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Originally Posted by Chrisc_o  I just had a thought while reading the explanation of panel thickness: if thinner panels will help you cover lower frequencies, then wouldn't something like the heat-shrink plastic film used to cover windows in the winter be a good material for this application? Cheap and easy to work with too. |
[Edit: sorry there was a typo.
Thicker panels will help cover lower frequencies. Anyway the paradox applies: the panel should not be too heavy]
There is a paradox. Bass trap work like a damped spring-mass system (like car suspension...), cavity being spring, membran being mass, absording material being damping. The membran must have enough mass (+ self stiffness but no inner damping in order to vibrate) for the spring-mass to work. In the other hand, the membran must not have too much mass in order to be 'bass transparent enough' i.e. to let the low frequency waves pass through it, be trapped into the cavity and engage the spring-mass-damping process...