Abstract: A headphone set includes a head band and a pair of speaker assemblies supplied on opposite ends of the headband. Each of the speaker assemblies comprises an earphone speaker for reproducing sound to be directed toward one of the wearer's ears, a relatively larger and more powerful broadcast speaker for reproducing sound to be broadcast in the vicinity of the headphone set; and an expandable speaker enclosure for supporting the earphone speaker and the broadcast speaker. Each speaker enclosure defines a sound chamber having an enclosed air volume for improving the acoustical characteristics of the headphone set and each speaker enclosure is shiftable between a collapsed configuration and an expanded configuration. When the speaker enclosures are shifted to their expanded configurations, the sound chambers have a relatively larger enclosed air volume. When they are shifted to their collapsed configurations relatively smaller enclosed air volumes.