Owens Corning 701, 703, 705

I found more Owens Corning measurements. I formatted/sorted them and did some additional calculations to show some points. The numbers speak for themselves. Owens Corning 701, 703, 705 Thickness: 1", 2", 3", 4" and one 6" All Measurements mounting direct to reflective background (no cavity). SORTED PER DENSITY VERSUS THICKNESS Freq: 125, 250, 500, 1000, 2000, 4000 Hz 1 inch OC 701 · 1.0" · 0.17 · 0.33 · 0.64 · 0.83 · 0.90 · 0.92 OC 703 · 1.0" · 0.11 · 0.28 · 0.68 · 0.90 · 0.93 · 0.96 OC 705 · 1.0" · 0.02 · 0.27 · 0.63 · 0.85 · 0.93 · 0.95 2 inch OC 701 · 2.0" · 0.22 · 0.67 · 0.98 · 1.02 · 0.98 · 1.00 OC 703 · 2.0" · 0.22 · 0.82 · 1.21 · 1.10 · 1.02 · 1.05 OC 703 · 2.0" · 0.17 · 0.86 · 1.14 · 1.07 · 1.02 · 0.98 OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.99 · 0.99 OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.98 · 0.98 3 inch OC 701 · 3.0" · 0.43 · 1.17 · 1.26 · 1.09 · 1.03 · 1.04 OC 703 · 3.0" · 0.53 · 1.19 · 1.21 · 1.08 · 1.01 · 1.04 OC 705 · 3.0" · 0.54 · 1.12 · 1.23 · 1.07 · 1.01 · 1.05 4 inch OC 701 · 4.0" · 0.73 · 1.29 · 1.22 · 1.06 · 1.00 · 0.97 OC 703 · 4.0" · 0.84 · 1.24 · 1.24 · 1.08 · 1.00 · 0.97 OC 705 · 4.0" · 0.75 · 1.19 · 1.17 · 1.05 · 0.97 · 0.98 6 inch OC 703 · 6.0" · 1.19 · 1.21 · 1.13 · 1.05 · 1.04 · 1.04 SORTED PER THICKNESS VERSUS DENSITY Freq: 125, 250, 500, 1000, 2000, 4000 Hz Owens Corning 701... 24 kg/m^3 - 1.5 pcf OC 701 · 1.0" · 0.17 · 0.33 · 0.64 · 0.83 · 0.90 · 0.92 OC 701 · 2.0" · 0.22 · 0.67 · 0.98 · 1.02 · 0.98 · 1.00 OC 701 · 3.0" · 0.43 · 1.17 · 1.26 · 1.09 · 1.03 · 1.04 OC 701 · 4.0" · 0.73 · 1.29 · 1.22 · 1.06 · 1.00 · 0.97 Owens Corning 703 ... 48 kg/m^3 - 3 pcf OC 703 · 1.0" · 0.11 · 0.28 · 0.68 · 0.90 · 0.93 · 0.96 OC 703 · 2.0" · 0.22 · 0.82 · 1.21 · 1.10 · 1.02 · 1.05 OC 703 · 2.0" · 0.17 · 0.86 · 1.14 · 1.07 · 1.02 · 0.98 OC 703 · 3.0" · 0.53 · 1.19 · 1.21 · 1.08 · 1.01 · 1.04 OC 703 · 4.0" · 0.84 · 1.24 · 1.24 · 1.08 · 1.00 · 0.97 OC 703 · 6.0" · 1.19 · 1.21 · 1.13 · 1.05 · 1.04 · 1.04 Owens Corning 705 ... 