speak up vs declare

speak up and declare both are verbs.

Word	Noun	Adjective	Verb	Adverb
speak up	No	No	Yes	No
declare	No	No	Yes	No

As verbs, declare is a hypernym of speak up; that is, declare is a word with a broader meaning than speak up:

speak up (verb)	declare (verb)
express one's opinion openly and without fear or hesitation	state emphatically and authoritatively
speak louder; raise one's voice	state firmly
	make a declaration (of dutiable goods) to a customs official
	declare to be
	announce publicly or officially
	proclaim one's support, sympathy, or opinion for or against
	designate (a trump suit or no-trump) with the final bid of a hand
	authorize payments of