subwoofer vs speaker system

subwoofer and speaker system both are nouns.

Word	Noun	Adjective	Verb	Adverb
subwoofer	Yes	No	No	No
speaker system	Yes	No	No	No

As nouns, speaker system is a hypernym of subwoofer; that is, speaker system is a word with a broader meaning than subwoofer:

subwoofer: a loudspeaker that is designed to reproduce very low bass frequencies
speaker system: electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance

Other hypernyms of subwoofer include loudspeaker, loudspeaker system, speaker, speaker unit.

subwoofer (noun)	speaker system (noun)
a loudspeaker that is designed to reproduce very low bass frequencies	electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance