimuli completely repeatable as long as I can cleanly see the fundamental tuning fork resonance in my measurements---the Q should be independent of how, or how much, the fork is stimulated. If anyone sees a fatal flaw in this approach and wants to help me avoid a big waste of time, let me know.
Anyway, I may eat crow later when I realize this isn't going to fly (crow that won't fly?) but I felt compelled to share my plans for a more quantitative approach so that my "hmmm, sounds different" post wouldn't offend the sensibilities of those who want to see the numbers. I have no doubt the vibrational behaviors of the two materials are quite different, but since I tend to be a numbers guy, I'll feel much better if I can make the tuning fork test work.
Few
I haven't yet conducted a quantitative test because life keeps getting in the way, but I did repeat my previous very coarse test, this time with rubber instead of sand, so that I wouldn't feel so guilty about not making faster progress. At first I thought the results were very similar to the sand composite because I was surprised by how hard the rubber crumb/polyurethane combination was. But, when I did a head-to-head comparison there's a pronounced difference between their responses to the "smack it on a concrete wall" test. The sand composite sounds almost like a rock when struck but the rubber crumb composite clearly sounds less hard---if that makes any sense.
I have to admit this mushy description of how things sound, without any quantified measurements, really runs counter to my preferred mode of operation, but until I can complete my more quantitative test I'm afraid it's the best I can offer.
Here's my tentative plan for a more quantitative approach: I plan to make tuning forks out of several different materials (mdf, polyurethane/sand, polyurethane/rubber crumb), but with the same dimensions, and compare their resonance frequencies and quality factors (Qs). I want to use tuning forks because I want to make the Q values as high as possible so that I can make the most reliable measurements. I'll probably stick piezo disks to the tines of the forks as accelerometers and then digitize the forks' responses after I somehow get them vibrating. I don't think it'll be crucial that I make the stimuli completely repeatable as long as I can cleanly see the fundamental tuning fork resonance in my measurements---the Q should be independent of how, or how much, the fork is stimulated. If anyone sees a fatal flaw in this approach and wants to help me avoid a big waste of time, let me know.
Anyway, I may eat crow later when I realize this isn't going to fly (crow that won't fly?) but I felt compelled to share my plans for a more quantitative approach so that my "hmmm, sounds different" post wouldn't offend the sensibilities of those who want to see the numbers. I have no doubt the vibrational behaviors of the two materials are quite different, but since I tend to be a numbers guy, I'll feel much better if I can make the tuning fork test work.
Few
Just wandering if there's a way to use accelerometer instead of microphone with software like Sound Easy.
Has anyone done such a travesty? 🙂
Has anyone done such a travesty? 🙂
I'm late to this thread, but I still thought that I would chime in. A friend and I are working on building concrete Elsinores, though we have gotten sidetracked lately.
We went to a tire recycler locally and bought eight 50lb bags of 30mesh tire rubber. 30 mesh is particles that will sift thru a .48mm screen, so this rubber is essentially dust. Cost was $12 per bag. With casting and testing, we are halfway thru one bag. Better safe than sorry though, I'll use it all for something.
We have had good luck with a mix of the following: One 80lb bag of Sakrete 5000+ concrete, added to a mixer already containing 1 gallon of water and 2 quarts of presoaked powdered rubber, 2oz of plasticizer/water reducer and a half handful of structural fiber. Dry powdered rubber retains air with a fury and will float to the top of your mix, so it is important that the rubber be presoaked in the gallon of water, and add 2 drops of dishwashing detergent to break surface tension.
This mix of concrete produces a concrete which goes "click" when struck with a ball-peen hammer, as compared to a loud resonant ring for pure concrete, but retains full strength/stiffness as far as we've been able to tell from various tests. Subwoofers made from this mix have been highly satisfying. Nothing else can Just Sit There the way a concrete speaker enclosure can. 😛
We went to a tire recycler locally and bought eight 50lb bags of 30mesh tire rubber. 30 mesh is particles that will sift thru a .48mm screen, so this rubber is essentially dust. Cost was $12 per bag. With casting and testing, we are halfway thru one bag. Better safe than sorry though, I'll use it all for something.
We have had good luck with a mix of the following: One 80lb bag of Sakrete 5000+ concrete, added to a mixer already containing 1 gallon of water and 2 quarts of presoaked powdered rubber, 2oz of plasticizer/water reducer and a half handful of structural fiber. Dry powdered rubber retains air with a fury and will float to the top of your mix, so it is important that the rubber be presoaked in the gallon of water, and add 2 drops of dishwashing detergent to break surface tension.
This mix of concrete produces a concrete which goes "click" when struck with a ball-peen hammer, as compared to a loud resonant ring for pure concrete, but retains full strength/stiffness as far as we've been able to tell from various tests. Subwoofers made from this mix have been highly satisfying. Nothing else can Just Sit There the way a concrete speaker enclosure can. 😛
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