With all the colors you can get in fleece nowadays could this be used to cover 703, or would it cut down on the absorption factor too much? it doesn't seem like it would, maybe wrong...
What I do to get a generial idea of the audio transparancy of a material, hold it up to the light. If you see through it easily, it is going to pass audio easily.
Also try blowing through it. If you can blow through it it will also pass audio.
None of those methods put into account the reflectiveness of the material itself. ANd they're not scientifically proven.
Mine is stripe patter. Just go to a fabric store and start pulling fabrics off the shelf. If it is thin enough and you like it, go for it! Could be burlap, could be muslin, could be silk, etc.
During forays into learnong about restoring my old speakers, (B&W, Thiel, Time Windows, etc) I was told by several sources that any double weave is sonically transparent.
Fleece is not a double weave, but then I guess burlap isnt either...
Unless you know that you are dealing with flameproofed material it is always best to buy some spray-on flameproofing.
That being said a fabric covered fiberglass panel is much safer than cheap foam on the walls because the fiberglass itself does not burn.
Don't get caught up in what kind of weave it is. Blow through it. If it puts up virtually no resistance it will do the job. It isn't a matter of the type of weave by how tight it is.