96 kg/m^3 - 6 pcf OC 705 · 1.0" · 0.02 · 0.27 · 0.63 · 0.85 · 0.93 · 0.95 OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.99 · 0.99 OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.98 · 0.98 OC 705 · 3.0" · 0.54 · 1.12 · 1.23 · 1.07 · 1.01 · 1.05 OC 705 · 4.0" · 0.75 · 1.19 · 1.17 · 1.05 · 0.97 · 0.98 ABSORPTION VALUES VERSUS MATERIAL THICKNESS AS % OF WAVELENGTH. Compare column 3 , giving the material thickness as a % of the wavelength, with the corresponding absorption in Column 2. You can compare them with the Engineering rules given before. It's clear that the traditional 1/4 wavelenght (25%) approach does NOT apply. This approach only relates to PLAIN waves at STRAIGHT incidence for DISCRETE frequencies: The picture below shows a theoretical simulation of the above described 1/4 wave approach (copyright). OC 701 · 1.0" · 25.4 mm 0125 Hz · 0.17 · 000.9% 0250 Hz · 0.33 · 001.8% 0500 Hz · 0.64 · 003.7% 1000 Hz · 0.83 · 007.4% 2000 Hz · 0.90 · 014.8% 4000 Hz · 0.92 · 029.6% OC 701 · 2.0" · 50.8 mm 0125 Hz · 0.22 · 001.8% 0250 Hz · 0.67 · 003.7% 0500 Hz · 0.98 · 007.4% 1000 Hz · 1.02 · 014.8% 2000 Hz · 0.98 · 029.6% 4000 Hz · 1.00 · 059.2% OC 701 · 3.0" · 76.2 mm 0125 Hz · 0.43 · 002.8% 0250 Hz · 1.17 · 005.5% 0500 Hz · 1.26 · 011.1% 1000 Hz · 1.09 · 022.2% 2000 Hz · 1.03 · 044.4% 4000 Hz · 1.04 · 088.8% OC 701 · 4.0" · 101.6 mm 0125 Hz · 0.73 · 003.7% 0250 Hz · 1.29 · 007.4% 0500 Hz · 1.22 · 014.8% 1000 Hz · 1.06 · 029.6% 2000 Hz · 1.00 · 059.2% 4000 Hz · 0.97 · 118.4% OC 703 · 1.0" · 25.4 mm 0125 Hz · 0.11 · 000.9% 0250 Hz · 0.28 · 001.8% 0500 Hz · 0.68 · 003.7% 1000 Hz · 0.90 · 007.4% 2000 Hz · 0.93 · 014.8% 4000 Hz · 0.96 · 029.6% OC 703 · 2.0" · 50.8 mm 0125 Hz · 0.22 · 001.8% 0250 Hz · 0.82 · 003.7% 0500 Hz · 1.21 · 007.4% 1000 Hz · 1.10 · 014.8% 2000 Hz · 1.02 · 029.6% 4000 Hz · 1.05 · 059.2% OC 703 · 2.0" · 50.8 mm 0125 Hz · 0.17 · 001.8% 0250 Hz · 0.86 · 003.7% 0500 Hz · 1.14 · 007.4% 1000 Hz · 1.07 · 014.8% 2000 Hz · 1.02 · 029.6% 4000 Hz · 0.98 · 059.2% OC 703 · 3.0" · 76.2 mm 0125 Hz · 0.53 · 002.8% 0250 Hz · 1.19 · 005.5% 0500 Hz · 1.21 · 011.1% 1000 Hz · 1.08 · 022.2% 2000 Hz · 1.01 · 044.4% 4000 Hz · 1.04 · 088.8% OC 703 · 4.0" · 101.6 mm 0125 Hz · 0.84 · 003.7% 0250 Hz · 1.24 · 007.4% 0500 Hz · 1.24 · 014.8% 1000 Hz · 1.08 · 029.6% 2000 Hz · 1.00 · 059.2% 4000 Hz · 0.97 · 118.4% OC 703 · 6.0" · 152.4 mm 0125 Hz · 1.19 · 005.5% 0250 Hz · 1.21 · 011.1% 0500 Hz · 1.13 · 022.2% 1000 Hz · 1.05 · 044.4% 2000 Hz · 1.04 · 088.8% 4000 Hz · 1.04 · 177.6% OC 705 · 1.0" · 25.4 mm 0125 Hz · 0.02 · 000.9% 0250 Hz · 0.27 · 001.8% 0500 Hz · 0.63 · 003.7% 1000 Hz · 0.85 · 007.4% 2000 Hz · 0.93 · 014.8% 4000 Hz · 0.95 · 029.6% OC 705 · 2.0" · 50.8 mm 0125 Hz · 0.16 · 001.8% 0250 Hz · 0.71 · 003.7% 0500 Hz · 1.02 · 007.4% 1000 Hz · 1.01 · 014.8% 2000 Hz · 0.99 · 029.6% 4000 Hz · 0.99 · 059.2% OC 705 · 2.0" · 50.8 mm 0125 Hz · 0.16 · 001.8% 0250 Hz · 0.71 · 003.7% 0500 Hz · 1.02 · 007.4% 1000 Hz · 1.01 · 014.8% 2000 Hz · 0.98 · 029.6% 4000 Hz · 0.98 · 059.2% OC 705 · 3.0" · 76.2 mm 0125 Hz · 0.54 · 002.8% 0250 Hz · 1.12 · 005.5% 0500 Hz · 1.23 · 011.1% 1000 Hz · 1.07 · 022.2% 2000 Hz · 1.01 · 044.4% 4000 Hz · 1.05 · 088.8% OC 705 · 4.0" · 101.6 mm 0125 Hz · 0.75 · 003.7% 0250 Hz · 1.19 · 007.4% 0500 Hz · 1.17 · 014.8% 1000 Hz · 1.05 · 029.6% 2000 Hz · 0.97 · 059.2% 4000 Hz · 0.98 · 118.4% Some additional comments: If interested: I measured here different densities of glassfiber in an acoustic laboratory (plain boards without special facing). In the range to ca 6 pcf (Isover glassfiber boards), I measured improvement unto 32 to 35 kg/m³ (2 to 2.2 pcf) which should equal about the OC 702 (but I couldn't find measurements of the OC 702). Only this can differ a bit by brand (production method). Absorption is mainly defined by entrance impedance and gasflow resistance and the behavior of a complex soundfield. As such one will measure different values in function of angle of incidence and the fact if one measure pure tones (sinuswaves) or broadband noise. The relation with mass (density) is only true in as far this mass goes hand in hand with the previous described properties. So this can be true, partly true or untrue but is wrong to state as a defining property for absorption. Melamine foam with a density of only 0.55 to 0.70 pcf has rather surprising absorption properties. So it's the cellular structure which mainly defines those properties. For straight incidence, increasing density can help, but for grazing/angled incidence lowering the density is often the way to go. Do not assume that a backwall is necessary only straight incidence. A sound field is a bit more complex. A lot of the velocity of the air particles happens in the neighborhoud almost parallel and at any angle to the wall. Best regards Eric

