m00n Posted October 18, 2003 Share Posted October 18, 2003 So for weeks I have been looking for some rigid fiberglass so I could build some bass traps. I finally said, hey, this can't be that hard to make my own, so.... I think to myself, "self, how can you do it yourself?". Here is what I have come up with... This is two peices of fiberglass stacked on top of each other. You can see how fluffy it is. Most likey fullier than this image shows because these two peices had already been smooshed by me. I unsmooshed them for this image. So again, from this fluff to this nice compace stuff. oh yeah, the m00nmeister strikes again. Don't ask for any acoustic numbers cause I don't have any. Quote Link to comment Share on other sites More sharing options...
prodj101 Posted October 18, 2003 Share Posted October 18, 2003 I have seen peoplpe than cover that with some sort of fabric to make achieve a high wife approval factor. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 18, 2003 Author Share Posted October 18, 2003 Oh yeah... for sure dude. This is only a prototype of what will go into my absorbtion panels... Na... No way I would just hang it in my theater like this. If for no other reason, I can only imagine it would be a health hazard. Quote Link to comment Share on other sites More sharing options...
danechristian Posted October 18, 2003 Share Posted October 18, 2003 nice, keep us updated about your project. if it is a success, i might as well build mine and save money. Quote Link to comment Share on other sites More sharing options...
John Warren Posted October 18, 2003 Share Posted October 18, 2003 A 30Hz tone has a wavelength of 37.69 feet. Fiberglass will attenuate waves that are the same size as its thickness. If you line one side of you living room with 2' thick sheet of fiberglass you will attenuate anything 550Hz or higher since 550Hz has ~2' wavelength (do you see where this is going?). Likewise, assume you have a 1' x 1' X 37.69' long roll of fiberglass that you roll-out in front of your speaker (it's on-axis to your woofer). It has one dimension comparable to a 30Hz wavelength but only a minute fraction of the area of the wave will intersect it (the 1 sq. ft. dimension). So the total acoustic power converted to heat adiabatically is essentially zero. If you've ever been inside a large wedge-type anechoic chamber, you will understand (and see) immediately what is necessary to attenuate low frequencies. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 18, 2003 Author Share Posted October 18, 2003 John, there will be more to my absorbers than just fiberglass. Quote Link to comment Share on other sites More sharing options...
prodj101 Posted October 19, 2003 Share Posted October 19, 2003 ---------------- On 10/18/2003 11:31:49 PM m00n wrote: John, there will be more to my absorbers than just fiberglass. ---------------- [/blockquote lol Quote Link to comment Share on other sites More sharing options...
prodj101 Posted October 19, 2003 Share Posted October 19, 2003 hmmm, what is the purpose of putting insolation on the inside of subwoofers then if it has to be 30 feet thick to be effective at those frequencies? Quote Link to comment Share on other sites More sharing options...
John Warren Posted October 19, 2003 Share Posted October 19, 2003 ---------------- On 10/19/2003 1:37:09 AM prodj101 wrote: hmmm, what is the purpose of putting insolation on the inside of subwoofers then if it has to be 30 feet thick to be effective at those frequencies? ---------------- attenuation of harmonics iff they have wavelengths on the order of the fiberglass thickness. A jelly-roll of insulation placed in a 2' tall enclosure will attenuate 550Hz and up. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 19, 2003 Author Share Posted October 19, 2003 ---------------- On 10/19/2003 6:33:06 AM John Warren wrote: attenuation of harmonics iff they have wavelengths on the order of the fiberglass thickness. A jelly-roll of insulation placed in a 2' tall enclosure will attenuate 550Hz and up. ---------------- John, you are talking beyond my level of understanding here... What does attenuate mean? Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 19, 2003 Share Posted October 19, 2003 m00n, To attenuate is to reduce or lower the signal level. That said, there is more to sound control than most of us think. This is why the Sonex and Auralex products cost more than we think they should. You can spend a lot of money and especially time, to get nowhere on your bass traps, if you don't understand the theory and figure out how to put it into practice. For instance, the chapel at the college where I work has horrible acoustics. Ceiling is 60 to 100 feet high. A person speaking sounds awful! There is too high a reverberant field. To cancel all that, has been estimated to cost upwards of $250k. It was designed for one pupose only, a pipe organ with 32ft pipes. If the room were smaller, there would be distortion when playing the lowest notes. The rub is that they never bought the pipe organ, because of budget constraints. That was twenty some years ago, and they have been living with the nightmare ever since. It's ugly too. Needless to say, they aren't spending money on the acoustics either. Marvel Quote Link to comment Share on other sites More sharing options...
