Formula for tube trap?

Hello everyone, long time lurker here and ex member of the Yahoo acoustics group (Eric Desart, et al). I'm in the process of sourcing some stuff to build some tube traps, but would like to hear from practical experience if there IS such thing as a formula to determine which is the best ratio between diameter and fiberglass thickness for any given frequency range. I have also considered purchasing rolls of fiberglass mats and just stacking them up in corners (away from the walls), after having them covered in burlap. The second approach would cost some $130 per corner (2 rolls / corner for appx 8' height), while the "hollow tube" approach would only cost appx. $75 / corner. (FYI my prices are for material sourced here in southern Switzerland. The brand is ISOVER). Thank you so much for your kind answers. Take care, Paul Weber

Paul, There's no magic to a tube shape. Basically, what matters most is total surface area and thickness. --Ethan

Hi Ethan... honoured by your qualified response :) so basically the good old axiom "wider, thicker, lower" still applies (i.e. the wider and thicker it is, the lower the absorbed frequency range)? Thank you so much! Paul Weber