Thanks Eric, good to see you floating around still Bryan Giles

Great info. Now what about prices! That would help.

check you local supplier My Supplier quoted me .75 sq.ft. for 703 unfaced. which yeilds the lower LF #'s Bryan Giles Calling OC's Toll free number will help. I called and they had a local supplier call me back within 24 hours

giles117 wrote:

Thanks Eric, good to see you floating around still Bryan Giles

:oops: :oops: :oops: :P Thanks, I thought it could be useful (to be honest entered it in 3 groups, once made was easy to copy). About prices of mineral wool: With exception of local market situations (certain types are more standard than others). One pays for wool in function of the amount of spinned fibre. So the cost is directly linear related to the density. However due to handling, packaging and transport this becomes more expensive relative to the amount of fibre. So this disrupts this linearity. As such a 703 will cost somewhat less than double the 701, and the 705 somewhat less than double the 703. Regards Eric Simplified: Fibre is spinned at a constant rate. To make higher densities or larger thicknesses, one slows down the subsequent production chain (weaving, backing etc).

Eric, thanks for the link - been following it (with occasional comments) over on RO, but appreciate your posting it here too. I kind of intuitively knew how they got the different densities, since I work in a heavy manufacturing situation (Process Instrumentation & Control, rare metals manufacture) but it's good to verify, plus others without similar background may not have had any idea how this is accomplished. To your knowledge, has anyone ever tried to "sculpt" rigid fiberglas (cut "V" grooves in it) in order to compare to the "scupted" foams for grazing incidence measurements? I've not seen anything along these lines, kind of curious whether it would be a good thing or not. It certainly would be a messy operation... Steve

I use Roxul AFB Mineral wool. They are over the border in Canada. My supplier is about 30 minutes from me. I believe I get the prices I get because they are so close to each other. .25/sq ft 2" .35/sq ft 4" .16/sq ft 1" Bryan Giles A bundle of 18 1" 2x4 sheets runs me about $16.00 A bundle of 4 4" sx4 sheets runs me about $11.00

Hello Steve

knightfly wrote:

Eric, thanks for the link - been following it (with occasional comments) over on RO, but appreciate your posting it here too. To your knowledge, has anyone ever tried to "sculpt" rigid fiberglas (cut "V" grooves in it) in order to compare to the "scupted" foams for grazing incidence measurements? I've not seen anything along these lines, kind of curious whether it would be a good thing or not. It certainly would be a messy operation... Steve

Sculpting wool is standard for anechoic room wedges (they excist in all kinds of shapes). However the acoustic effect is extremely minor and only meant to obtain the extreme stringent specs for anechoic rooms. In practice this is hardly measurable (they are measured in extreme large impedance tubes. A second area where sculted wool is used is as filling for perforated steel ceilings (to fill those profiles, following this shape). In general sculpting wool should mainly have acoustic disadvantages. Sculpting has only effect when the sculting becomes large versus the wavelength. This means that for the low frequencies, the disadvantage of removing wool by the sculpture is much more bad than any gain one could have (even for traveling waves this sculpture is seen as ca plain material). For foam it has some sense, since the traditional acoustic polyether and polyester foams have an higher entrance impedance than wool (more surface reflection). As such profiling foam mainly compensates (mids and highs) for the less good material properties, at the expense of low frequent absorption (removed material). The better the basic material (as wool) the less effect this sculpture has, only leaving the disadvantages. In fact this commercial sculpting of foam is derived from the first wedges ever installed in Germany (Herz institute) think somewhere in the 40ies (have exact data somewhere). It's a bit the magic (+ huge PR budgets) which keeps it alive. In the industry lots of acoustic foam is used for technical applications, but in 99 % this is plain flat foam. This market is MUCH larger than for the sculpted foam, only unknown in the studio world. With Melamine which has different properties this sculpting becomes bad or less desirable. Problem for the producers: how to explain/sell that to potential customers. Therefore you'll notice that lots of producers will still use pyramides with Melamine, but make the sculpture much less high (base versus sculpture changes in favour of base). Best regards Eric

Hi Eric & Steve

In the industry lots of acoustic foam is used for technical applications, but in 99 % this is plain flat foam. This market is MUCH larger than for the sculpted foam, only unknown in the studio world.

Exactly ! Few months ago i check with BASF about their BASOTECT, i think is kind of melamine and u know how they sell this thing...... they sell by each container, frist i was thinking to use them to replace 703, but can't affort to buy a container of foam, now i am trying to buy them through some building contractor ! but can't find yet ! Anyway do u think i can susitule the glass fiber with Basotect ? and heard that a company made a metal penal trap with this foam as damper, are they good for studio use ? Thanx

hi feni, Basotect is the BASF name for Melamine Resin foam which is a patented BASF product. All other Melamine foam used world-wide either comes directly from BASF or is produced under BASF license. You find it under lots of names as Willtec etc. To find a supplier it's easier that you give your location. Maybe somebody can help you. But in general, rockwool or glassfiber is still a lot cheaper. so why should you choose Melamine? There are of course valid reasons, but standard glassfiber or rockwool is very hard to beat. Eric PS: it's not surprising that you can't buy minor quantities at BASF itself.

