I have just finished listening to Scott L and Bob D, two excellent speakers who have a 7-CD series with a Big Book Study / Lecture they did in 2008. It can be downloaded here:
http://www.xa-speakers.org/pafiledb.php?action=category&id=91
Download the files that end with the string “96.mp3” (the “32.mp3” files are smaller but sound a lot worse)