I'd love to see some development of an adjustable limp membrane design. Something like a panel with stretched fabric of some kind to attach different weights pinned on in an array on the fabric. Assuming that would work, of course!
@waxx and Krivium; I agree corners are good places to put absorbers but superchunks consisting of resitive absorbers only are pretty useless versus low frequencies. To show any signifacant results these have to be 1/10 to 1/7 of a wavelength in thickness. 30 Hz have a wave length of 11,3 m / 32,5 feet ... -No corner absorber will be thick enough.
https://www.google.com/url?sa=t&rct...assbass1.pdf&usg=AOvVaw07wKeJAY7-5CFk3_YpoWY7
https://www.google.com/url?sa=t&rct...example1.pdf&usg=AOvVaw1KEEngn9GjLrTmb7-X8-p_
edit: sorry i can't load the files at the moment but you have the link for limp membrane absorber and a layout example.
They are simple but effective, more recent development of the principle can be found but they are commercial offer.
https://www.google.com/url?sa=t&rct...example1.pdf&usg=AOvVaw1KEEngn9GjLrTmb7-X8-p_
edit: sorry i can't load the files at the moment but you have the link for limp membrane absorber and a layout example.
They are simple but effective, more recent development of the principle can be found but they are commercial offer.
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Hi Pano,
Mlv ( mass loaded vinyl). The kind of stuff used as acoustic 'barrier' in stacked material solution for soundproofing/ insulation for wall, ceiling or floor.
Here is some exemple of what you are looking for:
Auralex Acoustics | Total Sound Control
Noise S.T.O.P. Vinyl Barrier | Mass Loaded Vinyl Sound Barrier
Mass Loaded Vinyl - Vinyl Soundproofing Material | Soundproof Cow
Mlv ( mass loaded vinyl). The kind of stuff used as acoustic 'barrier' in stacked material solution for soundproofing/ insulation for wall, ceiling or floor.
Here is some exemple of what you are looking for:
Auralex Acoustics | Total Sound Control
Noise S.T.O.P. Vinyl Barrier | Mass Loaded Vinyl Sound Barrier
Mass Loaded Vinyl - Vinyl Soundproofing Material | Soundproof Cow
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The offer from: Acoustic Foam & Low Frequency Sound Absorption Specialists seems really interesting to me. They sell dedicated units and plans to the keeners. Their own design is a bit more complicated that the one from Tim Farrent. They use a double membrane resonnator and some charcoal powder (same kind used in odour or water filter) in place of the fiberglass. The cabinet use some sort of CLD too. Pretty advanced stuff, they have some nice youtube video imho.
How To Build A Diaphragmatic Absorber – Acoustic Fields
Nice explanation ( abit of self advertising though but it is fair ...).
Nice explanation ( abit of self advertising though but it is fair ...).
For years I've been using Ultra Touch cotton insulation made by Bonded Logic. My friends on the west coasts turned me on to it. It performs well in the low end and isn't too expensive. I notice that they have some new products for acoustics.
Echo Eliminator™ Acoustic Panels << Bonded Logic
The 2" thickness seems as good or better than the foam. Check it out.
Echo Eliminator™ Acoustic Panels << Bonded Logic
The 2" thickness seems as good or better than the foam. Check it out.
If you are in EU some materials close to the one Pano linked can be found. In France we have this: Metisse(R), l'isolation durable | Metisse
It is made from recycled cotton (blue jeans which if not reused should have been burned) by an association called 'Le Relais' (which help people with social difficulties getting back 'on tracks'). The material have good acoustical properties is well priced and good for our planet and society. This particular one could be used for sound insulation as well as absorbent in room treatment. Win/win materials imo.
It is made from recycled cotton (blue jeans which if not reused should have been burned) by an association called 'Le Relais' (which help people with social difficulties getting back 'on tracks'). The material have good acoustical properties is well priced and good for our planet and society. This particular one could be used for sound insulation as well as absorbent in room treatment. Win/win materials imo.
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Maybe we could start a dedicated thread about materials and their use?
It could be easier as a reference for someone interested in doing treatments ( whatever the treatments are as differents materials could see a use within different strategy applied).
For instance MLV is initialy used as part of a CLD ( Constrained Layer Damping - in 'double leaf' strategy usually) for sound proofing/ insulation but can see a use in a Limp membrane absorber.
