This Video shows the basic theory about membrane bass trap,
how to build them and some results for example

https://amcoustics.com/tools/amroc?l=...

https://gearspace.com/board/basstrap...

http://www.acousticmodelling.com/8lay...

http://downloads.bbc.co.uk/rd/pubs/re...

0:00 what are membrane bass traps
1:02 some history
3:56 room modes
5:49 formulas
7:19 optional materials
9:38 calculation
14:31 the built
17:33 results
20:04 tip
20:25 more results