m00n Posted October 20, 2003 Author Share Posted October 20, 2003 Ok... So I made some panels of this which I am now using in one of my multitraps. Here it is unpacked, Here it is after I packed it with the screen mesh and bailing wire. My analysis of this project: "F" this man, what a pain in the arse. I would suggest that if you need some rigid fiberglass, take the extra time to locate some because this is a slow tedious project making this crap. It works and it is very dence, but gawd..... I spent 5 times as long making three of these rigid panels as I did making the frame for my bass trap. What a time sink. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted October 20, 2003 Share Posted October 20, 2003 m00n: I have looked at many products for this application and was not able to get my hands on the holy grail of acoustic products, Owens Corning Type 703 fiberglass boards. They come in several thicknesses, but are available only to professional businesses. I even called OC and begged to get some. A 3" piece will absorb down to 250 hz. I decided to do the next best thing. While skulking around in my attic I saw that my A/C ducts were covered with a 1" piece of dense fiberglass. I went to my local A/C and heating supply and found 4x8 sheets of the stuff. I purchased 10, they would only sell me a box for cash, and I went to work. My panels are made of three sheets, cut to size stacked together with the aluminum backing removed. I don't have a way to measure the absorption coefficients, but they work very well for the high and mid frequencies. You can see them hanging in my HT. I think this type of set up will be easier for you to do what you want. It certainly is a lot easier. The fiberglass sheets are very dense, so no pressing required. For the low frequencies, I made tube traps. In case you wouldn't mind some suggestions. I used a poly batting to cover the flat panel trap before I covered it with acoustic material so that I didn't have a problem with fiberglass floating around the room. I made the bass tube traps with a similar product, this time it is commercial pipe insulation that can be purchased from an A/C supplier if you look around. The pipe insulation comes in various thicknesses and various diameters. Very cool product for that application. Quote Link to comment Share on other sites More sharing options...
artto Posted October 20, 2003 Share Posted October 20, 2003 ---------------- On 10/18/2003 8:54:00 PM John Warren wrote: A 30Hz tone has a wavelength of 37.69 feet. Fiberglass will attenuate waves that are the same size as its thickness. If you line one side of you living room with 2' thick sheet of fiberglass you will attenuate anything 550Hz or higher since 550Hz has ~2' wavelength (do you see where this is going?). ---------------- John, you are quite correct. However, objects that can be used for reflection and absorption only need to be one-half of the wavelength to be effective. Actually, they can be quite effective down to one-fourth of the wavelength. And the absorption coefficient is also affected by the density & porosity of the material as well as the size of it's surface area. You are also correct in mentioning the diagonal intersection of the sound absorption surface can be important. This can be quite effective, especially if used in room corners where more depth is easily achieved without sacrificing as much space. I have Auralex LENRDs (Low End Node Reduction Device) in my rooms rear vertical corners & a 16 section across the rear wall-ceiling corner (28 wide room). It makes a BIG difference. (and moon, it only costs $300, no work, no mess, easy to move, experiment, cool colors, the NRC is known, etc, etc.) Quote Link to comment Share on other sites More sharing options...
m00n Posted October 20, 2003 Author Share Posted October 20, 2003 hey thanks Rudy, if I need to buy more material, I may just go that route. I do know where you can get some 703 and 705, but I was too cheap to pay shipping not to mention it's rather spendy. http://www.realtraps.com/fiberglass.htm''>http://www.realtraps.com/fiberglass.htm'>http://www.realtraps.com/fiberglass.htm Quote Link to comment Share on other sites More sharing options...
artto Posted October 20, 2003 Share Posted October 20, 2003 ---------------- On 10/20/2003 4:54:44 PM Rudy81 wrote: m00n: I have looked at many products for this application and was not able to get my hands on the holy grail of acoustic products, Owens Corning Type 703 fiberglass boards. They come in several thicknesses, but are available only to professional businesses. I even called OC and begged to get some. A 3" piece will absorb down to 250 hz. ---------------- Just for the record, forget about Ownens Corning Type 703 & 705FR rigid fiberglass insulation that Ethan Winer's book & website quote. I called Owens Corning because I couldn't get any info on it either (I'm an architect). They informed me that it is no longer available. They have gone to foam based products. Quote Link to comment Share on other sites More sharing options...
m00n Posted October 20, 2003 Author Share Posted October 20, 2003 artto, that is good to know. I suspect it is going to make a lot of people unhappy because that is the elite stuff over on the recording.org forum. Quote Link to comment Share on other sites More sharing options...
John Warren Posted October 20, 2003 Share Posted October 20, 2003 ---------------- On 10/20/2003 5:40:31 PM artto wrote: objects that can be used for reflection and absorption only need to be one-half of the wavelength to be effective. Actually, they can be quite effective down to one-fourth of the wavelength. >>agreed, they will have an effect even at 1/4 wl. Point here is that low frequencies have large wavelengths and attenuation of LF waves must be thru a suitable meterial with a thickness "on a scale comparable to the wl". 1/4 wl offers attenuation but at a significantly lower efficacy than even 1/3. I suspect that most "bass" problems associated with room acoustics are in the higher frequencies ranges (100-300Hz) were wavelengths are on the order of 10 ft or less. At these frequencies 1/2 an 1/4 wave attenuators are not outrageous in size either. ---------------- Quote Link to comment Share on other sites More sharing options...
formica Posted October 22, 2003 Share Posted October 22, 2003 ---------------- On 10/20/2003 5:46:16 PM artto wrote: Just for the record, forget about Ownens Corning Type 703 & 705FR rigid fiberglass insulation that Ethan Winer's book & website quote. ---------------- Here you go... Owens Corning 700 Series Insulation and you'll get detailed info in the Specifications links like Exterior Wall Thermal Insulation in the: Guide for Exterior Wall ThermalInsulation.doc These are both on their current web site as well as Fall 2003 Sweets catalog. Not all local distributors are as knowledgeable as others... so they may have looked in the acoustic section while these are actually thermal panels. I haven't tried buying any yet, so I can't comment on availability but we have some pretty good local commercial suppliers we deal with. Later... Rob Quote Link to comment Share on other sites More sharing options...
j-malotky Posted October 22, 2003 Share Posted October 22, 2003 Moon Here is a pic of the Klipsch chamber showing the cones on the door looking constructed simular to what you are doing. I like your idea. JM Quote Link to comment Share on other sites More sharing options...
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