An acoustic enclosure such as a loudspeaker (10) uses within the cabinet adsorbent material, and/or containment means (22) for the adsorbent material, which is at least partially hydrophobic. Preferably, the material is activated carbon treated to provide it with hydrophobic properties. Preferably, the adsorbent material is treated with a silicon-containing compound. This improves the acoustic compliance of the acoustic enclosure.