Hi Eric Thanx for the reply ! My location is HongKong, i did contact BASF HK/China but they don't have supplier infor for me, any accoustic matrial is not easy to find here ! or very expansive, even 703. u can only get 2" 703 so i have to stack them together if i want to make a 4" boardband module, but with yr infor now i am quite happy to know that just 2" 703 can do more than i knew before. There are 2 main reason i want to use non- fiberglass product beause... Reason 1- i have a very very sensitive skin, my arms turn red every time i touch them !......... Reason 2 - space for experiment is very limit in my place, most of the work is inside my apartment, my wife wants to kill me every time i cut the glass fiber ! So if melamine can replace 703 in terms of accoustical usage, i rather pay a bit ( just a bit ) more for it ! on the others hand i may save money on housing the 703. Eric ! what do u think ? is it worth for me to keep on seaching for basotect supplier ? Thanx ! and hope u understand my english ! Feni

Hello feni, Find it difficult to compare prices for you. That's more defined by local market situations. Maybe you can find coton wool, ployester or polyether (as in matraces) foam? From an acoustic point of view, Melamine is about as good as wool, say a little bit less good. It's acoustically certainly a valid alternative. From the point of view of fire properties, within the foam world, it's the best alternative around. It's difficult to rate the different solutions for you without knowing the cost. Here the basic Melamine will be 2,5 to 3 times more expensive than a valid naked glassfiber alternative (but that depends on density). Best regards Eric

OK so I can get this straight. The number like 703 does not apply to the actual thickness of the material, just the model? Like 703 is 3" and 705 is 5" thick? I want 4" boards.

Thanx again Eric

Find it difficult to compare prices for you. That's more defined by local market situations.

Yes ! fully understandable, if a different about, 2.5 to 3 times, i think, at least it worth for a try ! Now i am looking at the Borchure they sent to me, The CSR & CBA seem very interesting to me ( i think u did read it ! right ! ). They claim that A CBA ( product using Basotect with metal sheet ) " with thickness of 25cm which in the frz. range from 30Hz upwards allows the maintenance of free accoustic field conditions even in relatively small rooms." Do u think it's possible ?? honestly don't quite understand what means " Free accoustic Field" in this situation ! But why on the DIN 52215 & DIN 52212 graph, they don't look very impressive, especially on the LOW (125Hz) side, may be i don't fully understand the DIN system or comparing in a wrong concept !

Maybe you can find coton wool, ployester or polyether (as in matraces) foam?

Infect i did try! after i saw a foam corner trap made with ployester, claimed that it can go down to 45hz ( anyone try this ? ), badly it cost 3 to 4 times more if ship from England. Anyway all i found locally were closed cell foam. many supplier even don't know their product are close or open cell. i sound like a idiot to talk with them (or may be i was), :( So after all this disappointing search, i forced to use glassfiber together with my skin problems !

From an acoustic point of view, Melamine is about as good as wool, say a little bit less good. It's acoustically certainly a valid alternative. From the point of view of fire properties, within the foam world, it's the best alternative around.

Glad to know that ! thanx Eric ! i have to reset my english system inside my head for awhile and will come back to u and others great members here later ! Ciao !

feni You're welcome. You ask a lot of details with very specific end-product codes. If you have links it's always easier to check what exactly you're talking about. The question is not necessarilly. Is this a good absorber (you can make panel/membrane absorbers in lots of ways), but what do you need. You'll notice in the group that Helmholtz slat resonators are used a lot. To check if you have open cell foam, just blow trough it. If you get a blown-up red head while trying it's closed cell foam. :lol: Regards Eric[/url]

