[Jason Nugent]

Hi, folks,

I was looking at some absorption coefficients for both OFI-48 and OC703, both of which are 3pcf rigid fibreglass board, and the numbers in the low frequency region are quite different.  

I'm getting my numbers here:

http://www.bobgolds.com/AbsorptionCoefficients.htm

They seem to be different by more than what I'd call "experimental error".   For instance, OFI-48 is 0.03 at 80Hz and OC703 is 0.11.  I know it's harder to measure accurately at lower frequencies.  Does anyone know if these two products are manufacturered sufficiently different to account for at least some of this discrepancy?

Thanks,
Jason

[Ethan Winer]

Jason,

> I know it's harder to measure accurately at lower frequencies. <

That's my guess. Also, labs vary even at certified frequencies. Looking at the data for those same materials when 4 inches thick, it appears 703 is a bit better. But not a 4 to 1 disparity as with the 1 inch thick stuff. When the material is 1 inch thick and you measure at 80 Hz, the measurements are "down in the noise" anyway. Further, 1 inch thick is nowhere near adequate for bass trapping.

--Ethan

[Jason Nugent]

Ethan,

Thanks for the reply.  I was curious about this because I have 36 sheets of 1" OFI-48 to build a bunch of corner bass traps with.  Probably SuperChunk traps.  It'll give me a maximum depth of 12" in my corners, if I cut each 2x4 piece into 8 triangles.

Jason