[Mike-48]

I'm looking for comparable data on 4" and 6" Alpha panels, specifically relative absorption around 100 Hz (for reducing SBIR). Unfortunately, the former was tested by Riverbank, and the latter by the U of Salford. The absorption coefficient at 100 Hz is shown as about 0.7 for the thinner panel and 0.6 for the thicker, if I'm reading the reports right. That seems backwards to me.

I have thicker material elsewhere in the room (including Soffit Traps), and in this spot, 4" panels would be less intrusive. Maybe they are enough?  (I have 2" ASC panels in the location now, which I'd use in other areas.)

[JWL.GIK]

That's not correct, though I don't have the test data in front of me. I do know the different labs use different units of measurement (one "standard" and one metric) so the results have to be converted. Easiest is to convert both data sets to raw sabins I believe.

The 6" panel will outperform the 4" panel at 100Hz and below, they all use the same absorbent material, there's just more of it.

The 4" panel will give a sleeker fit & finish no question. But there's also no question the 6" panel helps more with SBIR and everything else under 100-150Hz or so. Both will be a lot better than a 2" panel.

[Mike-48]

Thanks, James. It's more or less the answer I expected. Probably will go for the 4" in this location. I have 6" on the front walls, and they are big!

EDIT: And @JWL.GIK : if you find comparable data, please post or PM me. Thanks!