The phrase "a serious speech" is correct and usable in written English.
It can be used when referring to a speech that addresses important or grave topics, often requiring a formal tone.
Example: "The president delivered a serious speech addressing the nation's challenges and the need for unity."
Alternatives: "a solemn address" or "a grave talk."
In the classroom Mr. Rabb becomes involved with a sad boy named Tyquan who has a serious speech problem.
Mr Cameron can argue he backed up the Norway visit with a serious speech on the environment, complete with policy substance.
The businessman has a serious speech impediment, relies on a feeding tube and requires 24-hour care, but his doctor has not declared him incapacitated.
Billed as "a serious speech for serious times", it takes delusional optimism for Clegg to claim "our journey" is "dealing with our debts and delivering growth", while every month the deficit soars, growth declines and demand is dead.
Clinton began his speech, as he always does now, with a disclaimer, saying that if he wanted to, he could certainly give a big "whoop-dee-do" speech that would get everybody riled up, but that this was a serious time in America, and it deserved a serious speech.
By David Daiches The New Yorker, April 5, 1952 P. 96 An Englishman relates the story of the morning he delivered a speech on Britain's postwar economy to the Early Birds Breakfast Club in Washington D.C. Having prepared a serious speech for a serious meeting, he was shocked to find a group of yelling, whooping, back-slapping executives having a rowdy time and singing silly bird songs.
Lord Warner, former health minister in the Blair government, now chairing a project to improve London hospitals "It was a very serious speech and the contrast with Tony [Blair's] was very considerable.
Peter Feaver, a former Bush administration official who handled Iraq strategy and now teaches at Duke University, and who has signed two letters from national security officials opposing Mr. Trump's candidacy, praised Mr. Trump for giving a "surprisingly serious" speech on counterterrorism.
In a wide-ranging and serious speech that was well received by delegates, Balls warned that: "Hard times will last longer than all of us hoped".
Then she stepped to the podium to deliver a sweeping, if not always serious, speech reflecting many of the ideals of the Obama administration, optimism in the face of a global economic crisis and a few traces of her own groundbreaking role as a woman in politics.
She proceeded to give a serious, sturdy speech of a certain kind; if not quite AIPAC-ready, it was a speech extremely careful not to ruffle anyone's delicate feelings or becloud her last days as Secretary of State.