Some foam/ rockwool/cotton insulation material could be used as absorbent material as well as soundproofing or part of diffusor strategy...
It could make things easier for people located in different parts of the world to find alternative material easily locally located too as some things are not availlable worldwide or under differents name in different locations.
It could be easier as a reference for someone interested in doing treatments ( whatever the treatments are as differents materials could see a use within different strategy applied).
For instance MLV is initialy used as part of a CLD ( Constrained Layer Damping - in 'double leaf' strategy usually) for sound proofing/ insulation but can see a use in a Limp membrane absorber.
Some foam/ rockwool/cotton insulation material could be used as absorbent material as well as soundproofing or part of diffusor strategy...
It could make things easier for people located in different parts of the world to find alternative material easily locally located too as some things are not availlable worldwide or under differents name in different locations.
One thing to note is if you make deep corner bass traps you want less dense material like the Owens Corning Pink Fluffy instead of Rockwool (unless they have a light desnity matieral too). You can check out a comparison here: Multi-Layer Absorption Calculator
That model has been verified a few times at Gearslutz as being relatively accurate. The 15000 Pa.s/m2 is roughly the flow resistivity quoted for rockwool in a few places. 5000 Pa.s/m2 is the pink fluffy. As you can see, you get about .65 instead of .5 absorption co-efficient at 30Hz.
Edit to add: Anyone building absorption panels should really swing through this site and take a look. It lists various absorption co-efficients for various materials at different thicknesses and distance from wall. http://www.bobgolds.com/AbsorptionCoefficients.htm
Hi,
I don't know your Owens's products... i'm located in EU and we don't have access to same materials in here. Some are equivalents and as it can be seen in the comparaison this is the characteristic which are important given you know your target.
In the room i've build material used were almost always the same and Rockwool products was the ones used so i talk of what i've used and know are effective (about what is another question ). My experience has been positive with Limp membrane absorbers for low end and the size/effectiveness is impressive in that case imo.
As we are talking about domestic rooms i think this is of interest ( cost is another matter as the one i've seen used where $$$). Like i said i'm not saying superchunk or other approach don't work but my point is one size does not fit all, more particularly about small rooms.
I think that now we have access to relatively cheap measurement gear a correct approach is to take measurement in room and then decide what to do from here (define a strategy). This is even more true for lows. The common sense tells that low best spot for treatment is corner which is true most of the time but in practice build technique, physical layout (openings like doors or windows) may change that in a big way.
Better to have a 3d mapping of modal behavior and define where to place treatment ( for higher efficienc) and at which frequencies from here. But it is my view, others may be as valid as mine.
I don't know your Owens's products... i'm located in EU and we don't have access to same materials in here. Some are equivalents and as it can be seen in the comparaison this is the characteristic which are important given you know your target.
In the room i've build material used were almost always the same and Rockwool products was the ones used so i talk of what i've used and know are effective (about what is another question
). My experience has been positive with Limp membrane absorbers for low end and the size/effectiveness is impressive in that case imo. As we are talking about domestic rooms i think this is of interest ( cost is another matter as the one i've seen used where $$$). Like i said i'm not saying superchunk or other approach don't work but my point is one size does not fit all, more particularly about small rooms.
I think that now we have access to relatively cheap measurement gear a correct approach is to take measurement in room and then decide what to do from here (define a strategy). This is even more true for lows. The common sense tells that low best spot for treatment is corner which is true most of the time but in practice build technique, physical layout (openings like doors or windows) may change that in a big way.
Better to have a 3d mapping of modal behavior and define where to place treatment ( for higher efficienc) and at which frequencies from here. But it is my view, others may be as valid as mine.
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Thanks Munk for that link, there is so much info there. Be sure to put it in the new thread. 
It's interesting to compare some different materials. The Ultra Touch cotton that I like does well, but it can be $$$. Good old fluffy fiberglass meant for inside walls does well enough, and is cheap. That's would I used in my panels, sometimes in double thickness. Good value for money.
It's interesting to compare some different materials. The Ultra Touch cotton that I like does well, but it can be $$$. Good old fluffy fiberglass meant for inside walls does well enough, and is cheap. That's would I used in my panels, sometimes in double thickness. Good value for money.
I have the German software called CARA. I think it has been discontinued.
CARA lets me 3D model a room, absorbers, diffusers, furniture and even speaker and model the results. It's helpful.
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