Which fabric is best for panel & trap covering? Berlin?

Hi there! I'm in the midst of building some bass traps & sound panels. - Can anyone suggest the "best" fabric to use for it's covering? - How about the density? - Is Viscose, Polyester or Cotton best? Or a mix of ingredients? - And where can I order it or buy it in Germany!? Thank you all so much if u can share any wisdom !!!

shinyboy wrote:

Can anyone suggest the "best" fabric to use for it's covering?

The text below is from my Acoustics FAQ. --Ethan

Nearly any porous fabric is appropriate, and one popular brand is Guilford type FR701. Unfortunately, it's very expensive. One key feature of FR701 is that it's made of polyester so it won't shrink or loosen with changes in humidity when stretched on a frame. But polyester is a common material available in many styles and patterns at any local fabric store. Another feature of FR701 is that it's one of the few commercial fabrics rated to be acoustically transparent. But since you're not using it as speaker grill cloth to place in front of a tweeter, that feature too is not necessary. Shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. The standard test for acoustic fabric is to hold it to your mouth and try to blow air through it. If you can blow through it easily, it will pass sound into the fiberglass. Burlap and Muslin are two inexpensive options, but nearly any soft fabric will work and also keep the glass fibers safely in place.

thank you Ethan!

Felt is another popular option as it comes in a range of colours. cheers john

Ethan Winer wrote:

......... Shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. .........

Being shiny in itself has little to do with it. Lots of shiny fabrics (as non-shiny) have acceptable/good blow through properties (gas-flow resistance). Being shiny or glossy will not reflect more sound. The reason it's shiny or glossy is the molecular structure where the roughness is small compared to the wavelengths of light, not sound. Visible light: wavelengths between 380 and 780 nanometer (0.00000038 m - 0.00000078 m) Sound roughly between: 0.0172 and 17 m (20000 and 20 Hz) Hence even a 20000 Hz pitch, with extreme small audio wavelength has a wavelength still > 22000 larger than the largest visible light-wave. If one should express (very poetic license) the largest visible light-wave as an audio Frequency than we have a frequency of +/- 436,000,000 Hz Glossy paint does not reflect sound better than mat paint if both have a closed surface. Sound doesn't notice these extreme small particles. I've seen more related comments about glossy or shiny versus mat paint. If sound has trouble seeing reflectors or objects very small compared to their wavelength it will certainly not react to microscopic particles.

Eric_Desart wrote:

Ethan Winer wrote:

......... Shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. .........

Being shiny in itself has little to do with it. Lots of shiny fabrics (as non-shiny) have acceptable/good blow through properties (gas-flow resistance). Being shiny or glossy will not reflect more sound. The reason it's shiny or glossy is the molecular structure where the roughness is small compared to the wavelengths of light, not sound. Visible light: wavelengths between 380 and 780 nanometer (0.00000038 m - 0.00000078 m) Sound roughly between: 0.0172 and 17 m (20000 and 20 Hz) Hence even a 20000 Hz pitch, with extreme small audio wavelength has a wavelength still > 22000 larger than the largest visible light-wave. If one should express (very poetic license) the largest visible light-wave as an audio Frequency than we have a frequency of +/- 436,000,000 Hz Glossy paint does not reflect sound better than mat paint if both have a closed surface. Sound doesn't notice these extreme small particles. I've seen more related comments about glossy or shiny versus mat paint. If sound has trouble seeing reflectors or objects very small compared to their wavelength it will certainly not react to microscopic particles.

"SOME shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. The standard test for acoustic fabric is to hold it to your mouth and try to blow air through it. If you can blow through it easily, it will pass sound into the fiberglass. Burlap and Muslin are two inexpensive options, but nearly any soft fabric will work and also keep the glass fibers safely in place." Ethan I guess that would fix it. :D Glenn

Glenn Also non-shiny fabrics can have a tight weave. The shiny thing is related with visual aspects. I was confronted with it about half a year back. I told a studio owner the traditional stuff and the blow through thing. Being a color/esteatics maniac, he meanly remembered that he could buy about anything he liked. He bought very expensive fabric, not shiny at all. A got a sample, blow trough it, and never had a piece of cloth in my hands with such a high gasflow resistance (and there was no synthetic covering of the fabric involved). I later could use it, taking the reflectivity into account, making use of it.

Glenn,

"SOME shiny fabrics having a tight weave should be avoided"

LOL, that's great. Thanks Glenn. I wonder what part of "having a tight weave" folks will not understand. :roll: --Ethan

Ethan, what Eric's merely trying to say is that the WEAVE itself is what should be tested, nevermind if it's glossy, shiny, mat or whatever. So by removing the word "shiny", yer done. ...shiny happy people.. .lalalaaaa. (nevermind) 8)

Ro wrote:

Ethan, what Eric's merely trying to say is that the WEAVE itself is what should be tested, nevermind if it's glossy, shiny, mat or whatever. So by removing the word "shiny", yer done.

Understood fully. I will leave "shiny" there because it describes a class of materials like silk and synthetic equivalents that are reflective. The key part is "fabrics having a tight weave" which is correct, and adding "shiny" does not detract from the explanation. The real issue is that some people nit-pick to death everything they can because they have nothing better to do with their day. :) --Ethan

Ethan Winer wrote:

The real issue is that some people nit-pick to death everything they can because they have nothing better to do with their day. :)

There is nothing wrong with using silk and equivalents, and a bit respect for a REAL acoustician who visits and contributes in groups only a minor fraction of the time and number of groups you spent and frequent on the web should not be wrong. I limited my correct comments to physical stuff. Ro's summary of my words is a perfect one. Gasflow resistance is the defining factor which can go surprisingly high. And high gasflow resistance (shiny or not) can even be an advantage as I used the fabric I described since it controls a bit high frequent absorption, and I hardly could blow through this NON-shiny fabric. It worked perfectly.

Eric_Desart wrote:

There is nothing wrong with using silk and equivalents

Probably fine for bass traps, but that's a terrible idea for first reflection panels.

and a bit respect for a REAL acoustician

LOL, I'm a REAL acoustician too! It says so right here on the diploma I found in a box of cereal. :) --Ethan

Ethan Winer wrote:

Eric_Desart wrote:

There is nothing wrong with using silk and equivalents

Probably fine for bass traps, but that's a terrible idea for first reflection panels.

UNtrue

Eric_Desart wrote:

UNtrue

There's a good discussion about this exact issue here: www.avsforum.com/avs-vb/showthread.php? ... st10803655 Also, there's a matter of taste. Some people prefer the sound of early / first reflections. I happen to think they're wrong, but who am I to tell someone else what they should like. --Ethan

Gentlemen! Thanks for all the sparkling information :) shinyboy :)