[rhdunn]

Simon Roper has a spoken equivalent for Northern English -- https://www.youtube.com/watch?v=90Zqn9_OQAw.

[PaulDavisThe1st]

He has a spoken one that isn't Northern English specific too: https://www.youtube.com/watch?v=842OX2_vCic

"From Olde English to Modern American English in One Monologue"

[petesergeant]

for a very specific dialect of Northern English. I struggled to understand much beyond 1950, and I had a good ear

[qingcharles]

LOL I'm from Northern England and I tapped out ~1850.

I remember my father and I having to enable the subtitles for Rab C Nesbitt when I was a kid. There are areas of Scotland (especially the isles) which are probably still unintelligible to most of the British population I would wager.