What is so special about Audible recordings that is unnattainable by Librivox? You mean sound quality? You mean some holy grail vocal mics? Or vocal talent? I don't get it.
Its not that high quality is unobtainable, it's that nobody at librivox seems to try to attain it. Sound quality is definitely uneven at librivox, ranging from poor to middling, and passages composed of multiple tales are rarely mixed together smoothly. The vocal talent is mostly adequate (I certainly find plenty of narrators I dislike on audible) but it also seems sort of unsupervised -- narrators who encounter unfamiliar words will mispronounce them. I honestly think they'd get more even results with TTS now that WaveNet is so good.
I'm impressed by what librivox has achieved with just volunteers, but the production values are nowhere near as high as most books on audible.
Ratings could be a partial fix for quality control but they have been opposing them for years (because they want to keep it fun and motivating for volunteer readers..): http://piratelibrary.com/2010/05/on-the-absence-of-ratings-a... (ratings are now available in some LibriVox apps though)
IMHO they are just doing injustice to a number of good readers in their catalogue who put real effort into their recordings, but get buried under those one can barely listen to.
I've listened to a few Librevox recordings. They're usually (though not always) tolerable. Occaisionlly good, but that's exceeding rare.
Good audiobooks -- and a friend listens to many -- are far more often vastly superior. Even then, a poor reader is exceedingly grating.
Libravox may improve with time. History of volunteer efforts has been compeling. But not yet.