I think I understand - bad, baaaaaaaad or bard. Here in t'Narth of England, it's path and bath like bad. Soft southerners say parth and barth. In the Hampshire area it's a more open sound, a bit more like baarth, but the main difference is between bad and bard. As someone who's lived in North, South and Midlands, I find myself using either randomly. But as to whether it's eether or eyether - A little Derbyshire lad comes from school and says 'Dad, are we supposed to say eether or eyether?" "Ay-ther, lad ay-ther" says his Dad.