Carl, to answer your questions on 700 series fiberglas - The "3" in 703 refers to density. In that particular case, the stuff has a density of 3 pounds per cubic foot. Carrying that out to it's (wishfully) logical conclusion, you would think that 705 would be 5 PCF, but it's not - neither is 701 = to 1 PCF, but they are kinda close - in actual fact, 701 is 1.5 PCF - here is a chart of the range Type 701: 1.5 pcf (24 kg/m3) 711: 1.65 pcf (26 kg/m3) 702: 2.3 pcf (37 kg/m3) ASTM C 303 703: 3.0 pcf (48 kg/m3) 704: 4.2 pcf (67 kg/m3) 705: 6.0 pcf (96 kg/m3) 707: 7.0 pcf (112 kg/m3) and here is the entire pdf for the 700 series, from OC's site http://www.owenscorning.com/comminsul/d ... Series.pdf Sorry about the wait... Steve

Carl, > The number like 703 does not apply to the actual thickness of the material, just the model? < Yes, exactly. You can buy 701, 703, and 705 all in various thickness. The model number refers to the density of the material, not the thickness. 703 weighs about 3 pounds per cubic foot, and 705 weighs about 6 pounds. --Ethan

Right, Ethan - the PDF covers all that, including what's standard, what's special order (forget it, you're not rich enough) and which versions are available in what thickness... Steve

Hi Eric Sorry ! Here are the links : http://www.basf.de/basf/html/plastics/i ... t_Br_e.pdf - Basotect Catalog, Pls checkout Page 8,9 and 10 http://www.primacoustic.com/Australis.html - Corner trap cliamed effective down to 45Hz. too good to be true ?

The question is not necessarilly. Is this a good absorber (you can make panel/membrane absorbers in lots of ways), but what do you need.

Bingo! Yes ! i need a bass trap that without any or with minimun side effect as u mentioned somewhere, a modular type and can be stand alone ! Pls ! :P :P

You'll notice in the group that Helmholtz slat resonators are used a lot.

Yeah ! i made a corner trap 4' tall, and thanks steve for his help ! but i think i brought the wrong type of slats, white oak instead of pine, may be too hard for slat resonator, then i made a 2' tall with 1" 703 infront of the wood panel ( about 1" air gap ) then cover with burlap, on top of the slat. i can't test them, they mainly for my home setup. still have a lot of problems will post some later, can't express myself in english within one GO !

To check if you have open cell foam, just blow trough it. If you get a blown-up red head while trying it's closed cell foam.

I will un zip the cussion of the sofa first then blow them with a hair dryer if air passed through !, i will stick them on the corner use my shouting test menthod to verify the efficents, will post result later, and i hope all of us should do the same test. and see which is the best ! :wink: :D :D Very nice to chat with u all ! Feni. time reset my system again ! Thanx again Eric !

Interesting post. Owens Cornings own test figures from their Noise Control Design Index only showed measurements to 4" of 703. The late Malcolm Chisholm postulated from experience that a full 6" of 703 provides about the best broadband absorption you can readily make yourself, which appears to correspond with your figures. I've built about a dozen or so boxes of 6"703. Best, Dave

Hello Feni, Both are interesting links. The BASF document: I hadn't seen it yet but knew that the FRAUNHOFER Institute in Germany had designed such a broadband absorber. They have a license with some company (should have to look for the name). You can be sure that they work perfect. FRAUNHOFER is about the largest research institute in Germany in ALL kinds of acoustics. Those absorbers are designed also as space saving substitutes for the traditional Anechoic room wedges, having extremely stringent specs they must comply with. Basically it's a combined membrane absorber with open foam on top (so membrane sits in-between, where bottom is spring for membrane and top foam takes care of all the rest) The other link are standard polyurethane foams, but the corner absorbers have a good and logical design. If you should put them further away from the corner (e.g. first 4" foam before placing corner trap) they become better. This number down to 40 Hz doesn't tell much about exact numbers. Basically putting a OC 703 or 705 accross the corner will give about the same effect (not speaking in exact numbers now). But when you want to use foam for allergenic reasons, the links you found give a good picture (lacking numbers at the 2nd link) Best regards Eric

