A loudspeaker in an enclosure (851821 for single, 851822 for multiple) reproduces sound passively or with a built-in driver but is not a complete amplifier set. An electric sound amplifier set (851850) is a system combining an amplifier with speakers as a functional unit. If the article is sold and functions as an integrated amplifier-plus-speaker system, 851850 is the likely classification; a standalone speaker cabinet goes under the loudspeaker subheadings. Borderline assemblies should be reviewed against the heading text and Section XVI notes, or a binding ruling requested.

Generally yes — headphones, earphones, and combined microphone/speaker sets fall under 851830 regardless of whether they use a wired or wireless connection, as the heading text does not restrict by transmission method. However, if a device's principal function is radio reception or telephony rather than audio reproduction, it may be pulled toward a different heading. Confirm classification against the specific article's function and any applicable CBP rulings.