HF reflection with broadband absorbers?

[Re-tox_stl]

Howdy yallz. In the next few weeks I am planning on making some more broadband panels. 6 to be specific, 2" x 24" x 48" out of roxul rock board 60 (as opposed to 703 because of rigid ness, cost, and according to my research, it has better absorption of lower freqs). Also I am going to be making these without frames. Just use some 3m to attach some burlap and attach them to the wall via rotofast anchor things (sold at ATS acoustics). Now my question is that I read somewhere that it is beneficial to face the panels with either paper or plastic underneath the fabric as to reflect some high frequencies and not kill my room. Would this be beneficial to me? My room is approx 25' x 11' x 7 or 8'. I have 4" 703 panels in the corners they will fit into and 2" panels at first reflection points. Also a little bit of foam to cut back on slapback and a 3" panel I made out of the fluffy stuff a while ago. If that helps at all

Thanks much! Drew

 

[JimmyS1969]

From what I have found in my research and use, 'adhered' paper to the front of a panel will increase it's ability to absorb low frequencies, as well as reflect back some of the high end. This is typically not recommended for first reflection points for obvious reasons. Corner traps yes. The problem you will have tho, is that a panel directly against the wall will not do much for the low end. They are way more efficient with a 4"+ air gap between the wall and panel. I have 12 2'X4'X4" panels (no paper) in my room, which is close to the size of yours. The room is far from dead.

 

[Re-tox_stl]

Gotcha. I did consider placing them off of the wall, but frankly I don't think I have the space to have panels jutting 6" from the wall. Just not practical at the time . If you have twelve though with good results, then I may just got for it with no paper. What if I were to coat the front of the panel in the adhesive that I will use to secure the fabric? Would that have a similar effect and reflect some highs? Or should I just forget it?

Drew

 

[JimmyS1969]

My personal opinion would be to just adhere the fabric on the sides and just pull the front taut. Though, I would build frames of 1X1" pine myself. Not sure how rigid that Roxul 60 Rockboard is. The Roxul 80 I used, would have looked like couch cushions without frames. Not so rigid. I'm not sure if the spray adhesive would have a reflective quality. Not like you would be adding a thick layer tho. It doesn't take much. Seems adhering at at least the edges of the face, may limit the amount of squishing in the corners by alleviating the need to 'pull' the fabric tight.