Steve, > Right, Ethan - the PDF covers all that < I replied before seeing that you already gave a perfect answer ... on the next page! --Ethan

Feni, > [Australis] Corner trap claimed effective down to 45Hz. too good to be true ? < Probably. A piece of tissue paper absorbs down to 45 Hz too. The question is how much? Since they don't give any data supporting that claim you should be very skeptical. --Ethan

Hi Eric Thanx for yr reply

They have a license with some company (should have to look for the name).

You can be sure that they work perfect. Yeah ! is called something like PLA or PAL , can't find the link now ! Infact they did Emailed me the contact of thier far east distributor for these low absorber, lost as well, due to a computer crash ! should get it back !

Basically it's a combined membrane absorber with open foam on top (so membrane sits in-between, where bottom is spring for membrane and top foam takes care of all the rest)

Like a sandwhich, Right ! seems i read somwhere, the foam is sticked directly on the metal sheet, no air gap needed. a neat and simple design not sure !

The other link are standard polyurethane foams, but the corner absorbers have a good and logical design.

For me it's the smarter in shape design than Pro corner (RPG) or Aularex, but man! costing 4 times more if ship from England ! already over price by itself.

Basically putting a OC 703 or 705 accross the corner will give about the same effect (not speaking in exact numbers now).

What different it make if a 4" 703 warp with burlap only and boxed (1/4 plywood, front with burlup) 4" 703, Placed accross the corner ? and what if a 4" flat foam ? they may be more or less a promised boardband with bonus on 100hz ? my 703 are all boxed !

But when you want to use foam for allergenic reasons, the links you found give a good picture (lacking numbers at the 2nd link)

Infact not only for allergenic reason, i do think foam will have protential to be a very good accoustic material, it's cleaner and easier to handle or shape. if i know the formular of the open cell foam, i am sure i will find some small pillow or cussion manufatory, to make me some 2lb/cu.ft foam for fun and do some experiment with them ! found some infor at Mike Shea book, but not much help ! OK! thanx a lot Eric ! by the way barefoot has posted a very very nice panel trap here ! He is one of those person that know how to build anything or at least some ideas in his head ! Hate him ! :twisted: OH! also thanx Ethan for yr advice too !

Hello feni

What different it make if a 4" 703 warp with burlap only and boxed (1/4 plywood, front with burlup) 4" 703, Placed accross the corner ? and what if a 4" flat foam ? they may be more or less a promised boardband with bonus on 100hz ? my 703 are all boxed !

I can't answer that exactly. It should be compared by measurements. Problem is making correct absorption measurements below 100 Hz (the lower freq the worse repetetivity). So just thinking out loud: I did measure (in lab) rockwool accross corner thickness 120 mm, boards were 1200 * 900 mm. Results down to 100 Hz extremely good. Lab had cutoff of 80 Hz. So it's difficult to study to very low frequencies. With the plywood front it becomes a paneltrap. So the response is more defined by the sizes (enclosed air volume versus panel weight). Comparing Melamine to wool will give some advantage to wool (Melamine has lower gasflowresistance). Comparing with polyurethane think still some advantage for wool. However it responds differently than Melamine. In the yahoo group there is now a consensus to use wool, but also add some wool to the wall behind. This isn't really measured/compared but is done as safety in analogy with the original patented corner (diagonal) absorption design (belonged to a Sweed but is expired now). But you can as well use an analogue principle with foam. And if one isn't sure, just make the foam somewhat thicker.

by the way barefoot has posted a very very nice panel trap here ! He is one of those person that know how to build anything or at least some ideas in his head ! Hate him !

It's indeed very good to get advice from knowledgeable people as barefoot. So I 100 % agree since the hate part is meant in funny way. Best regards Eric