A rotational moulding is used to form a loudspeaker housing with an outer shell (20) of thermoplastic material and a porous inner shell (21) of both fine and coarse thermoplastic material and expanding agent. The inner surface of the housing is granular due to the coarse material. Pref. thermoplastic material is polyethylene and equal quantities of fine and coarse material are used, the coarse material being 5 mm in size. The expanding agent is pref. diphenyloxide-4,4'-di-sulpho-hydrazide.
