hairy_hen said:

Both the DVD and Bluray versions of ESB and RotJ still use the '97 mixes as their main source, only splicing in individual new changes for each release. They haven't been remixed from scratch the way the first movie was.

I didn't know that and I find it interesting. I am really surprised that Lucasfilm didn't simply use the 1997 5.1 Mix as the main source during the creation of the problematic 6.1 Mix that was featured on the 2004 DVD of the first film. Even the 6.1 Mix on the 2011 Blu-Ray still has a few tiny flaws even though it corrected most of the problems the 2004 Mix had. I've noticed that there are still two missing sound effects.

I've compared the 1993 2.0 Surround Mixes on the 2006 DVDs of the Original Versions to the 6.1 Mixes on the 2011 Blu-Rays of the Special Editions and there are things I like better about the 1993 Mixes.