National Public Radio did a 15 minute program on Hank Williams The Unreleased Recordings back on October 25th. I’m finally getting around to putting up the link.
The segment was part of Weekend Edition hosted by Scott Simon and featured comments from Jett Williams and highlights from the Box Set.
Simon is s devoted fan and some of his comments are delightful. Jett Williams talks about the difference in sound quality from the MGM studio recordings, and the vocal quality on these radio acetates from WSM. Of course the MGM sessions were also recorded direct to disk so to speak on acetates. Jett says the studio recordings were not pure direct to disk but the sound was altered by limiters and compressors such as are used by recording studios and radio stations.
I always thought the Castle recordings were pure, but it certainly would be interesting to hear more about the recording technology used those days before tape came in. What were the differences between WSM recordings and Castle Studios? Were the ‘Health and Happiness’ shows recorded on the same equipment at Castle? Obviously, I don’t know much about this!
There’s more from Jett at the link, go to listen now button in upper left.
A Hank Williams Journal 
It’s my understanding that the non-Cincinatti stuff recorded in Nashville was cut direct to acetate – and the original 16″ acetate discs were lost by MGM/Universal decades ago, although there was some scant evidence they might be mis-catalogued in a warehouse somewhere. The radio transcripts were recorded in much the same way – and I think the radio transcriptions were recorded without compression because a radio station signal is significantly compressed already, and they were intended to be played over the radio only.
The Health and Happiness shows recorded in October 1949 come before Hank started recording in Nashville, so they may have been cut in Cincinatti at King studios.