Walkman vs stereophonic system

Walkman and stereophonic system both are nouns.

Word	Noun	Adjective	Verb	Adverb
Walkman	Yes	No	No	No
stereophonic system	Yes	No	No	No

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

Walkman: (trademark) a pocket-sized stereo system with light weight earphones
stereophonic system: reproducer in which two microphones feed two or more loudspeakers to give a three-dimensional effect to the sound

Other hypernyms of Walkman include stereo, stereo system, stereophony.

Walkman (noun)	stereophonic system (noun)
(trademark) a pocket-sized stereo system with light weight earphones	reproducer in which two microphones feed two or more loudspeakers to give a three-dimensional effect to the sound