one Question about absorbers

How airtight does the enclosure have to be? Tight as a drum? Can I use the existing drywall as a backing if the absorber is attached directly to it . . . how about a silicon seal? TIA, jim

Depends on what type absorber you're talking about - panel absorbers and helmholtz absorbers should be airtight, so the calculations come at least close to the reality; using various types of insulation covered with cloth, etc, don't matter at all. In fact, even panel absorbers will work without being sealed, but I don't have a clue how to predict what their response would be... Steve